US20040220429A1 - Process and catalyst for production of formaldehyde from dimethyl ether - Google Patents
Process and catalyst for production of formaldehyde from dimethyl ether Download PDFInfo
- Publication number
- US20040220429A1 US20040220429A1 US10/861,214 US86121404A US2004220429A1 US 20040220429 A1 US20040220429 A1 US 20040220429A1 US 86121404 A US86121404 A US 86121404A US 2004220429 A1 US2004220429 A1 US 2004220429A1
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- United States
- Prior art keywords
- oxide
- oxides
- molybdenum
- support
- moo
- 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.)
- Abandoned
Links
- 239000003054 catalyst Substances 0.000 title claims abstract description 124
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 title abstract description 158
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 title abstract description 137
- 238000000034 method Methods 0.000 title description 42
- 230000008569 process Effects 0.000 title description 39
- 238000004519 manufacturing process Methods 0.000 title description 17
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims abstract description 96
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 82
- 229910000476 molybdenum oxide Inorganic materials 0.000 claims abstract description 56
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 49
- 239000011733 molybdenum Substances 0.000 claims abstract description 46
- 229910001935 vanadium oxide Inorganic materials 0.000 claims abstract description 46
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical class [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 claims abstract description 43
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 36
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 35
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 62
- 239000010410 layer Substances 0.000 claims description 30
- 239000002356 single layer Substances 0.000 claims description 24
- 239000000203 mixture Substances 0.000 claims description 17
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical compound [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 claims description 17
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 12
- 229910052742 iron Inorganic materials 0.000 claims description 6
- 229910052684 Cerium Inorganic materials 0.000 claims description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 4
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 4
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 4
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 4
- 229910052709 silver Inorganic materials 0.000 claims description 4
- 239000004332 silver Substances 0.000 claims description 4
- 229910052718 tin Inorganic materials 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 239000011651 chromium Substances 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 239000010949 copper Substances 0.000 claims description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 2
- 229910017052 cobalt Inorganic materials 0.000 claims description 2
- 239000010941 cobalt Substances 0.000 claims description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 229910052702 rhenium Inorganic materials 0.000 claims description 2
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 claims description 2
- 239000010936 titanium Substances 0.000 claims description 2
- 229910052719 titanium Inorganic materials 0.000 claims description 2
- 238000006243 chemical reaction Methods 0.000 abstract description 70
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Chemical compound O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 description 65
- 229910052593 corundum Inorganic materials 0.000 description 57
- 229910001845 yogo sapphire Inorganic materials 0.000 description 57
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 53
- 229910015711 MoOx Inorganic materials 0.000 description 46
- 239000000047 product Substances 0.000 description 24
- 238000007254 oxidation reaction Methods 0.000 description 21
- 230000003647 oxidation Effects 0.000 description 19
- TZIHFWKZFHZASV-UHFFFAOYSA-N methyl formate Chemical compound COC=O TZIHFWKZFHZASV-UHFFFAOYSA-N 0.000 description 18
- 238000005470 impregnation Methods 0.000 description 17
- 239000003570 air Substances 0.000 description 16
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 15
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 15
- 229910052750 molybdenum Inorganic materials 0.000 description 15
- 229910006854 SnOx Inorganic materials 0.000 description 12
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 description 12
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 12
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 12
- 230000000694 effects Effects 0.000 description 11
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 10
- 125000004429 atom Chemical group 0.000 description 10
- 230000015572 biosynthetic process Effects 0.000 description 10
- 239000000243 solution Substances 0.000 description 10
- 229910052751 metal Inorganic materials 0.000 description 8
- 239000002184 metal Substances 0.000 description 8
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical class [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 7
- 229910002090 carbon oxide Inorganic materials 0.000 description 7
- 239000000395 magnesium oxide Substances 0.000 description 7
- 239000000376 reactant Substances 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- 229910002651 NO3 Inorganic materials 0.000 description 6
- 229910008320 ZrMo2 Inorganic materials 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 6
- 230000003247 decreasing effect Effects 0.000 description 6
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 6
- 230000009467 reduction Effects 0.000 description 6
- 239000000377 silicon dioxide Substances 0.000 description 6
- 229910052720 vanadium Inorganic materials 0.000 description 6
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 5
- 229910003320 CeOx Inorganic materials 0.000 description 5
- 229910015189 FeOx Inorganic materials 0.000 description 5
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 5
- 235000006408 oxalic acid Nutrition 0.000 description 5
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 5
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 229910006220 ZrO(OH)2 Inorganic materials 0.000 description 4
- 150000001335 aliphatic alkanes Chemical class 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 238000006555 catalytic reaction Methods 0.000 description 4
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 4
- 229940044927 ceric oxide Drugs 0.000 description 4
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- -1 stannic oxide Chemical class 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910003134 ZrOx Inorganic materials 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 150000001336 alkenes Chemical class 0.000 description 3
- 239000012080 ambient air Substances 0.000 description 3
- UNTBPXHCXVWYOI-UHFFFAOYSA-O azanium;oxido(dioxo)vanadium Chemical compound [NH4+].[O-][V](=O)=O UNTBPXHCXVWYOI-UHFFFAOYSA-O 0.000 description 3
- 229910052797 bismuth Inorganic materials 0.000 description 3
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 230000007062 hydrolysis Effects 0.000 description 3
- 238000006460 hydrolysis reaction Methods 0.000 description 3
- 239000003915 liquefied petroleum gas Substances 0.000 description 3
- 238000005839 oxidative dehydrogenation reaction Methods 0.000 description 3
- 125000004430 oxygen atom Chemical group O* 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 230000009257 reactivity Effects 0.000 description 3
- 238000003786 synthesis reaction Methods 0.000 description 3
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- QQONPFPTGQHPMA-UHFFFAOYSA-N Propene Chemical compound CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 2
- 238000001069 Raman spectroscopy Methods 0.000 description 2
- KGBUQHGXOAESDX-UHFFFAOYSA-N [Zr].OOO Chemical compound [Zr].OOO KGBUQHGXOAESDX-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 239000000908 ammonium hydroxide Substances 0.000 description 2
- 238000013459 approach Methods 0.000 description 2
- XUFUCDNVOXXQQC-UHFFFAOYSA-L azane;hydroxy-(hydroxy(dioxo)molybdenio)oxy-dioxomolybdenum Chemical compound N.N.O[Mo](=O)(=O)O[Mo](O)(=O)=O XUFUCDNVOXXQQC-UHFFFAOYSA-L 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000010348 incorporation Methods 0.000 description 2
- 239000011872 intimate mixture Substances 0.000 description 2
- ZXEKIIBDNHEJCQ-UHFFFAOYSA-N isobutanol Chemical compound CC(C)CO ZXEKIIBDNHEJCQ-UHFFFAOYSA-N 0.000 description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 2
- 239000011572 manganese Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- KHMOASUYFVRATF-UHFFFAOYSA-J tin(4+);tetrachloride;pentahydrate Chemical compound O.O.O.O.O.Cl[Sn](Cl)(Cl)Cl KHMOASUYFVRATF-UHFFFAOYSA-J 0.000 description 2
- 230000007306 turnover Effects 0.000 description 2
- IPCAPQRVQMIMAN-UHFFFAOYSA-L zirconyl chloride Chemical compound Cl[Zr](Cl)=O IPCAPQRVQMIMAN-UHFFFAOYSA-L 0.000 description 2
- 229910003158 γ-Al2O3 Inorganic materials 0.000 description 2
- 229910019626 (NH4)6Mo7O24 Inorganic materials 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 239000004254 Ammonium phosphate Substances 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical class [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 1
- 229910016553 CuOx Inorganic materials 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- 229910052770 Uranium Inorganic materials 0.000 description 1
- 238000004998 X ray absorption near edge structure spectroscopy Methods 0.000 description 1
- 238000000833 X-ray absorption fine structure spectroscopy Methods 0.000 description 1
- 238000002056 X-ray absorption spectroscopy Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- APUPEJJSWDHEBO-UHFFFAOYSA-P ammonium molybdate Chemical compound [NH4+].[NH4+].[O-][Mo]([O-])(=O)=O APUPEJJSWDHEBO-UHFFFAOYSA-P 0.000 description 1
- 235000018660 ammonium molybdate Nutrition 0.000 description 1
- 239000011609 ammonium molybdate Substances 0.000 description 1
- 229940010552 ammonium molybdate Drugs 0.000 description 1
- 229910000148 ammonium phosphate Inorganic materials 0.000 description 1
- 235000019289 ammonium phosphates Nutrition 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052810 boron oxide Inorganic materials 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 229910000420 cerium oxide Inorganic materials 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010960 commercial process Methods 0.000 description 1
- 238000010959 commercial synthesis reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000012084 conversion product Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 description 1
- 238000000867 diffuse reflectance ultraviolet--visible spectrophotometry Methods 0.000 description 1
- NKDDWNXOKDWJAK-UHFFFAOYSA-N dimethoxymethane Chemical compound COCOC NKDDWNXOKDWJAK-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000000921 elemental analysis Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000004817 gas chromatography Methods 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
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 235000013980 iron oxide Nutrition 0.000 description 1
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(III) nitrate Inorganic materials [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000013335 mesoporous material Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910003455 mixed metal oxide Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 150000002751 molybdenum Chemical class 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- MOWNZPNSYMGTMD-UHFFFAOYSA-N oxidoboron Chemical class O=[B] MOWNZPNSYMGTMD-UHFFFAOYSA-N 0.000 description 1
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 1
- 230000037361 pathway Effects 0.000 description 1
- 235000011007 phosphoric acid Nutrition 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910001392 phosphorus oxide Inorganic materials 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000004375 physisorption Methods 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 239000011669 selenium Substances 0.000 description 1
- 229910001961 silver nitrate Inorganic materials 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 229910001930 tungsten oxide Inorganic materials 0.000 description 1
- 238000002371 ultraviolet--visible spectrum Methods 0.000 description 1
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 1
- LSGOVYNHVSXFFJ-UHFFFAOYSA-N vanadate(3-) Chemical compound [O-][V]([O-])([O-])=O LSGOVYNHVSXFFJ-UHFFFAOYSA-N 0.000 description 1
- 150000003681 vanadium Chemical class 0.000 description 1
Classifications
-
- 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
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0201—Impregnation
-
- 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
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/20—Vanadium, niobium or tantalum
- B01J23/22—Vanadium
-
- 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
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/24—Chromium, molybdenum or tungsten
- B01J23/28—Molybdenum
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
- C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
- C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
- C07C45/37—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C47/00—Compounds having —CHO groups
- C07C47/02—Saturated compounds having —CHO groups bound to acyclic carbon atoms or to hydrogen
- C07C47/04—Formaldehyde
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- B01J35/391—
Definitions
- This invention relates to a process for production of formaldehyde, and optionally also methyl formate as a co-product, by oxidation of dimethyl ether (DME), and to catalysts for use in the process, including catalysts that are novel per se. In addition, this invention relates to the use of such novel catalysts in other processes.
- DME dimethyl ether
- Formaldehyde is widely used as an intermediate or basic building block in the commercial synthesis of many chemicals. Because of the existence of large reserves of methane worldwide it has been considered desirable for some time to develop processes to convert methane to more valuable chemicals. One such effort has been in the area of direct conversion of methane to formaldehyde via selective oxidation. However, this has not been particularly successful. Up to now, all such processes have resulted in low yields due to the tendency of the formaldehyde so produced being further oxidized to carbon oxides under the severe reaction conditions required for methane oxidation.
