CA1162181A - Catalyst composition and process for oxidation of ethylene to ethylene oxide - Google Patents
Catalyst composition and process for oxidation of ethylene to ethylene oxideInfo
- Publication number
- CA1162181A CA1162181A CA000347075A CA347075A CA1162181A CA 1162181 A CA1162181 A CA 1162181A CA 000347075 A CA000347075 A CA 000347075A CA 347075 A CA347075 A CA 347075A CA 1162181 A CA1162181 A CA 1162181A
- Authority
- CA
- Canada
- Prior art keywords
- catalyst
- silver
- cesium
- potassium
- alkali metal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000003054 catalyst Substances 0.000 title claims abstract description 336
- 238000000034 method Methods 0.000 title claims abstract description 94
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical compound C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 title claims abstract description 62
- 230000008569 process Effects 0.000 title claims abstract description 29
- 239000000203 mixture Substances 0.000 title claims description 45
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 title claims description 21
- 239000005977 Ethylene Substances 0.000 title claims description 21
- 238000007254 oxidation reaction Methods 0.000 title claims description 6
- 230000003647 oxidation Effects 0.000 title claims description 5
- 229910052709 silver Inorganic materials 0.000 claims abstract description 206
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims abstract description 191
- 239000004332 silver Substances 0.000 claims abstract description 188
- 229910052792 caesium Inorganic materials 0.000 claims abstract description 173
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 claims abstract description 155
- 229910052700 potassium Inorganic materials 0.000 claims abstract description 146
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims abstract description 127
- 239000011591 potassium Substances 0.000 claims abstract description 127
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 94
- 150000001340 alkali metals Chemical class 0.000 claims abstract description 90
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims abstract description 47
- 229910052708 sodium Inorganic materials 0.000 claims abstract description 47
- 239000011734 sodium Substances 0.000 claims abstract description 47
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 44
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 43
- 238000004519 manufacturing process Methods 0.000 claims abstract description 42
- 229910052701 rubidium Inorganic materials 0.000 claims abstract description 26
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 claims abstract description 26
- 238000006243 chemical reaction Methods 0.000 claims description 35
- 229910052760 oxygen Inorganic materials 0.000 claims description 26
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 25
- 239000001301 oxygen Substances 0.000 claims description 25
- 238000000151 deposition Methods 0.000 claims description 22
- 230000008021 deposition Effects 0.000 claims description 21
- 239000011148 porous material Substances 0.000 claims description 21
- 230000000694 effects Effects 0.000 claims description 20
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical group CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 claims description 18
- 239000002904 solvent Substances 0.000 claims description 17
- 239000007789 gas Substances 0.000 claims description 14
- GGCZERPQGJTIQP-UHFFFAOYSA-N sodium;9,10-dioxoanthracene-2-sulfonic acid Chemical compound [Na+].C1=CC=C2C(=O)C3=CC(S(=O)(=O)O)=CC=C3C(=O)C2=C1 GGCZERPQGJTIQP-UHFFFAOYSA-N 0.000 claims description 14
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 11
- 239000003112 inhibitor Substances 0.000 claims description 11
- 239000004310 lactic acid Substances 0.000 claims description 9
- 235000014655 lactic acid Nutrition 0.000 claims description 9
- 239000012808 vapor phase Substances 0.000 claims description 9
- 239000003085 diluting agent Substances 0.000 claims description 7
- 150000001412 amines Chemical group 0.000 claims description 6
- 230000006872 improvement Effects 0.000 claims description 6
- WSLDOOZREJYCGB-UHFFFAOYSA-N 1,2-Dichloroethane Chemical group ClCCCl WSLDOOZREJYCGB-UHFFFAOYSA-N 0.000 claims description 3
- 150000003839 salts Chemical class 0.000 claims description 3
- 238000010924 continuous production Methods 0.000 claims description 2
- 159000000001 potassium salts Chemical class 0.000 claims 1
- 239000000243 solution Substances 0.000 description 99
- 238000002474 experimental method Methods 0.000 description 63
- 238000002360 preparation method Methods 0.000 description 35
- 238000007792 addition Methods 0.000 description 24
- 238000010438 heat treatment Methods 0.000 description 18
- 239000000969 carrier Substances 0.000 description 17
- 239000000463 material Substances 0.000 description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 16
- 239000002245 particle Substances 0.000 description 16
- 230000000875 corresponding effect Effects 0.000 description 14
- NDVLTYZPCACLMA-UHFFFAOYSA-N silver oxide Chemical compound [O-2].[Ag+].[Ag+] NDVLTYZPCACLMA-UHFFFAOYSA-N 0.000 description 14
- 238000005470 impregnation Methods 0.000 description 13
- 230000002195 synergetic effect Effects 0.000 description 13
- 238000013461 design Methods 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 12
- 239000002184 metal Substances 0.000 description 11
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 10
- 239000003513 alkali Substances 0.000 description 10
- 239000012153 distilled water Substances 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 9
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 9
- 239000002131 composite material Substances 0.000 description 9
- -1 silver carboxylates Chemical class 0.000 description 9
- QZRLETONGKUVFA-UHFFFAOYSA-N [K].[Cs] Chemical compound [K].[Cs] QZRLETONGKUVFA-UHFFFAOYSA-N 0.000 description 8
- 229910002092 carbon dioxide Inorganic materials 0.000 description 8
- 238000005259 measurement Methods 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 239000001569 carbon dioxide Substances 0.000 description 7
- 230000009467 reduction Effects 0.000 description 7
- 229910001923 silver oxide Inorganic materials 0.000 description 7
- 238000004458 analytical method Methods 0.000 description 6
- HUCVOHYBFXVBRW-UHFFFAOYSA-M caesium hydroxide Inorganic materials [OH-].[Cs+] HUCVOHYBFXVBRW-UHFFFAOYSA-M 0.000 description 6
- 229910001507 metal halide Inorganic materials 0.000 description 6
- 150000005309 metal halides Chemical class 0.000 description 6
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 6
- 230000004044 response Effects 0.000 description 6
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 5
- 239000000654 additive Substances 0.000 description 5
- 229910001508 alkali metal halide Inorganic materials 0.000 description 5
- 150000008045 alkali metal halides Chemical class 0.000 description 5
- 230000003042 antagnostic effect Effects 0.000 description 5
- 239000012298 atmosphere Substances 0.000 description 5
- 239000003153 chemical reaction reagent Substances 0.000 description 5
- 229940000425 combination drug Drugs 0.000 description 5
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 5
- 229910052753 mercury Inorganic materials 0.000 description 5
- 239000000377 silicon dioxide Substances 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- 239000011885 synergistic combination Substances 0.000 description 5
- HZAXFHJVJLSVMW-UHFFFAOYSA-N 2-Aminoethan-1-ol Chemical compound NCCO HZAXFHJVJLSVMW-UHFFFAOYSA-N 0.000 description 4
- MFGOFGRYDNHJTA-UHFFFAOYSA-N 2-amino-1-(2-fluorophenyl)ethanol Chemical compound NCC(O)C1=CC=CC=C1F MFGOFGRYDNHJTA-UHFFFAOYSA-N 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 230000000996 additive effect Effects 0.000 description 4
- 230000003197 catalytic effect Effects 0.000 description 4
- 238000002485 combustion reaction Methods 0.000 description 4
- 229910052730 francium Inorganic materials 0.000 description 4
- KLMCZVJOEAUDNE-UHFFFAOYSA-N francium atom Chemical compound [Fr] KLMCZVJOEAUDNE-UHFFFAOYSA-N 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- GEVPUGOOGXGPIO-UHFFFAOYSA-N oxalic acid;dihydrate Chemical compound O.O.OC(=O)C(O)=O GEVPUGOOGXGPIO-UHFFFAOYSA-N 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 235000012239 silicon dioxide Nutrition 0.000 description 4
- 229910000108 silver(I,III) oxide Inorganic materials 0.000 description 4
- 238000011282 treatment Methods 0.000 description 4
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 3
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000000460 chlorine Substances 0.000 description 3
- 229910052801 chlorine Inorganic materials 0.000 description 3
- 150000001805 chlorine compounds Chemical class 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 230000018109 developmental process Effects 0.000 description 3
- 150000004820 halides Chemical class 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 3
- 238000012856 packing Methods 0.000 description 3
- 230000000704 physical effect Effects 0.000 description 3
- 229910000027 potassium carbonate Inorganic materials 0.000 description 3
- TYJJADVDDVDEDZ-UHFFFAOYSA-M potassium hydrogencarbonate Chemical compound [K+].OC([O-])=O TYJJADVDDVDEDZ-UHFFFAOYSA-M 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 239000000376 reactant Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 230000009044 synergistic interaction Effects 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- WMONZZDVKGUCLB-UHFFFAOYSA-N [K].[Ag].[Cs] Chemical compound [K].[Ag].[Cs] WMONZZDVKGUCLB-UHFFFAOYSA-N 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 150000001336 alkenes Chemical class 0.000 description 2
- 229910052787 antimony Inorganic materials 0.000 description 2
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 2
- 229910052788 barium Inorganic materials 0.000 description 2
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000000536 complexating effect Effects 0.000 description 2
- 239000008139 complexing agent Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 230000002596 correlated effect Effects 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 229910001882 dioxygen Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000007429 general method Methods 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- 238000013178 mathematical model Methods 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 238000001465 metallisation Methods 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- 229910052755 nonmetal Inorganic materials 0.000 description 2
- 235000006408 oxalic acid Nutrition 0.000 description 2
- 229960003903 oxygen Drugs 0.000 description 2
- 239000011236 particulate material Substances 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 235000011181 potassium carbonates Nutrition 0.000 description 2
- VKJKEPKFPUWCAS-UHFFFAOYSA-M potassium chlorate Chemical compound [K+].[O-]Cl(=O)=O VKJKEPKFPUWCAS-UHFFFAOYSA-M 0.000 description 2
- 229910001414 potassium ion Inorganic materials 0.000 description 2
- CHWRSCGUEQEHOH-UHFFFAOYSA-N potassium oxide Chemical compound [O-2].[K+].[K+] CHWRSCGUEQEHOH-UHFFFAOYSA-N 0.000 description 2
- 229910001950 potassium oxide Inorganic materials 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 150000003378 silver Chemical group 0.000 description 2
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical compound [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 2
- 229910001948 sodium oxide Inorganic materials 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 229910052716 thallium Inorganic materials 0.000 description 2
- BKVIYDNLLOSFOA-UHFFFAOYSA-N thallium Chemical compound [Tl] BKVIYDNLLOSFOA-UHFFFAOYSA-N 0.000 description 2
- 230000004584 weight gain Effects 0.000 description 2
- 235000019786 weight gain Nutrition 0.000 description 2
- VILCJCGEZXAXTO-UHFFFAOYSA-N 2,2,2-tetramine Chemical compound NCCNCCNCCN VILCJCGEZXAXTO-UHFFFAOYSA-N 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- FERIUCNNQQJTOY-UHFFFAOYSA-M Butyrate Chemical compound CCCC([O-])=O FERIUCNNQQJTOY-UHFFFAOYSA-M 0.000 description 1
- FERIUCNNQQJTOY-UHFFFAOYSA-N Butyric acid Natural products CCCC(O)=O FERIUCNNQQJTOY-UHFFFAOYSA-N 0.000 description 1
- 241000237074 Centris Species 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 241001397173 Kali <angiosperm> Species 0.000 description 1
- JVTAAEKCZFNVCJ-UHFFFAOYSA-M Lactate Chemical compound CC(O)C([O-])=O JVTAAEKCZFNVCJ-UHFFFAOYSA-M 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- 101100409194 Rattus norvegicus Ppargc1b gene Proteins 0.000 description 1
- 101150082969 SELP gene Proteins 0.000 description 1
- 101150036293 Selenop gene Proteins 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- INEKNOMFAWBMDA-UHFFFAOYSA-N [K].[Cs].[Ba] Chemical compound [K].[Cs].[Ba] INEKNOMFAWBMDA-UHFFFAOYSA-N 0.000 description 1
- JJFHSTASBVENMB-UHFFFAOYSA-N [Li].[Cs] Chemical compound [Li].[Cs] JJFHSTASBVENMB-UHFFFAOYSA-N 0.000 description 1
- BVWZFGDFKQCHAN-UHFFFAOYSA-N [Na].[Cs] Chemical compound [Na].[Cs] BVWZFGDFKQCHAN-UHFFFAOYSA-N 0.000 description 1
- FAWNVSNJFDIJRM-UHFFFAOYSA-N [Rb].[Cs] Chemical compound [Rb].[Cs] FAWNVSNJFDIJRM-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 229910001514 alkali metal chloride Inorganic materials 0.000 description 1
- 150000001339 alkali metal compounds Chemical class 0.000 description 1
- 229910001413 alkali metal ion Inorganic materials 0.000 description 1
- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 description 1
- 125000002947 alkylene group Chemical group 0.000 description 1
- LHIJANUOQQMGNT-UHFFFAOYSA-N aminoethylethanolamine Chemical compound NCCNCCO LHIJANUOQQMGNT-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- AIYUHDOJVYHVIT-UHFFFAOYSA-M caesium chloride Chemical compound [Cl-].[Cs+] AIYUHDOJVYHVIT-UHFFFAOYSA-M 0.000 description 1
- FLJPGEWQYJVDPF-UHFFFAOYSA-L caesium sulfate Chemical class [Cs+].[Cs+].[O-]S([O-])(=O)=O FLJPGEWQYJVDPF-UHFFFAOYSA-L 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 150000007942 carboxylates Chemical class 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 238000003889 chemical engineering Methods 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 235000014113 dietary fatty acids Nutrition 0.000 description 1
- MCWXGJITAZMZEV-UHFFFAOYSA-N dimethoate Chemical compound CNC(=O)CSP(=S)(OC)OC MCWXGJITAZMZEV-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000000194 fatty acid Substances 0.000 description 1
- 229930195729 fatty acid Natural products 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 230000001976 improved effect Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 229910001502 inorganic halide Inorganic materials 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 150000002642 lithium compounds Chemical class 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 229960003753 nitric oxide Drugs 0.000 description 1
- XITQUSLLOSKDTB-UHFFFAOYSA-N nitrofen Chemical compound C1=CC([N+](=O)[O-])=CC=C1OC1=CC=C(Cl)C=C1Cl XITQUSLLOSKDTB-UHFFFAOYSA-N 0.000 description 1
- JCXJVPUVTGWSNB-UHFFFAOYSA-N nitrogen dioxide Inorganic materials O=[N]=O JCXJVPUVTGWSNB-UHFFFAOYSA-N 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- JTJMJGYZQZDUJJ-UHFFFAOYSA-N phencyclidine Chemical compound C1CCCCN1C1(C=2C=CC=CC=2)CCCCC1 JTJMJGYZQZDUJJ-UHFFFAOYSA-N 0.000 description 1
- XNGIFLGASWRNHJ-UHFFFAOYSA-L phthalate(2-) Chemical compound [O-]C(=O)C1=CC=CC=C1C([O-])=O XNGIFLGASWRNHJ-UHFFFAOYSA-L 0.000 description 1
- 238000002459 porosimetry Methods 0.000 description 1
- 235000015320 potassium carbonate Nutrition 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 238000000611 regression analysis Methods 0.000 description 1
- 230000010076 replication Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- CQLFBEKRDQMJLZ-UHFFFAOYSA-M silver acetate Chemical compound [Ag+].CC([O-])=O CQLFBEKRDQMJLZ-UHFFFAOYSA-M 0.000 description 1
- 229940071536 silver acetate Drugs 0.000 description 1
- 229940100890 silver compound Drugs 0.000 description 1
- 150000003379 silver compounds Chemical class 0.000 description 1
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
- 229910001961 silver nitrate Inorganic materials 0.000 description 1
- LMEWRZSPCQHBOB-UHFFFAOYSA-M silver;2-hydroxypropanoate Chemical compound [Ag+].CC(O)C([O-])=O LMEWRZSPCQHBOB-UHFFFAOYSA-M 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- RBWSWDPRDBEWCR-RKJRWTFHSA-N sodium;(2r)-2-[(2r)-3,4-dihydroxy-5-oxo-2h-furan-2-yl]-2-hydroxyethanolate Chemical compound [Na+].[O-]C[C@@H](O)[C@H]1OC(=O)C(O)=C1O RBWSWDPRDBEWCR-RKJRWTFHSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000007619 statistical method Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
- 229940045605 vanadium Drugs 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D301/00—Preparation of oxiranes
- C07D301/02—Synthesis of the oxirane ring
- C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
- C07D301/04—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen
- C07D301/08—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase
- C07D301/10—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase with catalysts containing silver or gold
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/66—Silver or gold
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Catalysts (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to a supported silver catalyst for the manufacture of ethylene oxide which contains a combination of (a) cesium and (b) at least one other alkali metal selected from the group con-sisting of lithium, sodium, potassium, and rubidium, which combination comprises (a) and (b) in amounts in relation to the amount of silver therein sufficient to increase the efficiency of ethylene oxide manufacture to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as said catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount of (b). There is also described herein a process of making such catalyst and a process for producing ethylene oxide with such catalyst.
This invention relates to a supported silver catalyst for the manufacture of ethylene oxide which contains a combination of (a) cesium and (b) at least one other alkali metal selected from the group con-sisting of lithium, sodium, potassium, and rubidium, which combination comprises (a) and (b) in amounts in relation to the amount of silver therein sufficient to increase the efficiency of ethylene oxide manufacture to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as said catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount of (b). There is also described herein a process of making such catalyst and a process for producing ethylene oxide with such catalyst.
Description
21~31 12,439-1 This invention is concerned with silver catalysts, their manufacture and their use in the manufacture of ethylene oxide. The catalyst of this invention comprises a supported silver catalyst. The catalyst contains a combination of (a~ cesium and (b) at least one other alkali metal selected from the group c~nsisting of lithium, sodium, potassium and rubidium, wherein (a) and (b) are present in amounts in relation to the amount of silver therein sufficient to increase the efficiency of the ethylene oxide manufac~ure to a value greater than the effi-cienc~es obtainable under common operating conditions f~om respective catalysts which are the same as said catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the rcspective amount of (b). Thus, the catalyst, when utilized in the manufacture of ethylene oxide, con-tains a combination of cesium and one or more other alkali metals (excluding francium) in an amount which achieves a synergistic result as defined herein. In addition, the process of this invention defines such synergism as a function of the silver content of the catalyst. Thus, for any given amount of silver in the catalyst, the present invention provides the appropriate correlation of alkali metal and silver whereby particular combinations of cesium and one or more other alkali metals may be selected which achieve efficiencies in the manu-facture of ethylene oxide which exceed the higher efficiency obtainable with such amount of silver when in combination with the respective amount of either cesium or the other alkali metals in such mixture.
~
~ 1 62~8~
12,439-1 The manufacture of ethylene oxide by the re-action of oxygen or oxygen-conta.ining gases with ethylene in the presence of a silver catalyst is an old and very well developed art. For example, V. S. Patent No.
~
~ 1 62~8~
12,439-1 The manufacture of ethylene oxide by the re-action of oxygen or oxygen-conta.ining gases with ethylene in the presence of a silver catalyst is an old and very well developed art. For example, V. S. Patent No.
2,040,732, patented May 12, 1936, descrlbes the manu-facture of ethylene oxide by the reaction oE oxygen with ethylene in the presence of silver catalysts wb.ich con-tain a class of metal promoters. In Reissue U. S. Patent 20,370, dated May 18, 1937, Leforte discloses that ~he formation of olefin oxides may be effected by causing olefins to combine directly with molecular oxygen in the presence of a silver catalyst. From that point on, the prior art has focused its efforts on improving the catalyst's efficiency in producing ethylene oxide.
In characterizing this invention, the terms "conversion", "selectivity", and "yield" are employed as defined in U~ S. Patent No. 3,420,784, patented January 7, 1969, a~ column 3, lines 24-35 inclusive, This definition of "selectivity" is consistent with that disclosed in U. S. Patent No. 2,766,261 at column 6, lines 5-22, and U. S. Patent No. 3,144,916, lines 5~-61. The definitions of "yield" and "conversion" have more varied meaning in the art and are not to be employed as defined, for example, in the aforementioned U. S. Patent No. 2,766,261.
The terms "efficiency'` and "selectivity" as used throughout the specification and claims are intended to be synonomous.
Silver catalysts employed in the manufacture of ethylene oxide have undergone significant changes since their initial period of development. As reported 12,439-l by the art, silver particles were first deposited upon support materials with little attention being paid to support properties, such as surface area, pore volume and chemical inertness. As the art evolved, there develop-ed special ~echnologies related to carriers or supports con-taining silver that were more effective for the reaction of ethylene with oxygen to produce ethylene oxide. Today,~
most supports for the silver catalysts are particulate materials which can be loaded in the interior of a reactor wherein the reacting gases and the gaseous products of the reaction are capable of flowing in and about these particulate materials to pass through the reactor and be recovered. The shape of the support is a variable factor and the particular shape selected is peculiar to the reactor employed, the gas flow required, and the surface area which is desired for the optimization of the reaction with other factors also being considered The carriers that have been employed are typically made of inorganic materials, generally of a mineral nature. In most cases, the preferred carrier is made of alpha-alumina, such as has been described in the patent literature: see for example, U. S. Patents 2,294,383; 3,172,893; 3,332,887; 3,423,328; and 3,563,914.
The silver that is deposited on these carriers is typically in the form of small particles. The patent literature indicates that the size of the silver is a factor in the elfectiveness of the catalyst and in most cases fine particle silver i 5 obt2i.ned u~ilizing the standard processes in the art; see or exa~.ple, U. S.
Patent Nos. 2,554,459; 2,831,870; 3,423,328 ~specifies that silver particles of 150-400 angstroms are employed);
~ ~2~
12,439-1
In characterizing this invention, the terms "conversion", "selectivity", and "yield" are employed as defined in U~ S. Patent No. 3,420,784, patented January 7, 1969, a~ column 3, lines 24-35 inclusive, This definition of "selectivity" is consistent with that disclosed in U. S. Patent No. 2,766,261 at column 6, lines 5-22, and U. S. Patent No. 3,144,916, lines 5~-61. The definitions of "yield" and "conversion" have more varied meaning in the art and are not to be employed as defined, for example, in the aforementioned U. S. Patent No. 2,766,261.
The terms "efficiency'` and "selectivity" as used throughout the specification and claims are intended to be synonomous.
Silver catalysts employed in the manufacture of ethylene oxide have undergone significant changes since their initial period of development. As reported 12,439-l by the art, silver particles were first deposited upon support materials with little attention being paid to support properties, such as surface area, pore volume and chemical inertness. As the art evolved, there develop-ed special ~echnologies related to carriers or supports con-taining silver that were more effective for the reaction of ethylene with oxygen to produce ethylene oxide. Today,~
most supports for the silver catalysts are particulate materials which can be loaded in the interior of a reactor wherein the reacting gases and the gaseous products of the reaction are capable of flowing in and about these particulate materials to pass through the reactor and be recovered. The shape of the support is a variable factor and the particular shape selected is peculiar to the reactor employed, the gas flow required, and the surface area which is desired for the optimization of the reaction with other factors also being considered The carriers that have been employed are typically made of inorganic materials, generally of a mineral nature. In most cases, the preferred carrier is made of alpha-alumina, such as has been described in the patent literature: see for example, U. S. Patents 2,294,383; 3,172,893; 3,332,887; 3,423,328; and 3,563,914.
The silver that is deposited on these carriers is typically in the form of small particles. The patent literature indicates that the size of the silver is a factor in the elfectiveness of the catalyst and in most cases fine particle silver i 5 obt2i.ned u~ilizing the standard processes in the art; see or exa~.ple, U. S.
Patent Nos. 2,554,459; 2,831,870; 3,423,328 ~specifies that silver particles of 150-400 angstroms are employed);
~ ~2~
12,439-1
3,702,259 (disclosed a preparation procedure for forming silver particles less than 1 micron in diameter) and 3,758,418 (discloses silver particles having a diameter less than 1000 angstroms).
The deposition of silver onto the carrier can be achieved by a number of techniques but the two techniques which are most frequently employed involve, in one case, the impregnation of the support with a silver solution followed by heat treatment of the impregnated support to effect deposition of the silver on the support and, in the other case, the coating of the silver on the support by ~he precipitation of silver or the preformation of silver into a slurry such that the silver particles are deposited on the support and adhere to the support surface when the carrier or support is heated to remove the liquids present. These various procedures are exemplified in various U. S. Patents such as 2,773,844;
3,207,700; 3,501,407; and 3,664,970 (see British Patent 754,593), and 3,172,893.
