JP3854641B2 - Method for producing exhaust gas purification catalyst - Google Patents
Method for producing exhaust gas purification catalyst Download PDFInfo
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- JP3854641B2 JP3854641B2 JP52542798A JP52542798A JP3854641B2 JP 3854641 B2 JP3854641 B2 JP 3854641B2 JP 52542798 A JP52542798 A JP 52542798A JP 52542798 A JP52542798 A JP 52542798A JP 3854641 B2 JP3854641 B2 JP 3854641B2
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- Prior art keywords
- catalyst
- solution
- exhaust gas
- copper
- component
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- 239000003054 catalyst Substances 0.000 title claims description 131
- 238000004519 manufacturing process Methods 0.000 title claims description 25
- 238000000746 purification Methods 0.000 title claims description 20
- 239000010949 copper Substances 0.000 claims description 66
- 229910052802 copper Inorganic materials 0.000 claims description 65
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 64
- 229910052698 phosphorus Inorganic materials 0.000 claims description 60
- 239000011574 phosphorus Substances 0.000 claims description 60
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 50
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 30
- 229910000323 aluminium silicate Inorganic materials 0.000 claims description 27
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims description 25
- 239000002253 acid Substances 0.000 claims description 19
- 229910021529 ammonia Inorganic materials 0.000 claims description 14
- 239000000872 buffer Substances 0.000 claims description 12
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 10
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 claims description 7
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 7
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 7
- 229910017604 nitric acid Inorganic materials 0.000 claims description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 6
- USFZMSVCRYTOJT-UHFFFAOYSA-N Ammonium acetate Chemical compound N.CC(O)=O USFZMSVCRYTOJT-UHFFFAOYSA-N 0.000 claims description 3
- 239000005695 Ammonium acetate Substances 0.000 claims description 3
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 claims description 3
- 229940043376 ammonium acetate Drugs 0.000 claims description 3
- 235000019257 ammonium acetate Nutrition 0.000 claims description 3
- 235000019270 ammonium chloride Nutrition 0.000 claims description 3
- 239000001632 sodium acetate Substances 0.000 claims description 3
- 235000017281 sodium acetate Nutrition 0.000 claims description 3
- 239000007789 gas Substances 0.000 description 40
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 30
- -1 phosphorus compound Chemical class 0.000 description 20
- 238000006243 chemical reaction Methods 0.000 description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- 238000000034 method Methods 0.000 description 16
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 14
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 13
- 239000005749 Copper compound Substances 0.000 description 11
- 150000001880 copper compounds Chemical class 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 9
- 238000010025 steaming Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- 235000011007 phosphoric acid Nutrition 0.000 description 7
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 6
- 239000006172 buffering agent Substances 0.000 description 6
- 150000001875 compounds Chemical class 0.000 description 6
- 238000005342 ion exchange Methods 0.000 description 6
- 239000000377 silicon dioxide Substances 0.000 description 6
- 239000002904 solvent Substances 0.000 description 6
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 4
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
- 229910052783 alkali metal Inorganic materials 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- 235000011114 ammonium hydroxide Nutrition 0.000 description 4
- 238000002485 combustion reaction Methods 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 229930195733 hydrocarbon Natural products 0.000 description 4
- 150000002430 hydrocarbons Chemical class 0.000 description 4
- 230000000977 initiatory effect Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 229910021536 Zeolite Inorganic materials 0.000 description 3
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 238000010335 hydrothermal treatment Methods 0.000 description 3
- 238000011068 loading method Methods 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 235000019837 monoammonium phosphate Nutrition 0.000 description 3