- formaldehyde is commercially produced from methane indirectly, for instance, by first converting the methane to synthesis gas (CO and H 2 ), then reacting that to form methanol, and finally oxidizing the methanol to produce formaldehyde.
- synthesis gas CO and H 2
- the oxidation of methanol to formaldehyde has been extensively studied, and is the dominant process today for formaldehyde synthesis, typically using silver- or iron/molybdenum-based catalysts.
- Dimethyl ether is a generally environmentally benign molecule. Its physical properties resemble those of LPG (liquefied petroleum gases), and dimethyl ether thus can be transported within existing and developing LPG infrastructures. Like methanol, dimethyl ether can be produced from synthesis gas. These characteristics give it the potential to be a new, clean alternative fuel. This potential is expected to lead to the production of substantially larger quantities of dimethyl ether than in the past, thus making it available for use as an intermediate in production of other chemicals, including formaldehyde.
- LPG liquefied petroleum gases
- U.S. Pat. No. 4,435,602 describes a process for production of formaldehyde from dimethyl ether using naturally occurring manganese nodules as a catalyst.
- U.S. Pat. No. 4,439,624 describes such a process using an intimate mixture of bismuth, molybdenum and copper oxides, preferably prepared by coprecipitation.
- U.S. Pat. No. 4,442,307 describes such a process using an intimate mixture of bismuth, molybdenum and iron oxides, similarly prepared.
- 6,256,528 describes oxidation of dimethyl ether with a catalyst containing metallic silver to produce a mixture of products including formaldehyde, light alkanes, carbon oxides and water. Information in these patents indicates that formaldehyde was produced with reasonable yields, but that overoxidation of that product to carbon oxides occurred to an undesirable degree.
- this invention comprises a process for the production of formaldehyde by oxidation of dimethyl ether in the presence of a supported catalyst comprising molybdenum oxide, vanadium oxide or a mixture of molybdenum and vanadium oxides.
- the support is one that substantially does not react with the molybdenum or vanadium oxide to form unreducible mixed oxide(s).
- Preferred supports comprise alumina, zirconia, stannic oxide, titania, silica, ferric oxide, ceric oxide, other reducible metal oxides, and mixtures and combinations thereof.
- this invention comprises such a process in which the molybdenum and/or vanadium oxides are dispersed on the surface of the support, the surface density of the oxide or oxides on the support is greater than that for the isolated monomeric oxide or oxides, and in which the catalyst is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides.
- the surface density of the molybdenum and/or vanadium oxide or oxides on the support is approximately that of a monolayer of the oxide or oxides at the surface of the support.
- the catalyst comprises one or more reducible metal oxides. More preferably in this embodiment, the catalyst comprises a layer of the reducible metal oxide or oxides, most preferably stannic oxide, on a particulate support (preferably alumina and/or zirconia) with the molybdenum and/or vanadium oxide or oxides being present as an upper layer or layers on the layer of reducible metal oxide(s) layer.
- a particulate support preferably alumina and/or zirconia
- the surface density of the molybdenum and/or vanadium oxide or oxides on the support is greater than that for the isolated monomeric oxide or oxides, and the catalyst is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides.
- the surface density of the molybdenum and/or vanadium oxide or oxides on the support is approximately that of a monolayer of the oxide or oxides at the surface of the support.
- Catalysts of the above type in which the catalyst comprises one or more reducible metal oxides, particularly stannic oxide, and more particularly in which the molybdenum and/or vanadium oxide is supported on a layer or layers of reducible metal oxide or oxides, with the oxide layer or layers being disposed on a particulate alumina and/or zirconia, are novel and form another feature of this invention.
- Yet another aspect of this invention is the use of the novel catalysts just described to catalyze other processes, particularly oxidation of methanol to formaldehyde, oxidative dehydrogenation of alkanes, and oxidation of alkenes.
- a primary aspect of this invention comprises a process for the production of formaldehyde by oxidation of dimethyl ether in the presence of a supported catalyst comprising molybdenum oxide, vanadium oxide or a mixture of molybdenum and vanadium oxides.
- a supported catalyst comprising molybdenum oxide, vanadium oxide or a mixture of molybdenum and vanadium oxides.
- the oxides are supported on alumina (Al 2 O 3 ) and/or zirconia (ZrO 2 ), and more preferably on such a support that also includes one or more reducible metal oxides, as described herein.
- the molybdenum and/or vanadium oxides are dispersed on the surface of the support, the surface density of the oxide or oxides on the support is greater than that for the isolated monomeric oxide or oxides, and the catalyst is characterized by a substantial absence of bulk crystalline molybdenum or vanadium oxides. More preferably the molybdenum and/or vanadium oxides are dispersed on a layer or layers of a reducible oxide or oxides that is further supported on alumina, titania, silica or zirconia (if zirconia is not used as the above-mentioned layer).
- Catalysts of this type that comprise molybdenum or vanadium oxides supported on alumina or zirconia are described in several prior publications, for catalyzing the oxidative dehydrogenation of propane to propene. These include Chen, et al., in “Studies in Surface Science and Catalysis”, Vol. 136, pp. 507-512, J. J. Spivey, E. Iglesia and T. M. Fleisch, Ed. (Elsevier Science, B. V., 2001); Chen et al., J. Catalysis 189, 421 (2000), Khodakov et al., J. Catalysis 177, 343 (1998), Chen et al., J.
- the molybdenum and/or vanadium oxide is distributed on the surface of the support material in what is known as “small domain” distribution.
- the surface density of the oxide catalyst on the support (measured in units of Mo or V metal atoms per nm 2 ) is chosen so as to be greater than the surface density of the respective isolated monomeric oxide or oxides, but the catalyst overall is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides (corresponding to the oxide or oxides used in preparing the catalyst).
- bulk crystalline oxides is meant oxide(s) having a clear X-ray diffraction pattern.
- the crystallinity can be determined by X-ray diffraction based on the peak intensity ratio between one of the peaks of the supported metal oxide and one of the peaks of the support employed after calibration with a mixture of known amounts of the metal oxide and the support.
- substantially absence is meant that the supported catalyst contains less than about 5% of bulk crystalline molybdenum and/or vanadium oxide(s).
- the surface density of the catalyst affects the catalyst efficiency.
- catalysts of this type with relatively isolated oxide species for example monomolybdate or monovanadate species, have relatively few active sites on the support surface. These catalysts tend to retain their oxygen and thus provide rather low reaction rates for the oxidation of dimethyl ether to formaldehyde.
- catalysts having bulk crystals may possibly provide reasonable reaction rates per unit surface area.
- they also lack efficiency in the utilization of the oxide catalyst because a substantial amount of the oxide is located within the crystals and is thus not available for catalyzing the reaction.
- Bulk MoO 3 crystals also tend to be nonselective in their functioning, and can cause overreaction to produce carbon oxides rather than the desired products formaldehyde and methyl formate.
- the most preferred catalysts for this reaction tend to have a surface density of approximately a monolayer of catalyst on the support.
- the monolayer surface density depends primarily on the oxide chosen.
- the monolayer surface density is ⁇ 5.0 Mo atoms per square nanometer of support (Xie et al, Adv. Catal., 37, 1 (1990)).
- vanadium oxide this value is approximately 7.5 V atoms per square nanometer (Centi, Appl. Catal. A, 147, 267 (1996)).
- the term “monolayer” as used herein is meant to refer to these approximate surface densities.
- the catalyst is uniformly dispersed on the support, satisfactory results are obtainable with a preferred surface density of from approximately 50-300% of the monolayer capacity values for alumina supports, and approximately 50-400% of these values for zirconia supports. Overall, a preferred range of surface densities is from about 50 to about 300% of the monolayer capacity, for both molybdenum and vanadium oxides, for all supports usable in this invention.
- the molybdenum or vanadium oxide may be present as the oxide per se, represented by the general formulas MoO x and VO y , where x and y represent general values for oxygen in such molecules.
- MoO x the oxide generally comprises about three oxygen atoms per molybdenum atom; i.e., the general form of the oxide may be represented as MoO 3 , or molybdenum trioxide.
- VO y the oxide generally comprises about five oxygen atoms per two vanadium atoms, represented by the general formula V 2 O 5 , or vanadium pentoxide.
- the oxide may have an oxygen-to-metal atomic ratio that is not necessarily exactly 3:1 for molybdenum oxides or 5:2 for vanadium oxides.
- oxides used as a component of the support may be represented by more general formulas such as SnO x , FeO x and CeO x where the oxides generally comprise about 2, 1.5 and 2 oxygen atoms per metallic atom, respectively.
- such oxide may have an oxygen-to-metal atomic ratio that is not exactly these values.
- the molybdenum or vanadium oxides may form one or more complexes or compounds with the support. These complexes usually also will be an oxide such as polymolybdates and/or polyvanadates. Such molybdenum complexes may have general formulas such as ZrMo 2 O 8 . Vanadium complexes would generally be represented by the formula M 2x V 2y O (nx+5y) where M is the cationic ion of the support and n is the oxidation state of M, e.g., ZrV 2 O 7 . In any case, such complexes of molybdenum and vanadium oxides with the support are considered to be within the definition of the oxide catalysts to which this invention pertains.
- the larger MoO x domains undergo faster reduction compared to the smaller ones, and ZrMo 2 O 8 domains are more reducible than two-dimensional polymolybdate and MoO 3 domains at a given Mo surface density, reflecting the difference in the ability of these species to delocalize charge.
- the support may be selected among commonly used supports for such oxide catalysts, including mixtures of such supports, provided it allows or favors the formation of a monolayer of molybdenum and/or vanadium oxide on the surface of the support and otherwise is suitable for use in the production of formaldehyde from dimethyl ether.
- Some properties may make certain supports unsuitable for use in the process of this invention. For instance, supports that will react with the molybdenum and/or vanadium oxide to form any significant amounts of unreducible mixed bulk oxides, i.e. oxides that would undergo substantial formation of oxygen vacancies at temperatures below about 300-400° C., would in general not be suitable for use in this process.
- the catalyst preferably contains molybdenum or vanadium oxide, but may contain a combination of the two. When both oxides are present in the catalyst, one may be present as a layer of oxide on the support, preferably close to a monolayer, and the other present as a layer on top of the first oxide layer.
- Catalysts of this invention thus may comprise a layer, preferably approximately a monolayer, of one of molybdenum or vanadium oxide on a layer, preferably approximately a monolayer, of the other, on a support such as alumina or zirconia.
- the support may optionally further comprise a reducible metal oxide as described below.
- Preferred supports include alumina, zirconia, titania, silica, and reducible metal oxides such as stannic oxide, ferric oxide, ceric oxide, and mixtures or other combinations of two or more of these oxides. Particularly preferred are alumina, zirconia and stannic oxide, arid mixtures or other combinations of two or all three of them. Most preferred is a catalyst comprising alumina, titania, zirconia or silica modified by the incorporation of a layer or layers of a reducible oxide such as zirconia, stannic oxide, ferric oxide or ceric oxide deposited thereon.
