JP6273859B2 - Three-way catalyst and exhaust gas purification method using the same - Google Patents
Three-way catalyst and exhaust gas purification method using the same Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims description 131
- 238000000746 purification Methods 0.000 title claims description 37
- 238000000034 method Methods 0.000 title claims description 30
- 239000010949 copper Substances 0.000 claims description 111
- 229910052802 copper Inorganic materials 0.000 claims description 58
- 229910052721 tungsten Inorganic materials 0.000 claims description 53
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 46
- 239000007789 gas Substances 0.000 claims description 45
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 41
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 36
- 239000010937 tungsten Substances 0.000 claims description 36
- 229930195733 hydrocarbon Natural products 0.000 claims description 23
- 150000002430 hydrocarbons Chemical class 0.000 claims description 23
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 18
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 18
- 238000006243 chemical reaction Methods 0.000 claims description 17
- 238000002485 combustion reaction Methods 0.000 claims description 15
- 229910000420 cerium oxide Inorganic materials 0.000 claims description 11
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims description 11
- 229910052751 metal Inorganic materials 0.000 claims description 10
- 230000000052 comparative effect Effects 0.000 description 47
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 34
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 34
- 230000000694 effects Effects 0.000 description 18
- 230000003197 catalytic effect Effects 0.000 description 12
- OPQARKPSCNTWTJ-UHFFFAOYSA-L copper(ii) acetate Chemical compound [Cu+2].CC([O-])=O.CC([O-])=O OPQARKPSCNTWTJ-UHFFFAOYSA-L 0.000 description 11
- 238000011068 loading method Methods 0.000 description 11
- 238000011156 evaluation Methods 0.000 description 10
- 230000003647 oxidation Effects 0.000 description 10
- 238000007254 oxidation reaction Methods 0.000 description 10
- 238000012360 testing method Methods 0.000 description 9
- 239000002184 metal Substances 0.000 description 8
- 229910044991 metal oxide Inorganic materials 0.000 description 8
- 150000004706 metal oxides Chemical class 0.000 description 8
- 238000006722 reduction reaction Methods 0.000 description 8
- 239000000758 substrate Substances 0.000 description 7
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 6
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 229910000510 noble metal Inorganic materials 0.000 description 6
- QGUAJWGNOXCYJF-UHFFFAOYSA-N cobalt dinitrate hexahydrate Chemical compound O.O.O.O.O.O.[Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O QGUAJWGNOXCYJF-UHFFFAOYSA-N 0.000 description 5
- 238000001035 drying Methods 0.000 description 5
- 238000010304 firing Methods 0.000 description 5
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 5
- 150000003839 salts Chemical group 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 5
- 229910000314 transition metal oxide Inorganic materials 0.000 description 5
- 229910052684 Cerium Inorganic materials 0.000 description 4
- 230000001747 exhibiting effect Effects 0.000 description 4
- 239000010410 layer Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 239000004215 Carbon black (E152) Substances 0.000 description 3
- 229910021591 Copper(I) chloride Inorganic materials 0.000 description 3
- 229910002554 Fe(NO3)3·9H2O Inorganic materials 0.000 description 3
- 230000010757 Reduction Activity Effects 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 239000010953 base metal Substances 0.000 description 3
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 3
- 239000011247 coating layer Substances 0.000 description 3
- OXBLHERUFWYNTN-UHFFFAOYSA-M copper(I) chloride Chemical compound [Cu]Cl OXBLHERUFWYNTN-UHFFFAOYSA-M 0.000 description 3
- 239000012153 distilled water Substances 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 239000008188 pellet Substances 0.000 description 3
- 239000010970 precious metal Substances 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- 229910052723 transition metal Inorganic materials 0.000 description 3
- 150000003624 transition metals Chemical class 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- -1 alumina Chemical class 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 description 2
- 229910052878 cordierite Inorganic materials 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 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 2
- 239000000446 fuel Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002923 metal particle Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 239000010948 rhodium Substances 0.000 description 2
- 239000002356 single layer Substances 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 229910052727 yttrium Inorganic materials 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910004631 Ce(NO3)3.6H2O Inorganic materials 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910000365 copper sulfate Inorganic materials 0.000 description 1
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 description 1
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 1
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 239000011964 heteropoly acid Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 229910052809 inorganic oxide Inorganic materials 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
Description
本発明は、三元触媒及びそれを用いた排ガス浄化方法に関する。 The present invention relates to a three-way catalyst and an exhaust gas purification method using the same.
自動車等の内燃機関から排出される排ガス中に含まれる炭化水素（ＨＣ）類、一酸化炭素（ＣＯ）及び窒素酸化物（ＮＯｘ）等の有害成分を除去するために、従来から排ガス浄化用触媒が用いられてきた。このような排ガス浄化用触媒としては、理論空燃比で燃焼された排ガス中のＨＣ、ＣＯ及びＮＯｘを同時に浄化する三元触媒が知られており、例えばコーディエライト、金属等からなる耐熱性ハニカム基材にアルミナ、ジルコニア、セリア等の金属酸化物からなる担体層（触媒担体）を形成し、この担体層に白金（Ｐｔ）やロジウム（Ｒｈ）等の貴金属を担持させたものが広く知られている。しかしながら、これらの貴金属はいずれも産出国が特定の国に限定されしかも資源枯渇の問題を抱えている。 In order to remove harmful components such as hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NO x ) contained in exhaust gas discharged from internal combustion engines such as automobiles, it has been conventionally used for exhaust gas purification. Catalysts have been used. As such an exhaust gas purification catalyst, a three-way catalyst that simultaneously purifies HC, CO, and NOx in exhaust gas burned at a stoichiometric air-fuel ratio is known. For example, a heat-resistant honeycomb made of cordierite, metal, etc. It is widely known that a support layer (catalyst support) made of a metal oxide such as alumina, zirconia, or ceria is formed on a base material, and a noble metal such as platinum (Pt) or rhodium (Rh) is supported on this support layer. ing. However, all of these precious metals are limited to specific countries and have the problem of resource depletion.
このような課題を解決するために、近年、白金等の希少で高価な貴金属を使用しない排気浄化用触媒（貴金属フリー触媒）の研究が盛んに行われている。例えば、特開２０１０−１０４９７３号公報（特許文献１）には、貴金属を必須成分として用いない場合でも浄化性能を示す浄化触媒であって、平均粒子径が１ｎｍ〜２μｍであり、且つ、酸素の電子の結合エネルギが５３１．３ｅＶより低エネルギ側にシフトしている遷移金属酸化物（Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ及びＣｕの少なくとも１種の遷移元素を含む遷移金属酸化物）から成る触媒粉末と、前記遷移金属酸化物の表面に担持又は前記遷移金属酸化物と固溶体を形成している酸素放出材料（Ｃｅ、Ｐｒ、Ｎｄ、Ｙ及びＳｃの少なくとも１種の希土類元素を含む希土類酸化物）とを含有する浄化触媒、並びに、該浄化触媒においてＺｒ、Ｔｉ、Ｓｉ及びＷの少なくとも１種の元素を含む無機酸化物をさらに含有する浄化触媒が開示されている。しかしながら、特許文献１に開示されている浄化触媒は、触媒活性が十分ではなく、ＮＯｘ浄化性能が必ずしも十分なものではなかった。 In order to solve such problems, in recent years, research on exhaust purification catalysts (noble metal-free catalysts) that do not use rare and expensive noble metals such as platinum has been actively conducted. For example, JP 2010-104973 A (Patent Document 1) discloses a purification catalyst that exhibits purification performance even when no noble metal is used as an essential component, having an average particle diameter of 1 nm to 2 μm, A catalyst powder comprising a transition metal oxide (transition metal oxide containing at least one transition element of Mn, Fe, Co, Ni and Cu) whose electron binding energy is shifted to a lower energy side than 531.3 eV; An oxygen releasing material (a rare earth oxide containing at least one rare earth element of Ce, Pr, Nd, Y and Sc) supported on the surface of the transition metal oxide or forming a solid solution with the transition metal oxide; And a purification catalyst further containing an inorganic oxide containing at least one element of Zr, Ti, Si, and W in the purification catalyst. . However, the purification catalyst disclosed in Patent Document 1 does not have sufficient catalytic activity, and the NOx purification performance is not always sufficient.