- 229910052680 mordenite Inorganic materials 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000010457 zeolite Substances 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 150000003863 ammonium salts Chemical class 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 150000004820 halides Chemical class 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229910003002 lithium salt Inorganic materials 0.000 description 2
- 159000000002 lithium salts Chemical class 0.000 description 2
- 239000000395 magnesium oxide Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 150000003018 phosphorus compounds Chemical class 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 159000000000 sodium salts Chemical class 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- XDJWZONZDVNKDU-UHFFFAOYSA-N 1314-24-5 Chemical compound O=POP=O XDJWZONZDVNKDU-UHFFFAOYSA-N 0.000 description 1
- GIXFALHDORQSOQ-UHFFFAOYSA-N 2,4,6,8-tetrahydroxy-1,3,5,7,2$l^{5},4$l^{5},6$l^{5},8$l^{5}-tetraoxatetraphosphocane 2,4,6,8-tetraoxide Chemical compound OP1(=O)OP(O)(=O)OP(O)(=O)OP(O)(=O)O1 GIXFALHDORQSOQ-UHFFFAOYSA-N 0.000 description 1
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910021594 Copper(II) fluoride Inorganic materials 0.000 description 1
- UEZVMMHDMIWARA-UHFFFAOYSA-N Metaphosphoric acid Chemical compound OP(=O)=O UEZVMMHDMIWARA-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 1
- 239000001099 ammonium carbonate Substances 0.000 description 1
- 235000012501 ammonium carbonate Nutrition 0.000 description 1
- ZRIUUUJAJJNDSS-UHFFFAOYSA-N ammonium phosphates Chemical compound [NH4+].[NH4+].[NH4+].[O-]P([O-])([O-])=O ZRIUUUJAJJNDSS-UHFFFAOYSA-N 0.000 description 1
- DNCQWNWCEBTKGC-UHFFFAOYSA-N azane;phosphorous acid Chemical compound N.N.OP(O)O DNCQWNWCEBTKGC-UHFFFAOYSA-N 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- ODWXUNBKCRECNW-UHFFFAOYSA-M bromocopper(1+) Chemical compound Br[Cu+] ODWXUNBKCRECNW-UHFFFAOYSA-M 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 150000004770 chalcogenides Chemical class 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229940116318 copper carbonate Drugs 0.000 description 1
- 150000004699 copper complex Chemical class 0.000 description 1
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 description 1
- OPQARKPSCNTWTJ-UHFFFAOYSA-L copper(ii) acetate Chemical compound [Cu+2].CC([O-])=O.CC([O-])=O OPQARKPSCNTWTJ-UHFFFAOYSA-L 0.000 description 1
- GWFAVIIMQDUCRA-UHFFFAOYSA-L copper(ii) fluoride Chemical compound [F-].[F-].[Cu+2] GWFAVIIMQDUCRA-UHFFFAOYSA-L 0.000 description 1
- GEZOTWYUIKXWOA-UHFFFAOYSA-L copper;carbonate Chemical compound [Cu+2].[O-]C([O-])=O GEZOTWYUIKXWOA-UHFFFAOYSA-L 0.000 description 1
- QYCVHILLJSYYBD-UHFFFAOYSA-L copper;oxalate Chemical compound [Cu+2].[O-]C(=O)C([O-])=O QYCVHILLJSYYBD-UHFFFAOYSA-L 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- AZSFNUJOCKMOGB-UHFFFAOYSA-N cyclotriphosphoric acid Chemical compound OP1(=O)OP(O)(=O)OP(O)(=O)O1 AZSFNUJOCKMOGB-UHFFFAOYSA-N 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000003247 decreasing 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
- 229910000388 diammonium phosphate Inorganic materials 0.000 description 1
- 235000019838 diammonium phosphate Nutrition 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- YWEUIGNSBFLMFL-UHFFFAOYSA-N diphosphonate Chemical compound O=P(=O)OP(=O)=O YWEUIGNSBFLMFL-UHFFFAOYSA-N 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 229910001657 ferrierite group Inorganic materials 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002366 halogen compounds Chemical class 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical class [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- TVZISJTYELEYPI-UHFFFAOYSA-N hypodiphosphoric acid Chemical compound OP(O)(=O)P(O)(O)=O TVZISJTYELEYPI-UHFFFAOYSA-N 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- ACVYVLVWPXVTIT-UHFFFAOYSA-N phosphinic acid Chemical compound O[PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-N 0.000 description 1
- OJMIONKXNSYLSR-UHFFFAOYSA-N phosphorous acid Chemical compound OP(O)O OJMIONKXNSYLSR-UHFFFAOYSA-N 0.000 description 1
- CYQAYERJWZKYML-UHFFFAOYSA-N phosphorus pentasulfide Chemical compound S1P(S2)(=S)SP3(=S)SP1(=S)SP2(=S)S3 CYQAYERJWZKYML-UHFFFAOYSA-N 0.000 description 1
- DLYUQMMRRRQYAE-UHFFFAOYSA-N phosphorus pentoxide Inorganic materials O1P(O2)(=O)OP3(=O)OP1(=O)OP2(=O)O3 DLYUQMMRRRQYAE-UHFFFAOYSA-N 0.000 description 1
- VSAISIQCTGDGPU-UHFFFAOYSA-N phosphorus trioxide Inorganic materials O1P(O2)OP3OP1OP2O3 VSAISIQCTGDGPU-UHFFFAOYSA-N 0.000 description 1
- 239000002798 polar solvent Substances 0.000 description 1
- 229920000137 polyphosphoric acid Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 159000000001 potassium salts Chemical class 0.000 description 1