- the supports that are suitable for use in this process may be used in any of their available forms, including forms that as of the present time might not yet have been developed, or may have been developed but have not yet been commercialized. Both high and low surface area supports may be used, including materials known by the acronym MCM (standing for Mobil Compositions of Matter), e.g., MCM-41. These are recently developed mesoporous materials (often comprising silica) and are described in Kresge, et al., (Nature, 359, 710 (1992)) and by Corma (Chem. Rev., 97, 2373 (1997)). High surface area supports of various physical types are preferred for use in the invention from the point of view of efficiency in that they may produce greater amounts of product per unit mass of overall catalyst.
- Reducible metal oxides suitable for inclusion in the catalysts of this invention are those in which at least a fraction of the metal cations undergo a one- or two-electron reduction during contact with a reactant such as hydrogen, dimethyl ether, methanol, alkanes or alkenes at typical temperatures of catalytic oxidation reactions, whether or not such metal oxides function as catalyst for the reaction in question.
- the fraction of the reducible metal oxide that undergoes such reduction need not be large, as the effect of the reducible metal oxide is continuous.
- Such reducible metal oxides include reducible oxides of tin, iron, cerium, manganese, cobalt, nickel, chromium, rhenium, titanium, silver and copper, and mixtures thereof. Of these, oxides of tin (e.g., stannic oxide), iron (e.g., ferric oxide) and cerium (e.g., ceric oxide) are preferred, with stannic oxide being most preferred for such catalysts of this invention.
- Novel catalysts of this invention include those in which the support comprises a layer of a reducible metal oxide disposed on a particulate alumina and/or zirconia (except where zirconia is used as the above-mentioned layer), or a layer of zirconia disposed on a particulate alumina, particularly those in which the layer of or zirconia has a surface density close to that of a monolayer of that substance.
- Exemplary catalysts may comprise molybdenum and/or vanadium oxide on a near-monolayer of stannic oxide disposed on a particulate (preferably high surface area) alumina.
- Novel catalysts of this invention also include those in which the reducible metal oxide or oxides is incorporated into the support.
- reducible metal oxides aid in catalyst performance by decreasing the temperature required for the reduction of some of the molybdenum and/or vanadium atoms from their highest oxidation state.
- novel catalysts of this invention that contain reducible metal oxides also are suitable as catalysts for other reactions and processes, including but not limited to oxidation of methanol to produce formaldehyde, oxidative dehydrogenation of alkanes, and oxidation of alkenes.
- the catalysts of the invention are prepared by typical means, for instance by impregnation, particularly incipient wetness impregnation, of the support with an aqueous solution containing molybdenum and/or vanadium, e.g. using a salt such as an ammonium molybdate or vanadate, for instance, ammonium di- or heptamolybdate or ammonium metavanadate.
- a salt such as an ammonium molybdate or vanadate, for instance, ammonium di- or heptamolybdate or ammonium metavanadate.
- the preparation is carried out so as to disperse the molybdenum and/or vanadium oxide over the surface of the support and the amounts are chosen so as to achieve a desired surface density.
- the reducible metal oxide may be first deposited on the particulate support, for instance by impregnation such as incipient wetness impregnation. Then the molybdenum and/or vanadium oxide is deposited on the support in a second step, e.g. a second impregnation. Preparation of such catalysts by incipient wetness impregnation is described in the Chen et al. and Khodakov et al. publications mentioned above.
- Catalysts of this invention may alternatively be prepared by other means such as chemical vapor deposition of layers, precipitation, sol-gel methods and the like. Reducible metal oxides may be incorporated into the catalysts either before or after the incorporation of the molybdenum and/or vanadium oxides.
- the primary products of the reaction are formaldehyde and methyl formate.
- Production of methyl formate can be increased if desired, by decreasing the surface density of metal oxide or choosing a specific support such as stannic oxide and/or zirconia, or it may be decreased (which is generally preferred since formaldehyde is typically the preferred product) by providing a catalyst having a surface density close to the value for a monolayer of catalyst, which, as will be shown below, generally has the highest selectivity to formaldehyde of the catalysts of the invention.
- production of methyl formate is to be expected in such a process, and is not especially detrimental as methyl formate has uses of its own as a chemical intermediate and can readily be separated from the reaction products and forwarded to other process units for such uses.
- Methanol is also produced in processes of this type, but it dehydrates relatively readily to re-form dimethyl ether.
- the methanol produced can be recovered and recycled.
- methanol produced by this reaction may be forwarded to another unit, either for production of further formaldehyde using a typical catalyst for that process, or for other uses as a chemical intermediate. Methanol formation therefore can be essentially disregarded in calculating selectivity of the dimethyl ether to formaldehyde.
- the feed to the process may include, in addition to dimethyl ether, mixtures of dimethyl ether and methanol, provided that dimethyl ether is the major component of such mixtures.
- the oxidizing agent may be air, oxygen-enriched air, or even pure oxygen (though this is likely to be unnecessarily costly).
- the process of this invention may be run in equipment ranging in size from microreactors (e.g. microchannel reactors) to full-sized commercial process equipment.
- a commercial installation will include typical process expedients such as recycle streams, for efficient use of reactants and reaction products, and may be integrated with process units for production of dimethyl ether or for production of products from formaldehyde.
- the process of this invention exhibits both improved conversions of dimethyl ether as well as improved selectivity to formaldehyde, and can achieve these results at lower temperatures.
- the process of this invention may be operated in general at temperatures of from about 150 to about 400° C., preferably from about 180 to about 350° C., most preferably from about 150 to about 320° C. Operating pressures are about 0.1-100 atm, preferably about 1-20 atm. Residence time generally ranges from about 1 to about 60 seconds.
- Supported MoO x catalysts were prepared by incipient wetness impregnation of ZrO(OH) 2 , SnO 2 , or Al 2 O 3 , respectively, with aqueous (NH 4 ) 2 Mo 2 O 8 (99%, Aldrich) solutions (13-15).
- ZrO(OH) 2 was prepared by hydrolysis of aqueous zirconyl chloride solutions (>98%, Aldrich) using NH 4 OH (14.8 N), followed by drying in ambient air at 393 K overnight.
- SnO 2 was prepared by hydrolysis of tin (IV) chloride pentahydrate (98%, Alfa Aesar) with NH 4 OH (14.8 N), followed by treatment in flowing dry air at 773 K for 3 h.
- Dimethyl ether reactions were carried out in a fixed-bed quartz microreactor using catalysts (0.3 g) diluted with quartz powder (1 g) in order to prevent local high temperatures caused by the exothermic nature of the reaction.
- the reactant mixture consisted of 80 kPa DME and 18 kPa O 2 , and 2 kPa N 2 was used as an internal standard.
- Reactants and products were analyzed by on-line gas chromatography (Hewlett-Packard 6890 GC) using flame ionization and thermal conductivity detectors and methyl-silicone capillary and Porapak® Q packed columns.
- Table 1 shows catalytic results obtained at 513 K on MoO x domains supported on Al 2 O 3 , ZrO 2 and SnO 2 with similar Mo surface densities (6.4-7.0 Mo-atoms/nm 2 ), alone and compared with results reported in previous patents. Rates and selectivities (in all tables) were measured as a function of DME conversion, which was changed by varying the reactant residence time. DME conversion rates and formaldehyde selectivities were extrapolated to zero reactant residence time in order to obtain primary DME conversion rates and selectivities. DME conversion rates and selectivities are reported in two forms in the results shown in Table 1.
- MgO molybdenum oxide supported on magnesium oxide.
- MgO was prepared by contacting MgO (>98%, Aldrich) with deionized water at 355-365 K for 4 h, followed by treatment in flowing dry air at 773 K for 8 h.
- MoO x domains supported on MgO did not give detectable DME conversion rates, apparently as a result of the formation of mixed metal oxides, which are unable to undergo reduction-oxidation cycles required for catalytic DME conversion turnovers at these temperatures. This support thus appears unsuitable for use with the catalysts in this process.
- Table 3 shows results of a study comparing reaction rates and selectivity at temperatures of 473-533 K (200-250° C.).
- the catalyst used contained 15 wt. % MoO 3 on alumina with a surface density of 7.0 Mo/nm 2 .
- the reaction rate increased significantly, and selectivity to formaldehyde (as opposed to methyl formate) also increased significantly.
- TABLE 3 Effects of temperature on primary DME reaction rates and primary products on MoO x /Al 2 O 3 catalyst (15 wt. % MoO 3 ; 7.0 Mo/nm 2 ) (80.0 kPa, 18 kPa O 2 and 2 kPa N 2 ).
- the catalysts were prepared by incipient wetness impregnation of precipitated zirconium oxyhydroxide (ZrO(OH) 2 ) with an aqueous solution of ammonium dimolybdate [(NH 4 ) 2 Mo 2 O 8 ] (99%, Aldrich).
- Zirconium oxyhydroxide (ZrO(OH) 2 ) was prepared by precipitation of a zirconyl chloride solution (98%, Aldrich) at a constant pH of 10 by controlling the rate of addition of ammonium hydroxide solution (29.8%, Fisher Sci.).
- the catalysts were systematically characterized by means of powder X-ray diffraction (XRD), diffuse reflectance UV-visible, Raman, and X-ray absorption (XANES/XAFS) spectroscopies. Surface areas were measured by N2 physisorption using standard multipoint BET method. Mo surface density is expressed as the number of Mo atoms per square nanometer BET surface area (Mo/nm 2 ). The catalysts so prepared are listed in Table 4. TABLE 4 Surface areas and Mo surface density for MoO x /ZrO 2 catalysts treated at 723, 773 and 873 K. 723 K 773 K 873 K MoO 3 Loading Surface area Mo surface density Surface area Mo surface density Surface area Mo surface density Surface area Mo surface density Surface area Mo surface Sample (wt.
- Tables 5 and 6 show the results using catalysts so prepared and calcined at 773 K and 873 K, respectively. Both catalysts demonstrated very good dimethyl ether conversion rates and selectivity, with better performance being exhibited in general by the catalyst that had been calcined at 873 K. TABLE 5 Effects of surface density of MoO x /ZrO 2 catalysts (calcined at 773 K) on primary DME reaction rates and primary products at 513 K (80.0 kPa, 18 kPa O 2 and 2 kPa N 2 ). MoO 3 loading Mo surface density Rate d Rate d Selectivity (%) d (MoO 3 wt.
- the V 5+ concentrations in the solution were varied in order to get desired V content in the final catalysts. After impregnation, samples were dried in air at 393 K and treated in dry air at 773 K (500° C.) for 3 h.
- SnO x and ZrO x -modified Al 2 O 3 supports (SnO x /Al 2 O 3 and ZrO x /Al 2 O 3 ) were prepared by incipient wetness impregnation of Al 2 O 3 (Degussa A G, ⁇ 100 m 2 /g or 180 m 2 /g) with isobutanol solutions of Sn(i-C 4 H 9 O) 4 and Zr(i-C 4 H 9 O) 4 (Aldrich, 99.8%), respectively at 289 K under dry N 2 atmosphere for 5 h, followed by drying at 393 K overnight and then treating in flowing dry air (Airgas, zero grade) at 673 K for 3 h.