The surface area provided by the suppor~ has been the subject of considerable interest in the develop-ment of silver catalysts. Disclosures concerning the surface area of the catalyst carrier can be found in U. S. Patent 2,766,261 (which discloses that a surface area of 0.002-10 m2/gm is suitable); U. S. Patent 3,172,893 (which depicts a porosity of 35-65% and a pore diameter of 80-200 microns); U. S. Patent 3,725,307 (which depicts a surface area of less than 1 m2/gm and an average pore diameter of 10-15 microns); U. S. Patent ~62~
12,439-1 3,664,970 (which utilizes a support having a minimum porosity of about 30%, at least 90% of the pores having diameters in the range of 1-30 microns, and the average of such diameters being in the range of 4-10 microns);
and U. S. Paten~ 3,563,914 (which utilizes a catalyst support having a surface area of less than 1 m2/gm, a volume of 0.23 ml/gm and a particle size between 0.074 and 0.30 mm).
In the very earliest developments of silver catalysts for the manufacture of ethylene oxide, it has been determined that a number of metals when present in combination with the silver could act as promoters of the silver catalyst. These materials in themselves are not catalysts but contribute to enhance the rate or amount of oxide production. Cne of the problems in determining whether or not these ~.etals act as promoters is the nature of the reaction`itself. The reaction between oxygen and ethylene to form ethylene oxide is a highly exothermic reaction. However, even more exothermic than that re-action is the combustion of ethylene or ethylene oxideto carbon dioxide. These reactions occur simultaneously and the critical factor in determining the effectiveness of the over,-all process is the measure of control one has over these two competing reactions. Inevitably, a material which enhances the production of ethylene oxide might also be considered a material which inhibits the complete combustion of ethylene to ethylene oxide to carbon dioxide. Thus, there is a problem in defining whether that material which is termed as a promoter is in fact an inhibitor of the combustion reaction. It is well known ~3S218~
12,439-1 that there are materials which when added to the reaction result in less carbon dioxide being formed and such materials are termed inhibitors. There are also ~aterials which when provided with the catalysts result in greater production of ethylene oxide and those materials are termed promoters. Whether the latter materials are in reality inhibitors or promoters seems to be an irrelevant issue. What is significant is that the outcome of the reaction is favorable to the production of ethylene oxide.
For that reason, when determining or characterizing a catalytic process for producing ethylene oxide a signifi-cant factor entering into or qualifying that process is the selectivity of the process to produce ethylene oxide, selectivity being as defined previously.
The use of alkali metals as promoters for the silver catalyzèd production of ethylene oxide is extremely well known in the art. As far back as U. S. Patent 2,177,361 issued October 1939 there is found a teaching of the use of alkali metals in silver catalysts. U. S.
Patent 2,238,471 discloses that lithium was very desirable as a promoter but that potassium and cesium were detri-mental The examples of that patent utilize essentially 10% by weight of potassium hydroxide or cesium hydroxide to the silver oxide employed in making the catalyst. Later, U. S. Patent 2,404,438 stated that sodium and lithium were effective promoters for this reaction. Essentially the same teaching could be found in U. S. Patent 2,424,084. U. S.
Patent 2,424,086 generalized about alkali metals as pro-moters and specified sodium in particular. In U. S.
1~ 82~8~
12,439-1 Patent 2,671,764, the patentees believed that alkali metals in the form of their sulfates would be effective as promoters for such silver catalysts. In particular, the patentees stated that sodium, potassium, lithium, rubidium or cesium sulfates may be used as promoters. U. S. Patent 2,765,283 described the pretreatment of a support with a dilute solution of a chlorine containing compo~nd and indicated that such chlorine compounds should be inorganic.
Particular illustrations cited of suitable inorganic chlorine compounds i~cluded sodium chloride, lithium chloride and potassium chlorate. This patent specified that the amount of the inorganic chlorine containing compound which is deposited on the catalyst support is from 0.0001% to 0.2%
by weight, based on the weight of the support. U. S.
Patent 2,615,900 to Sears describes the use of metal halide in the treatment of the supported catalyst and specifies that such halides can be of alkali metals such as lithium, sodium, potassium, and cesium. The metal halide is present in the range of 0.01% to 50% based upon the weight of metallic silver. The patent also specif ies that mixtures of the individual metal halides generally classified in the patent may be used to advan-tage to enhance the break-in period of a new catalyst composition while at the same time maintain a moderate but steady activity of the catalyst over an extended period of time during normal operation. Thus, one particular metal halide treated catalyst would provide a short-term high initial activity whereas another of the metal halides would provide a longer term moderate activity for the catalyst. This patent takes the position 1 ~ ~2 18 1 12,439-1 that the metal halides which are provided in the catalyst serve to inhibit the combustion of ethylene to carbon dioxide and thus classifies these materials as catalyst depressants or anticatalytic materials. U. S Patent 2,709,173 describes the use of a silver catalyst for making ethylene oxide in which there are provided simultaneously with the introduction of the silver catalyst to the solid support any of the alkali metal halides such as lithium, sodium, potassium, and rubidium compou~lds of chlorine, bromine and iodine, to enhance the overall production of ethylene oxide. The patent specifies small amounts "of less than about 0.5~/o are desirable". In particular the patent emphasizes "proportions of alkali metal halide within the range of about 0.0001 to about 0.1%" are most preferred. The patent states that "although the preferred catalyst composition contains a separate promoter it is not always necessary since during preparation of the catalyst the alkali metal halide may be converted to some ex~ent to the corresponding alkali metal oxide which acts as a promoter".
U. S. Patent 2,766,261 appears to draw from the teachings of U. S. Patent 2,238,474 in that cesium and potassium are said to be detrimental in silver catalysts; sodium and lithium are suggested as useful promoters. However, U. S.
Patent 2,769,016 finds that sodium, po~assium and lithium are promoters when used in the silver catalysts.
This latter patent also recommends the pretreatment cf the support with dilute solutions of sodium chloride, lithium chlcride or potassium chlorate. U. S. Patent 2,799,687 to Gould et al states that the addition of metal 1 1~2~81 12,439-1 halides within the range described by Sears in U. S.
Patent 2,615,900 is not productive of optimum results.
This is said to be especially true in the case of alkali metal halides, particularly the chloride and fluoride of sodium and potassium. The patentees recommend that the inorganic halide component of the catalyst be maintained within the range of 0.01-5 weight percent, preferably .01 to 0.1 weight percent, based on the weight of the "silver oxidative catalytic component", i.e., the silver salt transformed into elemental silver. U. S. Patent 3,144,416 mentions a variety of metals as promoters and one of them is cesium. U. S. Patent 3,258,433 indicates th~t sodium is an effective promoter. U. S. Patent 3,563,913 recommends the use of alkali me~als such as lithium compounds as promoters. The preferred amount of promoting material is said to be about 0.03 to 0.5%, by weight, of metal oxide based on the weight of the support. U. S.
Patent 3,585,217 states that alkali metal chlorides "are known to counteract the formation of carbon dioxide" and "may be incorporated into the catalyst". U. S. Patent No.
3,125,538 discloses a supported silver catalyst contain-ing a coincidentally deposited alkali metal selected from among potassium, rubidium and cesium in a specified gram atom ratio relative to silver. The weight of silver is preferably 2-5% by weight, of the catalyst. The patentees characterize this catalyst as being especially suitable for the reaction of nitric oxide with propylene. U. S.
Patent ~os. 3,962,136 and 4,012,4~5 disclose the identical catalyst as being useful for ethylene oxide production.
U. S. Patent 3,962,136 describes the coincidental 1 J ~2181 12,439-1-C
deposition of al~ali metal with the silver on the support, the alkali metals being present in their final form on the support in the form of an oxide in which the oxide con-sists of cesium, rubidium or mixtures of both, optionally combined with a minor amount of an oxide of potassium.
The amount of such oxide is from about 4.0 x 10-5 gew/kg to about 8.0 x 10-3 gew/kg of total catalyst. However, U. S. Patent 4,010,115, patented March 1,1977, dis-tinguishes itself by employing as the oxide of the alkali etal the oxide of potassium optionally combined with a parent minor amount of an oxide rubidium or cesium. The/applica-tion of U. S. Patents 3,962,136 and 4,010,115, and others, contains some interesting data deserving of comment.
According to example 2 which contains some comparative experiments, there is described the manufacture of a catalyst which contains 310 parts per million by weight of coincidentally-added potassium and that catalyst when employed as an ethylene oxidation catalyst was found to be inactive for the production of ethylene oxide. Even so, we find that that amount of potassium in the catalyst lies within the range disclosed in U. S. Patent 4,010,115 to be effective for the production of ethylene oxide, although no data is shown in the patent to support that view.
Belgium Patent 821,439, based upon British Patent Specification 1,489,335, discloses that a catalyst can be made that is equivalent to that produced in U. S. Patent Nos. 3,962,136, 4,012,425, and Patent 4,010,115 to Neilsen et al. by varying the procedure by which the alkali 1 1 6~81 12,14g-1-C
metal is supplied to the support. In the Belgium Patent and its British equivalent, a porous refractory support of a specified surface area is first impregnated with an alkali metal to deposit it on the support metal in specified quantities (both the quantities and the nature of the porous support being equivalent to that which is set forth in the aforementioned Nielsen et al U. S. Patents), the support is then dried to fix the alkali metal and there-after the silver is supplied to the support. This pro-cedure is a sequential deposition of the alkali metal promoter and the silver catalyst and yet essentially the same type of catalyst was produced by the simultaneous deposition of alkali metal and silver as evidenced by a comparison of ~he data in the examples of the ~elgium Patent with the data set forth in the aforementioned Nielsen et al U. S. Patents. The criticality in the method of deposition of alkali metal upon the support appears doubtful in the face of that type of disclosure and the disclosure of U. S. Patent Nos. 4,033,903 and 4,125,480 which describe subjecting a used silver-containing catalyst with a post-addition of one or more of potassium, rubidium or cesium. Apparently such treatment regenerates the catalyst's ability to enhance selectivity to ethylene oxide. Another patent which tends to indicate that a post-addition of alkali metal such as cesium gives results equivalent to either pre-addition or simultaneous addition is U. S. Patent 4,066,575.
U. S. Patent 3,962,136 and its companion patents were derived from a parent application filed January 7, ]972, now abandoned, U. S.
t 1 62~8~
12,439-1-C
Patent 3,962,136 discloses that the "highest level of selectivity obtainable with potassium modified catalysts at otherwise comparable conditions typically is lower than that obtainable with rubidium or cesium-modified catalysts" (see column 2, lines ~8-42). The parent application contains a drawing which depicts the relative effectiveness of rubidium, cesium and potassium to enhance the selectivity of ethylene oxide when utilized in a silver catalyst. The drawing shows that the curve C
which represents cesium addition provides the greatest degree of enhancement of selectivity while curve B which represents rubidium addition is intermediate and superior to potassium addition represented by curve A. In an amendment filed on April 11, 1975, in parent application (filed June 19, 1974) to U. S. Patent 4,010,115, the applicant urges that the invention and claims do not involve "synergistic effects with the use of mixtures"
of the alkali metals. The same statement was made in the amendment received on April 11, 1975 in the parent application (filed May 20, 1974) to U. S. Patent 4,012,425.
German Offenlegungsschrift 2,640,540 discloses in its examples a silver catalyst for ethylene oxide production containing sodium and either potassium, rubidium or cesium. Table I of this disclosure provides the alkali content of all catalysts prepared in the examples, many of which contain sodium, potassium and cesium. A footnote 1 ~218~
12,439-1 to the Table states that the presence of potassium in all catalysts tested (except for one which was free of cesium) was due to impurities present in the support, the level of such impurities being below that specified as being useful for the invention. The disclosure does not suggest that cesium may be combined with potassium and/or sodium to advantage nor does the efficiency data provided in the Table demonstrate any synergistic inter-action of cesium with sodium or the potassium impurities in the catalysts.
Japanese Application Publication Disclosure No. 95213/75 is directed to a process for producing ethylene oxide using a catalyst composition comprising silver, barium, potassium and cesium in specified atomic ratios. Table I of this disclosure summarizes the efficiencies achieved with the various catalyst composi-tions of the examples. No synergism with cesium and potassium was demonstrated by any of the cesium-potassium-barium mixtures of the examples. Indeed, a comparison of some examples among Table I appears to demonstrate the absencè of a cesium-potassium synergism, namely, the efficiency achieved with a cesium-potassium mixture is shown to be lower than the efficiency achieved with the same amount of cesium in the absence of potassium.
For example, Examples 3 and 7 relate to catalysts having an identical atomic ratio of cesium to silver (.05 atoms/
100 atoms Ag~, but differing potassium contents, the atomic ratio of potassium in Example 3 being .001 atoms K/lO0 atoms Ag and the corresponding ratio in Example 7 12,439-1 being .05. The efficiency achieved in Example 3 was 76.4% and that of Example 7 was 75.9%. Thus, the increased potassium content in E~ample 7 resulte~ in a decrease in catalyst efficiency. Similarly, Examples 1 and 4 relate to catalysts havinv an identical atomic ratio of cesium to silver, with the catalyst of Example 1 containing an amount of potassium one order of magnitude greater than the catalyst of Example 4. Yet, the efficiencies reported for both catalysts are essentially the same, 76.7% and 76.6% for Examples 1 and 4, respectively.
U. S. Patent 4,039,561 discloses a catalyst for preparing ethylene oxide containing silver, tin, antimony, thallium, potassium, cesium and oxygen in specified atomic ratios. Mixtures of cesium and potassium are not dis-closed to be desirable combinations. Indeed, Table I
of the patent discloses a silver-cesium-potassium com-bination which is designated as a "control" example not in accord with the disclosed invention and which achieved a selectivity of 73.0%, a value markedly lower than the selectivities achieved in the 45 Examples listed in Tables 2 and 3. Moreover, the efficiencies provided in Tables 2 and 3 for the various catalysts fail to demon-strate the existence of any synergistic combination of cesium and potassium among the numerous combination of elements which were employed in the catalysts. It is also note-worthy that the aforesaid U. S. Patent 4,039,561 claims the priority of a Japanese application filed in 1973, and that subsequent to such filing the same appli-cant filed Japanese Application Publication No. 25703/77 12,439-1 which discloses a catalyst for ethylene oxide manufacture comprised of the same metallic elements disclosed in the U. S. Patent with the exception of cesium and potassium. The efficiencies disclosed in the examples of the latter Japanese Application are similar to those shown in the U. S. Patent. The effect of cesium and potassium in the catalyst composition disclosed in the U. S.
Patent is therefore presumably insignificant.
Belgium Patent 854,904 discloses silver catalysts containing various mixtures of sodium and cesium. U. K.
Patent Application GB 2,002252A discloses, in Table 2, supported silver catalysts containing various mixtures of cesium and thallium, some of which additionally contain potassium or antimony. U. S. Patent 4,007,135 broadly discloses (in column 2, lines 25-30) silver catalysts for alkylene oxide`production containing silver "together with a promoting amount of at least one promoter selected from lithium, potassium, sodium, rubidium, cesium, copper, gold, magnesium, zinc, cadmium, strontium, calcium, ~ niobium, tantalum, molybdenum, tungsten, chromium, vana-dium and barium...". European Patent Publication No.
0003642 discloses, in Table 3, silver-containing catalysts ~which include mixtures of potassium and cesium, and a catalyst containing sodium and cesium. The above publica-tions do not indicate a synergistic interaction of cesium with otne~ alkali metals. !
Belgium Patent 867,045 discloses supported silver catalysts containing what is referred to as an effective proportion of lithium and a substantially lesser amount of alkali metal selected from among cesium, rubidium and/or 1 1 62~
12,439-1 potassi~n. Table I of the patent discloses three catalysts all of which contain cesium, sodium, potassium and lithium, the lithium concentration being at least one order of magnitude greater than the concentration of cesium or potassium. Referring to Table I, the catalysts Ll, L2 and L3 have markedly different concentrations of cesium, potassium and sodium, but are shown in Table II to provide substantiallv similar selectivities. There is no indication of a synergistic interaction of cesium with either potassium or sodium in the silver catalysts dis-closed.
Belgium Patent 867,185 discloses supported silver catalysts for ethylene oxide production containing a specified amount of potassium and at least one other alkali metal selected from rubidium and cesium. Table I dis-closes the composition of 14 potassium-containing catalysts, two of which contain potassium in combination with cesium (catalysts G and H). The selectivities of catalysts G and H are shown to be identical at a pressure of 1.03 bars, but differ slightly at the higher pressure of 16.55 bars.
No silver-potassium-cesium synergism can be discerned from the data.
This invention distinguishes over the prior art in the fact that the silver catalyst employed in manufacturing ethylene oxide utilizes at least two alkali metals (excluding francium~, one of which is cesium, each of the alkali metals being present in an amount such that the combination thereof in relation to the amount of silver in the catalyst provides a synergy in terms of ethylene oxide selectivity and a selectivity which is greater than has been contemplated or disclosed by any prior art.
1 ~ ~2 1 8 .t In accordance with one aspect of the present invention, there is provided a silver catalyst deposited on a macroporous support having a surface area less than lOm2/g and in a form and size for use in a fixed bed tu~ular reactor used in a commercial operation for the manufacture of ethylene oxide by vapor phase reaction of ethylene and oxygen or an oxygen-containing gas in gaseous admixture with diluent and inhibitor, which catalyst contains 2 to 20 weight percent silver and a combination of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, which combination compri-ses (a) and (b) in amounts in relation to the amount of silver therein sufficient to increase synergistically the efficiency of the ethylene oxide manufacture to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as the catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount o (b).
In the detailed description of the invention which follows, reference will be made to the graphical representation of the accompanying drawings, wherein:
Figures 1 and 2 show contour lines drawn at constant efficiency and temperature in the potassium~
cesium concentration space with the darker lines represen-ting selectivity contours (selectivity values indicated for each line) and with the lighter, broken lines repre-senting temperature contours (temperatures indicatedfor each line).
116218~
The catalysts of the invention are characterized by a combination of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium so as to achieve a syner-gistic result, i.e., an efficiency greater than the greater value obtainable under common conditions from respective catalysts which are the same as said catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount of (b). Catalysts in accord with the invention are comprised of silver, cesium and at least one other alkali metal (excluding francium) deposited onto the surface of a porous support, the particular mixture of silver and alkali metals being correlated to produce a synergistic result.
The invention as hereinafter described defines the binary alkali metal combinations of cesium-lithium, cesium-sodium, cesium-potassium and cesium-rubidium, which in co~bination with silver provide a synergistic result for a particular catalyst carrier and catalyst preparation. The catalysts of the invention are not, however, restricted to binary combinations of alkali metal. Other alkali metals may advantageously be added to any of the aforementioned synergistic binary co~bina-tions for the purpose of raising or lowering the catalyst operating temperature, improving the initial catalyst activity during the start-up period and/or improving the aging characteristics of the catalyst over prolonged periods of operation. In some ` ~62181 12,439-1 instances, the addition of a third or even a fourth alkali metal to an otherwise synergistic binary combination will effect a further increase in catalyst efficiency.
The mathematical relation.ships from which are derived the synergistic binary a~kali metal co~binations of the invention are set forth below and described, for purposes of illustration, in terms of a cesium-potassium combination. Binary combinations of cesium with any of the other alkali metals in accordance with the invention are readily determined by an analogous procedure wherein the particular alkali metal of interest is substituted for potassium in the procedure described below.
The relationship of cesium, potassium and silver to ach.Fve a synergistic result as herein defLned is characterized with the aid of a mathematical equation, or model, which correlates efficiency as a function of weight percent silver, weight percent cesium and weight percent potassium deposited on the catalyst support. Thus, synergism with mixtures of cesium and potassium can be obtained at any concentration of silver in the finished catalyst.
The general form of the mathematical equation, hereinafter referred to as the "Efficiency ~odel", defines efficiency (or selectivity) as a function of weight per-cents (wt. %) of silver, cesium and potassium deposited on the catalyst support as follows:
Efficiency, % = bo + bl(BG) + b2(BCs) + b3(BK) + b4(BG)2 + b5(BCs)2 + b6(BK)2 + b7(BG x BCs) + b8(BG x BK) + b9(BCs x BK) 12,439-1 where:
o' 1' b2~ b3~ b4~ bs~ b6, b7, b8 and bg are the respective coefficients for each term of the Efficiency Model, and comprise a set of constants determined for a particular catalyst carrier and a particular~method of catalyst preparation following a designed se~ of experi-ments as hereinafter described. The value of some of these coefficients may be zero.
BG = (wt. % Ag - wt. % Ag);
0 where, wt. % Ag = average value of wt. % Ag used in .he designed set of experiments.
BCs = (wt. % Cs - wt % Cs);
where, wt. % Cs = average value of wt. % Cs used in the designed se; of experiments.
BK = (wt. % K - wt. % K);
where, wt. % K = ave-age value of wt. % K used in the designed set of experiments.
The designed set of experiments is most con-veniently planned in the format of a Composite Design in three independent variables as described by 0. L. Davies, "The Design and Analysis ~f Industrial Experiments", Hafner Publishing Company, 1960, P. 532-535. For this purpose, the three independent v,~riables are the weight percents of silver, cesium and potassium, respectively.
The ranges of each variable are chosen so that selec-tivity al:' activity of all catalysts in the designed -`
set of experimen s can be measured under the desired test conditions. It is therefore desirable to first conduct a few preliminary range finding experiments to 1~82181 12,439-1 determine the appropriate ranges of cesium and potassium for this purpose. Zero perc~llt cesium and/or potassium is a convenient lower limit for use in the Composite Design The upper concentration limit of cesium and potassium can be readily determined by a series of experi-- ments with catalysts containing successively larger amounts of either cesium or potassium as follows: An initial catal-,ist is prepared (using a preparation procedure, if desired, such as hereinafter disclosed in the Examples) containing a small amount (on the order of about 0.001 percent by weight) of either cesium or potassium with a fixed amount, say 7 percent by weight, of silver, and its selectivity then determined for the pro.iuction of ethylene oxide at the desired test conditions. This experiment is then repeated with a catalyst containing double the amount ~0.002 percent by weight) of the alkali metal and the experiment thus repeated in a series of experiments wherein eac~ succeeding experiment uses a catalyst containing double the alkali metal content of the catalyst of the previous experiment, until the measured selectivity of the last catalyst tested is less than that of the initial catalyst. The upper limit of cesium or potassium concentration is thus defined for the Composite Design.
The above-described interative procedure may be advantageously altered so as to more quickly determine the upper limit of concentration in the event it is observed that a two-fold increase in the alkali metal content of the catalyst does not produce a significant change in catalyst 12,439-1 selectivity. This is particularly likely to occur, for example, with catalysts containing lithium or sodium (depending upon the particular carrier and preparation procedure employed) in contrast to catalysts containing other alkali metals where, as a general rule, the efficiency response is more sensitive to increasing alkali con-centration. Accordingly, in the event the catalyst efficiency is virtually unchanged when the alkali content of the catalyst has been doubled, a ten-fold increase in alkali content should be employed in the above-described iteration until the measured efficiency of the last catalyst is less than that of the initial catalyst. Thereafter it may be desirable to repeat the last iterative step using a lower level of alkali, such as, a three or five-fold increase of alkali ~etal content, in order to more accurately deter-mine the upper limit of alkali metal concentration for ~he Composite Design.
The range of silver concentration in the Composite Design may typically be 6-16 weight percent, giving an average value of silver (wt. % ~) of 11 weight percent. Similarly, the ranges of cesium and potassium concentrations are typically from 0.0 to 0.02 weight percent For rubidium, the range is also typically from 0.0 to 0.02 weight percent, while for lithium and sodium, the ranges are typically 0.0 to 0.1 weight percent. For some carriers, the upper concentration limit of cesium and/or potassium may be 5 to 10 times greater. This is particularly likely to occur for carriers which contain exchangeable cations.