また、特開２０１２−１９６６６０号公報（特許文献２）には、３ｄ遷移金属の酸化物（Ｆｅ及び／又はＣｕ）と５価又は６価の遷移金属（Ｗ、Ｍｏ、Ｎｂ、及びＴａの少なくとも１種）の酸化物、及び／又は３ｄ遷移金属と５価又は６価の遷移金属との酸化物固溶体を含有する炭化水素選択酸化触媒、並びに、該触媒に酸化アルミニウム、酸化チタン、酸化ジルコニウム、酸化セリウム、及び二酸化珪素から選ばれる少なくとも１種をさらに含有することを特徴とする炭化水素選択酸化触媒が開示されている。しかしながら、特許文献２に開示されている触媒においても、３００℃前後の低温域における触媒活性が十分ではなく、ＮＯｘ浄化性能が必ずしも十分なものではなかった。 JP 2012-196660 A (Patent Document 2) discloses a 3d transition metal oxide (Fe and / or Cu) and a pentavalent or hexavalent transition metal (W, Mo, Nb, and Ta). 1 type) oxide and / or a hydrocarbon selective oxidation catalyst containing an oxide solid solution of a 3d transition metal and a pentavalent or hexavalent transition metal, and an aluminum oxide, titanium oxide, zirconium oxide, A hydrocarbon selective oxidation catalyst characterized by further containing at least one selected from cerium oxide and silicon dioxide is disclosed. However, even in the catalyst disclosed in Patent Document 2, the catalytic activity in a low temperature region around 300 ° C. is not sufficient, and the NOx purification performance is not always sufficient.
本発明は、前記従来技術の有する課題に鑑みてなされたものであり、貴金属を用いない場合であっても、排ガス中に含まれるＨＣ、ＣＯ及びＮＯｘを効率よく浄化することができる優れた排ガス浄化性能（高度に優れた触媒活性）を示す三元触媒及びそれを用いた排ガス浄化方法を提供することを目的とする。 The present invention has been made in view of the problems of the prior art, and is an excellent exhaust gas that can efficiently purify HC, CO, and NOx contained in the exhaust gas even when noble metal is not used. It is an object of the present invention to provide a three-way catalyst exhibiting purification performance (highly excellent catalytic activity) and an exhaust gas purification method using the same.
本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、酸化セリウム（ＣｅＯ２）を含む担体に、銅（Ｃｕ）及びタングステン（Ｗ）を担持すると共に、前記担体の比表面積とＣｕの担持量（ＣｕＯ換算）及びＷの担持量（ＷＯ３換算）が特定の関係となるようにすることにより、貴金属を用いない場合であっても優れた排ガス浄化性能（高度に優れた触媒活性）を発現させることが可能となることを見出し、本発明を完成するに至った。 As a result of intensive studies to achieve the above object, the present inventors supported copper (Cu) and tungsten (W) on a carrier containing cerium oxide (CeO 2 ), and the specific surface area of the carrier. loading amount of Cu loading of (CuO equivalent) and W (WO 3 equivalent) by such a specific relationship, even when not using the noble metal excellent exhaust gas purification performance (highly superior catalytic The inventors have found that it is possible to express (activity), and have completed the present invention.
すなわち、本発明の三元触媒は、炭化水素（ＨＣ）類、一酸化炭素（ＣＯ）及び窒素酸化物（ＮＯｘ）を含有する燃焼排ガスを接触させて前記３成分を浄化する三元触媒であって、酸化セリウム（ＣｅＯ２）を含む担体と、該担体に担持された銅（Ｃｕ）及びタングステン（Ｗ）とを含んでおり、前記担体におけるＣｅＯ ２ の含有量が該担体中の金属元素に対するＣｅの比率が７０モル％以上となる量であり、前記担体の比表面積とＣｕの担持量（ＣｕＯ換算）及びＷの担持量（ＷＯ３換算）が下記式（１）： That is, the three-way catalyst of the present invention is a three-way catalyst that purifies the three components by contacting a combustion exhaust gas containing hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). A support containing cerium oxide (CeO 2 ) and copper (Cu) and tungsten (W) supported on the support , and the content of CeO 2 in the support is relative to the metal element in the support The ratio of Ce is 70 mol% or more, and the specific surface area of the carrier, the supported amount of Cu (in terms of CuO), and the supported amount of W (in terms of WO 3 ) are represented by the following formula (1):
の関係を満たしているものであることを特徴とするものである。 It is characterized by satisfying the relationship.
上記本発明の三元触媒においては、前記担体の比表面積が、３０〜２００ｍ２／ｇの範囲にあることが好ましい。 In the above three-way catalyst of the present invention, the specific surface area of the carrier is preferably in the range of 30 to 200 m 2 / g.
また、上記本発明の三元触媒においては、前記タングステン（Ｗ）の含有量が、前記三元触媒の全質量に対してＷＯ３換算で１〜２５質量％の範囲にあることが好ましい。 In the three-way catalyst of the present invention, the content of tungsten (W) is preferably in the range of 1 to 25% by mass in terms of WO 3 with respect to the total mass of the three-way catalyst.
更に、上記本発明の三元触媒においては、前記銅（Ｃｕ）の含有量が、前記三元触媒の全質量に対してＣｕＯ換算で０．３〜１５質量％の範囲にあることが好ましい。 Furthermore, in the three-way catalyst of the present invention, the copper (Cu) content is preferably in the range of 0.3 to 15% by mass in terms of CuO with respect to the total mass of the three-way catalyst.
本発明の排ガス浄化方法は、前記本発明の三元触媒に内燃機関からの排ガスを接触せしめて排ガスを浄化することを特徴とするものである。 The exhaust gas purification method of the present invention is characterized in that exhaust gas is purified by bringing the exhaust gas from the internal combustion engine into contact with the three-way catalyst of the present invention.
なお、本発明の三元触媒及びそれを用いた排ガス浄化方法によって上記目的が達成される理由は必ずしも定かではないが、本発明者らは以下のように推察する。すなわち、本発明においては、セリア含有担体の表面上に銅（Ｃｕ）及びタングステン（Ｗ）が分散性の高い状態で担持されており、ＨＣによるＮＯ選択還元反応が十分発現されるようになるものと推察される。また、セリア（ＣｅＯ２）と銅（Ｃｕ）が高いＣＯ酸化能とＨＣ酸化能を有し、更に、セリア（ＣｅＯ２）とタングステン（Ｗ）とが相互作用することにより、前記タングステン（Ｗ）の近傍又は前記タングステン（Ｗ）上に担持された前記銅（Ｃｕ）の原子がより一層活性化されるため、高温域においてＮＯ還元活性が保ちつつ、低温域から高温域においても高水準のＮＯＸ浄化活性が達成されるようになるものと推察される。これらより、本発明の三元触媒においては、Ｃｕ／ＣｅＯ２の５００℃以上のＮＯ還元活性を保つと共に、２００℃から５００℃の温度域のＮＯの浄化率を向上させることができるようになるものと推察される。 The reason why the above object is achieved by the three-way catalyst of the present invention and the exhaust gas purification method using the same is not necessarily clear, but the present inventors speculate as follows. That is, in the present invention, copper (Cu) and tungsten (W) are supported in a highly dispersible state on the surface of the ceria-containing support, and the NO selective reduction reaction by HC is sufficiently expressed. It is guessed. In addition, ceria (CeO 2 ) and copper (Cu) have high CO oxidation ability and HC oxidation ability, and further, the ceria (CeO 2 ) and tungsten (W) interact, whereby the tungsten (W) The copper (Cu) atoms supported in the vicinity of or on the tungsten (W) are further activated, so that the NO reduction activity is maintained in the high temperature range, and the high level NO in the low temperature range to the high temperature range. It is presumed that X purification activity will be achieved. From these, in the three-way catalyst of the present invention, the NO reduction activity of Cu / CeO 2 at 500 ° C. or higher can be maintained, and the NO purification rate in the temperature range of 200 ° C. to 500 ° C. can be improved. Inferred.