- Airgas Airgas, zero grade
- CeO x and FeO x -modified Al 2 O 3 supports (CeO x /Al 2 O 3 and FeO x /Al 2 O 3 ) were prepared by incipient wetness impregnation of Al 2 O 3 (Degussa A G, 100 m 2 /g) with aqueous solutions of Ce(NO 3 ) 4 (Aldrich, 99.99%) and Fe(NO 3 ) 3 (Aldrich, 99.9%), respectively at 289 K for 5 h, followed by drying at 393 K overnight and then treating in flowing dry air (Airgas, zero grade) at 673 K for 3 h.
- Ce(NO 3 ) 4 Aldrich, 99.99%)
- Fe(NO 3 ) 3 Aldrich, 99.9%
- SnO 2 was prepared by hydrolysis of tin (IV) chloride pentahydrate (98%, Alfa Aesar) at a pH of ⁇ 7 using NH 4 OH (14.8 N, Fisher Scientific). The precipitates were washed with deionized water until the effluent was free of chloride ions. The resulting solids were treated in flowing dry air (Airgas, zero grade) at 773 K for 3 h. Supported MoO x catalysts were prepared by incipient wetness impregnation method using aqueous (NH 4 ) 6 Mo 7 O 24 (Aldrich, 99%) solutions.
- Tables 11 and 12 show the effects of BET surface area of the MoO x and VO x catalysts on the primary DME conversion rates and product selectivities at 513 K.
- the rates normalized by the mass of the catalysts were proportional to their surface areas, while the rates normalized by Mo or V atoms and the HCHO selectivities were essentially independent of the surface area of the catalysts.
- the DME conversion rate per gram catalyst increased from 4.7 mmol/g-cat-h to 9.4 mmol/g-cat-h, i.e., by a factor of two as the surface area increased from 90.0 m 2 /g for MoO x /Al 2 O 3 (A) to 174.9 m 2 /g.
- the rate per Mo atom (4.7 vs. 5.1 mmol/g-atom Mo-h) and the primary HCHO selectivity (98.1% vs. 96.0%) values remained essentially unchanged, reflecting no change in the catalytic properties of the active MoO x sites with changing the surface area of the samples.
Abstract
Dimethyl ether is converted to formaldehyde using a supported catalyst comprising molybdenum and/or vanadium oxides. The surface density of the oxide(s) ranges from greater than that for the isolated monomeric oxides upwards, so long as there is a substantial absence of bulk crystalline molybdenum and/or vanadium oxide(s). Conversion and selectivity to formaldehyde are improved as compared to data reported for known catalysts. Also disclosed is a supported catalyst comprising molybdenum and/or vanadium oxides wherein the support comprises one or more reducible metal oxides, preferably a layer or layers of one or more reducible metal oxides disposed on the surface of a particulate alumina or zirconia support.
Description
- This is a continuation-in-part of application Ser. No. 10/081,047 filed Feb. 20, 2002.
- This invention relates to a process for production of formaldehyde, and optionally also methyl formate as a co-product, by oxidation of dimethyl ether (DME), and to catalysts for use in the process, including catalysts that are novel per se. In addition, this invention relates to the use of such novel catalysts in other processes.
- Formaldehyde is widely used as an intermediate or basic building block in the commercial synthesis of many chemicals. Because of the existence of large reserves of methane worldwide it has been considered desirable for some time to develop processes to convert methane to more valuable chemicals. One such effort has been in the area of direct conversion of methane to formaldehyde via selective oxidation. However, this has not been particularly successful. Up to now, all such processes have resulted in low yields due to the tendency of the formaldehyde so produced being further oxidized to carbon oxides under the severe reaction conditions required for methane oxidation.
- Instead, formaldehyde is commercially produced from methane indirectly, for instance, by first converting the methane to synthesis gas (CO and H2), then reacting that to form methanol, and finally oxidizing the methanol to produce formaldehyde. The oxidation of methanol to formaldehyde has been extensively studied, and is the dominant process today for formaldehyde synthesis, typically using silver- or iron/molybdenum-based catalysts.
- Another possible route to formaldehyde involves the oxidation of dimethyl ether (CH3OCH3) via cleavage of the C—O—C linkages. This process, however, has not been widely studied.
- Dimethyl ether is a generally environmentally benign molecule. Its physical properties resemble those of LPG (liquefied petroleum gases), and dimethyl ether thus can be transported within existing and developing LPG infrastructures. Like methanol, dimethyl ether can be produced from synthesis gas. These characteristics give it the potential to be a new, clean alternative fuel. This potential is expected to lead to the production of substantially larger quantities of dimethyl ether than in the past, thus making it available for use as an intermediate in production of other chemicals, including formaldehyde.
- Several patents disclose processes for producing formaldehyde from dimethyl ether using various catalysts. U.S. Pat. No. 2,075,100 describes such a process using a number of comparatively mild oxidation catalysts including platinum wire or foil, palladium black, and metals such as gold, silver, and copper. Vanadium pentoxide and iron, chromium and uranium sesqui-oxides are termed “very suitable”. U.S. Pat. No. 3,655,771 describes using catalysts containing tungsten oxide, alone or optionally with no more than 10% of an additive. The additives mentioned include bismuth, selenium, molybdenum, vanadium, phosphorus and boron oxides, as well as phosphoric acid, ammonium phosphate and ammonium chloride.
- More recently, U.S. Pat. No. 4,435,602 describes a process for production of formaldehyde from dimethyl ether using naturally occurring manganese nodules as a catalyst. U.S. Pat. No. 4,439,624 describes such a process using an intimate mixture of bismuth, molybdenum and copper oxides, preferably prepared by coprecipitation. U.S. Pat. No. 4,442,307 describes such a process using an intimate mixture of bismuth, molybdenum and iron oxides, similarly prepared. U.S. Pat. No. 6,256,528 describes oxidation of dimethyl ether with a catalyst containing metallic silver to produce a mixture of products including formaldehyde, light alkanes, carbon oxides and water. Information in these patents indicates that formaldehyde was produced with reasonable yields, but that overoxidation of that product to carbon oxides occurred to an undesirable degree.
- As described above, it would be advantageous to provide a process and associated process technology for production of formaldehyde from dimethyl ether with good conversion and good selectivity to formaldehyde. Preferably such a process could be operated without the occurrence of substantial direct oxidation of dimethyl ether to carbon oxides or further oxidation of product formaldehyde to carbon oxides, thus improving the chemical and energy efficiency of the process.
- In brief, in one aspect, this invention comprises a process for the production of formaldehyde by oxidation of dimethyl ether in the presence of a supported catalyst comprising molybdenum oxide, vanadium oxide or a mixture of molybdenum and vanadium oxides. The support is one that substantially does not react with the molybdenum or vanadium oxide to form unreducible mixed oxide(s). Preferred supports comprise alumina, zirconia, stannic oxide, titania, silica, ferric oxide, ceric oxide, other reducible metal oxides, and mixtures and combinations thereof.
- In one preferred embodiment this invention comprises such a process in which the molybdenum and/or vanadium oxides are dispersed on the surface of the support, the surface density of the oxide or oxides on the support is greater than that for the isolated monomeric oxide or oxides, and in which the catalyst is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides.
- Most preferably the surface density of the molybdenum and/or vanadium oxide or oxides on the support is approximately that of a monolayer of the oxide or oxides at the surface of the support.
- In another preferred embodiment, the catalyst comprises one or more reducible metal oxides. More preferably in this embodiment, the catalyst comprises a layer of the reducible metal oxide or oxides, most preferably stannic oxide, on a particulate support (preferably alumina and/or zirconia) with the molybdenum and/or vanadium oxide or oxides being present as an upper layer or layers on the layer of reducible metal oxide(s) layer. In this embodiment, preferably the surface density of the molybdenum and/or vanadium oxide or oxides on the support is greater than that for the isolated monomeric oxide or oxides, and the catalyst is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides. Most preferably the surface density of the molybdenum and/or vanadium oxide or oxides on the support is approximately that of a monolayer of the oxide or oxides at the surface of the support.
- Catalysts of the above type in which the catalyst comprises one or more reducible metal oxides, particularly stannic oxide, and more particularly in which the molybdenum and/or vanadium oxide is supported on a layer or layers of reducible metal oxide or oxides, with the oxide layer or layers being disposed on a particulate alumina and/or zirconia, are novel and form another feature of this invention.
- Yet another aspect of this invention is the use of the novel catalysts just described to catalyze other processes, particularly oxidation of methanol to formaldehyde, oxidative dehydrogenation of alkanes, and oxidation of alkenes.
- In brief, a primary aspect of this invention comprises a process for the production of formaldehyde by oxidation of dimethyl ether in the presence of a supported catalyst comprising molybdenum oxide, vanadium oxide or a mixture of molybdenum and vanadium oxides. Preferably the oxides are supported on alumina (Al2O3) and/or zirconia (ZrO2), and more preferably on such a support that also includes one or more reducible metal oxides, as described herein. Preferably, the molybdenum and/or vanadium oxides are dispersed on the surface of the support, the surface density of the oxide or oxides on the support is greater than that for the isolated monomeric oxide or oxides, and the catalyst is characterized by a substantial absence of bulk crystalline molybdenum or vanadium oxides. More preferably the molybdenum and//or vanadium oxides are dispersed on a layer or layers of a reducible oxide or oxides that is further supported on alumina, titania, silica or zirconia (if zirconia is not used as the above-mentioned layer).
- Catalysts of this type that comprise molybdenum or vanadium oxides supported on alumina or zirconia are described in several prior publications, for catalyzing the oxidative dehydrogenation of propane to propene. These include Chen, et al., in “Studies in Surface Science and Catalysis”, Vol. 136, pp. 507-512, J. J. Spivey, E. Iglesia and T. M. Fleisch, Ed. (Elsevier Science, B. V., 2001); Chen et al., J. Catalysis 189, 421 (2000), Khodakov et al., J. Catalysis 177, 343 (1998), Chen et al., J. Catalysis 198, 232 (2001) and Chen et al., J. Phys. Chem. B2011, 105, 646 (2001). These publications are hereby incorporated herein by reference. However, these publications do not disclose catalysts containing stannic oxide, titania, silica, or other supports, and do not discuss the usefulness or potential usefulness of the disclosed catalysts for reactions such as the production of formaldehyde from dimethyl ether.
- In the catalysts of this invention, the molybdenum and/or vanadium oxide is distributed on the surface of the support material in what is known as “small domain” distribution. The surface density of the oxide catalyst on the support (measured in units of Mo or V metal atoms per nm2) is chosen so as to be greater than the surface density of the respective isolated monomeric oxide or oxides, but the catalyst overall is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides (corresponding to the oxide or oxides used in preparing the catalyst). By “bulk crystalline oxides” is meant oxide(s) having a clear X-ray diffraction pattern. The crystallinity can be determined by X-ray diffraction based on the peak intensity ratio between one of the peaks of the supported metal oxide and one of the peaks of the support employed after calibration with a mixture of known amounts of the metal oxide and the support. By “substantial absence” is meant that the supported catalyst contains less than about 5% of bulk crystalline molybdenum and/or vanadium oxide(s).