- 235000019353 potassium silicate Nutrition 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 210000002345 respiratory system Anatomy 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- VKFFEYLSKIYTSJ-UHFFFAOYSA-N tetraazanium;phosphonato phosphate Chemical compound [NH4+].[NH4+].[NH4+].[NH4+].[O-]P([O-])(=O)OP([O-])([O-])=O VKFFEYLSKIYTSJ-UHFFFAOYSA-N 0.000 description 1
- 150000004684 trihydrates Chemical class 0.000 description 1
- UNXRWKVEANCORM-UHFFFAOYSA-N triphosphoric acid Chemical compound OP(O)(=O)OP(O)(=O)OP(O)(O)=O UNXRWKVEANCORM-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Catalysts (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Description
技術分野
本発明は、ガソリン自動車、ディーゼル自動車等の移動式内燃機関、コジェネレーション等の定置式内燃機関、ボイラー等の各種燃焼機、工業炉等から排出される窒素酸化物を無害なガスに還元除去するために特に有用な排ガス浄化用触媒の製造方法に関する。
背景技術
一般に移動式または定置式の内燃機関、各種燃焼機、工業炉から排出される排ガスには、ＮＯ、ＮＯ2等に代表される多量の窒素酸化物（ＮＯx）が含まれている。これらＮＯxは、光化学スモッグの原因となるばかりでなく、人体にとっては、呼吸器系の障害を引き起こす原因になるとも言われている。
これら排ガス中のＮＯxを低減する方法としては、従来より、触媒を用い、排ガスに含まれる一酸化炭素または炭化水素によりＮＯxを還元除去する方法が広く知られている。
また触媒としては、結晶性アルミノケイ酸塩等のゼオライト系の触媒担体にイオン交換、含侵法等の方法により各種の金属を担持した触媒が一般に用いられている。
特に、金属として銅を担持した結晶性アルミノケイ酸塩系触媒は、酸素を多量に含む排ガスに対して、ガス空間速度（ＧＨＳＶ）の高い条件下であっても、炭化水素を還元剤として排ガス中の窒素酸化物（ＮＯx）を効率的に浄化することができるため、移動式または定置式の内燃機関から排出される排ガスの浄化用触媒として大いに期待されている。
しかし、この銅担持結晶性アルミノケイ酸塩系触媒は、熱、水蒸気の処理により担持した銅の価数、酸化状態、分散状態が変化しやすい等、熱、水蒸気に対する耐久性に乏しく、６００℃以上の高温下で、あるいは多量の水分が含まれている排ガスに対しては、長期に安定な浄化性能が得られない問題があった。
このような問題を解決するため、本出願人は、特開平６−１３４３１４号公報において、耐久性が大幅に向上された排ガス浄化用触媒として、ペンタシル型の結晶性アルミノケイ酸塩を含む触媒担体に銅成分及びリン成分を担持した触媒を提案した。
しかし、銅成分とリン成分を均一に担持するのに好ましいイオン交換法により担持する場合、それぞれの成分を必要量担持するのに適した溶液のｐＨ域が相違するため、両成分を同時に適量担持できるｐＨ域は極めて狭く工業的装置でそのｐＨ域に保持することが困難であった。
また、各成分をそれぞれ好ましいｐＨ域で順次担持する方法を取ることも可能であるが、担持工程が多くなり、工業的に有利な方法とは言いがたい。
発明の開示
本発明は、上記観点からなされたもので、耐久性が高くかつ高効率で排ガスを浄化するのに適した銅成分とリン成分を含む排ガス浄化用触媒を、広いｐＨ域で安定して得ることのできる製造方法を提供することを目的とする。
本発明者等は鋭意研究の結果、銅成分及びリン成分の担持に際して使用する溶液のｐＨを、当初は高くし、担持工程の途中で低くすることにより、上記本発明の目的を効果的に達成しうることを見出し本発明を完成したものである。
すなわち、本発明の要旨は以下の通りである。
（１）ペンタシル型の結晶性アルミノケイ酸塩を含む触媒担体に、少なくとも銅成分及びリン成分が担持されている排ガス浄化触媒の製造方法において、少なくとも銅成分、リン成分、アンモニア及び緩衝剤を含み、かつｐＨが８．０以上である溶液に前記触媒担体を添加した後、当該溶液に酸を添加して当該溶液のｐＨを７．０以下として前記触媒担体に少なくとも銅成分及びリン成分を担持することを特徴とする排ガス浄化用触媒の製造方法。
（２）触媒担体を添加する前の溶液のｐＨが８．０〜１２．０である（１）に記載の排ガス浄化用触媒の製造方法。
（３）ペンタシル型の結晶性アルミノケイ酸塩を含む触媒担体に、少なくとも銅成分及びリン成分が担持されている排ガス浄化用触媒の製造法において、少なくとも銅成分、リン成分及びアンモニアを含み、かつｐＨが９．０以上である溶液に前記触媒担体を添加した後、当該溶液に酸を添加してｐＨを７．０以下として前記触媒担体に少なくとも銅成分及びリン成分を担持することを特徴とする排ガス浄化用触媒の製造方法。
（４）触媒担体を添加する前の溶液のｐＨが９．０〜１２．０である（３）に記載の排ガス浄化用触媒の製造方法。
（５）ペンタシル型の結晶性アルミノケイ酸塩がＭＦＩ構造を有するものである（１）乃至（４）のいずれかに記載の排ガス浄化触媒の製造方法。
（６）緩衝剤が硝酸アンモニウム、塩化アンモニウム、酢酸アンモニウム又は酢酸ナトリウムからなる群から選ばれる少なくとも一種である（１）乃至（５）のいずれかに記載の排ガス浄化触媒の製造方法。
（７）酸が硝酸、塩酸又は硫酸からなる群から選ばれる少なくとも一種である（１）乃至（６）のいずれかに記載の排ガス浄化触媒の製造方法。
発明の実施するための最良の形態
以下に、本発明の実施の形態を詳細に説明する。
まず、本発明により製造される排ガス浄化用触媒について説明する。
本発明では、ペンタシル型の結晶性アルミノケイ酸塩からなる触媒担体に特定の成分を担持して排ガス浄化用触媒とする。本発明において触媒担体としてペンタシル型の結晶性アルミノケイ酸塩を用いるのは、それ以外の結晶性アルミノケイ酸塩は、本来的に耐水熱性が低いとともに、リン成分を担持するとスチーミングに対する耐久性がさらに低下し、長期安定性が要求される触媒用の担体には適していないためである。
ここで、ペンタシル型の結晶性アルミノケイ酸塩とは、構成基本単位が酸素５員環で構成されるゼオライトであり、例えば、フェリエライト、モルデナイトまたはＭＦＩ構造を有するＺＳＭ−５、ＺＳＭ−１１等を挙げることができる。ここでＭＦＩ構造とは、ＺＳＭ−５と同一またはこれと類似した構造を指し、ＺＳＭ−５以外に、例えば、ＺＳＭ−８、ＺＳＭ−１１、ゼータ１、ゼータ３、Ｎｕ−４、Ｎｕ−５、ＴＺ−１、ＴＰＺ−１、ＩＳＩ−３、ＳＩＳ−５、ＡＺ−１等の構造が該当する。これらのペンタシル型の結晶性アルミノケイ酸塩は、それぞれ公知の製造方法に従って調製することができる。
これらのペンタシル型の結晶性アルミノケイ酸塩の中でも、耐熱水性に優れる点で、ＭＦＩ構造を有するものが好ましく、種結晶としてモルデナイトを使用して合成されたＺＳＭ−５が特に好ましい。また、上記ペンタシル型結晶性アルミノケイ酸塩の中でも１０〜２００の範囲のＳｉＯ2／Ａｌ2Ｏ3（モル比）を有するものが好ましい。該モル比が１０未満の場合、ゼオライト自体の耐水熱性が低くなり、これに起因して触媒の長期安定性が低下するおそれがあり、一方、該モル比が２００を超えると、イオン交換容量が小さいため担持できる活性金属の量が少なくなり、十分な活性が得られないことがある。本発明においては、これらのペンタシル型の結晶性アルミノケイ酸塩のうち１種単独でまたは２種以上を混合して触媒担体とすることができる。
尚、排ガス浄化性能等の触媒の特性を阻害しない範囲であれば、通常触媒担体として使用される酸化物等の各種化合物を上記ペンタシル型の結晶性アルミノケイ酸塩に添加して触媒担体とすることができる。例えば、銅成分及びリン成分の分散性を高める目的で、シリカ、アルミナ、シリカアルミナ、マグネシア、ジルコニア等を添加することができる。
また、本発明の排ガス浄化用触媒においては、前記触媒担体に少なくとも銅成分とリン成分が担持されている。
ここで、触媒担体に対する銅成分の担持量としては、触媒全体の重量に対して、ＣｕＯに換算して、０．８〜３０．０重量％となる範囲が好ましく、特に２．０〜１５．０重量％の範囲が好ましい。０．８重量％未満であると、銅の含有量が低いために充分な活性が得られず、一方３０．０重量％を超えると触媒担体表面に酸化銅（ＣｕＯ）等が凝集した形態で担持され、触媒担体の細孔が閉塞し、触媒の活性が低下することがある。
また、リン成分の担持量としては、触媒全体の重量に対して、Ｐ2Ｏ5に換算して、０．１〜５．０重量％となる範囲が好ましく、特に０．１〜２．０重量％の範囲が好ましい。０．１重量％未満であると、銅成分の安定性を十分に保持できないため、耐熱水性に優れた触媒が得られないことがあり、一方、５．０重量％を超えてもそれに見合う耐久性の向上が期待されない。
尚、本発明においては、触媒活性及び耐久性に悪影響を及ぼさない範囲であれば、銅およびリン成分以外の他の成分を含めることもできる。例えば、触媒活性を一層高めるために、Ｃｏ、Ｆｅ、Ｇａ、Ｉｎ等の金属成分を、あるいは触媒の耐久性を一層高めるために、希土類、アルカリ土類、Ｚｒ等の金属成分またはハロゲン化合物を添加してもよい。他の成分をも担持する場合、それぞれの成分の担持量は、触媒全体の重量に対して、通常、０．０５〜１０重量％程度である。
次に、排ガス浄化用触媒の製造方法について説明する。
本発明における排ガス浄化用触媒の製造方法としては、まず触媒担体に担持される銅成分とリン成分に対応する銅化合物とリン化合物を含有する担持用の溶液を調製する。
ここで、担持用の溶液の調整に用いる溶媒としては、触媒担体に活性成分を担持する等の触媒調整に際して、通常使用されている各種の溶媒、例えば水、アルコール（例えばメタノール、エタノール）等の極性溶媒から適宜選択して使用することができる。これらの中でも、実用面から通常は水を使用するのが好ましい。
また、銅化合物としては、銅を含有し、用いる溶媒に溶解する化合物であれば特に制限はなく、無機酸塩、ハロゲン化物、有機酸塩、錯体化合物等の各種銅化合物を使用することができる。例えば、無機酸塩としては、硝酸塩、炭酸銅等を、ハロゲン化物としてはフッ化銅、塩化銅、臭化銅等を、有機酸塩としては酢酸銅、蓚酸銅等を、また錯体化合物としては銅アンミン錯体、銅シアノ錯体等を挙げることができる。これらの銅化合物の中でも、触媒担体に均一に担持されやすい点で無機酸塩が好ましく、特に硝酸銅が好ましい。また、これらの銅化合物は、１種単独で又は２種以上を組み合わせて使用することができる。