本発明によれば、貴金属を用いない場合であっても、排ガス中に含まれるＨＣ、ＣＯ及びＮＯｘを効率よく浄化することができる優れた排ガス浄化性能（高度に優れた触媒活性）を示す三元触媒及びそれを用いた排ガス浄化方法を提供することが可能となる。 According to the present invention, even if no precious metal is used, excellent exhaust gas purification performance (highly excellent catalytic activity) that can efficiently purify HC, CO, and NOx contained in exhaust gas. It becomes possible to provide an original catalyst and an exhaust gas purification method using the same.
以下、本発明をその好適な実施形態に即して詳細に説明する。 Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.
［三元触媒］
先ず、本発明の三元触媒について説明する。すなわち、本発明の三元触媒は、炭化水素（ＨＣ）類、一酸化炭素（ＣＯ）及び窒素酸化物（ＮＯｘ）を含有する燃焼排ガスを接触させて前記３成分を浄化する三元触媒であって、酸化セリウム（ＣｅＯ２）を含む担体と、該担体に担持された銅（Ｃｕ）及びタングステン（Ｗ）とを含んでおり、前記担体の比表面積とＣｕの担持量（ＣｕＯ換算）及びＷの担持量（ＷＯ３換算）が下記式（１）：
[Three-way catalyst]
First, the three-way catalyst of the present invention will be described. That is, the three-way catalyst of the present invention is a three-way catalyst that purifies the three components by contacting a combustion exhaust gas containing hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). A support containing cerium oxide (CeO 2 ), and copper (Cu) and tungsten (W) supported on the support, and the specific surface area of the support and the supported amount of Cu (in terms of CuO) and W The loading amount (in terms of WO 3 ) of the following formula (1):
の関係を満たしているものであることを特徴とするものである。 It is characterized by satisfying the relationship.
（担体）
本発明にかかる担体は、酸化セリウム（ＣｅＯ２、セリア）を含む担体（セリア含有担体）であることが必要である。このようなセリア含有担体は、酸化セリウムを単独で用いてもよく、また酸化セリウムをその他の１種以上の金属酸化物と固溶させて得られる複合酸化物、又は、それらの混合物を用いることができる。
(Carrier)
The carrier according to the present invention needs to be a carrier (ceria-containing carrier) containing cerium oxide (CeO 2 , ceria). As such a ceria-containing support, cerium oxide may be used alone, or a composite oxide obtained by dissolving cerium oxide with one or more other metal oxides or a mixture thereof may be used. Can do.
本発明においては、このようなセリア含有担体におけるＣｅＯ２の含有量としては、特に制限されないが、セリア含有担体中の金属元素に対するＣｅの比率が５０モル％以上となる量であることが好ましく、７０モル％以上となる量であることがより好ましく、９０モル％以上となる量であることが特に好ましい。ＣｅＯ２の含有量が前記下限未満では、セリアと銅（Ｃｕ）及び／又はタングステン（Ｗ）との相互作用が十分に発現しないため、得られる三元触媒の排ガス浄化性能が不十分となる傾向にある。 In the present invention, the content of CeO 2 in such a ceria-containing support is not particularly limited, but is preferably an amount such that the ratio of Ce to metal elements in the ceria-containing support is 50 mol% or more. The amount is more preferably 70 mol% or more, and particularly preferably 90 mol% or more. When the content of CeO 2 is less than the lower limit, the interaction between ceria and copper (Cu) and / or tungsten (W) does not sufficiently develop, and the exhaust gas purification performance of the resulting three-way catalyst tends to be insufficient. It is in.
このような酸化セリウムを含む担体に含有させることが可能なセリウム以外の成分としては、触媒の担体に利用することが可能な公知の他の成分を適宜利用することができる。このようなセリア含有担体に含有するセリウム以外の他の成分としては、触媒の担体に利用することが可能な公知の他の成分を適宜利用することができる。このようなセリア含有担体に含有させることが可能なセリウム以外の他の成分としては、担体の熱安定性や触媒活性の観点から、例えば、チタニウム（Ｔｉ）、ケイ素（Ｓｉ）、リン（Ｐ）、ジルコニウム（Ｚｒ）、アルミニウム（Ａｌ）、イットリウム（Ｙ）、ランタン（Ｌａ）等の元素の酸化物を好適に用いることができる。また、このような他の成分を含有するセリア含有担体としては、セリアと他の成分の金属酸化物の混合物、セリアと他の成分の金属酸化物の固溶体、セリアと他の成分の金属酸化物の複合酸化物等が挙げられる。 As components other than cerium that can be contained in the carrier containing cerium oxide, other known components that can be used in the carrier of the catalyst can be appropriately used. As other components other than cerium contained in such a ceria-containing support, other known components that can be used in a catalyst support can be appropriately used. Examples of components other than cerium that can be contained in such a ceria-containing support include, for example, titanium (Ti), silicon (Si), and phosphorus (P) from the viewpoint of thermal stability and catalytic activity of the support. , Oxides of elements such as zirconium (Zr), aluminum (Al), yttrium (Y), and lanthanum (La) can be preferably used. The ceria-containing carrier containing such other components includes a mixture of ceria and other component metal oxides, a solid solution of ceria and other component metal oxides, and ceria and other component metal oxides. And the like.
また、このようなセリア含有担体の形状としては、特に制限されないが、高い比表面積が得られるという観点から、粉末状であることが好ましい。 In addition, the shape of such a ceria-containing carrier is not particularly limited, but is preferably a powder from the viewpoint of obtaining a high specific surface area.
更に、このようなセリア含有担体の比表面積としては、特に制限されないが、３０〜２００ｍ２／ｇの範囲にあることが好ましく、５０〜１５０ｍ２／ｇの範囲にあることがより好ましい。前記比表面積が前記上限を超えると、担体が焼結し易くなり、得られる三元触媒の耐熱性が低下する傾向にあり、他方、前記下限未満では、活性金属の分散性が低下する傾向にある。このような比表面積は、吸着等温線からＢＥＴ等温吸着式を用いてＢＥＴ比表面積として算出することができる。なお、このようなセリア含有担体の製造方法としては、特に制限されず、公知の方法を適宜採用することができる。また、このようなセリア含有担体としては、市販のものを用いてもよい。 Furthermore, as the specific surface area of such ceria-containing carrier is not particularly limited, preferably in the range of 30 to 200 m 2 / g, and more preferably in the range of 50 to 150 m 2 / g. When the specific surface area exceeds the upper limit, the support tends to sinter and the heat resistance of the resulting three-way catalyst tends to decrease. On the other hand, when the specific surface area is less than the lower limit, the dispersibility of the active metal tends to decrease. is there. Such a specific surface area can be calculated as a BET specific surface area from the adsorption isotherm using the BET isotherm adsorption equation. In addition, it does not restrict | limit especially as a manufacturing method of such a ceria containing support | carrier, A well-known method is employable suitably. Moreover, as such a ceria containing carrier, a commercially available product may be used.