- Surface densities of the catalysts in this invention are given in terms of nominal surface density. This value is calculated based on the elemental analysis of the molybdenum and/or vanadium oxide and on the surface area of the support, i.e., by dividing the number of metal atoms of the catalytic metal (Mo or V) in a given mass of sample by the surface area of the support (calculated from N2 absorption at its normal boiling point using the Brunauer-Emmett-Teller, or BET, equation). Where the metal oxide does not appreciably interact with the support to form a complex (as described below), this calculated surface density fairly closely conforms to the actual surface density of the metal atoms on the surface of the support. However, where an appreciable amount of a complex is formed between the metal oxide and the support, the (nominal) surface density represents what that value would be were a complex not formed.
- The surface density of the catalyst affects the catalyst efficiency. At one extreme, catalysts of this type with relatively isolated oxide species, for example monomolybdate or monovanadate species, have relatively few active sites on the support surface. These catalysts tend to retain their oxygen and thus provide rather low reaction rates for the oxidation of dimethyl ether to formaldehyde. At the other extreme, catalysts having bulk crystals may possibly provide reasonable reaction rates per unit surface area. However, they also lack efficiency in the utilization of the oxide catalyst because a substantial amount of the oxide is located within the crystals and is thus not available for catalyzing the reaction. Bulk MoO3 crystals also tend to be nonselective in their functioning, and can cause overreaction to produce carbon oxides rather than the desired products formaldehyde and methyl formate.
- It has been found that the most preferred catalysts for this reaction tend to have a surface density of approximately a monolayer of catalyst on the support. The monolayer surface density depends primarily on the oxide chosen. For molybdenum oxide, the monolayer surface density is ˜5.0 Mo atoms per square nanometer of support (Xie et al, Adv. Catal., 37, 1 (1990)). For vanadium oxide, this value is approximately 7.5 V atoms per square nanometer (Centi, Appl. Catal. A, 147, 267 (1996)). The term “monolayer” as used herein is meant to refer to these approximate surface densities. If the catalyst is uniformly dispersed on the support, satisfactory results are obtainable with a preferred surface density of from approximately 50-300% of the monolayer capacity values for alumina supports, and approximately 50-400% of these values for zirconia supports. Overall, a preferred range of surface densities is from about 50 to about 300% of the monolayer capacity, for both molybdenum and vanadium oxides, for all supports usable in this invention.
- The molybdenum or vanadium oxide may be present as the oxide per se, represented by the general formulas MoOx and VOy, where x and y represent general values for oxygen in such molecules. For MoOx, the oxide generally comprises about three oxygen atoms per molybdenum atom; i.e., the general form of the oxide may be represented as MoO3, or molybdenum trioxide. For VOy, the oxide generally comprises about five oxygen atoms per two vanadium atoms, represented by the general formula V2O5, or vanadium pentoxide. However, in a given case the oxide may have an oxygen-to-metal atomic ratio that is not necessarily exactly 3:1 for molybdenum oxides or 5:2 for vanadium oxides. Likewise, oxides used as a component of the support may be represented by more general formulas such as SnOx, FeOx and CeOx where the oxides generally comprise about 2, 1.5 and 2 oxygen atoms per metallic atom, respectively. However, in a given case, such oxide may have an oxygen-to-metal atomic ratio that is not exactly these values.
- In addition, the molybdenum or vanadium oxides may form one or more complexes or compounds with the support. These complexes usually also will be an oxide such as polymolybdates and/or polyvanadates. Such molybdenum complexes may have general formulas such as ZrMo2O8. Vanadium complexes would generally be represented by the formula M2xV2yO(nx+5y) where M is the cationic ion of the support and n is the oxidation state of M, e.g., ZrV2O7. In any case, such complexes of molybdenum and vanadium oxides with the support are considered to be within the definition of the oxide catalysts to which this invention pertains.
- For instance, with molybdenum oxide supported on zirconia, as seen in examples below, where the Mo surface density is below 6.4 Mo/nm2 the ZrO2 surface is covered predominantly by two-dimensional polymolybdates (irrespective of the temperature of preparation), and the MoOx domain size increases with increasing the Mo surface density. At Mo surface densities above 6.4 Mo/nm2, increase in the Mo surface density leads to the preferential formation of MoO3 or ZrMo2O8 crystallites on the ZrO2 surface after treatment in air at 723 and 773 K or at 873 K, respectively. This makes a fraction of the Mo active centers inaccessible to dimethyl ether reactions and thus, as described below, leads to a monotonic decrease in the primary dimethyl ether reaction rates with increasing Mo surface density (>6.4 Mo/nm2).
- For such samples where the surface density was greater than 6.4 Mo/nm2, the areal dimethyl ether reaction rates (per surface area) and primary selectivities approached constant values as the Mo surface density increased. This indicates that the MoO3 or ZrMo2O8 domains at the ZrO2 surface do not change in their local structure or surface properties, while their domain size grows with increasing the Mo surface density. The surface density of 6.4 Mo/nm2 exceeds the theoretical polymolybdate monolayer, which is about 5.0 Mo/nm2 Nevertheless, the catalyst sample with a surface density of 6.4 Mo/nm2 exhibited the highest dimethyl ether reaction rates among the zirconia-supported molybdenum catalyst samples. This appears to be a compromise between reactivity and accessibility of the MoOx sites. The samples having a ZrMo2O8 structure possess a higher reactivity compared to the samples having polymolybdates and MoO3 crystallines at a given Mo surface density, which is believed to be a result of the higher reducibility of the ZrMo2O8 species. The reducibility of the MoOx domains (characterized by a H2 temperature-programmed reduction method) was found also to be dependent on the domain size and structures of the MoOx species. The larger MoOx domains undergo faster reduction compared to the smaller ones, and ZrMo2O8 domains are more reducible than two-dimensional polymolybdate and MoO3 domains at a given Mo surface density, reflecting the difference in the ability of these species to delocalize charge.
- The support may be selected among commonly used supports for such oxide catalysts, including mixtures of such supports, provided it allows or favors the formation of a monolayer of molybdenum and/or vanadium oxide on the surface of the support and otherwise is suitable for use in the production of formaldehyde from dimethyl ether. Some properties may make certain supports unsuitable for use in the process of this invention. For instance, supports that will react with the molybdenum and/or vanadium oxide to form any significant amounts of unreducible mixed bulk oxides, i.e. oxides that would undergo substantial formation of oxygen vacancies at temperatures below about 300-400° C., would in general not be suitable for use in this process. One commonly used catalyst support, magnesium oxide, for example, was tested for suitability in this process and was found unsuitable. Supports that could cause undesired combustion of products to form carbon oxides under the operating conditions of this process, or that contain acid sites that could cause formation of excessive amounts of methanol under the conditions of this process also would not be suitable for use in this invention.
- The catalyst preferably contains molybdenum or vanadium oxide, but may contain a combination of the two. When both oxides are present in the catalyst, one may be present as a layer of oxide on the support, preferably close to a monolayer, and the other present as a layer on top of the first oxide layer. Catalysts of this invention thus may comprise a layer, preferably approximately a monolayer, of one of molybdenum or vanadium oxide on a layer, preferably approximately a monolayer, of the other, on a support such as alumina or zirconia. The support may optionally further comprise a reducible metal oxide as described below.
- Preferred supports include alumina, zirconia, titania, silica, and reducible metal oxides such as stannic oxide, ferric oxide, ceric oxide, and mixtures or other combinations of two or more of these oxides. Particularly preferred are alumina, zirconia and stannic oxide, arid mixtures or other combinations of two or all three of them. Most preferred is a catalyst comprising alumina, titania, zirconia or silica modified by the incorporation of a layer or layers of a reducible oxide such as zirconia, stannic oxide, ferric oxide or ceric oxide deposited thereon. The supports that are suitable for use in this process may be used in any of their available forms, including forms that as of the present time might not yet have been developed, or may have been developed but have not yet been commercialized. Both high and low surface area supports may be used, including materials known by the acronym MCM (standing for Mobil Compositions of Matter), e.g., MCM-41. These are recently developed mesoporous materials (often comprising silica) and are described in Kresge, et al., (Nature, 359, 710 (1992)) and by Corma (Chem. Rev., 97, 2373 (1997)). High surface area supports of various physical types are preferred for use in the invention from the point of view of efficiency in that they may produce greater amounts of product per unit mass of overall catalyst.
- Reducible metal oxides suitable for inclusion in the catalysts of this invention are those in which at least a fraction of the metal cations undergo a one- or two-electron reduction during contact with a reactant such as hydrogen, dimethyl ether, methanol, alkanes or alkenes at typical temperatures of catalytic oxidation reactions, whether or not such metal oxides function as catalyst for the reaction in question. The fraction of the reducible metal oxide that undergoes such reduction need not be large, as the effect of the reducible metal oxide is continuous. Such reducible metal oxides include reducible oxides of tin, iron, cerium, manganese, cobalt, nickel, chromium, rhenium, titanium, silver and copper, and mixtures thereof. Of these, oxides of tin (e.g., stannic oxide), iron (e.g., ferric oxide) and cerium (e.g., ceric oxide) are preferred, with stannic oxide being most preferred for such catalysts of this invention.
- Novel catalysts of this invention include those in which the support comprises a layer of a reducible metal oxide disposed on a particulate alumina and/or zirconia (except where zirconia is used as the above-mentioned layer), or a layer of zirconia disposed on a particulate alumina, particularly those in which the layer of or zirconia has a surface density close to that of a monolayer of that substance. Exemplary catalysts may comprise molybdenum and/or vanadium oxide on a near-monolayer of stannic oxide disposed on a particulate (preferably high surface area) alumina. Novel catalysts of this invention also include those in which the reducible metal oxide or oxides is incorporated into the support.
- Without intending to be bound by an explanation, it is believer that the reducible metal oxides aid in catalyst performance by decreasing the temperature required for the reduction of some of the molybdenum and/or vanadium atoms from their highest oxidation state.
- The novel catalysts of this invention that contain reducible metal oxides also are suitable as catalysts for other reactions and processes, including but not limited to oxidation of methanol to produce formaldehyde, oxidative dehydrogenation of alkanes, and oxidation of alkenes.
- The catalysts of the invention are prepared by typical means, for instance by impregnation, particularly incipient wetness impregnation, of the support with an aqueous solution containing molybdenum and/or vanadium, e.g. using a salt such as an ammonium molybdate or vanadate, for instance, ammonium di- or heptamolybdate or ammonium metavanadate. The preparation is carried out so as to disperse the molybdenum and/or vanadium oxide over the surface of the support and the amounts are chosen so as to achieve a desired surface density. Where the catalyst also comprises a reducible metal oxide, for instance as a layer on a particulate support, the reducible metal oxide may be first deposited on the particulate support, for instance by impregnation such as incipient wetness impregnation. Then the molybdenum and/or vanadium oxide is deposited on the support in a second step, e.g. a second impregnation. Preparation of such catalysts by incipient wetness impregnation is described in the Chen et al. and Khodakov et al. publications mentioned above.
- Catalysts of this invention may alternatively be prepared by other means such as chemical vapor deposition of layers, precipitation, sol-gel methods and the like. Reducible metal oxides may be incorporated into the catalysts either before or after the incorporation of the molybdenum and/or vanadium oxides.
- The primary products of the reaction are formaldehyde and methyl formate. Production of methyl formate can be increased if desired, by decreasing the surface density of metal oxide or choosing a specific support such as stannic oxide and/or zirconia, or it may be decreased (which is generally preferred since formaldehyde is typically the preferred product) by providing a catalyst having a surface density close to the value for a monolayer of catalyst, which, as will be shown below, generally has the highest selectivity to formaldehyde of the catalysts of the invention. However, production of methyl formate is to be expected in such a process, and is not especially detrimental as methyl formate has uses of its own as a chemical intermediate and can readily be separated from the reaction products and forwarded to other process units for such uses.