また、リン化合物としては、リンを含有し、用いる溶媒に溶解するか、あるいは相溶性のある化合物であれば特に制限はなく、無機リン酸及びその塩、またはカルコゲン化リン等の各種リン化合物を使用することができる。例えば無機リン酸としては、（ａ）オルトリン酸、メタリン酸、次リン酸、メタ亜リン酸または次亜リン酸等、各種酸化数のリン酸、（ｂ）オルトピロリン酸、メタピロリン酸、トリポリリン酸、テトラポリリン酸等のポリリン酸やトリメタリン酸、テトラメタリン酸、ヘキサメタリン酸等のポリメタリン酸等の縮合リン酸等を挙げることができる。また、その塩としては、上記無機リン酸のリチウム塩、ナトリウム塩あるいはカリウム塩等のアルカリ金属塩またはアンモニウム塩等を挙げることができる。またこれらの塩には、オルトリン酸三アルカリ金属塩またはオルトリン酸三アンモニウム等のいわゆる正塩の他に、オルトリン酸二水素アルカリ金属塩、オルトリン酸一水素アルカリ金属塩、オルトリン酸二水素アンモニウム、オトリン酸一水素アンモニウム、亜リン酸一水素アルカリ金属塩または亜リン酸一水素アンモニウム等のいわゆる水素塩が含まれる。またカルコゲン化リンとしては、五酸化リン、三酸化リン、五硫化リン等が挙げられる。これらのリン化合物の中でも、耐熱性に優れる触媒が得られやすいことから、リン酸のリチウム塩、ナトリウム塩またはアンモニウム塩が好ましく、特にオルトリン酸二水素アンモニウムが好ましい。また、これらのリン化合物は、１種単独で又は２種以上を組み合わせて使用することができる。
また、前記溶液中に含まれる銅化合物とリン化合物の量は、触媒担体への各成分の担持量により、あるいは溶液の温度またはｐＨ等の担持条件により異なるため、一概に特定することはできないが、通常、銅化合物は、０．２〜２．０ｍｍｏｌ／ｇ−ｃａｔと、またリン化合物は、０．０１〜１．０ｍｍｏｌ／ｇ−ｃａｔとすることが好ましい。銅化合物とリン化合物の量を、それぞれ２．０ｍｍｏｌ／ｇ−ｃａｔ、または１．０ｍｍｏｌ／ｇ−ｃａｔ以上とすると、銅成分またはリン成分が凝集した形態で触媒担体に担持され、充分な排ガス浄化性能を有する触媒が得られないことがある。一方、それぞれ０．２ｍｍｏｌ／ｇ−ｃａｔ、または０．０１ｍｍｏｌ／ｇ−ｃａｔ以下とすると、触媒担体に銅成分またはリン成分が担持されなかったり、一回の担持操作で担持される銅成分またはリン成分の量が少なく、実用的でない程度に多数回担持操作を繰返す必要が生じることがある。
尚、銅成分及びリン成分以外の成分をも触媒担体に担持する場合、その成分を含有し、用いる溶媒に溶解するその成分の化合物を適宜選択し、上記銅成分及びリン成分を含有する溶液に溶解させて一度の担持処理で同時に担持する方法が好ましいが、本発明の方法により銅成分及びリン成分を担持する前または後に別個に通常の担持処理を行い担持させることもできる。
次に本発明においては、緩衝剤を添加しないまま、あるいは緩衝剤を添加した後、アンモニアを添加して溶液のｐＨを調整する。
溶液のｐＨを調整するのは、前記銅化合物とリン化合物を含有する溶液中に十分な量の銅の錯体を形成するためである。また、アンモニアでｐＨを調製するのは、生成する銅アンミン錯体が、イオン状態、形態、大きさの点で、触媒担体に銅成分を均一に担持するのに、最も適しているからである。
ここで、添加するアンモニアとしては、特に制限はなく、市販のアンモニアまたはアンモニアを含む溶液をそのままあるいはそれらを担持用の溶液に用いる溶媒で薄めたものを適宜使用することができるが、通常０．５容量％以上のアンモニアを含むものを用いることが好ましい。０．５容量％未満のものを使用すると、ｐＨの調整に多量のアンモニア溶液を添加することとなり、担持用の溶液中の銅成分またはリン成分の濃度が著しく変化し、所望の濃度で担持できなくなることがある。
また、調整される溶液のｐＨは、本発明の態様として、後述する緩衝剤を添加してｐＨを調整する場合と緩衝剤を添加しないでｐＨを調整する場合で相違する。
すなわち、緩衝剤を添加しない場合には、９．０以上、好ましくは９．０〜１２．０の範囲に、一方予め緩衝剤を添加する場合には、８．０以上、好ましくは８．０〜１２．０の範囲に溶液のｐＨを調製する。溶液のｐＨをそれぞれ前者で９．０未満または後者で８．０未満とすると、溶液中に十分な量の銅アンミン錯体が形成されないため、触媒担体に銅成分を均一に担持することができず、結果として触媒の排ガス浄化性能が低下してしまうためである。
本発明では、前述の通り、本発明の一態様として緩衝剤を添加した後に溶液のｐＨを調整する。これは、緩衝剤を添加すると、より低いｐＨで十分な量の銅アンミン錯体を形成することができ、溶解度の高いリン化合物を、より効率的に触媒担体上に担持できるためである。
ここで用いる緩衝剤としては、特に制限はなく、市販のものを適宜選択して使用することができるが、ｐＨ７．０以上で作用するものが好ましい。ｐＨ７．０以下で作用する緩衝剤を用いると、溶液のｐＨを８．０以上に調整するのに必要以上に多量のアンモニアを添加することになるからである。好ましい緩衝剤としては、硝酸アンモニウム、塩化アンモニウム、酢酸アンモニウム、酢酸ナトリウム等を挙げることができる。これらの中でも、銅成分とリン成分を含む溶液を調製する際に用いる銅化合物およびリン化合物と共通するイオン成分を有する塩が特に好ましい。例えば、銅化合物として硝酸銅を、リン化合物としてリン酸二水素アンモニウムを用いる場合、緩衝剤としては、硝酸アンモニウムが最適となる。緩衝剤の使用量は、緩衝剤の種類により異なるが、通常２〜６モル／モルＣｕイオンの範囲で使用する。
次に、本発明においては、前記ｐＨを調整した担持用溶液を用いてペンタシル型の結晶性アルミノケイ酸塩を含む触媒担体に少なくとも銅成分及びリン成分を担持する。この担持方法について以下詳細に説明する。
本発明の担持方法としては、まず室温あるいは１０〜５０℃の範囲、より好ましくは１５〜４０℃の範囲に加熱あるいは冷却した前記担持用の溶液に、ペンタシル型の結晶性アルミノケイ酸塩を含む触媒担体を添加し、１〜１０時間程度、より好ましく１〜５時間静置あるいは好ましくは撹拌する。この過程で銅成分またはリン成分等が触媒担体のカチオンとイオン交換される。尚、ここで溶液の加熱、冷却あるいは撹拌に用いる機器に制限はなく、通常用いられる各種の機器を使用することができる。
次に、上記一定時間の処理の後、当該溶液に酸を加えて溶液のｐＨを７．０以下、好ましくは６．５〜４．０の範囲に調整する。溶液のｐＨを７．０以下に調整するのは、調整前のｐＨの溶液中に存在するイオン交換されていない銅成分またはリン成分を触媒担体に担持するためである。
ここで、ｐＨ調整に使用する酸としては、特に制限はなく、硝酸、塩酸、硫酸を使用することができる。この中でも耐久性の優れた触媒が得られ易い点で硝酸が好ましい。
また酸は、１分当たりｐＨが、０．２〜２程度低下する速度で添加するのが好ましい。ｐＨが１分当たり２以上変動すると、銅成分が凝集した形態で触媒上に担持され易くなり、充分な排ガス浄化性能を有する触媒が得られないことがあり、一方０．２以下としても時間をかけるに見合う銅成分の凝集防止効果が得られないからである。
また、溶液中のｐＨが部分的に急激に変化するのを防止するために、溶液を撹拌しながら酸を添加するのが好ましい。
本発明においては、酸を添加した後、更に、１０〜５０℃、より好ましくは１５〜４０℃の温度範囲に加熱あるいは冷却しながら０．５〜４時間、より好ましくは０．５〜２時間、溶液を静置あるいは撹拌する。この過程で、溶液中の銅成分およびリン成分が所望量だけ触媒担体に担持される。
本発明においては、銅成分とリン成分を触媒担体に担持した後、通常の方法で、溶液を濾過洗浄して固形分を回収し、乾燥する。具体的には、濾過は、ブフナーロート、加圧濾過器、フィルタープレス等の機器を用いて行い、また乾燥は、空気中１００〜２００℃の温度に、６〜２４時間保持して行う。本発明においては、通常一回の担持により所望量の銅成分とリン成分を触媒担体に担持できるが、銅成分とリン成分をさらに均一に担持する等の目的で複数回繰り返して、所望量の銅成分とリン成分を触媒担体上に担持することもできる。
こうして所望量の銅成分とリン成分が担持された触媒担体を、通常の方法により焼成して触媒を得る。焼成は、具体的には、マッフル炉、ロータリーキルン等、通常触媒の焼成に使用される機器を用いて、空気中５００〜７００℃の温度に０．５〜８時間保持して行う。
尚、本発明においては、焼成後、更に酸、アルカリ、熱、水蒸気、アンモニア、ハロゲン又は他の非金属化合物等の物質で適宜処理したものを触媒として使用することもできる。
また、得られた触媒は、通常粉末状であり、それをそのままの形態で触媒として使用することもできるが、用途により、例えばシリカ、アルミナ、シリカアルミナ、マグネシア、ジルコニア等のバインダーを用いて、球状、円柱状、星型状、ハニカム形状等の任意の形状に成形して使用することが好ましい。また、本触媒とは別個に作られた各種形状の担体基材に触媒粉末を塗布して用いることもできる。このような担体基材に用いる材料としては特に制限はなく、セラミックス、金属等の各種耐熱材料から適宜選択して使用することができる。例えば、自動車の排ガス用触媒として用いる場合には、特に高温での強度、長期耐熱性に優れるセラミックス、中でもコージェライト質で作られたハニカム形状の担体基材に、本触媒の粉末を塗布したものを用いるのが好ましい。
次に、本発明を実施例により具体的に説明するが、本発明は、これらの実施例によってなんら制限されるものではない。
実施例１
先ず、硫酸アルミニウム（１８水塩）３３７．５ｇ、硫酸（９７％）３６２．５ｇ、水８２５０ｇからなる溶液（溶液Ｉとする）、水ガラス（ＳｉＯ2：２８．５％、Ｎａ2Ｏ：９．５％、水：６２％）５２７５ｇ、水５０００ｇからなる溶液（溶液ＩＩとする）及び塩化ナトリウム９８７．５ｇ、水２３００ｇからなる溶液（溶液ＩＩＩとする）を用意した。
次に、溶液ＩとＩＩを同時に溶液ＩＩＩ中に滴下しながら混合した。この原料混合物を硫酸でｐＨ９．５に調整した後、種結晶としてモルデナイト〔ＳｉＯ2／Ａｌ2Ｏ3（モル比）＝２０〕１２．５ｇを添加した。
次に、この原料混合物を２５リットル容量のオートクレーブ中に入れ、密閉下１７０℃、３００ｒｐｍで攪拌しながら２０時間保持した。冷却後、反応混合物を濾過し、沈澱物を純水で充分洗浄した。この後、１２０℃で２０時間乾燥させることにより、ペンタシル型の結晶性アルミノケイ酸塩であるＺＳＭ−５構造（ＭＦＩ構造）の結晶性アルミノケイ酸塩を合成した。このアルミノケイ酸塩の粉末Ｘ線回折による測定結果を下記表１に示す。
次に、水２０８０ｇに、種酸銅の３水和塩１３２．５ｇ、リン酸二水素アンモニウム１１．１７ｇ及び硝酸アンモニウム１７８ｇを順次溶解した後、液温を３０℃に制御しながら、５％のアンモニア水を添加することで溶液のｐＨを８．５に調整して、銅成分、リン成分を含む担持用の溶液を調製した。この溶液に前記アルミノケイ酸塩５００ｇを加え、液温を３０℃に制御しながら４時間イオン交換を行った。その後、この溶液に３０％硝酸を添加してｐＨを６．０に調整した後更に１時間イオン交換を行った。その後このスラリー溶液を濾過し、得られた固形物を更に水洗した。次に、その固形物を１２０℃で２４時間乾燥した後、５００℃で４時間焼成することで目的とする触媒を得た。この触媒の銅成分の含有量はＣｕＯ換算で７．５ｗｔ％、リン成分の含有量はＰ2Ｏ5換算で１．３ｗｔ％であった。