また、本発明の三元触媒においては、酸素過剰下において高いＣＯ酸化能と高いＨＣ酸化能を発揮させ、炭化水素過剰下においてＨＣによるＮＯ選択還元反応を発現させ窒素酸化物の還元反応を達成するという観点から、前記セリア含有担体に後述する銅（Ｃｕ）並びに後述するタングステン（Ｗ）が担持されていることが必要である。本発明においては、セリア含有担体の表面上に銅（Ｃｕ）及びタングステン（Ｗ）が分散性の高い状態で担持されてＨＣによるＮＯ選択還元反応が十分発現されるようになるものと推察される。また、セリア（ＣｅＯ２）と銅（Ｃｕ）が高いＣＯ酸化能とＨＣ酸化能を有し、更に、セリア（ＣｅＯ２）とタングステン（Ｗ）とが相互作用することにより、前記タングステン（Ｗ）の近傍又は前記タングステン（Ｗ）上に担持された前記銅（Ｃｕ）の原子がより一層活性化されるため、高温域においてＮＯ還元活性が保ちつつ、低温域から高温域においても高水準のＮＯＸ浄化活性が達成されるようになるものと推察される。 In the three-way catalyst of the present invention, high CO oxidation ability and high HC oxidation ability are exhibited in excess of oxygen, and NO selective reduction reaction by HC is exhibited in excess of hydrocarbon, thereby achieving reduction of nitrogen oxides. Therefore, it is necessary that copper (Cu) described later and tungsten (W) described later are supported on the ceria-containing support. In the present invention, it is speculated that copper (Cu) and tungsten (W) are supported on the surface of the ceria-containing support in a highly dispersible state so that the NO selective reduction reaction by HC can be sufficiently expressed. . In addition, ceria (CeO 2 ) and copper (Cu) have high CO oxidation ability and HC oxidation ability, and further, the ceria (CeO 2 ) and tungsten (W) interact, whereby the tungsten (W) The copper (Cu) atoms supported in the vicinity of or on the tungsten (W) are further activated, so that the NO reduction activity is maintained in the high temperature range, and the high level NO in the low temperature range to the high temperature range. It is presumed that X purification activity will be achieved.
（担持金属／タングステン（Ｗ））
このような本発明の三元触媒においては、セリア含有担体に担持されたタングステン（Ｗ）を含んでいることが必要である。このようなタングステン（Ｗ）の担持量（含有量）としては、前記三元触媒の全質量に対して酸化物（ＷＯ３）換算で１〜２５質量％の範囲にあることが好ましく、２〜１５質量％の範囲であることがより好ましい。このようなタングステン（Ｗ）の担持量が前記下限未満では、セリアとタングステン（Ｗ）との相互作用が十分に発現しないため、得られる三元触媒の低温域におけるＮＯＸ浄化活性が不十分となる傾向にあり、他方、前記上限を超えると触媒の比表面積が低下するため、得られる三元触媒の低温域におけるＮＯＸ浄化活性が不十分となる傾向にある。
(Supported metal / tungsten (W))
Such a three-way catalyst of the present invention needs to contain tungsten (W) supported on a ceria-containing support. Such loading of tungsten (W) as (content) is preferably in the range of 1 to 25 wt% of an oxide (WO 3) in terms of the total weight of the three-way catalyst, 2 A range of 15% by mass is more preferred. When the amount of tungsten (W) supported is less than the lower limit, the interaction between ceria and tungsten (W) is not sufficiently exhibited, and thus the obtained three-way catalyst has insufficient NO X purification activity in the low temperature range. becomes it tends, while the specific surface area of the catalyst exceeds the above upper limit is lowered, there is a tendency that NO X purification activity at low-temperature region of the three-way catalysts obtained is insufficient.
（担持金属／銅（Ｃｕ））
このような本発明の三元触媒においては、セリア含有担体に担持された銅（Ｃｕ）を含んでいることが必要である。このような銅（Ｃｕ）の担持量（含有量）としては、前記三元触媒の全質量に対して酸化物（ＣｕＯ）換算で０．３〜１５質量％の範囲にあることが好ましく、２〜１０質量％の範囲であることがより好ましい。前記銅（Ｃｕ）の担持量が前記下限未満では、前記銅（Ｃｕ）元素に由来する触媒の活性点の数が少なくなるため、得られる三元触媒の低温域におけるＮＯＸ浄化活性が不十分となる傾向にあり、他方、前記上限を超えると反応に不活性な前記銅（Ｃｕ）元素の酸化物結晶（例えばＣｕＯの結晶等）が形成されるため、得られる三元触媒の低温域におけるＮＯＸ浄化活性が不十分となる傾向にある。
(Supported metal / Copper (Cu))
Such a three-way catalyst of the present invention needs to contain copper (Cu) supported on a ceria-containing support. The supported amount (content) of copper (Cu) is preferably in the range of 0.3 to 15% by mass in terms of oxide (CuO) with respect to the total mass of the three-way catalyst. More preferably, it is in the range of -10% by mass. The supported amount is less than the lower limit of the copper (Cu), since the number of active sites of the catalyst from the copper (Cu) element is reduced, insufficient NO X purification activity at low-temperature region of the three-way catalyst obtained On the other hand, when the upper limit is exceeded, oxide crystals of the copper (Cu) element that are inactive to the reaction (for example, CuO crystals) are formed. NO X purification activity tends to be insufficient.
（Ｃｕ及びＷの担持量と担体の比表面積との関係式）
このような本発明の三元触媒においては、前記セリア含有担体の比表面積とＣｕの担持量（ＣｕＯ換算）及びＷの担持量（ＷＯ３換算）が下記式（１）：
(Relationship between the amount of Cu and W supported and the specific surface area of the support)
In such a three-way catalyst of the present invention, the specific surface area of the ceria-containing support, the supported amount of Cu (in terms of CuO) and the supported amount of W (in terms of WO 3 ) are expressed by the following formula (1):
の関係を満たしているものであることが必要である。 It is necessary to satisfy the relationship.
（以下、上記式（１）中、「（５．７７×Ｃｕの担持量（質量％）＋３．６３×Ｗの担持量（質量％））／担体の比表面積（ｍ２／ｇ）」を関係式Ａとし、得られる値を数値Ａとする。）
なお、上記式（１）に記載の関係式におけるＣｕの担持量にかかる係数（Ａ）及びＷの担持量にかかる係数（Ｂ）は、次のように算出する。
Ａ＝（ＣｕＯ１ｇ中に含まれるＣｕの原子数）×（ＣｕＯのＣｕ原子１個が占有する面積）／１００＝５．７７
Ｂ＝（ＷＯ３１ｇ中に含まれるＷの原子数）×（ＷＯ３のＷ原子１個が占有する面積）／１００＝３．６３
上記式（１）においては、「（５．７７×Ｃｕの担持量（質量％）＋３．６３×Ｗの担持量（質量％））／担体の比表面積（ｍ２／ｇ）」の値が０．０５〜０．５の範囲となるようにすることが必要であり、０．１〜０．４の範囲となるようにすることが好ましく、０．１５〜０．３の範囲となるようにすることがより好ましい。このような前記値が前記下限未満では、前記Ｃｕ元素に由来する触媒活性点の不足及び活性点の性能を補佐するＷ量の不足により低温域におけるＮＯｘ浄化性能を十分に得ることができない傾向にある。他方、前記上限を超えると、ＣｅＯ２表面がＣｕ及びＷにより埋没してしまい、ＣｅＯ２とＣｕ又はＣｅＯ２とＷの相互作用の効果が得られなくなり、低温域におけるＮＯｘ浄化活性が不十分となる傾向にある。
（三元触媒の製造方法）
このような本発明の三元触媒は、タングステン（Ｗ）と銅（Ｃｕ）とを、酸化セリウム（ＣｅＯ２）を含むセリア含有担体に担持せしめることにより得ることができる。このように、前記セリア含有担体に前記タングステン（Ｗ）及び前記銅（Ｃｕ）を担持せしめる方法としては、特に制限されず、公知の方法を適宜採用することができる。例えば、（ｉ）タングステン（Ｗ）源及び前記銅（Ｃｕ）源を含有する水溶液に前記セリア含有担体を含浸させて前記タングステン（Ｗ）源並びに前記銅（Ｃｕ）源を前記担体に担持せしめた後に乾燥し、焼成する方法、（ｉｉ）前記タングステン（Ｗ）源及び前記銅（Ｃｕ）源、更には前記セリア含有担体を物理混合して焼成する方法、等を採用することができる。これらの方法の中でも、前記タングステン（Ｗ）及び前記銅（Ｃｕ）を高分散にセリア含有担体上に担持するという観点から、前記タングステン（Ｗ）源及び前記銅（Ｃｕ）源を含有する水溶液に前記セリア含有担体を含浸させて前記タングステン（Ｗ）源及び前記銅（Ｃｕ）源を前記担体に担持せしめた後に乾燥し、焼成する方法が好ましい。なお、このような方法において、乾燥や焼成の際の条件は特に制限されず、公知の条件を適宜採用することができ、例えば、乾燥条件としては８０〜１４０℃で１〜２４時間程度加熱する条件を、焼成条件としては３００〜６００℃で１〜５時間程度加熱する条件を、それぞれ採用してもよい。
(Hereinafter, in the above formula (1), “(5.77 × Cu supported amount (mass%) + 3.63 × W supported amount (mass%)) / specific surface area of support (m 2 / g)” (The relational expression A is used, and the obtained value is a numerical value A.)