- Methanol is also produced in processes of this type, but it dehydrates relatively readily to re-form dimethyl ether. The methanol produced can be recovered and recycled. Alternatively, methanol produced by this reaction may be forwarded to another unit, either for production of further formaldehyde using a typical catalyst for that process, or for other uses as a chemical intermediate. Methanol formation therefore can be essentially disregarded in calculating selectivity of the dimethyl ether to formaldehyde.
- The feed to the process may include, in addition to dimethyl ether, mixtures of dimethyl ether and methanol, provided that dimethyl ether is the major component of such mixtures. The oxidizing agent may be air, oxygen-enriched air, or even pure oxygen (though this is likely to be unnecessarily costly).
- The process of this invention may be run in equipment ranging in size from microreactors (e.g. microchannel reactors) to full-sized commercial process equipment. A commercial installation will include typical process expedients such as recycle streams, for efficient use of reactants and reaction products, and may be integrated with process units for production of dimethyl ether or for production of products from formaldehyde.
- As compared with data in patents mentioned above, the process of this invention exhibits both improved conversions of dimethyl ether as well as improved selectivity to formaldehyde, and can achieve these results at lower temperatures. The process of this invention may be operated in general at temperatures of from about 150 to about 400° C., preferably from about 180 to about 350° C., most preferably from about 150 to about 320° C. Operating pressures are about 0.1-100 atm, preferably about 1-20 atm. Residence time generally ranges from about 1 to about 60 seconds.
- The following are representative examples of this invention. These examples are provided by way of illustration only and not by way of limitation. Those of skill will readily recognize a variety of noncritical parameters that could be changed or modified to yield essentially similar results.
- Supported MoOx catalysts were prepared by incipient wetness impregnation of ZrO(OH)2, SnO2, or Al2O3, respectively, with aqueous (NH4)2Mo2O8 (99%, Aldrich) solutions (13-15). ZrO(OH)2 was prepared by hydrolysis of aqueous zirconyl chloride solutions (>98%, Aldrich) using NH4OH (14.8 N), followed by drying in ambient air at 393 K overnight. SnO2 was prepared by hydrolysis of tin (IV) chloride pentahydrate (98%, Alfa Aesar) with NH4OH (14.8 N), followed by treatment in flowing dry air at 773 K for 3 h. A commercial source of γ-Al2O3 (Degussa A G) was used without further treatment. All samples were dried after impregnation at 373 K in ambient air and then treated in flowing dry air at 773 K for 3 h. Bulk MoO3 powders were prepared by decomposition of (NH4)2Mo2O8 (99%, Aldrich) in flowing dry air at 773 K for 3 h.
- Dimethyl ether reactions were carried out in a fixed-bed quartz microreactor using catalysts (0.3 g) diluted with quartz powder (1 g) in order to prevent local high temperatures caused by the exothermic nature of the reaction. The reactant mixture consisted of 80 kPa DME and 18 kPa O2, and 2 kPa N2 was used as an internal standard. Reactants and products were analyzed by on-line gas chromatography (Hewlett-Packard 6890 GC) using flame ionization and thermal conductivity detectors and methyl-silicone capillary and Porapak® Q packed columns.
- Table 1 shows catalytic results obtained at 513 K on MoOx domains supported on Al2O3, ZrO2 and SnO2 with similar Mo surface densities (6.4-7.0 Mo-atoms/nm2), alone and compared with results reported in previous patents. Rates and selectivities (in all tables) were measured as a function of DME conversion, which was changed by varying the reactant residence time. DME conversion rates and formaldehyde selectivities were extrapolated to zero reactant residence time in order to obtain primary DME conversion rates and selectivities. DME conversion rates and selectivities are reported in two forms in the results shown in Table 1. One approach considers CH3OH as a DME conversion product; the other approach reports rates and selectivities on a CH3OH-free basis, which seems appropriate in view of the reversible nature of DME conversion to methanol and the pathways available for the ultimate conversion of both CH3OH and DME to HCHO.
- Primary reaction rates (normalized by catalyst mass) were much higher on the three catalysts of the invention than on catalysts previously reported in the patents, even at the lower temperatures used here. Rates were higher on SnO2 and ZrO2 supports than on Al2O3, but the primary formaldehyde selectivity (CH3OH-free) was almost 100% on MoOx/Al2O3. Pure supports showed very low DME conversion rates. A MoO3 sample with relatively low surface area gave a low DME conversion rate (per gram), but its areal rate resembled those on MoOx/Al2O3 and was 2-6 times lower than on MoOx supported on ZrO2 and SnO2. Thus, DME conversion appears to require small MoOx domains with much greater accessibility to reactants than those available in bulk MoO3 samples. Formaldehyde was not detected on MoO3 at 513 K, because of the low DME conversions attained. At higher temperatures (593 K), the primary HCHO selectivity was 52.9% (on a CH3OH-free basis) on bulk MoO3. MoOx/Al2O3 was the most selective catalyst for DME conversion to HCHO. Its primary HCHO selectivity was 79.1% (98.1%, CH3OH-free basis) and CO and CO2 (COx) were not detected as primary products.
- Included in these tests was a catalyst similarly prepared comprising molybdenum oxide supported on magnesium oxide. MgO was prepared by contacting MgO (>98%, Aldrich) with deionized water at 355-365 K for 4 h, followed by treatment in flowing dry air at 773 K for 8 h. As seen from Table 1, however, MoOx domains supported on MgO did not give detectable DME conversion rates, apparently as a result of the formation of mixed metal oxides, which are unable to undergo reduction-oxidation cycles required for catalytic DME conversion turnovers at these temperatures. This support thus appears unsuitable for use with the catalysts in this process.
TABLE 1 DME oxidation rates and selectivities on supported MoOx catalysts at 513 K (80.0 kPa, 18 kPa O2 and 2 kPa N2), on bulk MoO3, on pure supports, and on previously reported catalysts. DIMETHYL ETHER DME DME Mo Conversion Conversion Conversion Catalyst Surface surface Temper- Rated Rated Rated (MoO3 area density ature (mmol/ (mol/g-atom (10−5 Selectivity (%)d wt %) (m2/g) (Mo/nm2) (K) g-cat-h) Mo-h) mol/m2-h) CH3OH HCHO MFa DMMb COx c Reference MoO3/ZrO2 136.3 6.4 513 17.6 12.2 12.9 22.6 53.4 16.8 0.3 6.9 This study (20.7%) (13.6) (9.4) (69.0) (21.7) (0.4) (8.9) MoO3/SnO2 46.5 6.5 513 18.4 36.5 39.6 13.1 67.3 9.6 0 9.8 This study (7.2%) (16.0) (31.7) (77.6) (11.1) (0) (11.3) MoO3/Al2O3 90.0 7.0 513 5.8 5.7 6.6 19.7 79.9 1.6 0 0 This study (15.0%) (4.7) (4.6) (98.1) (1.9) (0) (0) MoO3/MgO 171.2 5.8 513 not detected not detected — — — — — — This study (24.0%) ZrO2 106.4 — 513 not detected — — — — — — — This study SnO2 48.8 — 513 0.6 — 1.2 29.7 0 0 0 70.3 This study Al2O3 110 — 513 0.2 — 0.2 82.9 0 0 0 17.1 This study MoO3 3.3 — 513 0.2 — 6.1 6.0 0 0 0 94.0 This study eAg — — 887 10.5 — — — 45.8 0 0 30.7 10 fBi—Mo— — — 773 3.1 — — 0 46.0 0 0 54.0 7 FeOx gBi—Mo— — — 773 2.9 — — 0 43.0 0 0 55.0 8 CuOx hMn nodules ˜230 — 623 1.7 — 0.7 — 49.0 — — — 9 - A parallel study showed that the catalytic properties of these MoOx domains depend sensitively on their size and local structure, which were varied by changing the Mo surface density on Al2O3 (1.6-11.3 Mo/nm2) and ZrO2 (2.2-30.6 Mo/nm2). Primary DME reaction rates increased from 2.3 to 5.7 mol/g-atom Mo-h as the Mo surface density increased from 1.6 to 7.0 Mo/nm2 on Al2O3 (Table 2). These rates increased from 0.6 to 12.2 mol/g-atom Mo-h as the Mo surface density increased from 2.2 to 6.4 Mo/nm2 on ZrO2. On both ZrO2 and Al2O3, DME conversion rates per Mo reached maximum values at surface densities of 6-7 Mo/nm2. Results are reported in Table 2.
- X-Ray diffraction and Raman, UV-visible, and X-ray absorption spectroscopies did not detect MoO3 crystallites in samples with surface densities below 7 Mo/nm2. In this Mo surface density range, most, if not all, MoOx species are accessible at surfaces and the DME conversion rates per Mo atom are equivalent to rates per exposed MoOx moiety (i.e. turnover rates). Therefore, the higher reaction rates attained with increasing surface density reflect a higher reactivity of exposed MoOx as the size and dimensionality of MoOx domains increases with increasing Mo surface density. The larger domains formed at higher MoOx surface densities (detected by measurements of their absorption edge energy in the UV-visible spectra) appear to undergo the redox cycles required for DME conversion to HCHO with greater ease than isolated monomolybdate species or smaller two-dimensional polymolybdate domains.
- This interpretation is consistent with the observed decrease in the temperature required for H2 reduction of Mo6+ to Mo4+ in these samples. Ultimately, DME conversion rates (per Mo) decreased at even higher Mo surface densities (>10 Mo/nm2), because the incipient formation of three-dimensional MoO3 clusters leads to increasingly inaccessible MoOx species.
- Primary formaldehyde selectivities also increased monotonically with increasing Mo surface density; they reached 79.1% (98.1% on a CH3OH-free basis) on MoOx/Al2O3 at 11.3 Mo/nm2. Methanol selectivities decreased as the Al2O3 support was covered with MoOx species, and the primary formaldehyde selectivity concurrently increased with increasing Mo surface density. Methyl formate and COx primary selectivities were very low on all Al2O3-supported MoOx samples. On Al2O3-supported samples with surface densities of 1.6 to 11.3 Mo/nm2, the CH3OH-free primary HCHO selectivity was 95.2-98.1% (Table 2).
TABLE 2 Effects of surface density of MoOx/Al2O3 catalysts on primary DME reaction rates and primary products at 513 K (80.0 kPa, 18 kPa O2 and 2 kPa N2). MoO3 loading Mo surface density Rated Rated Selectivity (%)d (MoO3 wt %) (Mo/nm2) (mol/g-atom Mo-h) (10−5 mol/m2-h) CH3OH HCHO MFa DMMb COx c 4.0% 1.6 2.3 0.6 34.1 62.8 2.5 0 0.8 (1.5)d (0.4)d (95.2) (3.7) (0) (1.2) 8.0% 3.4 3.9 2.2 27.0 70.5 2.4 0 0.2 (2.8) (1.6) (96.5) (3.2) (0) (0.3) 10.0% 4.5 5.2 4.0 22.1 76.3 1.5 0 0.1 (4.1) (3.1) (97.9) (1.9) (0) (0.1) 15.0% 7.0 5.7 6.6 19.5 79.1 1.6 0 0 (4.6) (5.3) (98.1) (1.9) (0) (0) 20.0% 11.3 3.8 7.1 19.4 79.0 1.6 0.1 0 (3.1) (5.7) (98.0) (1.9) (0.1) (0) - Table 3 shows results of a study comparing reaction rates and selectivity at temperatures of 473-533 K (200-250° C.). The catalyst used contained 15 wt. % MoO3 on alumina with a surface density of 7.0 Mo/nm2. As the temperature was increased from 473 to 533 K, the reaction rate increased significantly, and selectivity to formaldehyde (as opposed to methyl formate) also increased significantly.