1 ~ ~21~
12,439-1 Table 11.5 on page 533 of the aforementioned Davies Publication depicts a three-variable Composite Design scaled in units of - ~ , -1, 0, +1 and +C~
where -1 represents a "low level" of the respective variable; +l represents a "high level" of such variable;
O represents the average level of the variable; -o~
represents a level which is somewhat lower in value than that which is represented by -1; and +Cy~represents a level which is somewhat higher than that represented by +1. The particular choice of -~C and + o(is not critical. However, Table 11.6 on page 534 of the Davies Publication suggests values of -OC and + ~ which are particularly useful for a Composite Design in accordance with the present invention. The designed set of experi-ments is thus typically comprised of 16 to 20 experiments wherein catalysts of varying concentrations of silver, cesium, and potassium are tested. Thus, for example, a preferred Composlte Design in which the weight percent silver ranges from 7.0 to 15.0%; the weight percent cesium ranges from 0.0 to .02%; and the weight percent potassium ranges from 0.0 to 0.01% ..s c follows:
Wt. % Silver Wt. % Cesium Wt. % Potassium 9 0.005 0.002 13 0.005 0.002 9 0.015 0.002 13 0.015 0.002 9 0.005 0.~08 13 0.005 0.008 9 0.015 0.008 13 0.015 0.008 l 0.010 0.005 11 0.010 0.005 7 0.010 0.005 0.010 0.005 11 0.0 0.005 11 0.020 0.005 11 0 . 010 0 . O
11 O. 010 0 . 010 t 1 62181 12,439-1 The catalysts of the designed set of experi-Ments are tested by means well known in the art for measuri~g their selectivity and activity. A convenient measure of activity, i.e., the degree of conversion of reactant to product per unit time, is ~he temperature required to o~tain either a fixed ethylene oxide pro-duction or to achieve a chosen level of mole percent ethylene (or oxygen) conversion. Thus, a mathematical equation for catalyst temperature (Temperature Model) can be developed in a manner similar to the Efficiencv Model. That is, for each catalyst there is obtained two responses (selectivity and temperature) which are re-lated to the three controlled variables (weight percents of silver, cesium, and potassium). The relationship between each response and the controlled variables is obtained by fitting these data to equations, or mathematical models, by the method of least squares as described in Chapter 8 of "Statistical Methods in Research and Production", O.L. Davies and P.L. Golds.,ith, Long~an Group, Ltd., London, 4th Ed., 1976. In prac-tice, the fitting of mathematical models to such data is routinely done with the aid of a digital computer as described in "Applied Regression Analysis", N. R.
Draper and H. Smith, John Wiley and Sons, Inc., 1965.
The resulting models (the Efficiency Model and the Temperature Model) describe the relationship between the responses and the controlled variables.
It is well known in the art that the nu..ber of experiments required to establish mathematical re-1 1 62~81 12,439-1 lationships among several variables is dependent upon the reproducibility of the data. Thus, for a Composite Design containing approximately 16 experiments it may occasionally be necessary to repeat all or part of tne set of designed experiments in order to fir~ly establish the relationship between efficiency and weight percents of silver, cesium and potassium to an acceptable level of statistical confidence. In practice, it has been found that for a designed set of about 16 experiments wherein the weight percent of silver is varied from about 7% to about 15%, one complete replication of the designed experiments is usually sufficient to establish this relationship provided that the standard deviation of a single experimental test result is no greater than about 0.7% efficiency units. During the course of ex-perimentation, data other than from the designed set of experiments may be acquired which is useful for develop-ing the model as described above. For example, data acquired from the aforementioned preliminary range finding experiments as well as any additional experi-mental data which is available with regard to the particular catalyst carrier and method of preparation of interest is desirably included with that derived from the Composite Design, and the equations thus fitted to the data. Consequently, as a practical matter, data from about 30 to 60 experiments may be available for developing the Efficiency and Temperature ~odels.
12,439-l The general form of the mathematical equation, hereinafter referred as the "Temperature Model" defines ~e~perature as a function of weight percents of silver, cesium and potassium deposited on the catalyst support as follows: ~
Temp., C = aO + al(BG) + a2(BCs) + a3(BK) + a4(BG)2 + as~BCs)2 + a6(BK)2 ~ a7(BCs x BG) + ag(BG x BK) + ag(BCs x BK) where:
aO, al, a2, a3, a4, a5, a6, a7, a8 and a9 are the re-spective coefficients for each term in ~he Temperature Model which comprise a set of constants determined for a particular carrier and a particular method of catalyst preparation following the designed set of experiments as described above. The value of some of these coeffic-ients may be zero. BG, BCs, and B~ are as defined above.
The most convenient use of the Efficiency and Temperature Models for defining the area of synergism for any selected weight percent of silver in the catalyst is to depict efficiency and temperature responses in a graphical form, commonly referred to as contour ~aps, as described in Chapter 11 of the aforementioned "Design and Analysis of Industrial Experiments". Thus, Figures 1 and 2 depict the contour maps of efficiency and temp-erature for a selected carrier and catalyst preparation procedure at 7 and 13 weight percent silver~ respectively.
The contour maps were derived from a designed set of experiments in which the percent silver ranged from 5.88 to 16~05~/o; the percent cesium ran~ed from 0.00 ~ ~ ~2181 12,439-1 to 0.019%; and the percent potassium ranged from 0.00 to 0.021%. Table I below summa.izes the experimental data which was available for the selected carrier and catalyst preparation procedure and from which the con-tour maps were derived. The experiments were conducted in two different test reactors in accordance with the standard test procedure hereinafter described under the heading "Catalyst Comparisons". Two similar, but slight-ly different,carriers were used in the experiments.
10 Table I represents the experimental data on a common basis, namely, the data was adjusted to ccmpensate for observed differences between the reactors snd catalyst carriers employed.
621~1 12, 439- 1 TAgLE I
wt% A~ wt~ S w~e~p (~C)Efficienc~
11.14 0.00477 0.00158256.0 73.9 10.53 0.00897 0.0256.4 77.5 11.14 0.00479 0.0256.0 72.9 11.01 0.00941 0.00312256.0 ~7.4 11.21 0.00240 0.00080258.0 70,7 10.9~ 0.01865 0.0282.2 74,3 11.04 0.009~1 0.0257.~ 76.3 011.0'1 0.009~1 0.0255,0 76.3 11.09 0.01421 0.00412270.7 7j.7 10.41 0.0 0.0 263.068.5 10.1 0.0 0.0 265.068.-11.16 0.01909 0.00633292.6 72.G
10.9~ 0.01403 0.0267.0 76.7 10.70 0.01128 0.00379262.0 77.5 9.08 0.0190Q 0.00315293.0 71.8 9.31 0.00968 0.00645269.9 76.6 13.17 0.00617 0.00102254.9 74.2 20 9,10 0.00323 0.00214260.0 7~,7 13.14 O.OO91S 0.00613259.1 77.5 11.11 0.00950 0.00315259.6 77.6 11.31 0.0120~ 0.0260.3 77.4 11.05 0.00236 0.00078260.4 70.1 12.72 0.00311 0.0020725S.8 71.6 16.05 0.00941 0.00313263.0 77.7 5.88 0.00924 0.00306269.1 76.8 11.04 0,01421 0.00157268.9 76.7 10.89 0.00462 0,00450256.4 75.4 10.80 0.0 0.00613 260.5 69.9 B.93 0.00630 0.00105260.4 74.4 15.51 0.01288 0,0266.4 77.2 6.03 0.01341 0.0280.3 73.7 13.11 0.00897 0.00810266.2 77.1 - 28 ~
12, 439-1 IA.B L F
(continued) Ef f lc ienc w~t% AR wt% Cs w~/. X S~p. (-C~ %
16.00 0.00888 0.00800 264.3 77. ~3 10.93 0.0 0.01230 263.6 73.3 12.95 0.01562 0.00469 277.1 76~0 13.12 0.01313 0.00336 268.1 77.0 12.85 0.00150 0.0 26L.4 68.2 0 13.12 0.01047 0.00297 257.3 78.3 13.26 0.0178! 0.00540 282.3 74 ~ 5 12.91 0.0138' 0.00407 269.4 77.
12.91 0.0138' 0.00407 269.8 77.2 12.91 0.01038 0.0029j 257.0 7~.3 12.91 0.0103S 0.00'95 257.2 76.-.
13.00 0.00150 0,07100 299.0 6-~.
13.00 0,01036 O.OljO0 290.7 72.' 6.88 0.00150 0.01470 28~.6 73.7 7.14 0.01056 0,01220 289.' 7~.3 /.06 O.OOj94 0.01010 280.4 75~' 8.00 0.00727 0.00192 263.3 75.7 8.00 0.01153 0.00330 274.4 76.9 8.15 0.01171 0.00339 272.7 77.6 8.30 0,00749 0.00199 262.2 76.5 3.03 0.00150 0.0 268.0 69.0 7.00 0.01056 0.0 264.0 75.5 7.00 O.OlOS6 0,0~400 271.0 76.2 i ~ 62181 12,439-1 The specific Efficiency and Temperature Models derived from the sbove data by the aforementioned method of least square are as follows:
Efficiency, % ~ ~7.19 ~ 0.196(BG) + 133.4(BCs) + 120.5(BK) - 63787.0 rBCs)2 - 47229.0 (BK)2 ~ 52.1 (BG x BCs) - 60823.0 (~Cs x BK); and Temperature, C - 259.44 - 1.279(BG) + 1555.8(BCs) 1 794.1(BK) ~ 0.346$(BG)2 + 168544.0(BCs)2 ~ 147856.0(BI;)2 + 132807.0(BCs x BK) where: BG - (wt.% Ag - 11.0) BCs ~ (wt.~/o Cs - 0.01) BK ~ (wt.% K - 0.003) Figures 1 and 2 show contour lines of constant eff.ciency and temperature in potassium-cesium concen-tration space. The darker lines represent selectivit-contours with selectivity values being indicated for each line. The lighter, broken lines represent temp-erature contours with temperatures indicated in degrees centigrade. The efficiency and temperature for points in between the designated contour lines can be inter-polated. The maximum selectivity achievable for any combination of cesium and potassium as a function of cesium concentration is indicated by the curve labelled Se ~ ax This ~urve represents the maximum synergism achievable for any given level of cesium. The synergism curve (designated "A" in Figures 1 and 2) separates the region of synergism, as herein defined, and regions of ~6~81 12,439-1 additive and antagonistic effec~:s. Additive effects occur when the efficiency obtained with a combination of cesium and potassium is a weighted average of the efficiencies obtainable under common conditions from respective catalysts which are the same as the catalyst containing said combina-tion except that instead of containing both potassi~m and cesium, one contains the respective amount of cesium, and the other contains the respective amount of potassium. Anta-gonistic effects occur when the efficiency obtainable with a mixture of cesium and potassium is less than the efficiencies obtainable with corresponding catalysts which contain the respective amount of cesium, and the respective amount of potassium, individually, as described above. The area bound by ordinate, the abscissa and the synergism curve (curve "A") defines the area of synergism in accordance with the present invention. The area to the right of the synergism curve "A", represents the area of additive and antagonistic effects as described above, and thus defines mixtures not in accord with the present invention. For any given contour map the pre-ferred combinations of cesium and potassium are those whichproduce selectivities on or about the SelMax curve. However, in general, preferred mixtures are those wherein cesium and potassium are present in a weight ratio of from about 100:1 to 1:100 depending upon the particular catalyst carrier and preparation procedure of choice. For mixtures of cesium and lithium, or cesium and sodium, preferred mixtures are usually those wherein the alkali metals are present in a weight ratio of from about 1000:1 to 1:1000.
Referring to Figure 1, a catalyst containing for example, 0.003% Cs and 0% K has an efficiency of about 73%. The addition of approximately 0.008% K to this 12,439-1 catalyst results in an increase in efficiency to about 76.0%, the maximum selectivity at this level of cesium (i.e., the value on the SelMax curve). Further additions of potassium up to about .016% K (i.e., the value on curve "A"~ would yield efficiencies equal to or gr~ater ~han those obtainable with the given amount (0.003%) of cesium alone (i.e., no alkali metal other than cesi~l~ being present);
potassium additions beyond .016% K result in efficiencies lower than those obtainable with 0.003% of cesium alone, i.e., in the region of either additive or anta-gonistic effects. Yet, such amount of potassium which causes such antagonistic effects can still yield a catalyst with reasonably desirable selectivity and activity for a given mode of operation.
The region of synergism varies with the silver .
content of the catalyst as described by the Efficiency Model. Figure 2 illustrates the region of synergism at 13% silver. The SelMax curve and synergism curve (curve "A") of Figure 2 are as previously defined with reference to Figure l. Comparison of Figures 1 and 2 show that the efficiency contour lines are similar but are dis-placed with respect to the cesium and potassium axes. For example, the 76% efficiency contour line in Figure l envelops an area which is smaller than the area covered by the corresponding contour line in Figure 2. Further, the maximum value of selectivity obtainable at 7 weight percent silver, i.e., the maximum along the SelMax line, is slightly above 76% (Figure l) while the corresponding maximum for 13 weight percent silver is slightly above 77.8%
~Figure 2).
The Efficiency Model and th~ Temperature Model which are developed are specific to a particular method of ~ 3 621~
catalyst preparation, a particular carrier and a particu-lar binary alkali metal combination. Variations in either the method of preparation or the carrier or the particular binary combination may change the coefficients of the Models, and hence, the shape of the contour maps derived therefrom. Thus, the curves "A" and SelMa~ may comprise straight lines or curves, and may intercept one or both axes (viz., the cesium axis and that of the other alkali metal in the binary combination). For example, in Figures l and 2, curve "A" and SelMax intercept both axes, and intercept the cesium axis at an angle greater than 90.
However, for a different carrier, a different method of preparation or a different binary alkali metal combin-ation with cesium, the resultant curves "A" and SelMax may intercept the cesium axis at an angle less than 90, or may be parallel to one of the axes. The coefficlients of the Model and the resultant contour maps can be readily determined for any-of the aforementioned variations using the designed set of experiments as described above.
The concentration of silver in the finished catalyst may vary from about 2 to 20 weight percent, the preferred range being from about 6% to about 16%
by weight of silver. Lo~-er silver concentrations are preferred from an economic standpoint. However, the optimum silver concentration for any particular catalyst will be dependent upon economic factors as well as per-formance characteristics, such as, catalyst efficiency, rate of catalyst aging and reaction temperature.
A variety of procedures may be employed for preparing catalysts containing combinations of cesium and one or more other alkali metals (excluding francium) ~ ~ 6~181 in accordance with the present invention. In accordance with a further aspect of this invention, which constitutes a preferred catalyst preparation procedure, there is provided a process for preparing a supported silver cata-lyst for the commercial operation for the production of ethylene oxide by the vapor phase oxidation of ethylene with oxygen or an oxygen-containing gas in gaseous ad-mixture with diluent and inhibitor in a fixed bed tubular reactor, comprising: (1) impregnating a macroporous catalyst having a surface area less than 10 m2/g and in a form and size for use in a reactor used in the commercial operation with a solution comprising a solvent or solubilizing agent, silver salt sufficient to deposit the desired amount of silver on the support of 2 to 20 weight percent silver, and salts of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, sufficient to deposit respective amounts of (a) and (b) on the support such that the efficiency of ethylene oxide manufacture in the commercial operation using the finished catalyst is increased to a value greater than the effic-iencies obtainable under common conditions from respective catalysts which are the same as the catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a) and the other contains the respective amount of (b); and (2) treating the impregna-ted support to convert at least a fraction of the silver salt to silver metal and effect deposition of silver, (a) and (b), respectively, on surfaces of the support.
Silver and alkali metal deposition are generally accomplished by heating the carrier at elevated tempera-.,~ .,:i1 ~ 1 621~1 tures to evaporate the liquid within the support and effect deposition of the silver and alkali metal onto the interior and exterior carrier surfaces. Alternatively, a coating of silver and alkali metals may be formed on the carrier from an emulsion or slurry containing the same followed by heating the carrier as described above.
Impregnation of the carrier is generally the preferred technique for silver deposition because it utilizes silver more efficiently than coating procedures, the latter being generally unable to effect substantial silver depo-sition into the interior surfaces of the carrier. In addition, coated catalysts 1 1 621~1 12,439-1 are more susceptible to silver loss by mechanical abrasion.
The sequence of impregnating or depositing the surfaces of the carrier with silver and alkali metals is optional. Thus, impregnation and deposition~of silver and alkali metals may be effected coincidentally or se-quentially, i.e., the alkali metals may be deposited prior to, during, or subsequent to silver addition to the carrier.
The alkali metals may be deposited together or sequentially.
For example, cesium may be deposited first followed by the coincidental or sequential deposition of silver and the other alkali metal(s), or such other alkali metal(s) may be deposited first followed by coincidental or se-quential deposition of silver and cesium.
Impregnation of the catalyst carrier is effected using one or more solutions containing silver and alkali metal compounds in accordance with well-known procedures for coincidental or sequential depositions. For coinci-dental deposition, following impregnation the impregnated carrier is heat or chemically treated ~o reduce the silver compound to silver metal and deposit the alkali metals onto the catalyst surfaces. For sequential deposition, the carrier is initially impregnated with silver or alkali metal (depending upon the sequence employed) and then heat or chem cally treated as described above. This is followed by a second impregnation step and a correspond-ing heat or chemical treatment to produce the finished catalyst -ontaining silver and alkali metals.
The silver solution used to impregnate the carrier is comprised of a silver salt or compound in a 1 ~ ~21~1 12,439-1 solvent or complexing/solubilizing agent such as the silver solutions disclosed in the art. The particular silver salt employed is not critical and may be chosen, for e~ample, from among silver nitrate, silver oxide or silver carboxylates, such as, silver acetate, oxalate, citrate, phthalate, lactate, propionate, butyrate and higher fatty acid salts.
A wide variety of solvents or complexing/
solubilizing agents may be employed to solubilize silver to the desired concentration in the impregnating medium.
Among those disclosed in the art as being s~itable for this purpose are lactic acid (U. S. Patent Nos.
2,477,435 to Aries; and 3,501,417 to DeMaio); ammonia ~ U. S. Patent 2,463,228 to West et al); alcohols, such as ethylene glycol (U. S. Patent Nos. 2,825,701 to Endler et al; and 3,563,914 to Wattimena); and amines and aqueous mixtures of amines (U. S. Patent Nos. 2,459,896 to Schwarz; 3,563,914 to Wattimena; 3,702,259 to Nielsen;
and 4,097,414 to Cavitt).
Suitable alkali metal salts include all those soluble in the particular solvent or solubilizing agent employed. Accordingly, inorganic and organic salts of alkali metals, such as, nitrates, halides, hydroxides, sulfates and carboxylates may be used. When coincidentally deposited with silver, the alkali metal salt employed is preferably one which does not react with silver salt in solution in order to avoid premature silver precipitation from same. Thus, ~or example, alkali metal halides are preferably not used in lactic acid solution because they react with silver ions present therein.
Following impregnation of the catalyst carrier with silver and alkali metal salts, the impregnated carrier particles are separated from any remaining non-absorbed solution or slurry. This is conveniently accomplished by draining the excess impregnating medium or alternatively by using separation techniques, such as, filtration or centri~ugation. The impregnated carrier is then generally heat treated (e.g., roasted)to effect decomposition and reduction of the silver metal salt to metallic silver and the deposition of alkali metal ion. Such roasting may be carried out at a temperature of from about 100C
to 900C, preferably from 200 to 700C, for a period of time sufficient to convert substantially all of the silver salt to silver metal. In general, the higher the temperature, the shorter the required reduction period.
For example, at a temperature of from about 400C to 900C, reduction may be accomplished in about 1 to 5 minutes. Although a wide range of heating periods have been suggested in the art to thermally treat the impreg-nated support, (e.g., U.S. Patent 3,563,914 suggests heating for less than 300 seconds to dry but not roast reduce the catalyst; U.S. Patent 3,702,259 discloses heating from 2 to 8 hours at a temperature of from 100 to 375C to reduce the silver salt in the catalyst; and U.S. Patent 3,962,136 suggests ~ to 8 hours for the same temperature range) it is only important that the reduction time be correlated with temperature such that substantially complete reduction of the silver salt to metal is accom-plished. A continuous or step-wise heating program may be used for this purpose.
12,439-1 Heat treatment is preferably carried out in air, but a nitrogen or carbon dioxide atmosphere may also be employed. The equipment used for such heat treatment may use a static or flowing atmosphere of such gases to effect reduction.
The particle size of silver metal deposited upon the carrier is a function of the catalyst prepara-tion procedure employed. Thus, the particular choice of solvent and/or comple~ing agent, silver salt, heat treat-ment conditions and catalyst carrier may affect, to vary-ing degrees, the size of the resulting silver particle.
For carriers of general interest for the production of ethylene oxide, a distribution of silver particle sizes in the range of .05 to 2.0 microns is typically obtained.
However, the role of particle size of the silver catalyst upon the effectiveness of the catalyst in making ethylene oxide is not clearly understood. In view of the fact that the silver particles are known to migrate on the surface of the catalyst when used in the cat.alytic reaction re-sulting in a marked change in their size and shape, silverparticle size may not be a significant factor in affecting catalytic performance.
CARRIER SELECTION
The catalyst carrier employed in practicing the invention may be selP,cted from conventional, porous, refractory materials which are essentially inert to ethylene, ethylene oxide and other reactants and products at reaction conditions. These materials are generally labelled as "macroporous" and consist of porous materials 12,439-1 having surface areas less than 10 m2/g (square meters per gm of carrier) and preferably less than 1 m2/g. The surface area is measured by the conventional B.E.T. method described by Brunauer, S., Emmet, P., and Teller, E., in J. Am. Chem. Soc. Vol. 60, pp309-16, (1938). They are further characterized by pore -~olumes ranging from about 0.15 - 0.8 cc/g, preferably from about 0.2 - 0.6 cc/g.
Pore volumes may be measured by conventional mercury porosimetry or water absorption techniques. Median pore diameters for the above-descr;.bed carriers range from about 0.01 to lO0 microns, a more preferred range being from about 0.5 to 50 mi_rons.
The carrier should preferably not contain ions which are exchangeable with the alkali metals supplied to the catalyst, either in the preparation or use of the catalyst, so as to upset the amount of alkali metal which provides the desired synergism. If the carrier contains such ion, the ion should be removed by standard chemical techniques such as leaching. Moreover, if the carrier contains an amount of alkali metal, which is transferable to the silver whereby the synergistic combination is upset, then the carrier should be treated to remove such excess alkali metal or the amount of alkali metal supplied to the catalyst should be less than the synergistic amount, allowing the transferred alkali metal to effect the desired synergistic amounts.
The chemical composition of the carrier is not narrowly critical. Carriers may be composed, for example, of alpha-a~umina, silicon carbide, silicon dioxide, zirconia, magnesia and various clays. In general, ~ 1 S~
alpha-alumina based materials are preferred. These alpha-alumina based materials may be of very high purity, i.e., 98 + wt.% alpha-alumina, the remaining components being silica, alkali metal oxides (e.g., sodium oxide) and trace amounts of other metal and non-metal impurities;
or they may be of lower purity, i.e., about 80 wt.% alpha-alumina, the balance being a mixture of silicon dioxide, various alkali oxides, alkaline earth oxides, iron oxide, and other metal and non-metal oxides. The lower purity carriers are formulated so as 'o be inert under catalyst preparation and reaction conditions. A wide variety of such carriers are commercially available. The carriers may be in the form of pellets, extruded particles, spheres, rings and the like. The si~ze of the carriers may vary from about l/16" to ~". The carrier size is chosen to be consistent with the type of reactor employed. In general, for fixed bed reactor applications, sizes in the range of 1/8" to 3/8" have been found to be most suitable in the typical tubular reactor used in commercial operations.
The silver catalysts of the invention are par-ticularly suitable for use in the production of ethylene oxide by the vapor phase oxidation of ethylene with molec-ular oxygen. In accordance with another aspect of the present invention, there is provided in the continuous process for the production of ethylene oxide in a com-mercial operation wherein ethylene and oxygen provided as oxygen or as an oxygen-containing gas are reacted in vapor phase admixture with diluent and inhibitor at a temperature of from about 200C to 300C in the presence of a supported silver catalyst in a fixed bed tubular . ' , .
~6~181 reactor to form ethylene oxide, the improvement which comprises employing a supported silver catalyst which catalyst has a macroporous support having a surface area less than lO m2~g and is in a form and size for use in a reactor used in the commercial operation and which catalyst contains 2 to 20 weight percent silver a combina-tion of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, which combination comprises (a) and (b) in amounts in relation to the amount of silver therein sufficient to increase the efficiency of ethylene oxide manufacture in the commercial operation to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as the catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount of (b).
The reaction conditions for carrying out the vapor phase oxidation reaction to produce ethylene oxide are well-known and extensively described in the prior art. This applies to reaction conditions, such as, tempera-ture, pressure, residence time, concentration of reactants, diluents (e.g., nitrogen, methane and CO2), inhibitors (e.g., ethylene dichloride) and the like. In addition, the desirability of recycling unreacted feed, or employing a single-pass system, or using successive reactions to increase ethylene conversion by employing reactors in series arrangement can be readily determined by those skilled in the art. The particular mode of operation selected will usually be dictated by process economics.
Generally, the process is carried out by con-~ ~ 6~181 tinuously introducing a feed stream containing ethylene and oxygen to a catalyst-containing reactor at a tempera-ture of from about 200 to 300C, and a pressure which may vary from one atmosphere to about 30 atmospheres depending upon the mass velocity and productivity desired.