In addition, the coefficient (A) concerning the Cu loading amount and the coefficient (B) concerning the W loading amount in the relational expression described in the above formula (1) are calculated as follows.
A = (number of Cu atoms contained in 1 g of CuO) × (area occupied by one Cu atom of CuO) /100=5.77
B = (number of W atoms contained in 1 g of WO 3 ) × (area occupied by one W atom of WO 3 ) /100=3.63
In the above formula (1), the value of “(5.77 × Cu loading (mass%) + 3.63 × W loading (mass%)) / specific surface area of the carrier (m 2 / g)” is It is necessary to be in the range of 0.05 to 0.5, preferably in the range of 0.1 to 0.4, so that it is in the range of 0.15 to 0.3. More preferably. If the value is less than the lower limit, the NOx purification performance in the low temperature range tends not to be sufficiently obtained due to the lack of the catalytic active point derived from the Cu element and the lack of W amount that assists the performance of the active point. is there. On the other hand, when the upper limit is exceeded, the CeO 2 surface is buried by Cu and W, and the effect of the interaction between CeO 2 and Cu or CeO 2 and W cannot be obtained, and the NOx purification activity in the low temperature range is insufficient. Tend to be.
(Method for producing three-way catalyst)
Such a three-way catalyst of the present invention can be obtained by supporting tungsten (W) and copper (Cu) on a ceria-containing support containing cerium oxide (CeO 2 ). As described above, the method for supporting the tungsten (W) and the copper (Cu) on the ceria-containing support is not particularly limited, and a known method can be appropriately employed. For example, (i) an aqueous solution containing a tungsten (W) source and a copper (Cu) source is impregnated with the ceria-containing support, and the tungsten (W) source and the copper (Cu) source are supported on the support. A method of drying and firing later, (ii) a method of physically mixing and firing the tungsten (W) source and the copper (Cu) source, and further the ceria-containing support can be employed. Among these methods, from the viewpoint of supporting the tungsten (W) and the copper (Cu) on a ceria-containing support in a highly dispersed state, the aqueous solution containing the tungsten (W) source and the copper (Cu) source is used. A method of impregnating the ceria-containing support and supporting the tungsten (W) source and the copper (Cu) source on the support, followed by drying and firing is preferable. In addition, in such a method, the conditions in particular in drying and baking are not restrict | limited, Well-known conditions can be employ | adopted suitably, For example, as drying conditions, it heats at 80-140 degreeC for about 1 to 24 hours. As the firing conditions, conditions of heating at 300 to 600 ° C. for about 1 to 5 hours may be employed.
なお、このようなタングステン（Ｗ）源としては、タングステン（Ｗ）の塩であればよく、特に限定されないが、例えば、１原子の塩（例えば、ＨＷＯ４）、ポリ酸塩（例えば、（ＮＨ４）１０Ｗ１２Ｏ４１、（ＮＨ４）６ＨＷ１２Ｏ４０）、ＰやＳｉを含むヘテロポリ酸塩（例えば、Ｈ３ＰＷ１２Ｏ４０、Ｈ４ＳｉＷ１２Ｏ４０）が挙げられる。 Such a tungsten (W) source is not particularly limited as long as it is a salt of tungsten (W). For example, a salt of one atom (for example, HWO 4 ), a polyacid salt (for example, (NH) 4 ) 10 W 12 O 41 , (NH 4 ) 6 HW 12 O 40 ), and heteropoly acid salts containing P and Si (for example, H 3 PW 12 O 40 , H 4 SiW 12 O 40 ).
また、このような前記銅（Ｃｕ）源としては、前記銅（Ｃｕ）の塩であればよく、特に限定されないが、硝酸塩（例えば、硝酸銅［Ｃｕ（ＮＯ３）２］）、ハロゲン塩（例えば、塩化銅［ＣｕＣｌ４、ＣｕＣｌ２、ＣｕＣｌ等］）、硫酸塩（例えば、硫酸銅［ＣｕＳＯ４］）等が挙げられる。 The copper (Cu) source is not particularly limited as long as it is a salt of the copper (Cu), but is not limited to nitrate (for example, copper nitrate [Cu (NO 3 ) 2 ]), halogen salt ( For example, copper chloride [CuCl 4 , CuCl 2 , CuCl and the like]), sulfate (for example, copper sulfate [CuSO 4 ]) and the like can be given.
本発明の三元触媒においては、その形状（形態）としては、特に制限されず、例えば、粉粒状、粒状、球状、円筒状、螺旋状、ペレット状、ハニカム状が挙げられる。これらの形状、大きさなどは目的とする設計（触媒性能、使用条件など）に応じて任意に選択すればよい。ここで用いられる基材も特に制限されず、得られる触媒の用途等に応じて適宜選択されるが、モノリス状基材、ペレット状基材、プレート状基材等を好適に採用することができる。また、ここで用いられる基材の材質も特に制限されないが、コージェライト、炭化ケイ素、ムライト等のセラミックスからなる基材や、クロム及びアルミニウムを含むステンレススチール等の金属からなる基材が好適に採用することができる。また、このような基材に前記三元触媒を担持する方法も特に制限されず、公知の方法を適宜採用することができる。例えば、モノリス状基材に担体を担持せしめて担体の粉末からなるコート層を形成した後、前記コート層に前記金属粒子を担持せしめ、その後、前記コート層に前記第三の金属を担持せしめる方法や、あらかじめ前記金属粒子を担持せしめた担体を用い、これをモノリス状基材に担持せしめてコート層を形成した後、前記コート層に前記第三の金属を担持せしめる方法等を採用することができる。なお、本発明の三元触媒は、非多孔質であってもよく、多孔質であってもよい。 In the three-way catalyst of the present invention, the shape (form) is not particularly limited, and examples thereof include powder, granule, sphere, cylinder, spiral, pellet, and honeycomb. These shapes, sizes, etc. may be arbitrarily selected according to the target design (catalyst performance, use conditions, etc.). The substrate used here is not particularly limited, and is appropriately selected according to the use of the obtained catalyst, and a monolith substrate, pellet substrate, plate substrate and the like can be suitably employed. . The material of the base material used here is not particularly limited, but a base material made of a ceramic such as cordierite, silicon carbide, mullite, or a base material made of a metal such as stainless steel including chromium and aluminum is suitably used. can do. Further, the method for supporting the three-way catalyst on such a substrate is not particularly limited, and a known method can be appropriately employed. For example, a method in which a carrier is supported on a monolithic substrate to form a coating layer made of carrier powder, and then the metal particles are supported on the coating layer, and then the third metal is supported on the coating layer. Alternatively, a method in which a carrier on which the metal particles are previously supported is used, and this is supported on a monolithic substrate to form a coat layer, and then the third metal is supported on the coat layer may be employed. it can. The three-way catalyst of the present invention may be non-porous or porous.