TABLE 3 Effects of temperature on primary DME reaction rates and primary products on MoOx/Al2O3 catalyst (15 wt. % MoO3; 7.0 Mo/nm2) (80.0 kPa, 18 kPa O2 and 2 kPa N2). Rated (mol/ Selectivity (%)d Temperature g-atom Mo-h) CH3OH HCHO MFa DMMb COx c 473 1.3 24.2 69.2 4.2 0.2 2.1 (1.0) (91.2) (5.5) (0.3) (2.8) 493 2.9 23.8 73.1 2.0 0 1.2 (2.2) (95.9) (2.6) (0) (1.6) 513 5.7 19.5 79.1 1.6 0 0 (4.6) (98.1) (1.9) (0) (0) 533 12.9 17.3 81.0 1.8 0 0 (10.7) (97.9) (2.1) (0) (0) - A series of molybdenum oxide catalysts supported on zirconia, having a range of surface densities and prepared by calcining at two different temperatures was used to catalyze the production of formaldehyde from dimethyl ether.
- The catalysts were prepared by incipient wetness impregnation of precipitated zirconium oxyhydroxide (ZrO(OH)2) with an aqueous solution of ammonium dimolybdate [(NH4)2Mo2O8] (99%, Aldrich). Zirconium oxyhydroxide (ZrO(OH)2) was prepared by precipitation of a zirconyl chloride solution (98%, Aldrich) at a constant pH of 10 by controlling the rate of addition of ammonium hydroxide solution (29.8%, Fisher Sci.). After precipitation, the solids were washed with mildly basic ammonium hydroxide solution (pH˜6) until the effluent showed no chloride ions tested by a silver nitrate solution. The resulting solids were dried in air overnight at 393 K (120° C.). The dried solids were impregnated with an aqueous solution of ammonium dimolybdate at room temperature. The Mo6+ concentrations in the solution were varied in order to get desired Mo content in the final catalysts. After impregnation, samples were dried in air at 393 K and treated in dry air at 723, 773 or 873 K (450, 500 and 600° C.) for 3 h.
- The catalysts were systematically characterized by means of powder X-ray diffraction (XRD), diffuse reflectance UV-visible, Raman, and X-ray absorption (XANES/XAFS) spectroscopies. Surface areas were measured by N2 physisorption using standard multipoint BET method. Mo surface density is expressed as the number of Mo atoms per square nanometer BET surface area (Mo/nm2). The catalysts so prepared are listed in Table 4.
TABLE 4 Surface areas and Mo surface density for MoOx/ZrO2 catalysts treated at 723, 773 and 873 K. 723 K 773 K 873 K MoO3 Loading Surface area Mo surface density Surface area Mo surface density Surface area Mo surface Sample (wt. %) (m2/g) (Mo/nm2) (m2/g) (Mo/nm2) (m2/g) density (Mo/nm2) 1MoOx/ZrO2 1.0% 118.8 0.3 105.6 0.4 85.6 0.5 6MoOx/ZrO2 5.7% 130.0 1.8 110.3 2.2 97.1 2.5 11MoOx/ZrO2 11.0% 145.9 3.2 132.6 3.5 103.4 4.5 21MoOx/ZrO2 20.7% 153.7 5.6 136.3 6.4 102.7 8.4 29MoOx/ZrO2 29.3% 114.0 10.7 96.9 12.6 64.6 20.0 37MoOx/ZrO2 37.0% 99.6 15.5 73.9 20.9 49.3 31.4 44MoOx/ZrO2 44% 83.5 22.0 60.2 30.6 36.7 50.1 - Tables 5 and 6 show the results using catalysts so prepared and calcined at 773 K and 873 K, respectively. Both catalysts demonstrated very good dimethyl ether conversion rates and selectivity, with better performance being exhibited in general by the catalyst that had been calcined at 873 K.
TABLE 5 Effects of surface density of MoOx/ZrO2 catalysts (calcined at 773 K) on primary DME reaction rates and primary products at 513 K (80.0 kPa, 18 kPa O2 and 2 kPa N2). MoO3 loading Mo surface density Rated Rated Selectivity (%)d (MoO3 wt. %) (Mo/nm2) (mol/g-atom Mo-h) (10−5 mol/m2-h) CH3OH HCHO MFa DMMb COx c 11.0% 3.5 8.5 4.9 24.0 32.3 30.0 0 13.7 (6.5) (3.7) (42.5) (39.5) (0) (18.1) 20.7% 6.4 12.2 12.9 22.6 53.4 16.8 0.3 6.9 (9.4) (10.0) (68.9) (21.7) (0.4) (8.9) 29.3% 12.6 4.1 8.6 22.3 62.9 8.4 0.2 6.4 (3.2) (6.7) (80.8) (10.7) (0.2) (8.2) 37.0% 20.9 3.2 11.1 23.0 66.9 7.6 0.1 2.4 (2.5) (8.6) (86.9) (9.8) (0.1) (3.1) 44.0% 30.6 2.0 10.4 22.4 68.6 5.0 0 4.0 (1.6) (8.1) (88.4) (6.5) (0) (5.1) -
TABLE 6 Effects of surface density of MoOx/ZrO2 catalysts (calcined at 873 K) on primary DME reaction rates and primary products at 513 K (80.0 kPa, 18 kPa O2 and 2 kPa N2). MoO3 loading Mo surface density Rated Rated Selectivity (%)d (MoO3 wt. %) (Mo/nm2) (mol/g-atom Mo-h) (10−5 mol/m2-h) CH3OH HCHO MFa DMMb COx c 11.0% 4.5 23.0 17.0 24.9 46.0 23.5 0.4 5.2 (17.3) (13.0) (61.2) (31.3) (0.5) (7.0) 20.7% 8.4 46.5 51.7 23.7 60.1 11.5 0.8 4.0 (35.5) (39.5) (78.6) (15.1) (1.1) (5.2) 29.3% 20.0 19.0 60.0 24.1 59.6 12.2 0.9 3.2 (14.4) (45.5) (78.5) (16.1) (1.2) (4.2) 37.0% 31.4 11.7 61.1 24.9 58.3 12.6 1.1 3.0 (8.8) (45.9) (77.7) (16.8) (1.5) (4.0) 44.0% 50.1 7.4 61.3 27.8 60.1 10.4 0.9 1.3 (5.3) (44.3) (82.7) (14.4) (1.2) (3.8) - In other work, the effect of partial pressures on the reaction was investigated on the 44 MoOx/ZrO2 catalyst (50.1 Mo/nm2). The reaction rates nearly increased linearly as the DME partial pressure increased from 10 to 40 kPa, and then approached the constant values above 60 kPa. The primary selectivities to methyl formate and dimethoxymethane were almost independent of the DME partial pressure. The primary selectivity to COx decreased from 6.0% to the constant value of 1.5% while the selectivity to HCHO increased from 78.3 to 82.7% with increasing the DME pressure from 10 to 40 kPa.
- The catalysts were prepared by incipient wetness impregnation of γ-Al2O3 (Degussa A G) with an aqueous solution of ammonium metavanadate [NH4NO3] (99%, Aldrich) and oxalic acid (Mallinckrodt, analytical grade; NH4/NO3/oxalic acid=0.5 M) (the addition of oxalic acid improves the dissolution of NH4NO3 in water). The V5+ concentrations in the solution were varied in order to get desired V content in the final catalysts. After impregnation, samples were dried in air at 393 K and treated in dry air at 773 K (500° C.) for 3 h.
- On VOx/Al2O3 (8.0 V/nm 2) the CH3OH-free primary HCHO selectivity was 99.6% at 513 K and the primary DME reaction rate was 6.8 mol/g-atom V-h. Results are shown in Table 7.
TABLE 7 Primary DME reaction rates and primary products on VOx dispersed on different supports at 240° C. (80.0 kPa, 18 kPa O2 and 2 kPa N2). Catalyst V surface density Ratea Ratea Selectivity (%) (V2O5 wt. %) (V/nm2) (mol/g-atom V-h) (10−5 mol/m2-h) CH3OH HCHO MFb DMMc COx d VOx/Al2O3 8.0 8.0 6.7 14.72 84.96 0.26 0 0 (10.0%) (6.8) (5.6) (99.61) (0.3) VOx/ZrO2 6.2 13.1 8.5 5.2 37.9 9.2 0 47.7 (15%) (12.4) (8.1) (40.0) (9.7) (50.3) VOx/MgO 5.5 1.8 1.0 11.0 0 0 0 89.0 (20.0%) - Similarly, experiments were conducted using a catalyst containing molybdenum oxide on a support of alumina modified by stannic oxide, cerium oxide and ferric oxide.
- SnOx and ZrOx-modified Al2O3 supports (SnOx/Al2O3 and ZrOx/Al2O3) were prepared by incipient wetness impregnation of Al2O3 (Degussa A G, ˜100 m2/g or 180 m2/g) with isobutanol solutions of Sn(i-C4H9O)4 and Zr(i-C4H9O)4 (Aldrich, 99.8%), respectively at 289 K under dry N2 atmosphere for 5 h, followed by drying at 393 K overnight and then treating in flowing dry air (Airgas, zero grade) at 673 K for 3 h. CeOx and FeOx-modified Al2O3 supports (CeOx/Al2O3 and FeOx/Al2O3) were prepared by incipient wetness impregnation of Al2O3 (Degussa A G, 100 m2/g) with aqueous solutions of Ce(NO3)4 (Aldrich, 99.99%) and Fe(NO3)3 (Aldrich, 99.9%), respectively at 289 K for 5 h, followed by drying at 393 K overnight and then treating in flowing dry air (Airgas, zero grade) at 673 K for 3 h. SnO2 was prepared by hydrolysis of tin (IV) chloride pentahydrate (98%, Alfa Aesar) at a pH of ˜7 using NH4OH (14.8 N, Fisher Scientific). The precipitates were washed with deionized water until the effluent was free of chloride ions. The resulting solids were treated in flowing dry air (Airgas, zero grade) at 773 K for 3 h. Supported MoOx catalysts were prepared by incipient wetness impregnation method using aqueous (NH4)6Mo7O24 (Aldrich, 99%) solutions. Supported VOx catalysts were also prepared by incipient wetness impregnation method using an aqueous solution of ammonium metavanadate [NH4NO3] (Aldrich, 99%) and oxalic acid (Mallinckrodt, analytical grade; NH4NO3/oxalic acid=0.5 M). All samples were dried at 393 K in ambient air after impregnation and then treated in flowing dry air (Airgas, zero grade) at 773 K for 3 h. The Mo or V surface density for all supported samples is reported as Mo/nm2 or V/nm2, based on the Mo or V content and the BET surface area for each sample.