次に、前記触媒のＮＯxの還元除去性能を、以下に示す初期活性及びスチーミング処理（水熱処理）後の活性で評価した。
（１）初期活性の評価
先ず、ステンレス製の反応管に触媒２ｃｃを充填した後、反応管を後述の温度に保持し、処理ガスとしてモデルガスを、前記反応管にＧＨＳＶ＝８００００ｈ-1の条件で導入した。このモデルガスの組成はＮＯx：５００ｐｐｍ、Ｏ2：６．０％、Ｃ3Ｈ6／Ｃ3Ｈ8＝２（ＴＨＣ濃度として約２５００ｐｐｍ）、水１０％、窒素バランスである。ここで、ＴＨＣ（Ｔｏｔａｌ Ｈｙｄｒｏｃａｒｂｏｎ）濃度とは、各種炭化水素をメタンに換算した場合の濃度を言う。次に、この反応管の出口からのガスを化学発光式分析計に導入し、ＮＯx濃度を測定した。触媒反応後のモデルガスのＮＯx除去率は、反応管導入前後のモデルガスの濃度を比較することにより算出した。ＮＯx除去率は、反応管の温度、３００℃、３５０℃及び４００℃で、それぞれ評価した。その結果を下記の表２に示す。
（２）スチーミング処理（水熱処理）後の活性の評価
先ず、本実施例で調製した触媒を石英製の反応管に充填した後、反応管を７５０℃の温度に保持し、Ｃ3Ｈ6／Ｃ3Ｈ8＝２（ＴＨＣ濃度として約２５００ｐｐｍ）、Ｏ2：０．５％、水１０容量％を含む窒素ガスを、ＧＨＳＶ＝８００００ｈ-1の条件で１６時間導入し、スチーミング処理を行った。
次に、反応管を冷却後、抜き出した触媒を、ステンレス製反応管に充填し、上記初期活性の評価の場合と同一の条件で、同じモデルガスに対するＮＯx除去率を評価した。その結果を下記の表２に示す。
実施例２
実施例１において、硝酸アンモニウムを使用することなく、５％のアンモニア水を添加することで溶液のｐＨを１１．５に調整したこと以外は実施例１と同様にして実施例２の触媒を調製した。この触媒の銅成分の含有量はＣｕＯ換算で６．７ｗｔ％、リン成分の含有量はＰ2Ｏ5換算で１．１ｗｔ％であった。
実施例３
実施例１において、硝酸アンモニウムの代わりに炭酸アンモニウムを用いたこと以外は実施例１と同様にして実施例３の触媒を調製した。この触媒の銅成分の含有量はＣｕＯ換算で６．０ｗｔ％、リン成分の含有量はＰ2Ｏ5換算で１．２ｗｔ％であった。
実施例４
実施例１において、リン酸２水素アンモニウムの代わりに、ピロリン酸アンモニウムを用いたこと以外は実施例１と同様にして実施例４の触媒を調製した。この触媒の銅成分の含有量はＣｕＯ換算で７．３ｗｔ％、リン成分の含有量はＰ2Ｏ5換算で０．８ｗｔ％であった。
比較例１
実施例２において、５％アンモニア水による溶液のｐＨ調整を行わなかったこと（溶液のｐＨは２．５）および硝酸による溶液のｐＨ調整を行わなかったこと以外は実施例２と同様にして比較例１の触媒を調製した。この触媒の銅成分の含有量はＣｕＯ換算で２．６ｗｔ％、リン成分の含有量はＰ2Ｏ5換算で０．２ｗｔ％であった。
比較例２
実施例２において、５％のアンモニア水を添加することで溶液のｐＨを６．０に調整したこと以外は実施例２と同様にして比較例２の触媒を調製した。この触媒の銅成分の含有量はＣｕＯ換算で６．０ｗｔ％、リン成分の含有量はＰ2Ｏ5換算で１．０ｗｔ％であった。
比較例３
実施例２において、硝酸よる溶液のｐＨ調整を行わなかったこと以外は実施例２と同様にして比較例３の触媒を調製した。この触媒の銅成分の含有量はＣｕＯ換算で３．２ｗｔ％、リン成分の含有量はＰ2Ｏ5換算で０．０１ｗｔ％であった。
上記実施例２乃至４及び比較例１乃至３の触媒に対して、実施例１と同様の条件により、初期活性及びスチーミング処理（水熱処理）後の活性を評価した。それらの結果を下記の表２に示す。
産業上の利用分野
本発明に係る排ガス浄化触媒の製造方法によれば、高い耐久性を有し、高効率の排ガス浄化用触媒が安定して得られる。 Technical field
The present invention reduces and removes nitrogen oxides emitted from mobile internal combustion engines such as gasoline automobiles and diesel automobiles, stationary internal combustion engines such as cogeneration, various combustors such as boilers, industrial furnaces, and the like. In particular, the present invention relates to a method for producing an exhaust gas purifying catalyst that is particularly useful.
Background art
In general, NO, NO for exhaust gas discharged from mobile or stationary internal combustion engines, various combustors, and industrial furnaces2A large amount of nitrogen oxides (NO, etc.)x)It is included. These NOxIs said to cause not only photochemical smog, but also causes damage to the respiratory system for the human body.
NO in these exhaust gasesxAs a method of reducing NOx, NO is conventionally used by using a catalyst and carbon monoxide or hydrocarbons contained in exhaust gas.xA method for reducing and removing is widely known.
As the catalyst, a catalyst in which various metals are supported on a zeolite-based catalyst carrier such as crystalline aluminosilicate by a method such as ion exchange or impregnation is generally used.
In particular, a crystalline aluminosilicate-based catalyst supporting copper as a metal is used in an exhaust gas containing hydrocarbon as a reducing agent even under conditions of high gas space velocity (GHSV) against exhaust gas containing a large amount of oxygen. Nitrogen oxide (NOx) Is effectively expected as a catalyst for purifying exhaust gas discharged from a mobile or stationary internal combustion engine.
However, this copper-supported crystalline aluminosilicate-based catalyst has poor durability against heat and water vapor, such as the valence, oxidation state, and dispersion state of copper supported by heat and water vapor treatment, and is 600 ° C or higher. However, there has been a problem that stable purification performance cannot be obtained for a long period of time with respect to exhaust gas containing a large amount of water at a high temperature.
In order to solve such a problem, the applicant of the present invention disclosed in JP-A-6-134314 as a catalyst carrier containing pentasil-type crystalline aluminosilicate as an exhaust gas purification catalyst with greatly improved durability. A catalyst carrying copper and phosphorus components was proposed.
However, when supporting by the preferred ion exchange method to uniformly support the copper component and the phosphorus component, the pH range of the solution suitable for supporting the required amount of each component is different. The possible pH range was very narrow and it was difficult to maintain in that pH range with industrial equipment.
In addition, it is possible to adopt a method of sequentially supporting each component in a preferable pH range, but it is difficult to say that this is an industrially advantageous method because the number of supporting steps increases.