なお、このような三元触媒においては、本発明の効果を損なわない範囲で用いることが可能な他の成分を適宜担持してもよい。 In addition, in such a three-way catalyst, you may carry | support suitably the other component which can be used in the range which does not impair the effect of this invention.
また、本発明の三元触媒は、単独で用いてもよく、他の触媒と組み合わせて利用してもよい。このような他の触媒としては、特に制限されず、公知の触媒（例えば、自動車の排ガス浄化用触媒の場合は、酸化触媒、ＮＯｘ還元触媒、ＮＯｘ吸蔵還元型（ＮＳＲ触媒）、ＮＯｘ選択還元触媒（ＳＣＲ触媒）、Ｎ２Ｏ分解触媒、ＨＣ選択酸化触媒等）を適宜用いてもよい。 The three-way catalyst of the present invention may be used alone or in combination with other catalysts. Such other catalyst is not particularly limited, and is a known catalyst (for example, in the case of an automobile exhaust gas purification catalyst, an oxidation catalyst, a NOx reduction catalyst, a NOx occlusion reduction type (NSR catalyst), a NOx selective reduction catalyst. (SCR catalyst), N 2 O decomposition catalyst, HC selective oxidation catalyst, etc.) may be used as appropriate.
［三元触媒を用いた排ガス浄化方法］
次に、上記本発明の三元触媒を用いて内燃機関からの排ガスを浄化する本発明の方法について説明する。
[Exhaust gas purification method using a three-way catalyst]
Next, the method of the present invention for purifying exhaust gas from an internal combustion engine using the three-way catalyst of the present invention will be described.
本発明の排ガス浄化方法は、前記本発明の三元触媒に内燃機関からの排ガスを接触せしめて排ガスを浄化することを特徴とする方法である。 The exhaust gas purification method of the present invention is a method characterized by purifying exhaust gas by bringing exhaust gas from an internal combustion engine into contact with the three-way catalyst of the present invention.
このように、本発明は、内燃機関からの排ガスを上記本発明の三元触媒を用いて浄化する方法である。ここにおいて、内燃機関としては特に制限されず、公知の内燃機関を適宜利用でき、例えば、自動車の内燃機関（ガソリン車のエンジン、ディーゼルエンジンや燃料消費率の低い希薄燃焼式（リーンバーン）エンジン等）が挙げられる。 Thus, the present invention is a method for purifying exhaust gas from an internal combustion engine using the three-way catalyst of the present invention. Here, the internal combustion engine is not particularly limited, and a known internal combustion engine can be appropriately used. For example, an internal combustion engine of an automobile (an engine of a gasoline vehicle, a diesel engine, a lean burn engine having a low fuel consumption rate, etc.) ).
また、前記内燃機関からの排ガスを上記本発明の三元触媒に接触させるための具体的な方法は特に制限されるものではなく、公知の方法を適宜採用することができる。例えば、内燃機関からの排ガスのガス流路に、上記本発明の三元触媒を配置して排ガスを接触せしめる方法を採用してもよい。 Further, a specific method for bringing the exhaust gas from the internal combustion engine into contact with the three-way catalyst of the present invention is not particularly limited, and a known method can be appropriately employed. For example, a method of placing the three-way catalyst of the present invention in contact with the exhaust gas in the gas flow path of the exhaust gas from the internal combustion engine may be adopted.
以下、実施例及び比較例に基づいて本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.
（実施例１）
先ず、酢酸銅（Ｃｕ（ＣＨ３ＣＯＯ）２・Ｈ２Ｏ）０．６３ｇとメタタングステン酸アンモニウム（（ＮＨ４）６［Ｈ２Ｗ１２Ｏ４０］・６Ｈ２Ｏ）０．２３ｇを１００ｍｌの蒸留水に溶解し、そこへ市販品のＣｅＯ２（比表面積１６０ｍ２／ｇ）４．５０ｇを加えて含浸せしめ、１８０℃で加熱攪拌して蒸発乾燥させて凝固物を得た（蒸発乾固）。次に、得られた凝固物を、大気中で１２０℃、１２時間の条件で乾燥処理を行い、次いで、大気中で５００℃、４時間の条件で熱処理を行い、焼成して三元触媒を得た。
Example 1
First, 0.63 g of copper acetate (Cu (CH 3 COO) 2 .H 2 O) and 0.23 g of ammonium metatungstate ((NH 4 ) 6 [H 2 W 12 O 40 ] · 6H 2 O) in 100 ml Dissolved in distilled water, 4.50 g of commercially available CeO 2 (specific surface area 160 m 2 / g) was added and impregnated therein, heated and stirred at 180 ° C. and evaporated to dryness to obtain a solidified product (evaporated to dryness) ). Next, the obtained solidified product is dried in air at 120 ° C. for 12 hours, and then heat-treated in air at 500 ° C. for 4 hours, followed by calcination to form a three-way catalyst. Obtained.
（実施例２）
ＣｅＯ２として市販品のＣｅＯ２（比表面積１４６ｍ２／ｇ）４．５０ｇを用いた以外は実施例１と同様にして実施例２の三元触媒を得た。
(Example 2)
Except for using CeO 2 (specific surface area 146m 2 /G)4.50G commercially available as CeO 2 was obtained a three-way catalyst of Example 1 carried out in the same manner as Example 2.
（実施例３）
ＣｅＯ２として市販品のＣｅＯ２（比表面積１１９ｍ２／ｇ）４．５０ｇを用いた以外は実施例１と同様にして実施例３の三元触媒を得た。
(Example 3)
Except for using CeO 2 (specific surface area 119m 2 /g)4.50g commercially available as CeO 2 was obtained a three-way catalyst of Example 3 in the same manner as in Example 1.
（実施例４）
銅源として酢酸銅（Ｃｕ（ＣＨ３ＣＯＯ）２・Ｈ２Ｏ）０．０６ｇを用い、ＣｅＯ２として市販品のＣｅＯ２（比表面積１６０ｍ２／ｇ）４．７３ｇを用いた以外は実施例１と同様にして実施例４の三元触媒を得た。
Example 4
Using copper acetate (Cu (CH 3 COO) 2 · H 2 O) 0.06g as a copper source, except for using CeO 2 (specific surface area 160m 2 /g)4.73g commercially available as CeO 2 Example In the same manner as in Example 1, the three-way catalyst of Example 4 was obtained.
（実施例５）
銅源として酢酸銅（Ｃｕ（ＣＨ３ＣＯＯ）２・Ｈ２Ｏ）０．０６ｇを用い、ＣｅＯ２として市販品のＣｅＯ２（比表面積１４６ｍ２／ｇ）４．７３ｇを用いた以外は実施例１と同様にして実施例５の三元触媒を得た。
(Example 5)
Using copper acetate (Cu (CH 3 COO) 2 · H 2 O) 0.06g as a copper source, except for using CeO 2 (specific surface area 146m 2 /g)4.73g commercially available as CeO 2 Example In the same manner as in Example 1, a three-way catalyst of Example 5 was obtained.