- The catalysts retained the good selectivity of the molybdenum oxide/alumina catalysts but had higher activity. Results are reported in Tables 8 and 9. Table 10 shows results using vanadium oxide catalysts on alumina and on stannic oxide/alumina. As shown in Table 10, the DME conversion rates using VOx/SnOx/Al2O3 (5.5 Sn/nm2) were about 2.4 times than the rates on VOx/Al2O3 at 513K.
TABLE 8 Primary DME conversion rates and product selectivities for MoOx domains supported on Al2O3 modified with SnOx at different surface densities (1.5-11.2 Sn/nm2) and also on unmodified Al2O3 and SnO2 (˜7.0 Mo/nm2; 513 K; 80.0 kPa DME, 18 kPa O2 and 2 kPa N2). Support (MoO3 Sn surface density aDME conversion rate aPrimary selectivity (%) wt %) (Sn/nm2) (mol/g-atom Mo-h) HCHO bMF cDMM dCOx Al2O3 0 4.6 98.1 1.9 0 0 (15.0%) MoOx/SnO2 — 36.4 70.4 12.5 0 17.2 (5.9%) SnOx/Al2O3 1.5 5.4 97.2 2.8 0 0 (15.0%:) SnOx/Al2O3 2.8 7.1 98.0 2.0 0 0 (15.0%) SnOx/Al2O3 5.5 12.2 97.7 2.3 0 0 (15.0%) SnOx/Al2O3 11.2 12.9 97.6 2.4 0 0 (13.6%) -
TABLE 9 Primary DME conversion rates and product selectivities for MoOx domains supported on unmodified Al2O3, and on Al2O3 modified with near-single monolayer SnOx, ZrOx, CeOx, and FeOx (513 K; 80.0 kPa DME, 18 kPa O2 and 2 kPa N2). Catalyst Mo surface density aDME conversion rate aPrimary selectivity (%) (MoO3 wt %) (Mo/nm2) (mol/g-atom Mo-h) HCHO bMF cDMM dCOx MoOx/Al2O3 7.0 4.6 98.1 1.9 0 0 (15.0%) MoOx/SnOx/Al2O3 7.1 12.2 97.7 2.3 0 0 (15.0%) MoOx/ZrOx/Al2O3 6.8 8.7 98.6 1.4 0 0 (15.0%) MoOx/CeOx/Al2O3 6.6 6.8 98.8 1.2 0 0 (13.4%) MoOx/FeOx/Al2O3 6.7 6.2 99.7 0.3 0 0 (14.1%) -
TABLE 10 Primary DME conversion rates and product selectivities on VOx domains at near-single monolayer V surface density supported on unmodified and SnOx-modified Al2O3 (5.5 Sn/nm2) (513 K; 80.0 kPa DME, 18 kPa O2 and 2 kPa N2). Catalyst Mo surface density aDME Conversion Rate aPrimary selectivity (%) (MoO3 wt %) (Mo/nm2) (mol/g-atom Mo-h) HCHO bMF cDMM dCOx VOx/Al2O3 8.0 6.8 99.6 0.4 0 (10.0%) VOx/SnOx/Al2O3 7.9 16.3 97.7 2.3 0 (10.1%) - Tables 11 and 12 show the effects of BET surface area of the MoOx and VOx catalysts on the primary DME conversion rates and product selectivities at 513 K. The rates normalized by the mass of the catalysts were proportional to their surface areas, while the rates normalized by Mo or V atoms and the HCHO selectivities were essentially independent of the surface area of the catalysts.
- For example, on MoOx/Al2O3(B), the DME conversion rate per gram catalyst increased from 4.7 mmol/g-cat-h to 9.4 mmol/g-cat-h, i.e., by a factor of two as the surface area increased from 90.0 m2/g for MoOx/Al2O3(A) to 174.9 m2/g. The rate per Mo atom (4.7 vs. 5.1 mmol/g-atom Mo-h) and the primary HCHO selectivity (98.1% vs. 96.0%) values remained essentially unchanged, reflecting no change in the catalytic properties of the active MoOx sites with changing the surface area of the samples.
TABLE 11 Surface area effects on primary DME conversion rates and product selectivities for MoOx domains at near one monolayer surface density supported on unmodified and SnOx-modified Al2O3 (˜5.5 Sn/nm2) (513 K; 80.0 kPa DME, 18 kPa O2 and 2 kPa N2). BET surface Mo surface aDME conversion aDME conversion aPrimary HCHO selectivity area density rate rate (%) Support (m2/g-cat) (Mo/nm2) (mmol/g-cat-h) (mol/g-atom Mo-h) HCHO bMF cDMM dCOx Al2O3 (A) 90.0 7.0 4.7 4.6 98.1 1.9 0 0 (15.0%) Al2O3 (B) 174.7 6.4 9.4 5.1 95.9 3.1 0 0 (26.8%) SnO2/Al2O3 (A) 87.9 7.1 12.6 12.1 97.7 2.3 0 0 (15.0%) SnO2/Al2O3 (B) 150.3 6.4 18.4 11.4 98.2 1.8 0 0 (22.9%) -
TABLE 12 Surface area effects on primary DME conversion rates and product selectivities for VOx domains at near one monolayer surface density supported on unmodified and SnOx-modified Al2O3 (˜5.5 Sn/nm2) (513 K; 80.0 kPa DME, 18 kPa O2 and 2 kPa N2). BET surface V surface aDME conversion aDME conversion aPrimary HCHO selectivity Support area density rate rate (%) (V2O5%) (m2/g-cat) (V/nm2) (mmol/g-cat-h) (mol/g-atom V-h) HCHO bMF cDMM dCOx Al2O3 (A) 83.0 8.0 6.7 6.8 99.6 0.4 0 0 (10.0%) Al2O3 (B) 195.9 7.8 13.5 5.9 97.1 2.9 0 0 (23.2%) SnO2/Al2O3 (A) 84.3 7.9 16.2 16.3 97.7 2.3 0 0 (10.1%) SnO2/Al2O3 (B) 149.2 7.5 25.3 15.3 98.0 2.0 0 0 (16.8%) - All publications and patent applications cited in this specification are herein incorporated by reference as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference.
- Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes and modifications may be made thereto without departing from the spirit or scope of the appended claims.
Claims (9)
1-59. (canceled).
60. A catalyst comprising molybdenum oxide, vanadium oxide, or a mixture of molybdenum oxide and vanadium oxide supported on a support comprising one or more layers comprised of a reducible metal oxide or a mixture of reducible metal oxides, the reducible oxide layer or layers being disposed on a particulate alumina or zirconia support, in which the surface density of the molybdenum and/or vanadium oxide or oxides on the support is greater than that for the respective monomeric isolated oxide or oxides, and the catalyst is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides.
61. A catalyst according to claim 60 in which the reducible metal oxides are selected from reducible oxides of tin, iron, cerium, manganese, cobalt, nickel, chromium, rhenium, titanium, silver and copper, and mixtures thereof.
62. A catalyst according to claim 60 in which the reducible metal oxide is selected from oxides of tin, iron, cerium, and mixtures thereof.
63. A catalyst according to claim 60 in which the reducible metal oxide comprises stannic oxide.
64. A catalyst according to claim 60 in which the surface density of the molybdenum and/or vanadium oxide on the support is from about 50% of the surface density of a monolayer of the oxide or oxides to about 300% of the surface density of a monolayer of the oxide or oxides.
65. A catalyst according to claim 60 in which the surface density of the molybdenum and/or vanadium oxide or oxides on the support is approximately that of a monolayer of the oxide or oxides at the surface of the support.
66. A catalyst according to claim 60 comprising molybdenum oxide supported on a layer of stannic oxide that is disposed on a particulate alumina support, and in which the surface density of the molybdenum-oxide is from about 1.5 to about 20 Mo/nm2.
67. A catalyst according to claim 60 comprising molybdenum oxide supported on a layer of stannic oxide that is disposed on a particulate alumina support, and in which the surface density of the molybdenum oxide is approximately that of a monolayer of the oxide or oxides at the surface of the support.
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- 2003-02-20 WO PCT/US2003/005126 patent/WO2003070668A2/en active Application Filing
- 2003-02-20 EP EP03713561A patent/EP1485340A4/en not_active Withdrawn
- 2003-02-20 CN CNA2006101150181A patent/CN1931428A/en active Pending
- 2003-02-20 JP JP2003569578A patent/JP2005517727A/en not_active Withdrawn
- 2003-02-20 KR KR10-2004-7013017A patent/KR20040086421A/en not_active Application Discontinuation
- 2003-02-20 EA EA200401089A patent/EA007783B1/en not_active IP Right Cessation
- 2003-02-20 CA CA002476867A patent/CA2476867A1/en not_active Abandoned
- 2003-02-20 BR BR0307870-1A patent/BR0307870A/en not_active Application Discontinuation
- 2003-02-20 US US10/371,908 patent/US6781018B2/en not_active Expired - Lifetime
- 2003-02-20 CN CNA038064707A patent/CN1642891A/en active Pending
- 2003-02-20 AU AU2003217605A patent/AU2003217605A1/en not_active Abandoned
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Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2010034480A2 (en) * | 2008-09-24 | 2010-04-01 | Süd-Chemie AG | Catalyst for oxidizing methanol into formaldehyde |
WO2010034480A3 (en) * | 2008-09-24 | 2010-05-27 | Süd-Chemie AG | Catalyst for oxidizing methanol into formaldehyde |
CN103508863A (en) * | 2012-06-29 | 2014-01-15 | 中国科学院大连化学物理研究所 | Method for preparing anhydrous formaldehyde |
CN103508863B (en) * | 2012-06-29 | 2016-04-27 | 中国科学院大连化学物理研究所 | A kind of method preparing anhydrous formaldehyde |
CN102773115A (en) * | 2012-08-02 | 2012-11-14 | 江苏丹化煤制化学品工程技术有限公司 | Supported catalyst for diphenyl carbonate synthesis by reaction of phenylacetate and dimethyl carbonate and preparation method thereof |
CN113019388A (en) * | 2019-12-09 | 2021-06-25 | 中国科学院大连化学物理研究所 | Catalyst for preparing formaldehyde by oxidizing dimethyl ether, preparation and application thereof |
Also Published As
Publication number | Publication date |
---|---|
US20030166972A1 (en) | 2003-09-04 |
WO2003070668A2 (en) | 2003-08-28 |
US6781018B2 (en) | 2004-08-24 |
KR20040086421A (en) | 2004-10-08 |
AU2003217605A1 (en) | 2003-09-09 |
AU2003217605A2 (en) | 2003-09-09 |
EP1485340A4 (en) | 2005-06-08 |
EP1485340A2 (en) | 2004-12-15 |
CN1642891A (en) | 2005-07-20 |
EA200401089A1 (en) | 2004-12-30 |
US20040044252A1 (en) | 2004-03-04 |
CN1931428A (en) | 2007-03-21 |
CA2476867A1 (en) | 2003-08-28 |
EA007783B1 (en) | 2007-02-27 |
WO2003070668A3 (en) | 2004-02-12 |
BR0307870A (en) | 2004-12-28 |
JP2005517727A (en) | 2005-06-16 |
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