Disclosure of the invention
The present invention has been made from the above viewpoint, and it is possible to stably obtain an exhaust gas purifying catalyst containing a copper component and a phosphorus component, which are highly durable and suitable for purifying exhaust gas with high efficiency, in a wide pH range. An object of the present invention is to provide a production method capable of
As a result of intensive studies, the inventors of the present invention effectively achieved the object of the present invention by initially increasing the pH of the solution used for supporting the copper component and the phosphorus component and lowering the pH during the supporting step. The present invention has been completed by finding out what can be done.
That is, the gist of the present invention is as follows.
(1) In a method for producing an exhaust gas purification catalyst in which at least a copper component and a phosphorus component are supported on a catalyst carrier containing a pentasil-type crystalline aluminosilicate, at least a copper component, a phosphorus component, ammonia, and a buffering agent are included. In addition, after the catalyst carrier is added to a solution having a pH of 8.0 or higher, an acid is added to the solution so that the pH of the solution is 7.0 or lower, and at least a copper component and a phosphorus component are supported on the catalyst carrier. A method for producing an exhaust gas purifying catalyst.
(2) The method for producing an exhaust gas purifying catalyst according to (1), wherein the pH of the solution before adding the catalyst carrier is 8.0 to 12.0.
(3) In a method for producing an exhaust gas purifying catalyst in which at least a copper component and a phosphorus component are supported on a catalyst carrier containing a pentasil-type crystalline aluminosilicate, the catalyst carrier contains at least a copper component, a phosphorus component and ammonia, and a pH The catalyst carrier is added to a solution having a pH of 9.0 or more, and then an acid is added to the solution to adjust the pH to 7.0 or less so that at least a copper component and a phosphorus component are supported on the catalyst carrier. A method for producing an exhaust gas purifying catalyst.
(4) The method for producing an exhaust gas purifying catalyst according to (3), wherein the pH of the solution before adding the catalyst carrier is 9.0 to 12.0.
(5) The method for producing an exhaust gas purification catalyst according to any one of (1) to (4), wherein the pentasil type crystalline aluminosilicate has an MFI structure.
(6) The method for producing an exhaust gas purifying catalyst according to any one of (1) to (5), wherein the buffer is at least one selected from the group consisting of ammonium nitrate, ammonium chloride, ammonium acetate, and sodium acetate.
(7) The method for producing an exhaust gas purification catalyst according to any one of (1) to (6), wherein the acid is at least one selected from the group consisting of nitric acid, hydrochloric acid, or sulfuric acid.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
First, the exhaust gas purifying catalyst produced by the present invention will be described.
In the present invention, a specific component is supported on a catalyst carrier made of a pentasil type crystalline aluminosilicate to obtain an exhaust gas purification catalyst. In the present invention, a pentasil-type crystalline aluminosilicate is used as a catalyst carrier. Other crystalline aluminosilicates have inherently low hydrothermal resistance, and further support durability against steaming when a phosphorus component is supported. This is because it is not suitable for a carrier for a catalyst that requires a long-term stability.
Here, the pentasil-type crystalline aluminosilicate is a zeolite whose constitutional basic unit is composed of a five-membered oxygen ring. For example, ZSM-5, ZSM-11, etc. having a ferrierite, mordenite or MFI structure are used. Can be mentioned. Here, the MFI structure refers to a structure that is the same as or similar to ZSM-5, and other than ZSM-5, for example, ZSM-8, ZSM-11, Zeta 1, Zeta 3, Nu-4, Nu-5. , TZ-1, TPZ-1, ISI-3, SIS-5, AZ-1, and the like are applicable. These pentasil-type crystalline aluminosilicates can be prepared according to known production methods.
Among these pentasil-type crystalline aluminosilicates, those having an MFI structure are preferable from the viewpoint of excellent hot water resistance, and ZSM-5 synthesized using mordenite as a seed crystal is particularly preferable. Further, among the above-mentioned pentasil type crystalline aluminosilicates, SiO in the range of 10-200.2/ Al2OThreeThose having a (molar ratio) are preferred. When the molar ratio is less than 10, the hydrothermal resistance of the zeolite itself is lowered, which may reduce the long-term stability of the catalyst. On the other hand, when the molar ratio exceeds 200, the ion exchange capacity is decreased. Since the amount is small, the amount of active metal that can be supported decreases, and sufficient activity may not be obtained. In the present invention, these pentasil-type crystalline aluminosilicates can be used alone or in combination of two or more to form a catalyst carrier.
In addition, if it is within a range that does not impair the characteristics of the catalyst such as exhaust gas purification performance, various compounds such as oxides that are usually used as a catalyst carrier are added to the above pentasil type crystalline aluminosilicate to form a catalyst carrier. Can do. For example, silica, alumina, silica alumina, magnesia, zirconia, or the like can be added for the purpose of enhancing the dispersibility of the copper component and the phosphorus component.
In the exhaust gas purifying catalyst of the present invention, at least a copper component and a phosphorus component are supported on the catalyst carrier.
Here, the amount of the copper component supported on the catalyst carrier is preferably in the range of 0.8 to 30.0% by weight in terms of CuO, particularly 2.0 to 15. A range of 0% by weight is preferred. If it is less than 0.8% by weight, sufficient activity cannot be obtained because the copper content is low. On the other hand, if it exceeds 30.0% by weight, copper oxide (CuO) and the like are aggregated on the surface of the catalyst support. In some cases, the pores of the catalyst carrier are clogged and the activity of the catalyst is lowered.
The amount of the phosphorus component supported is P with respect to the total weight of the catalyst.2OFiveA range of 0.1 to 5.0% by weight is preferable, and a range of 0.1 to 2.0% by weight is particularly preferable. If the amount is less than 0.1% by weight, the stability of the copper component cannot be sufficiently maintained, so a catalyst having excellent hot water resistance may not be obtained. The improvement of sex is not expected.
In addition, in this invention, if it is a range which does not have a bad influence on catalyst activity and durability, other components other than a copper and phosphorus component can also be included. For example, metal components such as Co, Fe, Ga, and In are added to further increase the catalytic activity, or metal components such as rare earths, alkaline earths, and Zr, or halogen compounds are added to further increase the durability of the catalyst. May be. When other components are also supported, the supported amount of each component is usually about 0.05 to 10% by weight with respect to the weight of the whole catalyst.
Next, a method for producing an exhaust gas purification catalyst will be described.
As a method for producing an exhaust gas purifying catalyst in the present invention, first, a copper solution supported on a catalyst carrier, a copper compound corresponding to the phosphorus component, and a supporting solution containing the phosphorus compound are prepared.
Here, as a solvent used for the preparation of the solution for supporting, various solvents that are usually used for catalyst adjustment such as supporting an active component on a catalyst carrier, such as water, alcohol (for example, methanol, ethanol), etc. It can be used by appropriately selecting from polar solvents. Among these, it is usually preferable to use water from the practical aspect.
The copper compound is not particularly limited as long as it is a compound that contains copper and dissolves in the solvent to be used, and various copper compounds such as inorganic acid salts, halides, organic acid salts, and complex compounds can be used. . For example, as an inorganic acid salt, nitrate, copper carbonate, etc., as a halide, copper fluoride, copper chloride, copper bromide, etc., as an organic acid salt, copper acetate, copper oxalate, etc., and as a complex compound, A copper ammine complex, a copper cyano complex, etc. can be mentioned. Among these copper compounds, inorganic acid salts are preferable because copper is easily supported uniformly on the catalyst carrier, and copper nitrate is particularly preferable. Moreover, these copper compounds can be used individually by 1 type or in combination of 2 or more types.