（実施例６）
銅源として酢酸銅（Ｃｕ（ＣＨ３ＣＯＯ）２・Ｈ２Ｏ）０．０６ｇを用い、ＣｅＯ２として市販品のＣｅＯ２（比表面積１１９ｍ２／ｇ）４．７３ｇを用いた以外は実施例１と同様にして実施例６の三元触媒を得た。
(Example 6)
Using copper acetate (Cu (CH 3 COO) 2 · H 2 O) 0.06g as a copper source, except for using CeO 2 (specific surface area 119m 2 /g)4.73g commercially available as CeO 2 Example In the same manner as in Example 1, a three-way catalyst of Example 6 was obtained.
（実施例７）
銅源として酢酸銅（Ｃｕ（ＣＨ３ＣＯＯ）２・Ｈ２Ｏ）０．０６ｇを用い、ＣｅＯ２として市販品のＣｅＯ２（比表面積８１ｍ２／ｇ）４．７３ｇを用いた以外は実施例１と同様にして実施例７の三元触媒を得た。
(Example 7)
Using copper acetate (Cu (CH 3 COO) 2 · H 2 O) 0.06g as a copper source, except for using CeO 2 (specific surface area 81m 2 /g)4.73g commercially available as CeO 2 Example In the same manner as in Example 1, a three-way catalyst of Example 7 was obtained.
（実施例８）
タングステン源としてメタタングステン酸アンモニウム（（ＮＨ４）６［Ｈ２Ｗ１２Ｏ４０］・６Ｈ２Ｏ）０．０９ｇを用い、ＣｅＯ２として市販品のＣｅＯ２（比表面積１６０ｍ２／ｇ）４．６５ｇを用いた以外は実施例１と同様にして実施例８の三元触媒を得た。
(Example 8)
3. 0.09 g of ammonium metatungstate ((NH 4 ) 6 [H 2 W 12 O 40 ] · 6H 2 O) is used as a tungsten source, and CeO 2 is a commercially available product (specific surface area 160 m 2 / g) as CeO 2 . A three-way catalyst of Example 8 was obtained in the same manner as Example 1 except that 65 g was used.
（比較例１）
先ず、硝酸第二鉄（Ｆｅ（ＮＯ３）３・９Ｈ２Ｏ）５．０６ｇとメタタングステン酸アンモニウム（（ＮＨ４）６［Ｈ２Ｗ１２Ｏ４０］・６Ｈ２Ｏ）１．６０ｇを１００ｍｌの蒸留水に溶解し、そこへ市販品のＡｌ２Ｏ３（比表面積２００ｍ２／ｇ）３．００ｇを加えて含浸せしめ、１８０℃で加熱攪拌して蒸発乾燥させて凝固物を得た（蒸発乾固）。次に、得られた凝固物を、大気中で１２０℃、１２時間の条件で乾燥処理を行い、次いで、大気中で６００℃４時間の条件で熱処理を行い、焼成して比較用触媒を得た。
(Comparative Example 1)
First, ferric nitrate (Fe (NO 3) 3 · 9H 2 O) 5.06g and ammonium metatungstate ((NH 4) 6 [H 2 W 12 O 40] · 6H 2 O) 1.60g of 100ml Then, 3.00 g of commercially available Al 2 O 3 (specific surface area 200 m 2 / g) was added and impregnated therewith, and the mixture was heated and stirred at 180 ° C. and evaporated to dryness to obtain a solidified product ( Evaporation to dryness). Next, the obtained solidified product is dried in air at 120 ° C. for 12 hours, then heat-treated in air at 600 ° C. for 4 hours, and calcined to obtain a comparative catalyst. It was.
（比較例２）
先ず、硝酸コバルト六水和物（Ｃｏ（ＮＯ３）２・６Ｈ２Ｏ）５．７８ｇと硝酸セリウム（Ｃｅ（ＮＯ３）３・６Ｈ２Ｏ）０．５３ｇを１５０ｍｌの蒸留水に溶解し、そこへＮａＯＨ水溶液を滴下しｐＨを９に調整し、得られた沈殿物をろ過した後、少量の蒸留水を加え遠心分離機を用いて洗浄した。次に、大気中で１２０℃、１２時間の条件で乾燥処理を行い、次いで、大気中で４００℃４時間の条件で熱処理を行い、焼成して比較用触媒を得た。
(Comparative Example 2)
First, 5.78 g of cobalt nitrate hexahydrate (Co (NO 3 ) 2 .6H 2 O) and 0.53 g of cerium nitrate (Ce (NO 3 ) 3 .6H 2 O) were dissolved in 150 ml of distilled water. NaOH aqueous solution was dripped there, pH was adjusted to 9, After filtering the obtained deposit, a small amount of distilled water was added and it wash | cleaned using the centrifuge. Next, a drying treatment was performed in air at 120 ° C. for 12 hours, and then heat treatment was performed in air at 400 ° C. for 4 hours, followed by firing to obtain a comparative catalyst.
（比較例３）
ＣｅＯ２として市販品のＣｅＯ２（比表面積１６０ｍ２／ｇ）４．７５ｇを用い、タタングステン源としてのメタタングステン酸アンモニウムを用いなかった以外は実施例１と同様にして比較用触媒を得た。
(Comparative Example 3)
Using CeO 2 (specific surface area 160m 2 /g)4.75g commercially available as CeO 2, was except for not using ammonium metatungstate as data tungsten source in the same manner as in Example 1 to obtain a comparative catalyst .
（比較例４）
銅源としての酢酸銅の代わりに硝酸第二鉄（Ｆｅ（ＮＯ３）３・９Ｈ２Ｏ）１．２６ｇを用いた以外は実施例１と同様にして比較用触媒を得た。
(Comparative Example 4)
Except that in place of copper acetate as a copper source using ferric nitrate (Fe (NO 3) 3 · 9H 2 O) 1.26g in the same manner as in Example 1 to obtain a comparative catalyst.
（比較例５）
銅源としての酢酸銅の代わりに硝酸第二鉄（Ｆｅ（ＮＯ３）３・９Ｈ２Ｏ）１．２６ｇを用い、ＣｅＯ２として市販品のＣｅＯ２（比表面積１６０ｍ２／ｇ）４．７５ｇを用い、タタングステン源としてのメタタングステン酸アンモニウムを用いなかった以外は実施例１と同様にして比較用触媒を得た。
(Comparative Example 5)
Instead using ferric nitrate (Fe (NO 3) 3 · 9H 2 O) 1.26g to copper acetate as a copper source, CeO 2 commercially available as CeO 2 (specific surface area 160m 2 /g)4.75g A comparative catalyst was obtained in the same manner as in Example 1 except that ammonium metatungstate as a tungsten source was not used.
（比較例６）
銅源としての酢酸銅の代わりに硝酸コバルト六水和物（Ｃｏ（ＮＯ３）２・６Ｈ２Ｏ）０．９１ｇを用いた以外は実施例１と同様にして比較用触媒を得た。
(Comparative Example 6)
A comparative catalyst was obtained in the same manner as in Example 1 except that 0.91 g of cobalt nitrate hexahydrate (Co (NO 3 ) 2 .6H 2 O) was used instead of copper acetate as the copper source.
（比較例７）
銅源としての酢酸銅の代わりに硝酸コバルト六水和物（Ｃｏ（ＮＯ３）２・６Ｈ２Ｏ）０．９１ｇを用い、ＣｅＯ２として市販品のＣｅＯ２（比表面積１６０ｍ２／ｇ）４．７５ｇを用い、タタングステン源としてのメタタングステン酸アンモニウムを用いなかった以外は実施例１と同様にして比較用触媒を得た。
(Comparative Example 7)
Cobalt nitrate hexahydrate in place of copper acetate as a copper source (Co (NO 3) 2 · 6H 2 O) using a 0.91 g, CeO 2 (specific surface area 160 m 2 / g) of commercially available as CeO 2 4 A comparative catalyst was obtained in the same manner as in Example 1 except that .75 g was used and ammonium metatungstate was not used as a tungsten source.