Residence times in large-scale reactors are generally on the order of about 1-5 seconds. Oxygen may be supplied to the reaction in an oxygen~containing stream, such as, air or as commercial oxygen. The resulting ethylene oxide is separated and recovered from the reaction pro-ducts using conventional methods.
The invention is illustrated further by the catalyst comparisons which are now discussed in relation to Tables II to VI and the experimental results set forth therein.
The catalysts cited in the Tables below were all evaluated for comparison purposes under standard test conditions using backmixed, bottom-agitated "Magne-drive" autoclaves as described in Figure 2 of the paper by J.M. Berty entitled "Reactor for Vapor Phase Catalytic Studies", in Chemical Engineering Progress, Vol. 70, No. 5, ; ~
,~,,, d ~6~1Bl 12,439-1 pages 78-84, lg74. The reactor was operated at 1.0 mole % ethylene oxide in the outlet gas under the following standard inlet conditions:
Component Mole %
Oxygen 6.0 Ethylene 8.0 Ethane 0.50 Carbon Dioxide 6.5 Nitrogen Balance of Gas Parts per million Ethylene Chloride = 7.5 The pressure was maintained constant at 275 psig and the total outlet flow maintained at 22.6 SCFH.(l) The outlet ethylene oxide concentration was maintained at 1.0% by adjusting the reaction temperature. Thus, temperature (C) and catalyst efficiency are obtained as the responses describing the catalyst performance.
A typical catalvst test procedure is comprised of the following steps:
1. 80 cc of catalyst is charged to a backmixed autoclave The volur,le of catalyst is measured in a 1"
I.D. graduated cylinder after tapping the cylinder several times to thoroughly pack the catalyst. The weight of the catalyst is noted.
2. The backmixed autoclave is heated to about reaction temperature in a nitrogen flow of 20 SCFH with the fan operating at 1500 rpm. The nitrogen flow is then discontinued and the above-described feed stream is introduced into the reactor. The total gas outlet -(1~ SCFH refers to cubic feet per hour at standard temper-ature and pressure, namely, 0C and one atmosphere.
~ ~ 6;~181 12,439-1 flow is adjusted to 22.6 SCFH. The temperature is adjusted over the next few hours so that the ethylene oxide concentration in the outlet gas is approximately 1.0%
3. The outlet oxide concentration is monitored over the next 4-6 days to make certain that the catalyst has reached its peak steady state performance. The temperature is periodically adjusted to achieve 1%
outlet oxide. The selectivity of the catalyst to ethylene oxide and the temperature are thus obtained.
The standard deviation of a single test result reporting catalyst efficiency in accordance with the procedure described above is 0.7% efficiency units.
Tables II through VI below summarize test re-sults obtained with silver catalysts in the absence of additives and those containing cesium in combination with one or more alkali metals selected from among lithium, sodium, potassium and rubidium. Tests were carried out using a variety of catalyst carriers and different 2Q preparation procedures. Catalysts which were prepared by the same method of preparation on a similar ca-;rier are identified in the Tables by a common number TABLE II
B PERIMENT Wt.~g Wt.%Cs Wt.%X ~EFF** TEMP.(CC) 1 A 11.14 0.00479 0.0000 71.7 256 1 B 11.14 0.00477 0.00158 73.9 256 1 C 10.8g 0.00461 0.00450 75.4 256 1 D 10.41 0.0000 0.0000 68.4 265 1 E 10.80 0.0000 0.00613 69.9 261 1 F 10.93 0.0000 0.0123 73.3 264 1 G 10.90 0.0000 0.0210 66.6 299 1 H 11.04 0.00941 0.0000 75.6 256 1 I 11.06 0.00941 0.00313 76.9 258 1 J 10.92 0.0186 0.0000 73.1 283 1 K 11.16 0.0191 0.00633 72.0 293 1 L 8.04 0.004 0.008 76.0 269.3 1 M 7.84 -- 0.0078 75.0 263.8 1 N 8.28 0.0041 -- 73.8 258.3 1 O 8.07 -- __ 67.3 260.0 1 P 14.97 -- -- 66.7 252.9 1 Q 15.19 0.00405 -- 72.6 252.0 1 R 14.80 -- 0.0079 75~5 255.5 1 S 15.10 0.004 0.0081 77.9 256.6 2 A 17.4 0.000 0.093 73.5 278 2 B 16.6 0.0044 0.088 74.7 279 2 C 16.5 0.0085 0.089 74.2 278 2 D 17.3 0.000 0.000 ~8-67* 284-299 2 E 17.0 0.0044 0.0016 70.8 276 2 F 15.7 0.0044 0.069 74.1 280 2 G 16.5 0.0092 0.0028 72.2 275 2 H 16.5 0.0092 0.088 73.2 287 * Due to rapid deactivation of this catalyst, initial and final perform~nces, respectively, are given.
**"EFF" is the abbreviation for efficiency as previously defined.
12,439-l Experiments lB and lC demonstrate the synergism achieved with silver catalysts containing mixtures of cesium and potassium in accordance with the invention relative to the "cesium only" catalyst of lA which con-tained essentially the same concentratlon of silver and cesium but contained no potassium. As used herein, the term "cesium only" refers to a catalyst wherein cesium is the only alkali metal deposited upon the carrier. The terms "potassium only", "lithium only", and "sodium only" are correspondingly defined for the respective catalysts. Thus, the efficiency achieved with combination of alkali metals in experiment lB was about 2% higher than that achieved with the corresponding cesium only catalyst of experiment lA. The further addition of K from a level of .00158%
(Example lB) to a level of 0.~045% K (experiment lC) while maintaining Ag and Cs essentially constant provided an even greater improvement in efficiency relative to lA, namely, about 3.7%. The catalyst of experiment lD con-tained no cesium or potassium and provided a relatively low 68.4% efficiency. Experiments lE, F, and G demon-strate that "potassium only" catalysts which con-tained essentially the same amount of silver as catal-ysts lB and lC achieved a selectivity no higher than 73.3%, significantly below that achieved with the catalysts of lB and lC containing mixtures of cesium and potassium. It should also be noted that in addition to providing higher efficiency, the catalysts of the invention (lB and lC) operated at lower tempe~atures than the potassium only catalysts (lE, lF and lG), thus indicating higher catalyst activity. Although the cesium only catalyst (lA) operated at the same low temperature as catalysts lB and lC, it provided a sub-stantially lower efficiency.
- ~5 -12,439-1 The catalyst of experiment lH was a cesium only catalys~ containing Cs at a level nearly double that of catalysts lA, B and C. The addition of .0031%
potassium to a catalyst of such composition produced an efficiency improvement of greater than 1% as shown in Example 1.
Experiments lJ and lK are illustrative of a non-synergistic combination of Cs and K. Thus, the addition of K to the cesium only catalyst of lJ contain-ing about 11% Ag and a relatively high Cs concentration of0.0186% resulted in a catalyst (lK) having a lower efficiency and higher operating temperature. That is to say, the combination of K and Cs in experiment lK did not produce a synergistic result. Consequently, such cesium-potassium mixture is not in accord with the present invention.
Experiments lL through 10 demonstrate the synergism of the present invention for catalysts con-taining approximately 8% silver. The efficiency of catalyst lL which contained a synergistic combination of cesium and potassium was 1% higher than the potassium only catalyst of lM, and more than 2% higher than the efficiency of the cesium only catalyst of lN. Silver catalyst lO which contained no cesium or potassium achieved an efficiency nearly 9% below that of catalyst lL.
Experiments lP through lS demonstrate the synergism of the present invention for catalyst con-taining approximately 15% silver. The efficiency of catalyst lS which contained a synergistic mixture of 1 16~181 12,439~1 cesium and potassium was ~ore than 5% higher than the cesium only catalyst of lQ which contained the respective amount of cesium in such mixture, and about 2.5% higher than the potassium only catalyst of lR which contained ~he respective amount of potassium in s~ch mixture. Catalyst lP which contained no additives achieved an efficiency about 11% lower than catalyst lS.
Experiments 2B and 2C demonstrate the efficiencies achieved with potassium-cesium mixtures for a catalyst containing about 17% silver compared to the potassium only catalyst of experiment 2A. The addition of .0044%
cesium in experiment 2B resulted in an improved effi-ciency of 74.7% compared to the 73.5% efficiency achieved in experiment 2A. The silver catalyst of 2D which had no alkali metal deposited on the carrier is provided in the Table for comparative purposes.
A comparison of experiments 2E and 2F show that when the K concentration was increased from .0016% to .06~% while maintaining the Cs level constant, a greater than 3% improvement in efficiency was achieved. Li~e-wise, a comparison of experiments 2G and 2H demonstrates that when the potassium concentration was increased while maintaining the silver and cesium levels constant, a 1% improvement in efficiency resulted.
Three catalysts containing 7% Ag were prepared containing the optimum cesium concentration as determined from the Efficiency Model, supra, obtained from a designed set of experiments. The catalysts (experiments 3A, B and C) ~ 1 621~1 12,439-1 all contained about 7.0 w~. % silver and 0.00906 wt. %
cesium, with no potassium being present. To demonstrate the operation of the Efficiency Model, three additional catalysts were prepared (experiments 3D, E and F), each containing about 7.0% silver, 0 00906% cesium and 0.004%
potassium. The difference in the performance of the cesium/
potassium catalysts relative to the cesium only catalysts was predicted from the Efficiency Model ~o be about 0.6%
efficiency units. As noted below in Table III, the actual observed difference in performance was found to be 0.7%, which is regarded to reflect agreement with the prediction of the Efficiency Model. Experiment 3G provides the effi-ciency of a potassium only catalyst containing silver and potassium at the same concentration as the catalysts of experiments 3D, E and F, thus demonstrating the synergism achieved with the cesium-potassium combination.
12,439-1 TABLE III
Cesium Only Catalysts: 7.0~/O A~, 0.00906% Cs Experiment /O Eff. T, C
3A 75.4 263.9 3B 75.7 ~ 261.4 3C 75.4 266.1 Average: 75.5 + 0.17-'~
Cesium Plus Potassium Catalysts: 7.0% Ag, 0.00906% Cs, 0.004% K
3D 76.0 271.4 3E 76.1 271.5 3F 76.4 270.9 Average: 76.2 + 0.21*
Potassium Only Catalyst: 7.0% A~, 0.0040% K
3G 72.8 265.3 * Values reflect standard deviations.
Table IV below demonstrates the synergism achieved with a combination of cesium and lithium (experiment 4C) relative to the corresponding cesium only catalyst of experiment 4A and the corresponding lithium only catalyst of experiment 4B. Thus, the catalyst of 4C
was about 10% more efficient than the lithium only catalyst of 4B and about 3.5% more efficient than the cesium only catalyst of 4A.
Exper,ment 4D demonstrates that when the lithium concentration of catalyst 4C was increased about ten-fold, ~,9 _ 12,439-1 the resulting efficiency was reduced by more than 3%.
However, a comparison of catalysts 4D and 4E discloses that the efficiency obtained with catalyst 4D was increased by increasing the cesium concentration from 0~0053% to 0.0300%. It should be noted .hat the cesium only catalyst of experiment 4G (corresponding to the cesium concentration of 4E~ was inactive; that is, at that concentration of cesium, no ethylene oxide was produced. Yet, the com-bination of this concentration of cesium with 0.0300%
lithium resulted in a very active catalyst (4E).
Similarly, the lithium only catalyst of 4F (corresponding to the lithium concentration of 4E) provided a relatively low efficiency of 65.4%. Thus, the synergism achieved in catalyst 4E is underscored by the sharp contrast of its efficiency relative to the poor results achieved with catalysts 4F and 4G.
1 162~81 12, 439- 1 _, o~
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12,439-1 -Table V below demonstrates the synergism achieved with the catalyst of experiment SC relatlve to the corresponding cesium only catalyst of experiment 5A
and the corresponding sodium only catalyst of experiment 5B. Thus, the catalyst of 5C was 6% more e~ficient than the cesium only catalyst of 5A and 7.2V~ more efficient than the sodium only catalyst of 5B. Experiment 5D discloses that increasing the sodium concentration ten-fold relative to the concentration in catalyst 5C
had the effect of lowering the catalyst efficiency.
~ 1 62181 12, 439-1 /
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x 1 ~ ~21# 1 12,439-1 Table VI below demonstrates the synergism achieved with a catalyst containing silver and cesium in combination with potassium, sodiu~ and lithium as indicated in experiment 6A. The presence of chloride ion in the catalyst concentrations of 6A, B and C
indicates that at least a portion of the alkali metal salts used in the catalyst preparation procedure were in the form of chlorides. The efficiency achieved with the synergistic combination of experir,~ent 6A was about 1.2% greater than the efficiency of the corresponding cesium only catalyst of 6C and about 9% greater than the corres?onding combination of potassiu~, sodium and lithium of catalyst 6B.
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~ ~6~181 12,439-l The catalysts of the invention can be prepared with a variety of carriers and preparation procedures.
The defined synergism obtainable with combinations of cesium with the other alkali metals is not restricted, for example, to a particular type or chemical composition of catalyst carrier, to a particular sequence of silver and alkali metal deposition, or to a special class of solvents or solubilizing agents used in the preparation procedure.
In the following examples detailed procedures are provided as illustrative of methods and carriers which are useful for preparing catalysts according to the invention. These examples are by way of illustra-tion only, and are not to be construed as limiting the scope of the invention described herein.
A catalyst containing 11.14 wt.% Ag, .00477 wt.~ Cs and .00158 wt.~ K was prepared as hereinafter described on an alpha-alumina carrier "A" having the following chemical composition and physical properties:
Chemical Composition of Carrier "A"
Alpha~Alumina 98.5 wt.%
Silicon Dioxide 0.74 wt.%
Calcium Oxide0.22 wt.%
Sodium Oxide0.16 wt.%
Ferric Oxide0.14 wt.%
Potassium Oxide 0.04 wt.%
Magnesium Oxide 0.03 wt.%
Physical Properties of Carrier "A"
Surface Area (1) ~ 0.3 m~/g Pore Volume (2) ~~ 0.50 cc/g ~or water absorption) Packing Density (3) 0.70 g/ml Median Pore Diameter (4) 21 microns Pore Size Distr~b~tion, % Total Pore Volume (4) Pore Size, Microns % TPV
0.1 - 1.0 1.5 1.0 - 10.0 38.5 10.0 - 30.0 20.0 30 - 100 32.0 > 100 8.0 (1) Method of measurement described in "Adsorption, Surface Area and Porosity", S.J. Gregg and X.S.W. Sing, Academic Press (1967), pages 316-321.
(2) Method of Measurement as described in ASTM C20-46.
(3) Calculated value based on conventional measurement of the weight of the carrier in a known volume container.
The deposition of silver onto the carrier can be achieved by a number of techniques but the two techniques which are most frequently employed involve, in one case, the impregnation of the support with a silver solution followed by heat treatment of the impregnated support to effect deposition of the silver on the support and, in the other case, the coating of the silver on the support by ~he precipitation of silver or the preformation of silver into a slurry such that the silver particles are deposited on the support and adhere to the support surface when the carrier or support is heated to remove the liquids present. These various procedures are exemplified in various U. S. Patents such as 2,773,844;
3,207,700; 3,501,407; and 3,664,970 (see British Patent 754,593), and 3,172,893.
The surface area provided by the suppor~ has been the subject of considerable interest in the develop-ment of silver catalysts. Disclosures concerning the surface area of the catalyst carrier can be found in U. S. Patent 2,766,261 (which discloses that a surface area of 0.002-10 m2/gm is suitable); U. S. Patent 3,172,893 (which depicts a porosity of 35-65% and a pore diameter of 80-200 microns); U. S. Patent 3,725,307 (which depicts a surface area of less than 1 m2/gm and an average pore diameter of 10-15 microns); U. S. Patent ~62~
12,439-1 3,664,970 (which utilizes a support having a minimum porosity of about 30%, at least 90% of the pores having diameters in the range of 1-30 microns, and the average of such diameters being in the range of 4-10 microns);
and U. S. Paten~ 3,563,914 (which utilizes a catalyst support having a surface area of less than 1 m2/gm, a volume of 0.23 ml/gm and a particle size between 0.074 and 0.30 mm).
In the very earliest developments of silver catalysts for the manufacture of ethylene oxide, it has been determined that a number of metals when present in combination with the silver could act as promoters of the silver catalyst. These materials in themselves are not catalysts but contribute to enhance the rate or amount of oxide production. Cne of the problems in determining whether or not these ~.etals act as promoters is the nature of the reaction`itself. The reaction between oxygen and ethylene to form ethylene oxide is a highly exothermic reaction. However, even more exothermic than that re-action is the combustion of ethylene or ethylene oxideto carbon dioxide. These reactions occur simultaneously and the critical factor in determining the effectiveness of the over,-all process is the measure of control one has over these two competing reactions. Inevitably, a material which enhances the production of ethylene oxide might also be considered a material which inhibits the complete combustion of ethylene to ethylene oxide to carbon dioxide. Thus, there is a problem in defining whether that material which is termed as a promoter is in fact an inhibitor of the combustion reaction. It is well known ~3S218~
12,439-1 that there are materials which when added to the reaction result in less carbon dioxide being formed and such materials are termed inhibitors. There are also ~aterials which when provided with the catalysts result in greater production of ethylene oxide and those materials are termed promoters. Whether the latter materials are in reality inhibitors or promoters seems to be an irrelevant issue. What is significant is that the outcome of the reaction is favorable to the production of ethylene oxide.
For that reason, when determining or characterizing a catalytic process for producing ethylene oxide a signifi-cant factor entering into or qualifying that process is the selectivity of the process to produce ethylene oxide, selectivity being as defined previously.
The use of alkali metals as promoters for the silver catalyzèd production of ethylene oxide is extremely well known in the art. As far back as U. S. Patent 2,177,361 issued October 1939 there is found a teaching of the use of alkali metals in silver catalysts. U. S.
Patent 2,238,471 discloses that lithium was very desirable as a promoter but that potassium and cesium were detri-mental The examples of that patent utilize essentially 10% by weight of potassium hydroxide or cesium hydroxide to the silver oxide employed in making the catalyst. Later, U. S. Patent 2,404,438 stated that sodium and lithium were effective promoters for this reaction. Essentially the same teaching could be found in U. S. Patent 2,424,084. U. S.
Patent 2,424,086 generalized about alkali metals as pro-moters and specified sodium in particular. In U. S.
1~ 82~8~
12,439-1 Patent 2,671,764, the patentees believed that alkali metals in the form of their sulfates would be effective as promoters for such silver catalysts. In particular, the patentees stated that sodium, potassium, lithium, rubidium or cesium sulfates may be used as promoters. U. S. Patent 2,765,283 described the pretreatment of a support with a dilute solution of a chlorine containing compo~nd and indicated that such chlorine compounds should be inorganic.
Particular illustrations cited of suitable inorganic chlorine compounds i~cluded sodium chloride, lithium chloride and potassium chlorate. This patent specified that the amount of the inorganic chlorine containing compound which is deposited on the catalyst support is from 0.0001% to 0.2%
by weight, based on the weight of the support. U. S.
Patent 2,615,900 to Sears describes the use of metal halide in the treatment of the supported catalyst and specifies that such halides can be of alkali metals such as lithium, sodium, potassium, and cesium. The metal halide is present in the range of 0.01% to 50% based upon the weight of metallic silver. The patent also specif ies that mixtures of the individual metal halides generally classified in the patent may be used to advan-tage to enhance the break-in period of a new catalyst composition while at the same time maintain a moderate but steady activity of the catalyst over an extended period of time during normal operation. Thus, one particular metal halide treated catalyst would provide a short-term high initial activity whereas another of the metal halides would provide a longer term moderate activity for the catalyst. This patent takes the position 1 ~ ~2 18 1 12,439-1 that the metal halides which are provided in the catalyst serve to inhibit the combustion of ethylene to carbon dioxide and thus classifies these materials as catalyst depressants or anticatalytic materials. U. S Patent 2,709,173 describes the use of a silver catalyst for making ethylene oxide in which there are provided simultaneously with the introduction of the silver catalyst to the solid support any of the alkali metal halides such as lithium, sodium, potassium, and rubidium compou~lds of chlorine, bromine and iodine, to enhance the overall production of ethylene oxide. The patent specifies small amounts "of less than about 0.5~/o are desirable". In particular the patent emphasizes "proportions of alkali metal halide within the range of about 0.0001 to about 0.1%" are most preferred. The patent states that "although the preferred catalyst composition contains a separate promoter it is not always necessary since during preparation of the catalyst the alkali metal halide may be converted to some ex~ent to the corresponding alkali metal oxide which acts as a promoter".
U. S. Patent 2,766,261 appears to draw from the teachings of U. S. Patent 2,238,474 in that cesium and potassium are said to be detrimental in silver catalysts; sodium and lithium are suggested as useful promoters. However, U. S.
Patent 2,769,016 finds that sodium, po~assium and lithium are promoters when used in the silver catalysts.
This latter patent also recommends the pretreatment cf the support with dilute solutions of sodium chloride, lithium chlcride or potassium chlorate. U. S. Patent 2,799,687 to Gould et al states that the addition of metal 1 1~2~81 12,439-1 halides within the range described by Sears in U. S.
Patent 2,615,900 is not productive of optimum results.
This is said to be especially true in the case of alkali metal halides, particularly the chloride and fluoride of sodium and potassium. The patentees recommend that the inorganic halide component of the catalyst be maintained within the range of 0.01-5 weight percent, preferably .01 to 0.1 weight percent, based on the weight of the "silver oxidative catalytic component", i.e., the silver salt transformed into elemental silver. U. S. Patent 3,144,416 mentions a variety of metals as promoters and one of them is cesium. U. S. Patent 3,258,433 indicates th~t sodium is an effective promoter. U. S. Patent 3,563,913 recommends the use of alkali me~als such as lithium compounds as promoters. The preferred amount of promoting material is said to be about 0.03 to 0.5%, by weight, of metal oxide based on the weight of the support. U. S.
Patent 3,585,217 states that alkali metal chlorides "are known to counteract the formation of carbon dioxide" and "may be incorporated into the catalyst". U. S. Patent No.
3,125,538 discloses a supported silver catalyst contain-ing a coincidentally deposited alkali metal selected from among potassium, rubidium and cesium in a specified gram atom ratio relative to silver. The weight of silver is preferably 2-5% by weight, of the catalyst. The patentees characterize this catalyst as being especially suitable for the reaction of nitric oxide with propylene. U. S.
Patent ~os. 3,962,136 and 4,012,4~5 disclose the identical catalyst as being useful for ethylene oxide production.
U. S. Patent 3,962,136 describes the coincidental 1 J ~2181 12,439-1-C
deposition of al~ali metal with the silver on the support, the alkali metals being present in their final form on the support in the form of an oxide in which the oxide con-sists of cesium, rubidium or mixtures of both, optionally combined with a minor amount of an oxide of potassium.
The amount of such oxide is from about 4.0 x 10-5 gew/kg to about 8.0 x 10-3 gew/kg of total catalyst. However, U. S. Patent 4,010,115, patented March 1,1977, dis-tinguishes itself by employing as the oxide of the alkali etal the oxide of potassium optionally combined with a parent minor amount of an oxide rubidium or cesium. The/applica-tion of U. S. Patents 3,962,136 and 4,010,115, and others, contains some interesting data deserving of comment.
According to example 2 which contains some comparative experiments, there is described the manufacture of a catalyst which contains 310 parts per million by weight of coincidentally-added potassium and that catalyst when employed as an ethylene oxidation catalyst was found to be inactive for the production of ethylene oxide. Even so, we find that that amount of potassium in the catalyst lies within the range disclosed in U. S. Patent 4,010,115 to be effective for the production of ethylene oxide, although no data is shown in the patent to support that view.
Belgium Patent 821,439, based upon British Patent Specification 1,489,335, discloses that a catalyst can be made that is equivalent to that produced in U. S. Patent Nos. 3,962,136, 4,012,425, and Patent 4,010,115 to Neilsen et al. by varying the procedure by which the alkali 1 1 6~81 12,14g-1-C
metal is supplied to the support. In the Belgium Patent and its British equivalent, a porous refractory support of a specified surface area is first impregnated with an alkali metal to deposit it on the support metal in specified quantities (both the quantities and the nature of the porous support being equivalent to that which is set forth in the aforementioned Nielsen et al U. S. Patents), the support is then dried to fix the alkali metal and there-after the silver is supplied to the support. This pro-cedure is a sequential deposition of the alkali metal promoter and the silver catalyst and yet essentially the same type of catalyst was produced by the simultaneous deposition of alkali metal and silver as evidenced by a comparison of ~he data in the examples of the ~elgium Patent with the data set forth in the aforementioned Nielsen et al U. S. Patents. The criticality in the method of deposition of alkali metal upon the support appears doubtful in the face of that type of disclosure and the disclosure of U. S. Patent Nos. 4,033,903 and 4,125,480 which describe subjecting a used silver-containing catalyst with a post-addition of one or more of potassium, rubidium or cesium. Apparently such treatment regenerates the catalyst's ability to enhance selectivity to ethylene oxide. Another patent which tends to indicate that a post-addition of alkali metal such as cesium gives results equivalent to either pre-addition or simultaneous addition is U. S. Patent 4,066,575.