The phosphorus compound is not particularly limited as long as it contains phosphorus and dissolves in the solvent to be used or is a compatible compound, and various phosphorous compounds such as inorganic phosphoric acid and salts thereof, or chalcogenide phosphorus can be used. Can be used. For example, as inorganic phosphoric acid, (a) orthophosphoric acid, metaphosphoric acid, hypophosphoric acid, metaphosphorous acid or hypophosphorous acid, etc., phosphoric acid having various oxidation numbers, (b) orthopyrophosphoric acid, metapyrrolic acid, tripolyphosphoric acid And polyphosphoric acid such as tetrapolyphosphoric acid and condensed phosphoric acid such as polymetaphosphoric acid such as trimetaphosphoric acid, tetrametaphosphoric acid and hexametaphosphoric acid. Examples of the salt include alkali metal salts such as lithium salts, sodium salts, and potassium salts of the above inorganic phosphoric acid, ammonium salts, and the like. In addition to these so-called normal salts such as trialkali metal orthophosphate or triammonium orthophosphate, these salts include alkali metal dihydrogen orthophosphate, alkali metal monohydrogen orthophosphate, ammonium dihydrogen orthophosphate, otoline. Examples include so-called hydrogen salts such as ammonium monohydrogen phosphate, alkali metal monohydrogen phosphite or ammonium monohydrogen phosphite. Examples of phosphorus chalcogenides include phosphorus pentoxide, phosphorus trioxide, and phosphorus pentasulfide. Among these phosphorus compounds, a lithium salt, sodium salt or ammonium salt of phosphoric acid is preferred, and ammonium dihydrogen orthophosphate is particularly preferred because a catalyst having excellent heat resistance can be easily obtained. Moreover, these phosphorus compounds can be used individually by 1 type or in combination of 2 or more types.
Further, the amount of the copper compound and the phosphorus compound contained in the solution differs depending on the amount of each component supported on the catalyst carrier or the loading conditions such as the temperature or pH of the solution, and thus cannot be specified in general. Usually, the copper compound is preferably 0.2 to 2.0 mmol / g-cat, and the phosphorus compound is preferably 0.01 to 1.0 mmol / g-cat. When the amount of the copper compound and the phosphorus compound is 2.0 mmol / g-cat or 1.0 mmol / g-cat or more, respectively, the copper carrier or the phosphorus component is supported on the catalyst carrier in an aggregated state, and sufficient exhaust gas purification A catalyst having performance may not be obtained. On the other hand, when the amount is 0.2 mmol / g-cat or 0.01 mmol / g-cat or less, respectively, the copper component or phosphorus component is not supported on the catalyst support, or the copper component or phosphorus supported by a single support operation. It may be necessary to repeat the loading operation as many times as the amount of the components is small and impractical.
When a component other than the copper component and the phosphorus component is also supported on the catalyst carrier, a compound containing the component and dissolved in the solvent to be used is appropriately selected, and the solution containing the copper component and the phosphorus component is selected. Although the method of dissolving and carrying simultaneously by one carrying process is preferable, it can be carried out by carrying out a normal carrying process separately before or after carrying the copper component and the phosphorus component by the method of the present invention.
Next, in the present invention, the pH of the solution is adjusted by adding ammonia without adding the buffer or after adding the buffer.
The pH of the solution is adjusted in order to form a sufficient amount of copper complex in the solution containing the copper compound and the phosphorus compound. The pH is adjusted with ammonia because the produced copper ammine complex is most suitable for uniformly supporting the copper component on the catalyst carrier in terms of ionic state, form and size.
Here, the ammonia to be added is not particularly limited, and commercially available ammonia or a solution containing ammonia as it is or diluted with a solvent used for a supporting solution can be appropriately used. It is preferable to use one containing 5% by volume or more of ammonia. If less than 0.5% by volume is used, a large amount of ammonia solution is added to adjust the pH, and the concentration of the copper component or phosphorus component in the solution for supporting changes significantly, so that it can be supported at the desired concentration. It may disappear.
Moreover, the pH of the solution to be adjusted is different between the case where the pH is adjusted by adding a buffering agent described later and the case where the pH is adjusted without adding the buffering agent, as an aspect of the present invention.
That is, when no buffer is added, it is 9.0 or more, preferably 9.0 to 12.0, while when a buffer is added in advance, 8.0 or more, preferably 8.0. Adjust the pH of the solution in the range of ~ 12.0. If the pH of the solution is less than 9.0 in the former or less than 8.0 in the latter, a sufficient amount of copper ammine complex cannot be formed in the solution, so that the copper component cannot be uniformly supported on the catalyst support. As a result, the exhaust gas purification performance of the catalyst is deteriorated.
In the present invention, as described above, the pH of the solution is adjusted after adding a buffer as one embodiment of the present invention. This is because when a buffer is added, a sufficient amount of copper ammine complex can be formed at a lower pH, and a highly soluble phosphorus compound can be more efficiently supported on the catalyst support.
There is no restriction | limiting in particular as a buffering agent used here, Although a commercially available thing can be selected suitably and used, What acts at pH 7.0 or more is preferable. This is because if a buffering agent that acts at pH 7.0 or lower is used, a larger amount of ammonia than necessary is added to adjust the pH of the solution to 8.0 or higher. Preferred buffering agents include ammonium nitrate, ammonium chloride, ammonium acetate, sodium acetate and the like. Among these, a salt having an ionic component in common with a copper compound and a phosphorus compound used when preparing a solution containing a copper component and a phosphorus component is particularly preferable. For example, when copper nitrate is used as the copper compound and ammonium dihydrogen phosphate is used as the phosphorus compound, ammonium nitrate is optimal as the buffer. The amount of the buffer used varies depending on the type of the buffer, but is usually in the range of 2 to 6 mol / mol Cu ions.
Next, in the present invention, at least a copper component and a phosphorus component are supported on a catalyst carrier containing a pentasil-type crystalline aluminosilicate, using the above-described supporting solution adjusted in pH. This supporting method will be described in detail below.
As the supporting method of the present invention, a catalyst containing pentasil type crystalline aluminosilicate in the supporting solution heated or cooled to room temperature or in the range of 10 to 50 ° C., more preferably in the range of 15 to 40 ° C. A carrier is added, and the mixture is allowed to stand for 1 to 10 hours, more preferably 1 to 5 hours, or preferably stirred. In this process, the copper component or the phosphorus component is ion-exchanged with the cation of the catalyst support. In addition, there is no restriction | limiting in the apparatus used for a heating, cooling, or stirring of a solution here, The various apparatus normally used can be used.
Next, after the treatment for a certain period of time, an acid is added to the solution to adjust the pH of the solution to 7.0 or less, preferably 6.5 to 4.0. The reason why the pH of the solution is adjusted to 7.0 or lower is to support the non-ion-exchanged copper component or phosphorus component present in the solution having the pH before the adjustment on the catalyst support.
Here, there is no restriction | limiting in particular as an acid used for pH adjustment, Nitric acid, hydrochloric acid, and a sulfuric acid can be used. Among these, nitric acid is preferable because a catalyst having excellent durability can be easily obtained.
The acid is preferably added at such a rate that the pH is reduced by about 0.2 to 2 per minute. If the pH fluctuates by 2 or more per minute, the copper component tends to be supported on the catalyst in an aggregated state, and a catalyst having sufficient exhaust gas purification performance may not be obtained. This is because an effect of preventing aggregation of the copper component commensurate with the amount cannot be obtained.
In order to prevent the pH in the solution from changing abruptly partially, it is preferable to add the acid while stirring the solution.
In the present invention, after the addition of the acid, further heating or cooling to a temperature range of 10 to 50 ° C., more preferably 15 to 40 ° C., for 0.5 to 4 hours, more preferably 0.5 to 2 hours. Let the solution stand or stir. In this process, a desired amount of the copper component and the phosphorus component in the solution are supported on the catalyst support.
In the present invention, after the copper component and the phosphorus component are supported on the catalyst carrier, the solution is filtered and washed by an ordinary method to recover the solid content and dried. Specifically, the filtration is performed using an apparatus such as a Buchner funnel, a pressure filter, or a filter press, and the drying is performed at a temperature of 100 to 200 ° C. in air for 6 to 24 hours. In the present invention, a desired amount of copper component and phosphorus component can usually be supported on the catalyst carrier by a single loading, but it is repeated several times for the purpose of more uniformly supporting the copper component and phosphorus component, etc. A copper component and a phosphorus component can also be supported on the catalyst carrier.
In this way, a catalyst carrier carrying a desired amount of copper component and phosphorus component is calcined by a conventional method to obtain a catalyst. The calcination is specifically carried out by holding at a temperature of 500 to 700 ° C. in air for 0.5 to 8 hours using an apparatus usually used for calcination of a catalyst such as a muffle furnace or a rotary kiln.
In the present invention, a catalyst that is appropriately treated with a substance such as acid, alkali, heat, steam, ammonia, halogen, or other non-metallic compound after firing can be used as a catalyst.