U. S. Patent 3,962,136 and its companion patents were derived from a parent application filed January 7, ]972, now abandoned, U. S.
t 1 62~8~
12,439-1-C
Patent 3,962,136 discloses that the "highest level of selectivity obtainable with potassium modified catalysts at otherwise comparable conditions typically is lower than that obtainable with rubidium or cesium-modified catalysts" (see column 2, lines ~8-42). The parent application contains a drawing which depicts the relative effectiveness of rubidium, cesium and potassium to enhance the selectivity of ethylene oxide when utilized in a silver catalyst. The drawing shows that the curve C
which represents cesium addition provides the greatest degree of enhancement of selectivity while curve B which represents rubidium addition is intermediate and superior to potassium addition represented by curve A. In an amendment filed on April 11, 1975, in parent application (filed June 19, 1974) to U. S. Patent 4,010,115, the applicant urges that the invention and claims do not involve "synergistic effects with the use of mixtures"
of the alkali metals. The same statement was made in the amendment received on April 11, 1975 in the parent application (filed May 20, 1974) to U. S. Patent 4,012,425.
German Offenlegungsschrift 2,640,540 discloses in its examples a silver catalyst for ethylene oxide production containing sodium and either potassium, rubidium or cesium. Table I of this disclosure provides the alkali content of all catalysts prepared in the examples, many of which contain sodium, potassium and cesium. A footnote 1 ~218~
12,439-1 to the Table states that the presence of potassium in all catalysts tested (except for one which was free of cesium) was due to impurities present in the support, the level of such impurities being below that specified as being useful for the invention. The disclosure does not suggest that cesium may be combined with potassium and/or sodium to advantage nor does the efficiency data provided in the Table demonstrate any synergistic inter-action of cesium with sodium or the potassium impurities in the catalysts.
Japanese Application Publication Disclosure No. 95213/75 is directed to a process for producing ethylene oxide using a catalyst composition comprising silver, barium, potassium and cesium in specified atomic ratios. Table I of this disclosure summarizes the efficiencies achieved with the various catalyst composi-tions of the examples. No synergism with cesium and potassium was demonstrated by any of the cesium-potassium-barium mixtures of the examples. Indeed, a comparison of some examples among Table I appears to demonstrate the absencè of a cesium-potassium synergism, namely, the efficiency achieved with a cesium-potassium mixture is shown to be lower than the efficiency achieved with the same amount of cesium in the absence of potassium.
For example, Examples 3 and 7 relate to catalysts having an identical atomic ratio of cesium to silver (.05 atoms/
100 atoms Ag~, but differing potassium contents, the atomic ratio of potassium in Example 3 being .001 atoms K/lO0 atoms Ag and the corresponding ratio in Example 7 12,439-1 being .05. The efficiency achieved in Example 3 was 76.4% and that of Example 7 was 75.9%. Thus, the increased potassium content in E~ample 7 resulte~ in a decrease in catalyst efficiency. Similarly, Examples 1 and 4 relate to catalysts havinv an identical atomic ratio of cesium to silver, with the catalyst of Example 1 containing an amount of potassium one order of magnitude greater than the catalyst of Example 4. Yet, the efficiencies reported for both catalysts are essentially the same, 76.7% and 76.6% for Examples 1 and 4, respectively.
U. S. Patent 4,039,561 discloses a catalyst for preparing ethylene oxide containing silver, tin, antimony, thallium, potassium, cesium and oxygen in specified atomic ratios. Mixtures of cesium and potassium are not dis-closed to be desirable combinations. Indeed, Table I
of the patent discloses a silver-cesium-potassium com-bination which is designated as a "control" example not in accord with the disclosed invention and which achieved a selectivity of 73.0%, a value markedly lower than the selectivities achieved in the 45 Examples listed in Tables 2 and 3. Moreover, the efficiencies provided in Tables 2 and 3 for the various catalysts fail to demon-strate the existence of any synergistic combination of cesium and potassium among the numerous combination of elements which were employed in the catalysts. It is also note-worthy that the aforesaid U. S. Patent 4,039,561 claims the priority of a Japanese application filed in 1973, and that subsequent to such filing the same appli-cant filed Japanese Application Publication No. 25703/77 12,439-1 which discloses a catalyst for ethylene oxide manufacture comprised of the same metallic elements disclosed in the U. S. Patent with the exception of cesium and potassium. The efficiencies disclosed in the examples of the latter Japanese Application are similar to those shown in the U. S. Patent. The effect of cesium and potassium in the catalyst composition disclosed in the U. S.
Patent is therefore presumably insignificant.
Belgium Patent 854,904 discloses silver catalysts containing various mixtures of sodium and cesium. U. K.
Patent Application GB 2,002252A discloses, in Table 2, supported silver catalysts containing various mixtures of cesium and thallium, some of which additionally contain potassium or antimony. U. S. Patent 4,007,135 broadly discloses (in column 2, lines 25-30) silver catalysts for alkylene oxide`production containing silver "together with a promoting amount of at least one promoter selected from lithium, potassium, sodium, rubidium, cesium, copper, gold, magnesium, zinc, cadmium, strontium, calcium, ~ niobium, tantalum, molybdenum, tungsten, chromium, vana-dium and barium...". European Patent Publication No.
0003642 discloses, in Table 3, silver-containing catalysts ~which include mixtures of potassium and cesium, and a catalyst containing sodium and cesium. The above publica-tions do not indicate a synergistic interaction of cesium with otne~ alkali metals. !
Belgium Patent 867,045 discloses supported silver catalysts containing what is referred to as an effective proportion of lithium and a substantially lesser amount of alkali metal selected from among cesium, rubidium and/or 1 1 62~
12,439-1 potassi~n. Table I of the patent discloses three catalysts all of which contain cesium, sodium, potassium and lithium, the lithium concentration being at least one order of magnitude greater than the concentration of cesium or potassium. Referring to Table I, the catalysts Ll, L2 and L3 have markedly different concentrations of cesium, potassium and sodium, but are shown in Table II to provide substantiallv similar selectivities. There is no indication of a synergistic interaction of cesium with either potassium or sodium in the silver catalysts dis-closed.
Belgium Patent 867,185 discloses supported silver catalysts for ethylene oxide production containing a specified amount of potassium and at least one other alkali metal selected from rubidium and cesium. Table I dis-closes the composition of 14 potassium-containing catalysts, two of which contain potassium in combination with cesium (catalysts G and H). The selectivities of catalysts G and H are shown to be identical at a pressure of 1.03 bars, but differ slightly at the higher pressure of 16.55 bars.
No silver-potassium-cesium synergism can be discerned from the data.
This invention distinguishes over the prior art in the fact that the silver catalyst employed in manufacturing ethylene oxide utilizes at least two alkali metals (excluding francium~, one of which is cesium, each of the alkali metals being present in an amount such that the combination thereof in relation to the amount of silver in the catalyst provides a synergy in terms of ethylene oxide selectivity and a selectivity which is greater than has been contemplated or disclosed by any prior art.
1 ~ ~2 1 8 .t In accordance with one aspect of the present invention, there is provided a silver catalyst deposited on a macroporous support having a surface area less than lOm2/g and in a form and size for use in a fixed bed tu~ular reactor used in a commercial operation for the manufacture of ethylene oxide by vapor phase reaction of ethylene and oxygen or an oxygen-containing gas in gaseous admixture with diluent and inhibitor, which catalyst contains 2 to 20 weight percent silver and a combination of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, which combination compri-ses (a) and (b) in amounts in relation to the amount of silver therein sufficient to increase synergistically the efficiency of the ethylene oxide manufacture to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as the catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount o (b).
In the detailed description of the invention which follows, reference will be made to the graphical representation of the accompanying drawings, wherein:
Figures 1 and 2 show contour lines drawn at constant efficiency and temperature in the potassium~
cesium concentration space with the darker lines represen-ting selectivity contours (selectivity values indicated for each line) and with the lighter, broken lines repre-senting temperature contours (temperatures indicatedfor each line).
116218~
The catalysts of the invention are characterized by a combination of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium so as to achieve a syner-gistic result, i.e., an efficiency greater than the greater value obtainable under common conditions from respective catalysts which are the same as said catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount of (b). Catalysts in accord with the invention are comprised of silver, cesium and at least one other alkali metal (excluding francium) deposited onto the surface of a porous support, the particular mixture of silver and alkali metals being correlated to produce a synergistic result.
The invention as hereinafter described defines the binary alkali metal combinations of cesium-lithium, cesium-sodium, cesium-potassium and cesium-rubidium, which in co~bination with silver provide a synergistic result for a particular catalyst carrier and catalyst preparation. The catalysts of the invention are not, however, restricted to binary combinations of alkali metal. Other alkali metals may advantageously be added to any of the aforementioned synergistic binary co~bina-tions for the purpose of raising or lowering the catalyst operating temperature, improving the initial catalyst activity during the start-up period and/or improving the aging characteristics of the catalyst over prolonged periods of operation. In some ` ~62181 12,439-1 instances, the addition of a third or even a fourth alkali metal to an otherwise synergistic binary combination will effect a further increase in catalyst efficiency.
The mathematical relation.ships from which are derived the synergistic binary a~kali metal co~binations of the invention are set forth below and described, for purposes of illustration, in terms of a cesium-potassium combination. Binary combinations of cesium with any of the other alkali metals in accordance with the invention are readily determined by an analogous procedure wherein the particular alkali metal of interest is substituted for potassium in the procedure described below.
The relationship of cesium, potassium and silver to ach.Fve a synergistic result as herein defLned is characterized with the aid of a mathematical equation, or model, which correlates efficiency as a function of weight percent silver, weight percent cesium and weight percent potassium deposited on the catalyst support. Thus, synergism with mixtures of cesium and potassium can be obtained at any concentration of silver in the finished catalyst.
The general form of the mathematical equation, hereinafter referred to as the "Efficiency ~odel", defines efficiency (or selectivity) as a function of weight per-cents (wt. %) of silver, cesium and potassium deposited on the catalyst support as follows:
Efficiency, % = bo + bl(BG) + b2(BCs) + b3(BK) + b4(BG)2 + b5(BCs)2 + b6(BK)2 + b7(BG x BCs) + b8(BG x BK) + b9(BCs x BK) 12,439-1 where:
o' 1' b2~ b3~ b4~ bs~ b6, b7, b8 and bg are the respective coefficients for each term of the Efficiency Model, and comprise a set of constants determined for a particular catalyst carrier and a particular~method of catalyst preparation following a designed se~ of experi-ments as hereinafter described. The value of some of these coefficients may be zero.
BG = (wt. % Ag - wt. % Ag);
0 where, wt. % Ag = average value of wt. % Ag used in .he designed set of experiments.
BCs = (wt. % Cs - wt % Cs);
where, wt. % Cs = average value of wt. % Cs used in the designed se; of experiments.
BK = (wt. % K - wt. % K);
where, wt. % K = ave-age value of wt. % K used in the designed set of experiments.
The designed set of experiments is most con-veniently planned in the format of a Composite Design in three independent variables as described by 0. L. Davies, "The Design and Analysis ~f Industrial Experiments", Hafner Publishing Company, 1960, P. 532-535. For this purpose, the three independent v,~riables are the weight percents of silver, cesium and potassium, respectively.
The ranges of each variable are chosen so that selec-tivity al:' activity of all catalysts in the designed -`
set of experimen s can be measured under the desired test conditions. It is therefore desirable to first conduct a few preliminary range finding experiments to 1~82181 12,439-1 determine the appropriate ranges of cesium and potassium for this purpose. Zero perc~llt cesium and/or potassium is a convenient lower limit for use in the Composite Design The upper concentration limit of cesium and potassium can be readily determined by a series of experi-- ments with catalysts containing successively larger amounts of either cesium or potassium as follows: An initial catal-,ist is prepared (using a preparation procedure, if desired, such as hereinafter disclosed in the Examples) containing a small amount (on the order of about 0.001 percent by weight) of either cesium or potassium with a fixed amount, say 7 percent by weight, of silver, and its selectivity then determined for the pro.iuction of ethylene oxide at the desired test conditions. This experiment is then repeated with a catalyst containing double the amount ~0.002 percent by weight) of the alkali metal and the experiment thus repeated in a series of experiments wherein eac~ succeeding experiment uses a catalyst containing double the alkali metal content of the catalyst of the previous experiment, until the measured selectivity of the last catalyst tested is less than that of the initial catalyst. The upper limit of cesium or potassium concentration is thus defined for the Composite Design.
The above-described interative procedure may be advantageously altered so as to more quickly determine the upper limit of concentration in the event it is observed that a two-fold increase in the alkali metal content of the catalyst does not produce a significant change in catalyst 12,439-1 selectivity. This is particularly likely to occur, for example, with catalysts containing lithium or sodium (depending upon the particular carrier and preparation procedure employed) in contrast to catalysts containing other alkali metals where, as a general rule, the efficiency response is more sensitive to increasing alkali con-centration. Accordingly, in the event the catalyst efficiency is virtually unchanged when the alkali content of the catalyst has been doubled, a ten-fold increase in alkali content should be employed in the above-described iteration until the measured efficiency of the last catalyst is less than that of the initial catalyst. Thereafter it may be desirable to repeat the last iterative step using a lower level of alkali, such as, a three or five-fold increase of alkali ~etal content, in order to more accurately deter-mine the upper limit of alkali metal concentration for ~he Composite Design.
The range of silver concentration in the Composite Design may typically be 6-16 weight percent, giving an average value of silver (wt. % ~) of 11 weight percent. Similarly, the ranges of cesium and potassium concentrations are typically from 0.0 to 0.02 weight percent For rubidium, the range is also typically from 0.0 to 0.02 weight percent, while for lithium and sodium, the ranges are typically 0.0 to 0.1 weight percent. For some carriers, the upper concentration limit of cesium and/or potassium may be 5 to 10 times greater. This is particularly likely to occur for carriers which contain exchangeable cations.
1 ~ ~21~
12,439-1 Table 11.5 on page 533 of the aforementioned Davies Publication depicts a three-variable Composite Design scaled in units of - ~ , -1, 0, +1 and +C~
where -1 represents a "low level" of the respective variable; +l represents a "high level" of such variable;
O represents the average level of the variable; -o~
represents a level which is somewhat lower in value than that which is represented by -1; and +Cy~represents a level which is somewhat higher than that represented by +1. The particular choice of -~C and + o(is not critical. However, Table 11.6 on page 534 of the Davies Publication suggests values of -OC and + ~ which are particularly useful for a Composite Design in accordance with the present invention. The designed set of experi-ments is thus typically comprised of 16 to 20 experiments wherein catalysts of varying concentrations of silver, cesium, and potassium are tested. Thus, for example, a preferred Composlte Design in which the weight percent silver ranges from 7.0 to 15.0%; the weight percent cesium ranges from 0.0 to .02%; and the weight percent potassium ranges from 0.0 to 0.01% ..s c follows:
Wt. % Silver Wt. % Cesium Wt. % Potassium 9 0.005 0.002 13 0.005 0.002 9 0.015 0.002 13 0.015 0.002 9 0.005 0.~08 13 0.005 0.008 9 0.015 0.008 13 0.015 0.008 l 0.010 0.005 11 0.010 0.005 7 0.010 0.005 0.010 0.005 11 0.0 0.005 11 0.020 0.005 11 0 . 010 0 . O
11 O. 010 0 . 010 t 1 62181 12,439-1 The catalysts of the designed set of experi-Ments are tested by means well known in the art for measuri~g their selectivity and activity. A convenient measure of activity, i.e., the degree of conversion of reactant to product per unit time, is ~he temperature required to o~tain either a fixed ethylene oxide pro-duction or to achieve a chosen level of mole percent ethylene (or oxygen) conversion. Thus, a mathematical equation for catalyst temperature (Temperature Model) can be developed in a manner similar to the Efficiencv Model. That is, for each catalyst there is obtained two responses (selectivity and temperature) which are re-lated to the three controlled variables (weight percents of silver, cesium, and potassium). The relationship between each response and the controlled variables is obtained by fitting these data to equations, or mathematical models, by the method of least squares as described in Chapter 8 of "Statistical Methods in Research and Production", O.L. Davies and P.L. Golds.,ith, Long~an Group, Ltd., London, 4th Ed., 1976. In prac-tice, the fitting of mathematical models to such data is routinely done with the aid of a digital computer as described in "Applied Regression Analysis", N. R.
Draper and H. Smith, John Wiley and Sons, Inc., 1965.
The resulting models (the Efficiency Model and the Temperature Model) describe the relationship between the responses and the controlled variables.
It is well known in the art that the nu..ber of experiments required to establish mathematical re-1 1 62~81 12,439-1 lationships among several variables is dependent upon the reproducibility of the data. Thus, for a Composite Design containing approximately 16 experiments it may occasionally be necessary to repeat all or part of tne set of designed experiments in order to fir~ly establish the relationship between efficiency and weight percents of silver, cesium and potassium to an acceptable level of statistical confidence. In practice, it has been found that for a designed set of about 16 experiments wherein the weight percent of silver is varied from about 7% to about 15%, one complete replication of the designed experiments is usually sufficient to establish this relationship provided that the standard deviation of a single experimental test result is no greater than about 0.7% efficiency units. During the course of ex-perimentation, data other than from the designed set of experiments may be acquired which is useful for develop-ing the model as described above. For example, data acquired from the aforementioned preliminary range finding experiments as well as any additional experi-mental data which is available with regard to the particular catalyst carrier and method of preparation of interest is desirably included with that derived from the Composite Design, and the equations thus fitted to the data. Consequently, as a practical matter, data from about 30 to 60 experiments may be available for developing the Efficiency and Temperature ~odels.
12,439-l The general form of the mathematical equation, hereinafter referred as the "Temperature Model" defines ~e~perature as a function of weight percents of silver, cesium and potassium deposited on the catalyst support as follows: ~
Temp., C = aO + al(BG) + a2(BCs) + a3(BK) + a4(BG)2 + as~BCs)2 + a6(BK)2 ~ a7(BCs x BG) + ag(BG x BK) + ag(BCs x BK) where:
aO, al, a2, a3, a4, a5, a6, a7, a8 and a9 are the re-spective coefficients for each term in ~he Temperature Model which comprise a set of constants determined for a particular carrier and a particular method of catalyst preparation following the designed set of experiments as described above. The value of some of these coeffic-ients may be zero. BG, BCs, and B~ are as defined above.
The most convenient use of the Efficiency and Temperature Models for defining the area of synergism for any selected weight percent of silver in the catalyst is to depict efficiency and temperature responses in a graphical form, commonly referred to as contour ~aps, as described in Chapter 11 of the aforementioned "Design and Analysis of Industrial Experiments". Thus, Figures 1 and 2 depict the contour maps of efficiency and temp-erature for a selected carrier and catalyst preparation procedure at 7 and 13 weight percent silver~ respectively.
The contour maps were derived from a designed set of experiments in which the percent silver ranged from 5.88 to 16~05~/o; the percent cesium ran~ed from 0.00 ~ ~ ~2181 12,439-1 to 0.019%; and the percent potassium ranged from 0.00 to 0.021%. Table I below summa.izes the experimental data which was available for the selected carrier and catalyst preparation procedure and from which the con-tour maps were derived. The experiments were conducted in two different test reactors in accordance with the standard test procedure hereinafter described under the heading "Catalyst Comparisons". Two similar, but slight-ly different,carriers were used in the experiments.
10 Table I represents the experimental data on a common basis, namely, the data was adjusted to ccmpensate for observed differences between the reactors snd catalyst carriers employed.
621~1 12, 439- 1 TAgLE I
wt% A~ wt~ S w~e~p (~C)Efficienc~
11.14 0.00477 0.00158256.0 73.9 10.53 0.00897 0.0256.4 77.5 11.14 0.00479 0.0256.0 72.9 11.01 0.00941 0.00312256.0 ~7.4 11.21 0.00240 0.00080258.0 70,7 10.9~ 0.01865 0.0282.2 74,3 11.04 0.009~1 0.0257.~ 76.3 011.0'1 0.009~1 0.0255,0 76.3 11.09 0.01421 0.00412270.7 7j.7 10.41 0.0 0.0 263.068.5 10.1 0.0 0.0 265.068.-11.16 0.01909 0.00633292.6 72.G
10.9~ 0.01403 0.0267.0 76.7 10.70 0.01128 0.00379262.0 77.5 9.08 0.0190Q 0.00315293.0 71.8 9.31 0.00968 0.00645269.9 76.6 13.17 0.00617 0.00102254.9 74.2 20 9,10 0.00323 0.00214260.0 7~,7 13.14 O.OO91S 0.00613259.1 77.5 11.11 0.00950 0.00315259.6 77.6 11.31 0.0120~ 0.0260.3 77.4 11.05 0.00236 0.00078260.4 70.1 12.72 0.00311 0.0020725S.8 71.6 16.05 0.00941 0.00313263.0 77.7 5.88 0.00924 0.00306269.1 76.8 11.04 0,01421 0.00157268.9 76.7 10.89 0.00462 0,00450256.4 75.4 10.80 0.0 0.00613 260.5 69.9 B.93 0.00630 0.00105260.4 74.4 15.51 0.01288 0,0266.4 77.2 6.03 0.01341 0.0280.3 73.7 13.11 0.00897 0.00810266.2 77.1 - 28 ~
12, 439-1 IA.B L F
(continued) Ef f lc ienc w~t% AR wt% Cs w~/. X S~p. (-C~ %
16.00 0.00888 0.00800 264.3 77. ~3 10.93 0.0 0.01230 263.6 73.3 12.95 0.01562 0.00469 277.1 76~0 13.12 0.01313 0.00336 268.1 77.0 12.85 0.00150 0.0 26L.4 68.2 0 13.12 0.01047 0.00297 257.3 78.3 13.26 0.0178! 0.00540 282.3 74 ~ 5 12.91 0.0138' 0.00407 269.4 77.
12.91 0.0138' 0.00407 269.8 77.2 12.91 0.01038 0.0029j 257.0 7~.3 12.91 0.0103S 0.00'95 257.2 76.-.
13.00 0.00150 0,07100 299.0 6-~.
13.00 0,01036 O.OljO0 290.7 72.' 6.88 0.00150 0.01470 28~.6 73.7 7.14 0.01056 0,01220 289.' 7~.3 /.06 O.OOj94 0.01010 280.4 75~' 8.00 0.00727 0.00192 263.3 75.7 8.00 0.01153 0.00330 274.4 76.9 8.15 0.01171 0.00339 272.7 77.6 8.30 0,00749 0.00199 262.2 76.5 3.03 0.00150 0.0 268.0 69.0 7.00 0.01056 0.0 264.0 75.5 7.00 O.OlOS6 0,0~400 271.0 76.2 i ~ 62181 12,439-1 The specific Efficiency and Temperature Models derived from the sbove data by the aforementioned method of least square are as follows:
Efficiency, % ~ ~7.19 ~ 0.196(BG) + 133.4(BCs) + 120.5(BK) - 63787.0 rBCs)2 - 47229.0 (BK)2 ~ 52.1 (BG x BCs) - 60823.0 (~Cs x BK); and Temperature, C - 259.44 - 1.279(BG) + 1555.8(BCs) 1 794.1(BK) ~ 0.346$(BG)2 + 168544.0(BCs)2 ~ 147856.0(BI;)2 + 132807.0(BCs x BK) where: BG - (wt.% Ag - 11.0) BCs ~ (wt.~/o Cs - 0.01) BK ~ (wt.% K - 0.003) Figures 1 and 2 show contour lines of constant eff.ciency and temperature in potassium-cesium concen-tration space. The darker lines represent selectivit-contours with selectivity values being indicated for each line. The lighter, broken lines represent temp-erature contours with temperatures indicated in degrees centigrade. The efficiency and temperature for points in between the designated contour lines can be inter-polated. The maximum selectivity achievable for any combination of cesium and potassium as a function of cesium concentration is indicated by the curve labelled Se ~ ax This ~urve represents the maximum synergism achievable for any given level of cesium. The synergism curve (designated "A" in Figures 1 and 2) separates the region of synergism, as herein defined, and regions of ~6~81 12,439-1 additive and antagonistic effec~:s. Additive effects occur when the efficiency obtained with a combination of cesium and potassium is a weighted average of the efficiencies obtainable under common conditions from respective catalysts which are the same as the catalyst containing said combina-tion except that instead of containing both potassi~m and cesium, one contains the respective amount of cesium, and the other contains the respective amount of potassium. Anta-gonistic effects occur when the efficiency obtainable with a mixture of cesium and potassium is less than the efficiencies obtainable with corresponding catalysts which contain the respective amount of cesium, and the respective amount of potassium, individually, as described above. The area bound by ordinate, the abscissa and the synergism curve (curve "A") defines the area of synergism in accordance with the present invention. The area to the right of the synergism curve "A", represents the area of additive and antagonistic effects as described above, and thus defines mixtures not in accord with the present invention. For any given contour map the pre-ferred combinations of cesium and potassium are those whichproduce selectivities on or about the SelMax curve. However, in general, preferred mixtures are those wherein cesium and potassium are present in a weight ratio of from about 100:1 to 1:100 depending upon the particular catalyst carrier and preparation procedure of choice. For mixtures of cesium and lithium, or cesium and sodium, preferred mixtures are usually those wherein the alkali metals are present in a weight ratio of from about 1000:1 to 1:1000.
Referring to Figure 1, a catalyst containing for example, 0.003% Cs and 0% K has an efficiency of about 73%. The addition of approximately 0.008% K to this 12,439-1 catalyst results in an increase in efficiency to about 76.0%, the maximum selectivity at this level of cesium (i.e., the value on the SelMax curve). Further additions of potassium up to about .016% K (i.e., the value on curve "A"~ would yield efficiencies equal to or gr~ater ~han those obtainable with the given amount (0.003%) of cesium alone (i.e., no alkali metal other than cesi~l~ being present);
potassium additions beyond .016% K result in efficiencies lower than those obtainable with 0.003% of cesium alone, i.e., in the region of either additive or anta-gonistic effects. Yet, such amount of potassium which causes such antagonistic effects can still yield a catalyst with reasonably desirable selectivity and activity for a given mode of operation.
The region of synergism varies with the silver .
content of the catalyst as described by the Efficiency Model. Figure 2 illustrates the region of synergism at 13% silver. The SelMax curve and synergism curve (curve "A") of Figure 2 are as previously defined with reference to Figure l. Comparison of Figures 1 and 2 show that the efficiency contour lines are similar but are dis-placed with respect to the cesium and potassium axes. For example, the 76% efficiency contour line in Figure l envelops an area which is smaller than the area covered by the corresponding contour line in Figure 2. Further, the maximum value of selectivity obtainable at 7 weight percent silver, i.e., the maximum along the SelMax line, is slightly above 76% (Figure l) while the corresponding maximum for 13 weight percent silver is slightly above 77.8%
~Figure 2).
The Efficiency Model and th~ Temperature Model which are developed are specific to a particular method of ~ 3 621~
catalyst preparation, a particular carrier and a particu-lar binary alkali metal combination. Variations in either the method of preparation or the carrier or the particular binary combination may change the coefficients of the Models, and hence, the shape of the contour maps derived therefrom. Thus, the curves "A" and SelMa~ may comprise straight lines or curves, and may intercept one or both axes (viz., the cesium axis and that of the other alkali metal in the binary combination). For example, in Figures l and 2, curve "A" and SelMax intercept both axes, and intercept the cesium axis at an angle greater than 90.
However, for a different carrier, a different method of preparation or a different binary alkali metal combin-ation with cesium, the resultant curves "A" and SelMax may intercept the cesium axis at an angle less than 90, or may be parallel to one of the axes. The coefficlients of the Model and the resultant contour maps can be readily determined for any-of the aforementioned variations using the designed set of experiments as described above.
The concentration of silver in the finished catalyst may vary from about 2 to 20 weight percent, the preferred range being from about 6% to about 16%
by weight of silver. Lo~-er silver concentrations are preferred from an economic standpoint. However, the optimum silver concentration for any particular catalyst will be dependent upon economic factors as well as per-formance characteristics, such as, catalyst efficiency, rate of catalyst aging and reaction temperature.
A variety of procedures may be employed for preparing catalysts containing combinations of cesium and one or more other alkali metals (excluding francium) ~ ~ 6~181 in accordance with the present invention. In accordance with a further aspect of this invention, which constitutes a preferred catalyst preparation procedure, there is provided a process for preparing a supported silver cata-lyst for the commercial operation for the production of ethylene oxide by the vapor phase oxidation of ethylene with oxygen or an oxygen-containing gas in gaseous ad-mixture with diluent and inhibitor in a fixed bed tubular reactor, comprising: (1) impregnating a macroporous catalyst having a surface area less than 10 m2/g and in a form and size for use in a reactor used in the commercial operation with a solution comprising a solvent or solubilizing agent, silver salt sufficient to deposit the desired amount of silver on the support of 2 to 20 weight percent silver, and salts of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, sufficient to deposit respective amounts of (a) and (b) on the support such that the efficiency of ethylene oxide manufacture in the commercial operation using the finished catalyst is increased to a value greater than the effic-iencies obtainable under common conditions from respective catalysts which are the same as the catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a) and the other contains the respective amount of (b); and (2) treating the impregna-ted support to convert at least a fraction of the silver salt to silver metal and effect deposition of silver, (a) and (b), respectively, on surfaces of the support.
Silver and alkali metal deposition are generally accomplished by heating the carrier at elevated tempera-.,~ .,:i1 ~ 1 621~1 tures to evaporate the liquid within the support and effect deposition of the silver and alkali metal onto the interior and exterior carrier surfaces. Alternatively, a coating of silver and alkali metals may be formed on the carrier from an emulsion or slurry containing the same followed by heating the carrier as described above.
Impregnation of the carrier is generally the preferred technique for silver deposition because it utilizes silver more efficiently than coating procedures, the latter being generally unable to effect substantial silver depo-sition into the interior surfaces of the carrier. In addition, coated catalysts 1 1 621~1 12,439-1 are more susceptible to silver loss by mechanical abrasion.
The sequence of impregnating or depositing the surfaces of the carrier with silver and alkali metals is optional. Thus, impregnation and deposition~of silver and alkali metals may be effected coincidentally or se-quentially, i.e., the alkali metals may be deposited prior to, during, or subsequent to silver addition to the carrier.
The alkali metals may be deposited together or sequentially.
For example, cesium may be deposited first followed by the coincidental or sequential deposition of silver and the other alkali metal(s), or such other alkali metal(s) may be deposited first followed by coincidental or se-quential deposition of silver and cesium.
Impregnation of the catalyst carrier is effected using one or more solutions containing silver and alkali metal compounds in accordance with well-known procedures for coincidental or sequential depositions. For coinci-dental deposition, following impregnation the impregnated carrier is heat or chemically treated ~o reduce the silver compound to silver metal and deposit the alkali metals onto the catalyst surfaces. For sequential deposition, the carrier is initially impregnated with silver or alkali metal (depending upon the sequence employed) and then heat or chem cally treated as described above. This is followed by a second impregnation step and a correspond-ing heat or chemical treatment to produce the finished catalyst -ontaining silver and alkali metals.
The silver solution used to impregnate the carrier is comprised of a silver salt or compound in a 1 ~ ~21~1 12,439-1 solvent or complexing/solubilizing agent such as the silver solutions disclosed in the art. The particular silver salt employed is not critical and may be chosen, for e~ample, from among silver nitrate, silver oxide or silver carboxylates, such as, silver acetate, oxalate, citrate, phthalate, lactate, propionate, butyrate and higher fatty acid salts.
A wide variety of solvents or complexing/
solubilizing agents may be employed to solubilize silver to the desired concentration in the impregnating medium.
Among those disclosed in the art as being s~itable for this purpose are lactic acid (U. S. Patent Nos.
2,477,435 to Aries; and 3,501,417 to DeMaio); ammonia ~ U. S. Patent 2,463,228 to West et al); alcohols, such as ethylene glycol (U. S. Patent Nos. 2,825,701 to Endler et al; and 3,563,914 to Wattimena); and amines and aqueous mixtures of amines (U. S. Patent Nos. 2,459,896 to Schwarz; 3,563,914 to Wattimena; 3,702,259 to Nielsen;
and 4,097,414 to Cavitt).
Suitable alkali metal salts include all those soluble in the particular solvent or solubilizing agent employed. Accordingly, inorganic and organic salts of alkali metals, such as, nitrates, halides, hydroxides, sulfates and carboxylates may be used. When coincidentally deposited with silver, the alkali metal salt employed is preferably one which does not react with silver salt in solution in order to avoid premature silver precipitation from same. Thus, ~or example, alkali metal halides are preferably not used in lactic acid solution because they react with silver ions present therein.
Following impregnation of the catalyst carrier with silver and alkali metal salts, the impregnated carrier particles are separated from any remaining non-absorbed solution or slurry. This is conveniently accomplished by draining the excess impregnating medium or alternatively by using separation techniques, such as, filtration or centri~ugation. The impregnated carrier is then generally heat treated (e.g., roasted)to effect decomposition and reduction of the silver metal salt to metallic silver and the deposition of alkali metal ion. Such roasting may be carried out at a temperature of from about 100C
to 900C, preferably from 200 to 700C, for a period of time sufficient to convert substantially all of the silver salt to silver metal. In general, the higher the temperature, the shorter the required reduction period.
For example, at a temperature of from about 400C to 900C, reduction may be accomplished in about 1 to 5 minutes. Although a wide range of heating periods have been suggested in the art to thermally treat the impreg-nated support, (e.g., U.S. Patent 3,563,914 suggests heating for less than 300 seconds to dry but not roast reduce the catalyst; U.S. Patent 3,702,259 discloses heating from 2 to 8 hours at a temperature of from 100 to 375C to reduce the silver salt in the catalyst; and U.S. Patent 3,962,136 suggests ~ to 8 hours for the same temperature range) it is only important that the reduction time be correlated with temperature such that substantially complete reduction of the silver salt to metal is accom-plished. A continuous or step-wise heating program may be used for this purpose.
12,439-1 Heat treatment is preferably carried out in air, but a nitrogen or carbon dioxide atmosphere may also be employed. The equipment used for such heat treatment may use a static or flowing atmosphere of such gases to effect reduction.
The particle size of silver metal deposited upon the carrier is a function of the catalyst prepara-tion procedure employed. Thus, the particular choice of solvent and/or comple~ing agent, silver salt, heat treat-ment conditions and catalyst carrier may affect, to vary-ing degrees, the size of the resulting silver particle.
For carriers of general interest for the production of ethylene oxide, a distribution of silver particle sizes in the range of .05 to 2.0 microns is typically obtained.
However, the role of particle size of the silver catalyst upon the effectiveness of the catalyst in making ethylene oxide is not clearly understood. In view of the fact that the silver particles are known to migrate on the surface of the catalyst when used in the cat.alytic reaction re-sulting in a marked change in their size and shape, silverparticle size may not be a significant factor in affecting catalytic performance.
CARRIER SELECTION
The catalyst carrier employed in practicing the invention may be selP,cted from conventional, porous, refractory materials which are essentially inert to ethylene, ethylene oxide and other reactants and products at reaction conditions. These materials are generally labelled as "macroporous" and consist of porous materials 12,439-1 having surface areas less than 10 m2/g (square meters per gm of carrier) and preferably less than 1 m2/g. The surface area is measured by the conventional B.E.T. method described by Brunauer, S., Emmet, P., and Teller, E., in J. Am. Chem. Soc. Vol. 60, pp309-16, (1938). They are further characterized by pore -~olumes ranging from about 0.15 - 0.8 cc/g, preferably from about 0.2 - 0.6 cc/g.
Pore volumes may be measured by conventional mercury porosimetry or water absorption techniques. Median pore diameters for the above-descr;.bed carriers range from about 0.01 to lO0 microns, a more preferred range being from about 0.5 to 50 mi_rons.
The carrier should preferably not contain ions which are exchangeable with the alkali metals supplied to the catalyst, either in the preparation or use of the catalyst, so as to upset the amount of alkali metal which provides the desired synergism. If the carrier contains such ion, the ion should be removed by standard chemical techniques such as leaching. Moreover, if the carrier contains an amount of alkali metal, which is transferable to the silver whereby the synergistic combination is upset, then the carrier should be treated to remove such excess alkali metal or the amount of alkali metal supplied to the catalyst should be less than the synergistic amount, allowing the transferred alkali metal to effect the desired synergistic amounts.
The chemical composition of the carrier is not narrowly critical. Carriers may be composed, for example, of alpha-a~umina, silicon carbide, silicon dioxide, zirconia, magnesia and various clays. In general, ~ 1 S~
alpha-alumina based materials are preferred. These alpha-alumina based materials may be of very high purity, i.e., 98 + wt.% alpha-alumina, the remaining components being silica, alkali metal oxides (e.g., sodium oxide) and trace amounts of other metal and non-metal impurities;
or they may be of lower purity, i.e., about 80 wt.% alpha-alumina, the balance being a mixture of silicon dioxide, various alkali oxides, alkaline earth oxides, iron oxide, and other metal and non-metal oxides. The lower purity carriers are formulated so as 'o be inert under catalyst preparation and reaction conditions. A wide variety of such carriers are commercially available. The carriers may be in the form of pellets, extruded particles, spheres, rings and the like. The si~ze of the carriers may vary from about l/16" to ~". The carrier size is chosen to be consistent with the type of reactor employed. In general, for fixed bed reactor applications, sizes in the range of 1/8" to 3/8" have been found to be most suitable in the typical tubular reactor used in commercial operations.
The silver catalysts of the invention are par-ticularly suitable for use in the production of ethylene oxide by the vapor phase oxidation of ethylene with molec-ular oxygen. In accordance with another aspect of the present invention, there is provided in the continuous process for the production of ethylene oxide in a com-mercial operation wherein ethylene and oxygen provided as oxygen or as an oxygen-containing gas are reacted in vapor phase admixture with diluent and inhibitor at a temperature of from about 200C to 300C in the presence of a supported silver catalyst in a fixed bed tubular . ' , .
~6~181 reactor to form ethylene oxide, the improvement which comprises employing a supported silver catalyst which catalyst has a macroporous support having a surface area less than lO m2~g and is in a form and size for use in a reactor used in the commercial operation and which catalyst contains 2 to 20 weight percent silver a combina-tion of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, which combination comprises (a) and (b) in amounts in relation to the amount of silver therein sufficient to increase the efficiency of ethylene oxide manufacture in the commercial operation to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as the catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount of (b).
The reaction conditions for carrying out the vapor phase oxidation reaction to produce ethylene oxide are well-known and extensively described in the prior art. This applies to reaction conditions, such as, tempera-ture, pressure, residence time, concentration of reactants, diluents (e.g., nitrogen, methane and CO2), inhibitors (e.g., ethylene dichloride) and the like. In addition, the desirability of recycling unreacted feed, or employing a single-pass system, or using successive reactions to increase ethylene conversion by employing reactors in series arrangement can be readily determined by those skilled in the art. The particular mode of operation selected will usually be dictated by process economics.
Generally, the process is carried out by con-~ ~ 6~181 tinuously introducing a feed stream containing ethylene and oxygen to a catalyst-containing reactor at a tempera-ture of from about 200 to 300C, and a pressure which may vary from one atmosphere to about 30 atmospheres depending upon the mass velocity and productivity desired.
Residence times in large-scale reactors are generally on the order of about 1-5 seconds. Oxygen may be supplied to the reaction in an oxygen~containing stream, such as, air or as commercial oxygen. The resulting ethylene oxide is separated and recovered from the reaction pro-ducts using conventional methods.
The invention is illustrated further by the catalyst comparisons which are now discussed in relation to Tables II to VI and the experimental results set forth therein.
The catalysts cited in the Tables below were all evaluated for comparison purposes under standard test conditions using backmixed, bottom-agitated "Magne-drive" autoclaves as described in Figure 2 of the paper by J.M. Berty entitled "Reactor for Vapor Phase Catalytic Studies", in Chemical Engineering Progress, Vol. 70, No. 5, ; ~
,~,,, d ~6~1Bl 12,439-1 pages 78-84, lg74. The reactor was operated at 1.0 mole % ethylene oxide in the outlet gas under the following standard inlet conditions:
Component Mole %
Oxygen 6.0 Ethylene 8.0 Ethane 0.50 Carbon Dioxide 6.5 Nitrogen Balance of Gas Parts per million Ethylene Chloride = 7.5 The pressure was maintained constant at 275 psig and the total outlet flow maintained at 22.6 SCFH.(l) The outlet ethylene oxide concentration was maintained at 1.0% by adjusting the reaction temperature. Thus, temperature (C) and catalyst efficiency are obtained as the responses describing the catalyst performance.
A typical catalvst test procedure is comprised of the following steps:
1. 80 cc of catalyst is charged to a backmixed autoclave The volur,le of catalyst is measured in a 1"
I.D. graduated cylinder after tapping the cylinder several times to thoroughly pack the catalyst. The weight of the catalyst is noted.
2. The backmixed autoclave is heated to about reaction temperature in a nitrogen flow of 20 SCFH with the fan operating at 1500 rpm. The nitrogen flow is then discontinued and the above-described feed stream is introduced into the reactor. The total gas outlet -(1~ SCFH refers to cubic feet per hour at standard temper-ature and pressure, namely, 0C and one atmosphere.
~ ~ 6;~181 12,439-1 flow is adjusted to 22.6 SCFH. The temperature is adjusted over the next few hours so that the ethylene oxide concentration in the outlet gas is approximately 1.0%
3. The outlet oxide concentration is monitored over the next 4-6 days to make certain that the catalyst has reached its peak steady state performance. The temperature is periodically adjusted to achieve 1%
outlet oxide. The selectivity of the catalyst to ethylene oxide and the temperature are thus obtained.
The standard deviation of a single test result reporting catalyst efficiency in accordance with the procedure described above is 0.7% efficiency units.
Tables II through VI below summarize test re-sults obtained with silver catalysts in the absence of additives and those containing cesium in combination with one or more alkali metals selected from among lithium, sodium, potassium and rubidium. Tests were carried out using a variety of catalyst carriers and different 2Q preparation procedures. Catalysts which were prepared by the same method of preparation on a similar ca-;rier are identified in the Tables by a common number TABLE II
B PERIMENT Wt.~g Wt.%Cs Wt.%X ~EFF** TEMP.(CC) 1 A 11.14 0.00479 0.0000 71.7 256 1 B 11.14 0.00477 0.00158 73.9 256 1 C 10.8g 0.00461 0.00450 75.4 256 1 D 10.41 0.0000 0.0000 68.4 265 1 E 10.80 0.0000 0.00613 69.9 261 1 F 10.93 0.0000 0.0123 73.3 264 1 G 10.90 0.0000 0.0210 66.6 299 1 H 11.04 0.00941 0.0000 75.6 256 1 I 11.06 0.00941 0.00313 76.9 258 1 J 10.92 0.0186 0.0000 73.1 283 1 K 11.16 0.0191 0.00633 72.0 293 1 L 8.04 0.004 0.008 76.0 269.3 1 M 7.84 -- 0.0078 75.0 263.8 1 N 8.28 0.0041 -- 73.8 258.3 1 O 8.07 -- __ 67.3 260.0 1 P 14.97 -- -- 66.7 252.9 1 Q 15.19 0.00405 -- 72.6 252.0 1 R 14.80 -- 0.0079 75~5 255.5 1 S 15.10 0.004 0.0081 77.9 256.6 2 A 17.4 0.000 0.093 73.5 278 2 B 16.6 0.0044 0.088 74.7 279 2 C 16.5 0.0085 0.089 74.2 278 2 D 17.3 0.000 0.000 ~8-67* 284-299 2 E 17.0 0.0044 0.0016 70.8 276 2 F 15.7 0.0044 0.069 74.1 280 2 G 16.5 0.0092 0.0028 72.2 275 2 H 16.5 0.0092 0.088 73.2 287 * Due to rapid deactivation of this catalyst, initial and final perform~nces, respectively, are given.
**"EFF" is the abbreviation for efficiency as previously defined.
12,439-l Experiments lB and lC demonstrate the synergism achieved with silver catalysts containing mixtures of cesium and potassium in accordance with the invention relative to the "cesium only" catalyst of lA which con-tained essentially the same concentratlon of silver and cesium but contained no potassium. As used herein, the term "cesium only" refers to a catalyst wherein cesium is the only alkali metal deposited upon the carrier. The terms "potassium only", "lithium only", and "sodium only" are correspondingly defined for the respective catalysts. Thus, the efficiency achieved with combination of alkali metals in experiment lB was about 2% higher than that achieved with the corresponding cesium only catalyst of experiment lA. The further addition of K from a level of .00158%
(Example lB) to a level of 0.~045% K (experiment lC) while maintaining Ag and Cs essentially constant provided an even greater improvement in efficiency relative to lA, namely, about 3.7%. The catalyst of experiment lD con-tained no cesium or potassium and provided a relatively low 68.4% efficiency. Experiments lE, F, and G demon-strate that "potassium only" catalysts which con-tained essentially the same amount of silver as catal-ysts lB and lC achieved a selectivity no higher than 73.3%, significantly below that achieved with the catalysts of lB and lC containing mixtures of cesium and potassium. It should also be noted that in addition to providing higher efficiency, the catalysts of the invention (lB and lC) operated at lower tempe~atures than the potassium only catalysts (lE, lF and lG), thus indicating higher catalyst activity. Although the cesium only catalyst (lA) operated at the same low temperature as catalysts lB and lC, it provided a sub-stantially lower efficiency.
- ~5 -12,439-1 The catalyst of experiment lH was a cesium only catalys~ containing Cs at a level nearly double that of catalysts lA, B and C. The addition of .0031%
potassium to a catalyst of such composition produced an efficiency improvement of greater than 1% as shown in Example 1.
Experiments lJ and lK are illustrative of a non-synergistic combination of Cs and K. Thus, the addition of K to the cesium only catalyst of lJ contain-ing about 11% Ag and a relatively high Cs concentration of0.0186% resulted in a catalyst (lK) having a lower efficiency and higher operating temperature. That is to say, the combination of K and Cs in experiment lK did not produce a synergistic result. Consequently, such cesium-potassium mixture is not in accord with the present invention.
Experiments lL through 10 demonstrate the synergism of the present invention for catalysts con-taining approximately 8% silver. The efficiency of catalyst lL which contained a synergistic combination of cesium and potassium was 1% higher than the potassium only catalyst of lM, and more than 2% higher than the efficiency of the cesium only catalyst of lN. Silver catalyst lO which contained no cesium or potassium achieved an efficiency nearly 9% below that of catalyst lL.
Experiments lP through lS demonstrate the synergism of the present invention for catalyst con-taining approximately 15% silver. The efficiency of catalyst lS which contained a synergistic mixture of 1 16~181 12,439~1 cesium and potassium was ~ore than 5% higher than the cesium only catalyst of lQ which contained the respective amount of cesium in such mixture, and about 2.5% higher than the potassium only catalyst of lR which contained ~he respective amount of potassium in s~ch mixture. Catalyst lP which contained no additives achieved an efficiency about 11% lower than catalyst lS.
Experiments 2B and 2C demonstrate the efficiencies achieved with potassium-cesium mixtures for a catalyst containing about 17% silver compared to the potassium only catalyst of experiment 2A. The addition of .0044%
cesium in experiment 2B resulted in an improved effi-ciency of 74.7% compared to the 73.5% efficiency achieved in experiment 2A. The silver catalyst of 2D which had no alkali metal deposited on the carrier is provided in the Table for comparative purposes.
A comparison of experiments 2E and 2F show that when the K concentration was increased from .0016% to .06~% while maintaining the Cs level constant, a greater than 3% improvement in efficiency was achieved. Li~e-wise, a comparison of experiments 2G and 2H demonstrates that when the potassium concentration was increased while maintaining the silver and cesium levels constant, a 1% improvement in efficiency resulted.
Three catalysts containing 7% Ag were prepared containing the optimum cesium concentration as determined from the Efficiency Model, supra, obtained from a designed set of experiments. The catalysts (experiments 3A, B and C) ~ 1 621~1 12,439-1 all contained about 7.0 w~. % silver and 0.00906 wt. %
cesium, with no potassium being present. To demonstrate the operation of the Efficiency Model, three additional catalysts were prepared (experiments 3D, E and F), each containing about 7.0% silver, 0 00906% cesium and 0.004%
potassium. The difference in the performance of the cesium/
potassium catalysts relative to the cesium only catalysts was predicted from the Efficiency Model ~o be about 0.6%
efficiency units. As noted below in Table III, the actual observed difference in performance was found to be 0.7%, which is regarded to reflect agreement with the prediction of the Efficiency Model. Experiment 3G provides the effi-ciency of a potassium only catalyst containing silver and potassium at the same concentration as the catalysts of experiments 3D, E and F, thus demonstrating the synergism achieved with the cesium-potassium combination.