Further, the obtained catalyst is usually in a powder form, and it can be used as a catalyst as it is, but depending on the application, for example, using a binder such as silica, alumina, silica alumina, magnesia, zirconia, It is preferable to use it in any shape such as a spherical shape, a cylindrical shape, a star shape, or a honeycomb shape. Further, the catalyst powder can be applied to a carrier substrate of various shapes made separately from the present catalyst. There is no restriction | limiting in particular as a material used for such a support | carrier base material, It can select from various heat-resistant materials, such as ceramics and a metal, and can use it. For example, when used as an exhaust gas catalyst for automobiles, the catalyst powder is applied to a honeycomb-shaped carrier substrate made of cordierite, especially ceramics with excellent strength at high temperatures and long-term heat resistance. Is preferably used.
EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not restrict | limited at all by these Examples.
Example 1
First, a solution composed of 337.5 g of aluminum sulfate (18 hydrate), 362.5 g of sulfuric acid (97%), and 8250 g of water (solution I), water glass (SiO 22: 28.5%, Na2A solution (referred to as Solution II) consisting of 5275 g of O: 9.5%, water: 62%) and 5000 g of water and a solution consisting of 987.5 g of sodium chloride and 2300 g of water (referred to as Solution III) were prepared.
Next, solutions I and II were mixed while being dropped into solution III simultaneously. After adjusting this raw material mixture to pH 9.5 with sulfuric acid, mordenite [SiO2/ Al2OThree(Molar ratio) = 20] 12.5 g was added.
Next, this raw material mixture was put in a 25 liter autoclave, and kept for 20 hours while stirring at 170 ° C. and 300 rpm in a sealed state. After cooling, the reaction mixture was filtered, and the precipitate was thoroughly washed with pure water. Thereafter, by drying at 120 ° C. for 20 hours, a crystalline aluminosilicate having a ZSM-5 structure (MFI structure), which is a pentasil-type crystalline aluminosilicate, was synthesized. Table 1 below shows the results of measurement of this aluminosilicate by powder X-ray diffraction.
Next, 132.5 g of copper seed trihydrate, 11.17 g of ammonium dihydrogen phosphate and 178 g of ammonium nitrate were sequentially dissolved in 2080 g of water, and then 5% ammonia while controlling the liquid temperature at 30 ° C. The pH of the solution was adjusted to 8.5 by adding water to prepare a supporting solution containing a copper component and a phosphorus component. The aluminosilicate 500g was added to this solution, and ion exchange was performed for 4 hours, controlling liquid temperature at 30 degreeC. Thereafter, 30% nitric acid was added to the solution to adjust the pH to 6.0, and ion exchange was further performed for 1 hour. Thereafter, the slurry solution was filtered, and the obtained solid was further washed with water. Next, the solid was dried at 120 ° C. for 24 hours and then calcined at 500 ° C. for 4 hours to obtain the target catalyst. The copper component content of this catalyst is 7.5 wt% in terms of CuO, and the phosphorus component content is P.2OFiveIt was 1.3 wt% in terms of conversion.
Next, NO of the catalystxThe reduction and removal performance was evaluated by the following initial activity and activity after steaming (hydrothermal treatment).
(1) Evaluation of initial activity
First, after filling a stainless steel reaction tube with 2 cc of catalyst, the reaction tube is maintained at a temperature described later, a model gas is used as a processing gas, and GHSV = 80000 h is supplied to the reaction tube.-1Introduced under the conditions of The composition of this model gas is NOx: 500 ppm, O2: 6.0%, CThreeH6/ CThreeH8= 2 (THC concentration about 2500 ppm), water 10%, nitrogen balance. Here, the THC (Total Hydrocarbon) concentration refers to the concentration when various hydrocarbons are converted to methane. Next, the gas from the outlet of the reaction tube is introduced into the chemiluminescence analyzer, and NOxConcentration was measured. Model gas NO after catalytic reactionxThe removal rate was calculated by comparing the concentration of the model gas before and after introduction of the reaction tube. NOxThe removal rate was evaluated at a reaction tube temperature of 300 ° C., 350 ° C., and 400 ° C., respectively. The results are shown in Table 2 below.
(2) Evaluation of activity after steaming (hydrothermal treatment)
First, after filling the catalyst prepared in this example into a quartz reaction tube, the reaction tube was kept at a temperature of 750 ° C.ThreeH6/ CThreeH8= 2 (THC concentration about 2500 ppm), O2: 0.5%, nitrogen gas containing 10% by volume of water, GHSV = 80000h-1It introduced for 16 hours on the conditions of this, and performed the steaming process.
Next, after cooling the reaction tube, the extracted catalyst is filled in a stainless steel reaction tube, and under the same conditions as in the evaluation of the initial activity, NO for the same model gas is used.xThe removal rate was evaluated. The results are shown in Table 2 below.
Example 2
In Example 1, the catalyst of Example 2 was prepared in the same manner as Example 1 except that 5% ammonia water was added to adjust the pH of the solution to 11.5 without using ammonium nitrate. . The copper component content of this catalyst is 6.7 wt% in terms of CuO, and the phosphorus component content is P.2OFiveIt was 1.1 wt% in terms of conversion.
Example 3
The catalyst of Example 3 was prepared in the same manner as in Example 1 except that ammonium carbonate was used instead of ammonium nitrate. The copper component content of this catalyst is 6.0 wt% in terms of CuO, and the phosphorus component content is P.2OFiveIt was 1.2 wt% in terms of conversion.
Example 4
In Example 1, the catalyst of Example 4 was prepared in the same manner as Example 1 except that ammonium pyrophosphate was used instead of ammonium dihydrogen phosphate. The copper component content of this catalyst is 7.3 wt% in terms of CuO, and the phosphorus component content is P.2OFiveIt was 0.8 wt% in terms of conversion.
Comparative Example 1
In Example 2, comparison was made in the same manner as in Example 2 except that the pH of the solution was not adjusted with 5% aqueous ammonia (pH of the solution was 2.5) and the pH of the solution was not adjusted with nitric acid. The catalyst of Example 1 was prepared. The copper component content of this catalyst is 2.6 wt% in terms of CuO, and the phosphorus component content is P.2OFiveIt was 0.2 wt% in terms of conversion.
Comparative Example 2
In Example 2, a catalyst of Comparative Example 2 was prepared in the same manner as in Example 2 except that the pH of the solution was adjusted to 6.0 by adding 5% aqueous ammonia. The copper component content of this catalyst is 6.0 wt% in terms of CuO, and the phosphorus component content is P.2OFiveIt was 1.0 wt% in terms of conversion.
Comparative Example 3
In Example 2, the catalyst of Comparative Example 3 was prepared in the same manner as Example 2 except that the pH of the solution with nitric acid was not adjusted. The copper component content of this catalyst is 3.2 wt% in terms of CuO, and the phosphorus component content is P.2OFiveIt was 0.01 wt% in terms of conversion.
With respect to the catalysts of Examples 2 to 4 and Comparative Examples 1 to 3, the initial activity and the activity after the steaming treatment (hydrothermal treatment) were evaluated under the same conditions as in Example 1. The results are shown in Table 2 below.
Industrial application fields
According to the method for producing an exhaust gas purification catalyst according to the present invention, an exhaust gas purification catalyst having high durability and high efficiency can be stably obtained.
Claims (7)
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP1996/003471 WO1998023373A1 (en) | 1996-11-27 | 1996-11-27 | Process for producing a catalyst for cleaning exhaust gas |
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| Publication Number | Publication Date |
|---|---|
| JP3854641B2 true JP3854641B2 (en) | 2006-12-06 |
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| JP52542798A Expired - Fee Related JP3854641B2 (en) | 1996-11-27 | 1996-11-27 | Method for producing exhaust gas purification catalyst |
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|---|---|
| JP (1) | JP3854641B2 (en) |
| DE (1) | DE69633831T2 (en) |
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1996
- 1996-11-27 DE DE69633831T patent/DE69633831T2/en not_active Expired - Lifetime
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| DE69633831D1 (en) | 2004-12-16 |
| DE69633831T2 (en) | 2005-03-17 |
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