12,439-1 TABLE III
Cesium Only Catalysts: 7.0~/O A~, 0.00906% Cs Experiment /O Eff. T, C
3A 75.4 263.9 3B 75.7 ~ 261.4 3C 75.4 266.1 Average: 75.5 + 0.17-'~
Cesium Plus Potassium Catalysts: 7.0% Ag, 0.00906% Cs, 0.004% K
3D 76.0 271.4 3E 76.1 271.5 3F 76.4 270.9 Average: 76.2 + 0.21*
Potassium Only Catalyst: 7.0% A~, 0.0040% K
3G 72.8 265.3 * Values reflect standard deviations.
Table IV below demonstrates the synergism achieved with a combination of cesium and lithium (experiment 4C) relative to the corresponding cesium only catalyst of experiment 4A and the corresponding lithium only catalyst of experiment 4B. Thus, the catalyst of 4C
was about 10% more efficient than the lithium only catalyst of 4B and about 3.5% more efficient than the cesium only catalyst of 4A.
Exper,ment 4D demonstrates that when the lithium concentration of catalyst 4C was increased about ten-fold, ~,9 _ 12,439-1 the resulting efficiency was reduced by more than 3%.
However, a comparison of catalysts 4D and 4E discloses that the efficiency obtained with catalyst 4D was increased by increasing the cesium concentration from 0~0053% to 0.0300%. It should be noted .hat the cesium only catalyst of experiment 4G (corresponding to the cesium concentration of 4E~ was inactive; that is, at that concentration of cesium, no ethylene oxide was produced. Yet, the com-bination of this concentration of cesium with 0.0300%
lithium resulted in a very active catalyst (4E).
Similarly, the lithium only catalyst of 4F (corresponding to the lithium concentration of 4E) provided a relatively low efficiency of 65.4%. Thus, the synergism achieved in catalyst 4E is underscored by the sharp contrast of its efficiency relative to the poor results achieved with catalysts 4F and 4G.
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12,439-1 -Table V below demonstrates the synergism achieved with the catalyst of experiment SC relatlve to the corresponding cesium only catalyst of experiment 5A
and the corresponding sodium only catalyst of experiment 5B. Thus, the catalyst of 5C was 6% more e~ficient than the cesium only catalyst of 5A and 7.2V~ more efficient than the sodium only catalyst of 5B. Experiment 5D discloses that increasing the sodium concentration ten-fold relative to the concentration in catalyst 5C
had the effect of lowering the catalyst efficiency.
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x 1 ~ ~21# 1 12,439-1 Table VI below demonstrates the synergism achieved with a catalyst containing silver and cesium in combination with potassium, sodiu~ and lithium as indicated in experiment 6A. The presence of chloride ion in the catalyst concentrations of 6A, B and C
indicates that at least a portion of the alkali metal salts used in the catalyst preparation procedure were in the form of chlorides. The efficiency achieved with the synergistic combination of experir,~ent 6A was about 1.2% greater than the efficiency of the corresponding cesium only catalyst of 6C and about 9% greater than the corres?onding combination of potassiu~, sodium and lithium of catalyst 6B.
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~ ~6~181 12,439-l The catalysts of the invention can be prepared with a variety of carriers and preparation procedures.
The defined synergism obtainable with combinations of cesium with the other alkali metals is not restricted, for example, to a particular type or chemical composition of catalyst carrier, to a particular sequence of silver and alkali metal deposition, or to a special class of solvents or solubilizing agents used in the preparation procedure.
In the following examples detailed procedures are provided as illustrative of methods and carriers which are useful for preparing catalysts according to the invention. These examples are by way of illustra-tion only, and are not to be construed as limiting the scope of the invention described herein.
A catalyst containing 11.14 wt.% Ag, .00477 wt.~ Cs and .00158 wt.~ K was prepared as hereinafter described on an alpha-alumina carrier "A" having the following chemical composition and physical properties:
Chemical Composition of Carrier "A"
Alpha~Alumina 98.5 wt.%
Silicon Dioxide 0.74 wt.%
Calcium Oxide0.22 wt.%
Sodium Oxide0.16 wt.%
Ferric Oxide0.14 wt.%
Potassium Oxide 0.04 wt.%
Magnesium Oxide 0.03 wt.%
Physical Properties of Carrier "A"
Surface Area (1) ~ 0.3 m~/g Pore Volume (2) ~~ 0.50 cc/g ~or water absorption) Packing Density (3) 0.70 g/ml Median Pore Diameter (4) 21 microns Pore Size Distr~b~tion, % Total Pore Volume (4) Pore Size, Microns % TPV
0.1 - 1.0 1.5 1.0 - 10.0 38.5 10.0 - 30.0 20.0 30 - 100 32.0 > 100 8.0 (1) Method of measurement described in "Adsorption, Surface Area and Porosity", S.J. Gregg and X.S.W. Sing, Academic Press (1967), pages 316-321.
(2) Method of Measurement as described in ASTM C20-46.
(3) Calculated value based on conventional measurement of the weight of the carrier in a known volume container.
(4) Method of measurement described in "Application of Mercury Penetration to Materials Analysis", C.Orr Jr., Powder Technology, Vol. 3, pp. 117-123 (1970).
~~3 The carrier "A" was impregnated under vacuum as hereinafter described with a solution of silver salts and alkali me~tals. The impregnating solution was prepared at a concentration such that the finished catalyst contained the desired amounts of silver, cesium and potassium.
The required concentration of silver, cesium and potassium in solution for the given carrier is calculated from the packing density (grams/cc) and pore volume of the carrier which are either known or readily determined.
Assuming that all of the silver in the impregnating solu-tion contained in the pores of the carrier is deposited upon the carrier, approximately 21 wt.% silver in solution is necessary to prepare a catalyst containing about 11 wt.% silver on the catalyst. The required concentration of alkali metal in solution is obtained by dividing the solution silver concentration by the ratio of silver to cesium or potassium desired in the finished catalyst.
Thus, to obtain 11.0 wt.% Ag and .0047 wt.% Cs, the ratio is approximately `2330 and the required cesium concentra-tion in solution is .009 wt.%. In like manner, thesolution concentration of potassium was calculated to be .003 wt.%. The solution containing the desired concen-trations of silver and alkali metals was prepared as described below:
Impregnating Solution Preparation 80.16 gms of ethylenediamine (high purity grade) was mixed with 176 g of distilled water. 60.06 gms of anhydrous oxalic acid (reagent grade) was then added slowly to the solution at ambient temperature (23C) while continuous3y stirring. During this addition of oxalic acid, the solution temperature rose to about ?, :1 62181 40C due to the reaction exotherm. 147.25 gms of silver oxide powder (Handy and Harmon, 850 Third Avenue, New York, N.Y. 10022) was then added to the diamine-oxalic acid-water solution. Finally, 29.30 gms of monoethanolamine, 13.26 gms of aqueous Cs solution as hydroxide (.00444 g Cs/ml soln, or 0.0589 g Cs), 34.28 gms of aqueous K
solution as carbonate (.0005669 K/ml soln, or .0194 gms K) and 120.6 gms of distilled water were added to complete the solution. The solution was filtered and 0.9 grams of undissolved silver was recovered. The specific gravity of the resulting solution was about 1.328 g/ml.
Catalyst Preparation 125 g of Carrier "A" was impregnated in a 12"
long x 2" I.D. glass cylindrical vessel equipped with a side arm and suit~ble stopcocks for impregnating the carrier under va~uum. A 500 ml separatory funnel for containing the impregnating solution was inserted through a rubber stopper into the top of the impregnating vessel.
The impregnating vessel containing the carrier was evacu-ated to approximately 2 inches of mercury pressure for about 20 minutes after which the impregnating solution was slowly added to the carrier by opening the stopcock between the separatory funnel and the impregnating vessel until the carrier was completely immersed in solution, the pressure within the vessel being maintained at approx-imately 2 inches of mercury. Following addition ~f the solution, the vessel was opened to the atmosphere to attain atmospheric pressure, the carrier then remaining immersed in the impregnating solution at ambient conditions for about 1 hour, and thereafter drained of excess solu-tion for about 30 minutes. The impregnated carrier was ~J6~181 then heat treated as follows to effect reduction of silver salt and deposition of cesium and potassium ions on the catalyst surface. The impregnated carrier was spread out in a single layer on a 2-5/8" wide endless stainless steel belt (spiral weave) and transported through a 2"
x 2" square heating zone for 2.5 minutes, the heating zone being maintained at 500C by passing hot air upward th~ough the belt and about the catalyst particles at the rate of 266 SCFH. The hot air was generated by passing it through a 5 f~. long x 2" I.D. stainless steel pipe which was externally heated by an electric furnace (Lind-bergTM tubular furnace: 2-~" I.D., 3 feet long heating zone) capable of delivering 5400 watts. The heated air in the pipe was discharged from a square 2" x 2" discharge port located immediately beneath the moving belt carrying the catalyst carrier. After being roasted in the heating zone, the finished catalyst was weighed, and based upon the weight gain of the carrier, and the known ratios of silver to cesium and potassium in the impregnating solution, it was calculated to contain 11.14 wt.% of silver, 0.00477 wt.~ cesium and .00158 wt.% potassium.
By chemical analysis, described below, this catalyst was found to contain 10.88% Ag, in close agreement with the calculated value.
The analysis for silver was carried out by the following method: An approximately 50 g sample of catalyst was powdered in a mill and 10 g of the powdered sample weighed to the nearest 0.1 mg. The silver (and cesium, etc.) in the catalyst sample was dissolved in hot (80C) 50%, by volume, nitric acid solution. The insoluble alumina particles were filtered and washed with distilled f 7l 1 1 6~
water to remove all a &ering nitrate salts of Ag, Cs, etc. This solution was made up to 250 ml in a volumetric flask using distilled water. A 25 ml aliquot of this solution was titrated according to standard procedures using a 0.1 Normal solution of ammonium th~xyanate and ferric nitrate as indicator. The amount of Ag so determined in 250 ml solution was then used to calculate the weight percent silver in the catalyst sample.
Silver and alkali metal concentrations for all catalysts described in the specification are calculated values as described above.
Example 2 A catalyst containing 16.6 wt.% Ag, 0.0044 wt.%
Cs and 0.088 wt.% K was prepared as hereinafter described on a carrier "B" having the following characteristics:
Chemical Composition of Carr_er "B"
Alpha-Alumina 86.0 wt.%
Silicon Dioxide 11.8 wt.%
Calcium Oxide 0.24 wt.%
Sodium Oxide 0.69 wt.%
Ferr~ic Oxide 0.30 wt.%
Potassium Oxide 0.54 wt.%
Titanium Dioxide 0.34 wt.%
Physical Properties of Carrier "B"
Surface Area (1) 0.10 m2/g Pore Volume (2) 0.40 cc/g (or water absorption) Packing Density (3) 0.72 g/ml Median Pore Diameter (4) 22 microns , . , ~ .
, ...
~62181 Pore Size D istribution (4) Pore Size, microns % Total Pore Volume 0.1 - 1.0 0.0 1.0 - 10.0 12 10.0 - 30 55 > 1.00 0.0 (1) Method of measurement described in "Adsorption, Surface Area and Porosity", S.J. Gregg and K.S.W. Sing, Academic Press (1967), pages 316-321.
(2) Method of Measurement as described in ASTM C20-46.
(3) Calculated value based on conventional measurement of the weight of the carrier in a known volume container.
(4) Method of measurement described in "Application of Mercury Penetration to Materials Analysis", C.Orr Jr., Powder Technology, Vol. 3, pp. 117-123 (1970).
The preparation procedure consisted of the following steps:
li) 333.5 g of lactic acid (88% in water) was heated to about 75C and 1.44 g K2CO3 and 4.86 g of aqueous CsOH solution (containing .008 g/ml or .039 g Cs) added to the heated lactic acid, while stirring the solution.
(ii) 163.75 g Ag2O (Metz Metallurgical Corp., 3900 So. Clinton Ave., So. Plainfield, N.J.
07080) was incrementally added to the heated lactic acid with stirring so that the heat genera-ted from the exothermic reaction of Ag2O with lactic acid did not exceed about 85C. Most Ag2O and/or silver was left suspended in solution.
This suspension was dark brownlsh grey in colour.
(iii) Hydrogen peroxide (3.3 ml.) was incrementally added to the above Ag2O lactic acid solution while rapidly stirring to assist complete l 1 ~2181 dissolution of the suspended matter. A clear yellow solution was obtained, the solution temper-ature belng about 80C. (Small amounts of lactic acid or water were added to make up for any evaporation losses). This solution contained about 30.4% silver, 0.12~ K and .0078% Cs.
(iv) 189 grams of carrier "B" was evacuated and impregnated with the solution prepared in ~iii) while it was at its elevated temperature of aout 80C. The method of impregnating the carrier was as described in Example 1 with an additional step being that the cylindrical impregnating vessel containing the carrier was surrounded by a heating jacket which maintained the carrier temperature at about 80C during the impregnation procedure to insure that silver lactate remained in solution.
(v) The impregnated carrier of (iv) was heat treated at 400C for four minutes using the apparatus and general method described in Example 1.
Example 3 A catalyst containing 13.4 wt.% Ag, 0.0091 wt.~
Cs and 0.0027 wt.% K was prepared by the following procedure on Carrier "A" (described in Example 1).
Impregnating Solution Preparation 78.6 grams of triethylenetetramine (high purity grade) was mixed with 80 g of distilled water. 51.57 grams of oxalic acid dihydrate (reagent grade) was then added slowly to the continuously stirred amine solution.
During this addition, the temperature of the solution ~' increased to 60C due to the reaction exotherm. 5.83 g of aqueous cesium hydroxide solution (0.009728 g Cs/g solution) and 4.46 g of aqueous potassium carbonate solution (0.00369 of K/g solution) were then added to the solution followed by the addition of 89.26 g of silver oxide (Metz Metallurgical Corp.). Finally 15.28 g of monoethanolamine was added to the solution along with additional distilled water to produce a total solution volume of 250 nl. The solution was filtered and about 5 g of undissolved silver was recovered.
Catalyst Preparation 150 g of Carrier "A" was evacuated at room temperature and impregnated with the above-described impregnation solution in accordance with the procedure of Example 1. Following impregnation, heat treatment of the carrier was carried out at 500C for 2.5 minutes using the apparatus and method described in Example 1.
The composition of the finished catalyst, calcu~
lated from the weight gain of the carrier, was as stated ~o abo~e.
Example 4 A catalyst containing 13.04 wt.% Ag, 0.0089 wt.% Cs and 0.0026 wt.% K was prepared by the following procedure on Carrier "A" (described in Example 1).
Impregnating Solution Preparation 114.25 gams of aminoethylethanolamine (high purity grade) was mixed with 80 g of distilled water.
50.42 grams of oxalic acid dihydrate (reagent grade) was then slowly added to the continuously stirred amine solution~ the solution temperature rising to about 60C
due to the reaction exotherm. 5.84 g of aqueous cesium .
~ 1 62181 hydroxide solution (0.009723 g Cs/g solution) and 4.52 g of aqueous potassium carbonate solution (0.00369 g K/g solution) were then added to the solution followed by the addition of 89 g of silver oxide (Metz Metallurgical Corp.). Additional distilled water was then added to the solution to produce a total volume of 250 ml.
Catalyst Preparation 150 :g of Carrier "A" was evacuated and impreg-nated with the above-described solution in accordance with the procedure of Example 1. Heat treatment of the impregnated carrier was then carried out at 500C for 2.5 minutes using the apparatus and method as described in Example 1.
~ ~ B2~
12,439-1 Example 5 A catalyst having nominally the same composition as the catalyst of Example 1 (specifically, 11.1 wt. % ~g, 0.0048 wt. % Cs and 0.0016 wt. % K) was prepared as described in Example 1 except that the preparation of the impregnating solution was carried out using aq~eous solu-tions of cesium chloride and potassium chloride instead of cesium hydroxide and potassium carbonate, respectively.
Upon addition of such chloride salts to the silver-con-taining impregnating solution, the solution remained clear,i.e., no precipitation of silver chloride was observed.
Example 6 A catalyst having nominally the same composition as the catalyst of Example 1 except for the substitution of lithium for potassium (specifically 11.0 wt. %
Ag, 0.0047 wt. % Cs and 0.003 wt. % Li) was prepared as describèd in Example 1, the solution concentration of lithium being calculated to be 0.00573 wt. %. Accordingly, the preparation procedure of Example 1 was followed except that instead of adding potassium carbonate solution to the impregnating solution, 34 grams of an aqueous lithium solution as carbonate (0.001094 g lithium/ml, or 0.0372 g lithium) were added.
Example 7 A catalyst having nominally the same composition as the catalyst of Example 1 except for the substitution of sodium for potassium (specifically 11.0 wt. %
Ag, 0.0047 wt. % Cs and 0.01 wt. % sodium) was prepared in accordance with the procedure of Example 1, the solution concentration of sodium being calculated to be 0.0191 wt. %.
Thus, the procedure of Example 1 was followed except that ~6~
12,439-1 instead of adding potassium carbonate to the impregnating solution, 34 grams of an aqueous sodium solution as carbonate (0 00365 g sodium/ ml, or 0.12415 gram sodium) were added.
Example 8 A catalyst containing 12.59 wt. % Ag, 0.0088 wt.
/. Cs and 0.0025 wt. % K was prep~red on Carrier "A"
(described in Example 1) by a sequential impregnation method whereby potassi~m and cesium were deposited upon the carrier prior to the deposition of silver, as follows:
146.1 grams of Carrier "A" was impregnated with 250 ~1 of an aqueous solution containing 0.05696 g of cesiu~ as hydroxide and 0.1674 g of potassium as carbonate follow-ing the general method of impregnation described in Exa~ple 1. The impregnated carrier was then heat treaeed at 400C for 2.5 minutes in accordance with the procedure of Example 1 to deposit cesium and potassium ions on the carrier surface. Following this heat treatment, the carrier was impregnated with the silver-containing im-pregnating solution as described below:
Preparation of Silver-Containing ImPre~natin~ Solution 48.9 grams of ethylenediamine (high purity grade) was mixed with 80 cc of distilled water. 50.6g of oxalic acid dihydrate (reagent grade) was then added slowly to the solution over a period of one hour while conti-nuo~sly 6tirring. During this addition of oxalic acid, ~ ~ 62181 12,439-1 the solution temperature rose to about 40C due to the reaction exotherm. 89.34 grams of silver oxide powder (Metz Metallurgical Corp.) was then added to the diamine-oxalic acid-water solution. Finally, 17.84~grams of monoethanolamine was added to the solu~ion along with add~tional distllled water to provide a total solution volume of 250 ml.
CstalYst Preparation The aforementioned Csrrier "A" was impregnated with the above-descrlbed impregnating solution snd then heat treated at 400C for 2.5 minutes in accordance with the method described in Example 1.
Example 9 A catalyst containing 13.09 wt. % Ag, 0.00&9 wt. %
Cs and 0.0026 wt. % X was prepared on Carrier "A" (des-cribed in Example 1) by a sequential impregnation method whereby silver was deposited upon the carrier prior to the deposition of potassium and cesium, as follows:
Preparation of Silver-Containlng ImPre~nating Solution 48.43 grams of ethylenediamine (high purity grade) was mixed with 100 grams of distilled water. 50.75 grams of oxalic acid dihydrate (reagent grade) was then added slowly to the solution at ambient temperature while continuously stirring,the solut~on temperature rising to about 60C due to the reaction exotherm. 88.97 grams of silver oxide power (Metz Metallurgical Corp.) was then 1 1 6~18~ 12,439-1 added to the diamine-oxalic acid-water solution. Finally i7.7 grams of monoethanolamine and 44.0 grams of distilled water were added to complete the solution. The specific gravity of the solution was 1.3957.
Catalvst Preparation lS0 grams of Carrier "A" was impregnated with the above-described solution and then heat treated at 500C for 2.5 minutes in accordance with the method described in Example l. Following this heat treatment, the carrier was impregnated with the impregnating sol~tion as described belo~:
Pre~ n of Impre~natin~_Sol~ltion Containin~ Cesiu-and Potassium
~~3 The carrier "A" was impregnated under vacuum as hereinafter described with a solution of silver salts and alkali me~tals. The impregnating solution was prepared at a concentration such that the finished catalyst contained the desired amounts of silver, cesium and potassium.
The required concentration of silver, cesium and potassium in solution for the given carrier is calculated from the packing density (grams/cc) and pore volume of the carrier which are either known or readily determined.
Assuming that all of the silver in the impregnating solu-tion contained in the pores of the carrier is deposited upon the carrier, approximately 21 wt.% silver in solution is necessary to prepare a catalyst containing about 11 wt.% silver on the catalyst. The required concentration of alkali metal in solution is obtained by dividing the solution silver concentration by the ratio of silver to cesium or potassium desired in the finished catalyst.
Thus, to obtain 11.0 wt.% Ag and .0047 wt.% Cs, the ratio is approximately `2330 and the required cesium concentra-tion in solution is .009 wt.%. In like manner, thesolution concentration of potassium was calculated to be .003 wt.%. The solution containing the desired concen-trations of silver and alkali metals was prepared as described below:
Impregnating Solution Preparation 80.16 gms of ethylenediamine (high purity grade) was mixed with 176 g of distilled water. 60.06 gms of anhydrous oxalic acid (reagent grade) was then added slowly to the solution at ambient temperature (23C) while continuous3y stirring. During this addition of oxalic acid, the solution temperature rose to about ?, :1 62181 40C due to the reaction exotherm. 147.25 gms of silver oxide powder (Handy and Harmon, 850 Third Avenue, New York, N.Y. 10022) was then added to the diamine-oxalic acid-water solution. Finally, 29.30 gms of monoethanolamine, 13.26 gms of aqueous Cs solution as hydroxide (.00444 g Cs/ml soln, or 0.0589 g Cs), 34.28 gms of aqueous K
solution as carbonate (.0005669 K/ml soln, or .0194 gms K) and 120.6 gms of distilled water were added to complete the solution. The solution was filtered and 0.9 grams of undissolved silver was recovered. The specific gravity of the resulting solution was about 1.328 g/ml.
Catalyst Preparation 125 g of Carrier "A" was impregnated in a 12"
long x 2" I.D. glass cylindrical vessel equipped with a side arm and suit~ble stopcocks for impregnating the carrier under va~uum. A 500 ml separatory funnel for containing the impregnating solution was inserted through a rubber stopper into the top of the impregnating vessel.
The impregnating vessel containing the carrier was evacu-ated to approximately 2 inches of mercury pressure for about 20 minutes after which the impregnating solution was slowly added to the carrier by opening the stopcock between the separatory funnel and the impregnating vessel until the carrier was completely immersed in solution, the pressure within the vessel being maintained at approx-imately 2 inches of mercury. Following addition ~f the solution, the vessel was opened to the atmosphere to attain atmospheric pressure, the carrier then remaining immersed in the impregnating solution at ambient conditions for about 1 hour, and thereafter drained of excess solu-tion for about 30 minutes. The impregnated carrier was ~J6~181 then heat treated as follows to effect reduction of silver salt and deposition of cesium and potassium ions on the catalyst surface. The impregnated carrier was spread out in a single layer on a 2-5/8" wide endless stainless steel belt (spiral weave) and transported through a 2"
x 2" square heating zone for 2.5 minutes, the heating zone being maintained at 500C by passing hot air upward th~ough the belt and about the catalyst particles at the rate of 266 SCFH. The hot air was generated by passing it through a 5 f~. long x 2" I.D. stainless steel pipe which was externally heated by an electric furnace (Lind-bergTM tubular furnace: 2-~" I.D., 3 feet long heating zone) capable of delivering 5400 watts. The heated air in the pipe was discharged from a square 2" x 2" discharge port located immediately beneath the moving belt carrying the catalyst carrier. After being roasted in the heating zone, the finished catalyst was weighed, and based upon the weight gain of the carrier, and the known ratios of silver to cesium and potassium in the impregnating solution, it was calculated to contain 11.14 wt.% of silver, 0.00477 wt.~ cesium and .00158 wt.% potassium.
By chemical analysis, described below, this catalyst was found to contain 10.88% Ag, in close agreement with the calculated value.
The analysis for silver was carried out by the following method: An approximately 50 g sample of catalyst was powdered in a mill and 10 g of the powdered sample weighed to the nearest 0.1 mg. The silver (and cesium, etc.) in the catalyst sample was dissolved in hot (80C) 50%, by volume, nitric acid solution. The insoluble alumina particles were filtered and washed with distilled f 7l 1 1 6~
water to remove all a &ering nitrate salts of Ag, Cs, etc. This solution was made up to 250 ml in a volumetric flask using distilled water. A 25 ml aliquot of this solution was titrated according to standard procedures using a 0.1 Normal solution of ammonium th~xyanate and ferric nitrate as indicator. The amount of Ag so determined in 250 ml solution was then used to calculate the weight percent silver in the catalyst sample.
Silver and alkali metal concentrations for all catalysts described in the specification are calculated values as described above.
Example 2 A catalyst containing 16.6 wt.% Ag, 0.0044 wt.%
Cs and 0.088 wt.% K was prepared as hereinafter described on a carrier "B" having the following characteristics:
Chemical Composition of Carr_er "B"
Alpha-Alumina 86.0 wt.%
Silicon Dioxide 11.8 wt.%
Calcium Oxide 0.24 wt.%
Sodium Oxide 0.69 wt.%
Ferr~ic Oxide 0.30 wt.%
Potassium Oxide 0.54 wt.%
Titanium Dioxide 0.34 wt.%
Physical Properties of Carrier "B"
Surface Area (1) 0.10 m2/g Pore Volume (2) 0.40 cc/g (or water absorption) Packing Density (3) 0.72 g/ml Median Pore Diameter (4) 22 microns , . , ~ .
, ...
~62181 Pore Size D istribution (4) Pore Size, microns % Total Pore Volume 0.1 - 1.0 0.0 1.0 - 10.0 12 10.0 - 30 55 > 1.00 0.0 (1) Method of measurement described in "Adsorption, Surface Area and Porosity", S.J. Gregg and K.S.W. Sing, Academic Press (1967), pages 316-321.
(2) Method of Measurement as described in ASTM C20-46.
(3) Calculated value based on conventional measurement of the weight of the carrier in a known volume container.
(4) Method of measurement described in "Application of Mercury Penetration to Materials Analysis", C.Orr Jr., Powder Technology, Vol. 3, pp. 117-123 (1970).
The preparation procedure consisted of the following steps:
li) 333.5 g of lactic acid (88% in water) was heated to about 75C and 1.44 g K2CO3 and 4.86 g of aqueous CsOH solution (containing .008 g/ml or .039 g Cs) added to the heated lactic acid, while stirring the solution.
(ii) 163.75 g Ag2O (Metz Metallurgical Corp., 3900 So. Clinton Ave., So. Plainfield, N.J.
07080) was incrementally added to the heated lactic acid with stirring so that the heat genera-ted from the exothermic reaction of Ag2O with lactic acid did not exceed about 85C. Most Ag2O and/or silver was left suspended in solution.
This suspension was dark brownlsh grey in colour.
(iii) Hydrogen peroxide (3.3 ml.) was incrementally added to the above Ag2O lactic acid solution while rapidly stirring to assist complete l 1 ~2181 dissolution of the suspended matter. A clear yellow solution was obtained, the solution temper-ature belng about 80C. (Small amounts of lactic acid or water were added to make up for any evaporation losses). This solution contained about 30.4% silver, 0.12~ K and .0078% Cs.
(iv) 189 grams of carrier "B" was evacuated and impregnated with the solution prepared in ~iii) while it was at its elevated temperature of aout 80C. The method of impregnating the carrier was as described in Example 1 with an additional step being that the cylindrical impregnating vessel containing the carrier was surrounded by a heating jacket which maintained the carrier temperature at about 80C during the impregnation procedure to insure that silver lactate remained in solution.
(v) The impregnated carrier of (iv) was heat treated at 400C for four minutes using the apparatus and general method described in Example 1.
Example 3 A catalyst containing 13.4 wt.% Ag, 0.0091 wt.~
Cs and 0.0027 wt.% K was prepared by the following procedure on Carrier "A" (described in Example 1).
Impregnating Solution Preparation 78.6 grams of triethylenetetramine (high purity grade) was mixed with 80 g of distilled water. 51.57 grams of oxalic acid dihydrate (reagent grade) was then added slowly to the continuously stirred amine solution.
During this addition, the temperature of the solution ~' increased to 60C due to the reaction exotherm. 5.83 g of aqueous cesium hydroxide solution (0.009728 g Cs/g solution) and 4.46 g of aqueous potassium carbonate solution (0.00369 of K/g solution) were then added to the solution followed by the addition of 89.26 g of silver oxide (Metz Metallurgical Corp.). Finally 15.28 g of monoethanolamine was added to the solution along with additional distilled water to produce a total solution volume of 250 nl. The solution was filtered and about 5 g of undissolved silver was recovered.
Catalyst Preparation 150 g of Carrier "A" was evacuated at room temperature and impregnated with the above-described impregnation solution in accordance with the procedure of Example 1. Following impregnation, heat treatment of the carrier was carried out at 500C for 2.5 minutes using the apparatus and method described in Example 1.
The composition of the finished catalyst, calcu~
lated from the weight gain of the carrier, was as stated ~o abo~e.
Example 4 A catalyst containing 13.04 wt.% Ag, 0.0089 wt.% Cs and 0.0026 wt.% K was prepared by the following procedure on Carrier "A" (described in Example 1).
Impregnating Solution Preparation 114.25 gams of aminoethylethanolamine (high purity grade) was mixed with 80 g of distilled water.
50.42 grams of oxalic acid dihydrate (reagent grade) was then slowly added to the continuously stirred amine solution~ the solution temperature rising to about 60C
due to the reaction exotherm. 5.84 g of aqueous cesium .
~ 1 62181 hydroxide solution (0.009723 g Cs/g solution) and 4.52 g of aqueous potassium carbonate solution (0.00369 g K/g solution) were then added to the solution followed by the addition of 89 g of silver oxide (Metz Metallurgical Corp.). Additional distilled water was then added to the solution to produce a total volume of 250 ml.
Catalyst Preparation 150 :g of Carrier "A" was evacuated and impreg-nated with the above-described solution in accordance with the procedure of Example 1. Heat treatment of the impregnated carrier was then carried out at 500C for 2.5 minutes using the apparatus and method as described in Example 1.
~ ~ B2~
12,439-1 Example 5 A catalyst having nominally the same composition as the catalyst of Example 1 (specifically, 11.1 wt. % ~g, 0.0048 wt. % Cs and 0.0016 wt. % K) was prepared as described in Example 1 except that the preparation of the impregnating solution was carried out using aq~eous solu-tions of cesium chloride and potassium chloride instead of cesium hydroxide and potassium carbonate, respectively.
Upon addition of such chloride salts to the silver-con-taining impregnating solution, the solution remained clear,i.e., no precipitation of silver chloride was observed.
Example 6 A catalyst having nominally the same composition as the catalyst of Example 1 except for the substitution of lithium for potassium (specifically 11.0 wt. %
Ag, 0.0047 wt. % Cs and 0.003 wt. % Li) was prepared as describèd in Example 1, the solution concentration of lithium being calculated to be 0.00573 wt. %. Accordingly, the preparation procedure of Example 1 was followed except that instead of adding potassium carbonate solution to the impregnating solution, 34 grams of an aqueous lithium solution as carbonate (0.001094 g lithium/ml, or 0.0372 g lithium) were added.
Example 7 A catalyst having nominally the same composition as the catalyst of Example 1 except for the substitution of sodium for potassium (specifically 11.0 wt. %
Ag, 0.0047 wt. % Cs and 0.01 wt. % sodium) was prepared in accordance with the procedure of Example 1, the solution concentration of sodium being calculated to be 0.0191 wt. %.
Thus, the procedure of Example 1 was followed except that ~6~
12,439-1 instead of adding potassium carbonate to the impregnating solution, 34 grams of an aqueous sodium solution as carbonate (0 00365 g sodium/ ml, or 0.12415 gram sodium) were added.
Example 8 A catalyst containing 12.59 wt. % Ag, 0.0088 wt.
/. Cs and 0.0025 wt. % K was prep~red on Carrier "A"
(described in Example 1) by a sequential impregnation method whereby potassi~m and cesium were deposited upon the carrier prior to the deposition of silver, as follows:
146.1 grams of Carrier "A" was impregnated with 250 ~1 of an aqueous solution containing 0.05696 g of cesiu~ as hydroxide and 0.1674 g of potassium as carbonate follow-ing the general method of impregnation described in Exa~ple 1. The impregnated carrier was then heat treaeed at 400C for 2.5 minutes in accordance with the procedure of Example 1 to deposit cesium and potassium ions on the carrier surface. Following this heat treatment, the carrier was impregnated with the silver-containing im-pregnating solution as described below:
Preparation of Silver-Containing ImPre~natin~ Solution 48.9 grams of ethylenediamine (high purity grade) was mixed with 80 cc of distilled water. 50.6g of oxalic acid dihydrate (reagent grade) was then added slowly to the solution over a period of one hour while conti-nuo~sly 6tirring. During this addition of oxalic acid, ~ ~ 62181 12,439-1 the solution temperature rose to about 40C due to the reaction exotherm. 89.34 grams of silver oxide powder (Metz Metallurgical Corp.) was then added to the diamine-oxalic acid-water solution. Finally, 17.84~grams of monoethanolamine was added to the solu~ion along with add~tional distllled water to provide a total solution volume of 250 ml.
CstalYst Preparation The aforementioned Csrrier "A" was impregnated with the above-descrlbed impregnating solution snd then heat treated at 400C for 2.5 minutes in accordance with the method described in Example 1.
Example 9 A catalyst containing 13.09 wt. % Ag, 0.00&9 wt. %
Cs and 0.0026 wt. % X was prepared on Carrier "A" (des-cribed in Example 1) by a sequential impregnation method whereby silver was deposited upon the carrier prior to the deposition of potassium and cesium, as follows:
Preparation of Silver-Containlng ImPre~nating Solution 48.43 grams of ethylenediamine (high purity grade) was mixed with 100 grams of distilled water. 50.75 grams of oxalic acid dihydrate (reagent grade) was then added slowly to the solution at ambient temperature while continuously stirring,the solut~on temperature rising to about 60C due to the reaction exotherm. 88.97 grams of silver oxide power (Metz Metallurgical Corp.) was then 1 1 6~18~ 12,439-1 added to the diamine-oxalic acid-water solution. Finally i7.7 grams of monoethanolamine and 44.0 grams of distilled water were added to complete the solution. The specific gravity of the solution was 1.3957.
Catalvst Preparation lS0 grams of Carrier "A" was impregnated with the above-described solution and then heat treated at 500C for 2.5 minutes in accordance with the method described in Example l. Following this heat treatment, the carrier was impregnated with the impregnating sol~tion as described belo~:
Pre~ n of Impre~natin~_Sol~ltion Containin~ Cesiu-and Potassium
5.791 grams of aqueous cesium hydroxide solu-tion (0.009723 grams Cs/g solution) and 4.415 ~rams of aqueous p~tassium carbonate solution (0.00369 grams K/g solution) were added to a 250 ml volumetric cylinder and n-butanol then added to fill the cylinder to the 25Q ml mark. The cylinder was heated to 40C, sealed and shaken vigorously until a clear solution was obtained.
~'~
The above described silver-containing Carrier "A"
was impregnated under vacuum with the impregnating solution containing cesium and potassium for a period of 15 minutes, and then drained of excess solution using the method described in Example l. Heae treatment of ~he carrier was then carried out at 500C for 2.5 minutes in accordance wleh the method of EXample l.
~'~
The above described silver-containing Carrier "A"
was impregnated under vacuum with the impregnating solution containing cesium and potassium for a period of 15 minutes, and then drained of excess solution using the method described in Example l. Heae treatment of ~he carrier was then carried out at 500C for 2.5 minutes in accordance wleh the method of EXample l.
Claims (29)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A silver catalyst deposited on a macroporous support having a surface area less than 10 m2/g and in a form and size for use in a fixed bed tubular reactor used in a commercial operation for the manufacture of ethylene oxide by vapor phase reaction of ethylene and oxygen or an oxygen-containing gas in gaseous admixture with diluent and inhibitor, which catalyst contains 2 to 20 weight percent silver and a combination of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, which combination comprises (a) and (b) in amounts in relation to the amount of silver therein sufficient to increase synergistically the efficiency of said ethylene oxide manufacture to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as said catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount of (b).
2. The catalyst of claim 1 wherein silver is present in an amount of from about 6% to about 15% by weight.
3. The catalyst of claim 1 wherein said alkali metal is sodium.
4. The catalyst of claim 1 wherein said alkali metal is lithium.
5. The catalyst of claim 1 wherein said alkali metal is potassium.
6. The catalyst of claim 1 wherein said alkali metal is rubidium.
7. The catalyst of claim 5 wherein cesium and potassium are present in a weight ratio of from about 100:1 to about 1:100.
8. The catalyst of claim 1 wherein the catalyst support comprises alpha-alumina.
9. The catalyst of claim 1 wherein the surface area of the catalyst support is less than about 1 m2/gm.
10. The catalyst of claim 1 wherein the pore volume of the catalyst support is from about 0.2 to 0.6 cc/gram.
11. In the continuous process for the production of ethylene oxide in a commercial operation wherein ethylene and oxygen provided as oxygen or as an oxygen-containing gas are reacted in vapor phase admixture with diluent and inhibitor at a temperature of from about 200°C to 300°C in the presence of a supported silver catalyst in a fixed bed tubular reactor to form ethylene oxide, the improvement which comprises employing a supported silver catalyst which catalyst has a macroporous support having a surface area less than 10 m2/g and is in a form and size for use in a reactor used in said commercial operation and which catalyst contains 2 to 20 weight percent silver a combination of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, which combination comprises (a) and (b) in amounts in relation to the amount of silver therein sufficient to increase the efficiency of ethylene oxide manufacture in said commercial operation to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as said catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount of (b).
12. The process of claim 11 wherein said catalyst contains silver in an amount of from about 6% to about 16% by weight.
13. The process of claim 11 wherein said alkali metal is sodium.
14. The process of claim 11 wherein said alkali metal is lithium.
15. The process of claim 11 wherein said alkali metal is potassium.
16. The process of claim 11 wherein said alkali metal is rubidium.
17. The process of claim 15 wherein cesium and potassium are present in a weight ratio of from about 100:1 to about 1:100.
18. The process of claim 11 wherein the catalyst support comprises the alpha-alumina.
19. The process of claim 11 wherein the surface area of the catalyst support is less than about 1 meter square per gram.
20. The process of claim 11 wherein said inhibitor is ethylene dichloride.
21. A process for preparing a supported silver catalyst for the commercial operation for the production of ethylene oxide by the vapor phase oxidation of ethylene with oxygen or an oxygen-containing gas in gaseous admixture with diluent and inhibitor in a fixed bed tubular reactor, comprising:
(1) impregnating a macroporous catalyst having a surface area less than 10 m2/g and in a form and size for use in a reactor used in said commercial operation with a solution comprising a solvent or solubilizing agent, silver salt sufficient to deposit the desired amount of silver on said support of 2 to 20 weight percent silver, and salts of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, sufficient to deposit respective amounts of (a) and (b) on said support such that the efficiency of ethylene oxide manufacture in said commercial operation using the finished catalyst is increased to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as said catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a) and the other contains the respective amount of (b); and (2) treating the impregnated support to convert at least a fraction of the silver salt to silver metal and effect deposition of silver, (a) and (b), respectively, on surfaces of said support.
(1) impregnating a macroporous catalyst having a surface area less than 10 m2/g and in a form and size for use in a reactor used in said commercial operation with a solution comprising a solvent or solubilizing agent, silver salt sufficient to deposit the desired amount of silver on said support of 2 to 20 weight percent silver, and salts of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, sufficient to deposit respective amounts of (a) and (b) on said support such that the efficiency of ethylene oxide manufacture in said commercial operation using the finished catalyst is increased to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as said catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a) and the other contains the respective amount of (b); and (2) treating the impregnated support to convert at least a fraction of the silver salt to silver metal and effect deposition of silver, (a) and (b), respectively, on surfaces of said support.
22. The process of claim 21 wherein said solvent or solubilizing agent is lactic acid.
23. The process of claim 21 wherein said solvent or solubilizing agent is an amine or an aqueous mixture of amines.
24. The process of claim 21 wherein the impregnated support is heated at a temperature of from about 200°C to about 700°C.
25. The process of claim 21 wherein said alkali metal is sodium.
26. The process of claim 21 wherein said alkali metal is lithium.
27. The process of claim 21 wherein said alkali metal is potassium.
28. The process of claim 27 wherein cesium and potassium salts are present in solution in a concentration sufficient to deposit cesium and potassium, respectively, in a weight ratio of from about 100:1 to about 1:100.
29. The process of claim 21 wherein the amount of silver salt in solution is sufficient to deposit from about 6% to about 16%
by weight of silver on said support.
by weight of silver on said support.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US2172779A | 1979-03-20 | 1979-03-20 | |
US021,727 | 1979-03-20 | ||
US11629280A | 1980-02-13 | 1980-02-13 | |
US116,292 | 1987-11-03 |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1162181A true CA1162181A (en) | 1984-02-14 |
Family
ID=26695034
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000347075A Expired CA1162181A (en) | 1979-03-20 | 1980-03-05 | Catalyst composition and process for oxidation of ethylene to ethylene oxide |
Country Status (15)
Country | Link |
---|---|
AR (1) | AR223210A1 (en) |
AU (3) | AU5651480A (en) |
BR (1) | BR8001603A (en) |
CA (1) | CA1162181A (en) |
DD (2) | DD160187A5 (en) |
DE (1) | DE3010533A1 (en) |
ES (2) | ES8104803A1 (en) |
FR (1) | FR2451920A1 (en) |
GB (1) | GB2043481B (en) |
IN (2) | IN155337B (en) |
IT (1) | IT1130701B (en) |
NL (1) | NL8001615A (en) |
PL (1) | PL222819A1 (en) |
RO (1) | RO79689B (en) |
SE (1) | SE8002159L (en) |
Families Citing this family (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0059422B1 (en) * | 1981-02-25 | 1985-07-17 | Mitsubishi Petrochemical Co., Ltd. | Silver-based catalyst for production of ethylene oxide |
US4419276A (en) * | 1981-09-30 | 1983-12-06 | Union Carbide Corporation | Silver catalyst for the manufacture of ethylene oxide and a process for preparing the catalyst |
DE3272383D1 (en) * | 1981-12-30 | 1986-09-04 | Ici Plc | Catalysts for the production of alkylene oxides |
US4760042A (en) * | 1982-03-24 | 1988-07-26 | Scientific Design Company, Inc. | Process for preparing an alkali metal-promoted silver catalyst |
US4774222A (en) * | 1982-06-16 | 1988-09-27 | Scientific Design Company, Inc. | Catalyst for oxidation of ethylene to ethylene oxide and process for preparing the catalyst |
US4555501A (en) * | 1984-05-14 | 1985-11-26 | The Halcon Sd Group, Inc. | Process for preparing silver catalysts |
JPS6110570A (en) * | 1984-06-25 | 1986-01-18 | Mitsui Toatsu Chem Inc | Preparation of ethylene oxide |
EP0172565B1 (en) * | 1984-08-21 | 1991-03-13 | Mitsubishi Petrochemical Co., Ltd. | Silver catalyst for production of ethylene oxide from ethylene, and process for production thereof |
FR2597098B1 (en) * | 1986-04-11 | 1989-01-13 | Atochem | SILVER-BASED CATALYSTS FOR THE MANUFACTURE OF ETHYLENE OXIDE |
GB2190855A (en) * | 1986-05-28 | 1987-12-02 | Shell Int Research | Process for the preparation of a silver-containing catalyst |
DE3643248A1 (en) * | 1986-12-18 | 1988-06-30 | Basf Ag | SILVER CATALYST, ITS PRODUCTION AND USE |
US4908343A (en) * | 1987-02-20 | 1990-03-13 | Union Carbide Chemicals And Plastics Company Inc. | Catalyst composition for oxidation of ethylene to ethylene oxide |
US5057481A (en) * | 1987-02-20 | 1991-10-15 | Union Carbide Chemicals And Plastics Technology Corporation | Catalyst composition for oxidation of ethylene to ethylene oxide |
US5008413A (en) * | 1989-10-23 | 1991-04-16 | Scientific Design Company, Inc. | Catalyst for oxidation of ethylene to ethylene oxide |
GB2248068A (en) * | 1990-09-21 | 1992-03-25 | Exxon Chemical Patents Inc | Oil compositions and novel additives |
US6184175B1 (en) * | 1993-03-01 | 2001-02-06 | Scientic Design Company, Inc. | Process for preparing silver catalyst |
US5525740A (en) * | 1993-03-01 | 1996-06-11 | Scientific Design Company, Inc. | Process for preparing silver catalyst and process of using same to produce ethylene oxide |
US5602070A (en) * | 1995-01-09 | 1997-02-11 | Scientific Design Company, Inc. | Process for preparing silver catalyst |
US10159961B2 (en) * | 2006-04-18 | 2018-12-25 | Dow Global Technologies Llc | Alkylene oxide catalyst and use thereof |
USD813681S1 (en) | 2016-11-18 | 2018-03-27 | Can't Live Without It, LLC | Bottle |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2640540C3 (en) * | 1976-09-09 | 1988-07-28 | Basf Ag, 6700 Ludwigshafen | Catalyst for the production of ethylene oxide |
US4168247A (en) * | 1976-05-28 | 1979-09-18 | Imperial Chemical Industries Limited | Catalysts for the production of alkylene oxides |
DE2819595A1 (en) * | 1977-05-12 | 1978-12-07 | Basf Ag | CATALYST FOR THE PRODUCTION OF ETHYLENE OXIDE |
-
1980
- 1980-03-05 CA CA000347075A patent/CA1162181A/en not_active Expired
- 1980-03-17 IT IT20711/80A patent/IT1130701B/en active
- 1980-03-17 AU AU56514/80A patent/AU5651480A/en not_active Abandoned
- 1980-03-18 BR BR8001603A patent/BR8001603A/en unknown
- 1980-03-18 NL NL8001615A patent/NL8001615A/en not_active Application Discontinuation
- 1980-03-18 IN IN308/CAL/80A patent/IN155337B/en unknown
- 1980-03-18 ES ES489668A patent/ES8104803A1/en not_active Expired
- 1980-03-19 DD DD80232350A patent/DD160187A5/en unknown
- 1980-03-19 AR AR280355A patent/AR223210A1/en active
- 1980-03-19 FR FR8006095A patent/FR2451920A1/en active Granted
- 1980-03-19 GB GB8009237A patent/GB2043481B/en not_active Expired
- 1980-03-19 PL PL22281980A patent/PL222819A1/xx unknown
- 1980-03-19 DE DE19803010533 patent/DE3010533A1/en not_active Ceased
- 1980-03-19 DD DD80219762A patent/DD151878A5/en unknown
- 1980-03-19 RO RO100531A patent/RO79689B/en unknown
- 1980-03-19 SE SE8002159A patent/SE8002159L/en unknown
- 1980-12-12 ES ES497678A patent/ES8202694A1/en not_active Expired
-
1983
- 1983-06-09 IN IN731/CAL/83A patent/IN156399B/en unknown
-
1985
- 1985-12-05 AU AU50815/85A patent/AU5081585A/en not_active Abandoned
-
1988
- 1988-09-02 AU AU21788/88A patent/AU2178888A/en not_active Abandoned
Also Published As
Publication number | Publication date |
---|---|
SE8002159L (en) | 1980-11-14 |
DD160187A5 (en) | 1983-05-11 |
ES497678A0 (en) | 1982-03-01 |
GB2043481A (en) | 1980-10-08 |
AU2178888A (en) | 1988-12-08 |
ES489668A0 (en) | 1981-04-16 |
DE3010533A1 (en) | 1980-10-02 |
IT1130701B (en) | 1986-06-18 |
AU5081585A (en) | 1986-05-15 |
RO79689A (en) | 1985-04-17 |
PL222819A1 (en) | 1981-02-13 |
ES8202694A1 (en) | 1982-03-01 |
FR2451920A1 (en) | 1980-10-17 |
IN155337B (en) | 1985-01-19 |
NL8001615A (en) | 1980-09-23 |
IN156399B (en) | 1985-07-20 |
IT8020711A0 (en) | 1980-03-17 |
FR2451920B1 (en) | 1984-01-27 |
ES8104803A1 (en) | 1981-04-16 |
BR8001603A (en) | 1980-11-18 |
AU5651480A (en) | 1980-09-25 |
DD151878A5 (en) | 1981-11-11 |
GB2043481B (en) | 1984-03-07 |
AR223210A1 (en) | 1981-07-31 |
RO79689B (en) | 1985-04-30 |
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