（比較例８）
ＣｅＯ２として市販品のＣｅＯ２（比表面積８１ｍ２／ｇ）４．５０ｇを用いた以外は実施例１と同様にして比較用触媒を得た。
(Comparative Example 8)
Except for using CeO 2 (specific surface area 81m 2 /g)4.50g commercially available as CeO 2 got to comparative catalyst as in Example 1.
（比較例９）
銅源として酢酸銅（Ｃｕ（ＣＨ３ＣＯＯ）２・Ｈ２Ｏ）０．０６ｇを用い、ＣｅＯ２として市販品のＣｅＯ２（比表面積２６ｍ２／ｇ）４．５０ｇを用いた以外は実施例１と同様にして比較用触媒を得た。
(Comparative Example 9)
Using copper acetate (Cu (CH 3 COO) 2 · H 2 O) 0.06g as a copper source, except for using CeO 2 (specific surface area 26m 2 /g)4.50g commercially available as CeO 2 Example In the same manner as in Example 1, a comparative catalyst was obtained.
（比較例１０）
ＣｅＯ２として市販品のＣｅＯ２（比表面積５２ｍ２／ｇ）４．５０ｇを用いた以外は実施例１と同様にして比較用触媒を得た。
(Comparative Example 10)
Except for using CeO 2 (specific surface area 52m 2 /g)4.50g commercially available as CeO 2 got to comparative catalyst as in Example 1.
（比較例１１）
ＣｅＯ２として市販品のＣｅＯ２（比表面積２６ｍ２／ｇ）４．５０ｇを用いた以外は実施例１と同様にして比較用触媒を得た。
(Comparative Example 11)
Except for using CeO 2 (specific surface area 26m 2 /g)4.50g commercially available as CeO 2 got to comparative catalyst as in Example 1.
（比較例１２）
ＣｅＯ２として市販品のＣｅＯ２（比表面積７０ｍ２／ｇ）４．７５ｇを用い、銅源としての酢酸銅を用いなかった以外は実施例１と同様にして比較用触媒を得た。
(Comparative Example 12)
Using CeO 2 (specific surface area 70m 2 /g)4.75g commercially available as CeO 2, except for not using copper acetate as a copper source got to comparative catalyst as in Example 1.
（触媒評価試験）
実施例１〜８において得られた三元触媒試料及び比較例１〜１２において得られた比較用触媒試料について、以下に示す性能評価試験を行った。
(Catalyst evaluation test)
The following performance evaluation tests were performed on the three-way catalyst samples obtained in Examples 1 to 8 and the comparative catalyst samples obtained in Comparative Examples 1 to 12.
＜ＣｅＯ２担体の比表面積評価試験＞
ＣｅＯ２担体の比表面積は、吸着等温線からＢＥＴ等温吸着式を用いてＢＥＴ比表面積として算出した。すなわち、全自動比表面積測定装置（ＭＩＣＲＯ・ＤＡＴＡ社製、商品名「ＭＩＣＲＯ ＳＯＲＰ４２３２ＩＩ」）を用い、液体窒素温度（−１９６℃）におけるＮ２吸着を利用したＢｒｕｎａｕｅｒ−Ｅｍｍｅｔｔ−Ｔｅｌｌｅｒ（ＢＥＴ）一点法により算出した。
<Specific surface area evaluation test of CeO 2 carrier>
The specific surface area of the CeO 2 carrier was calculated as the BET specific surface area from the adsorption isotherm using the BET isotherm adsorption equation. That is, Brunauer-Emmett-Teller (BET) one-point method using N 2 adsorption at liquid nitrogen temperature (−196 ° C.) using a fully automatic specific surface area measuring device (trade name “MICRO SORP4232II” manufactured by MICRO DATA Co.). Calculated by
＜ＣｕとＷの合計面積の算出＞
ＣｕとＷの合計面積は、ＣｕとＷがＣｕＯとＷＯ３の状態でＣｅＯ２表面上にモノレイヤーを形成していると仮定し、各酸化物の密度と各成分の担持量から算出した。
<Calculation of total area of Cu and W>
The total area of Cu and W was calculated from the density of each oxide and the amount of each component supported, assuming that a monolayer was formed on the CeO 2 surface with Cu and W in the state of CuO and WO 3 .
＜関係式Ａによる値（数値Ａ）の算出＞
実施例１〜８において得られた三元触媒試料及び比較例１〜１２において得られた比較用触媒試料について、上記式（１）の「（５．７７×Ｃｕの担持量（質量％）＋３．６３×Ｗの担持量（質量％））／担体の比表面積（ｍ２／ｇ）」（関係式Ａ）における値を計算により求めた（数値Ａとする）。
<Calculation of value (numerical value A) by relational expression A>
For the three-way catalyst samples obtained in Examples 1 to 8 and the comparative catalyst samples obtained in Comparative Examples 1 to 12, “(5.77 × Cu loading (mass%) + 3 in the above formula (1)”. .63 × W loading (mass%) / specific surface area of support (m 2 / g) ”(relational formula A) was obtained by calculation (referred to as numerical value A).
＜触媒活性評価試験＞
先ず、実施例１〜８において得られた三元触媒試料及び比較例１〜１２において得られた比較用触媒試料を準備し、圧粉成型により１０００ｋｇｆ／ｃｍ２でペレット状に粉砕して、触媒活性の評価試験用の触媒試料（大きさ：５００〜７００μｍ）をそれぞれ調製した。
<Catalyst activity evaluation test>
First, the three-way catalyst sample obtained in Examples 1 to 8 and the comparative catalyst sample obtained in Comparative Examples 1 to 12 were prepared and pulverized into pellets at 1000 kgf / cm 2 by compaction molding. Catalyst samples (size: 500 to 700 μm) for activity evaluation tests were prepared.
次に、得られたペレット状の触媒試料を固定床流通式評価装置（ベスト測器製、製品名「ＣＡＴＡ−４０００」）にそれぞれ設置し、三元ガスを模擬した排気モデルガス（ＮＯ：３０００ｐｐｍ、ＣＯ：４５００ｐｐｍ、Ｃ３Ｈ６：１０００ｐｐｍ、Ｏ２：５２５０ｐｐｍ、ＣＯ２：１０ｖｏｌ％、Ｈ２Ｏ：３ｖｏｌ％、Ｎ２：残部）を、３００℃の温度条件下、３．５Ｌ／分の流量で１５分間供給した（前処理）。その後、各試料の温度を１００℃になるまで冷却した後、前記排気モデルガスを７Ｌ／分の流量で供給しながら２０℃／分の昇温速度で１００℃から６００℃まで加熱していき、供給した排気モデルガス中のＮＯの浄化率が１０％に到達する温度（ＮＯ転化温度、℃）（以下、「ＮＯ＿Ｔ１０」と表す。）及び供給した排気モデルガス中のＮＯが５０％浄化される温度（ＮＯ転化温度、℃）（以下、「ＮＯ＿Ｔ５０」と表す。）を測定した。得られた結果を、表１に示す。 Next, the obtained pellet-shaped catalyst sample was installed in a fixed bed flow evaluation device (manufactured by Best Sokki, product name “CATA-4000”), and an exhaust model gas (NO: 3000 ppm) simulating a ternary gas. , CO: 4500 ppm, C 3 H 6 : 1000 ppm, O 2 : 5250 ppm, CO 2 : 10 vol%, H 2 O: 3 vol%, N 2 : balance) at a temperature of 300 ° C. under 3.5 L / min It was supplied at a flow rate for 15 minutes (pretreatment). Then, after cooling the temperature of each sample to 100 ° C., the exhaust model gas is heated from 100 ° C. to 600 ° C. at a temperature rising rate of 20 ° C./min while supplying the exhaust model gas at a flow rate of 7 L / min. The temperature at which the NO purification rate in the supplied exhaust model gas reaches 10% (NO conversion temperature, ° C.) (hereinafter referred to as “NO_T10”) and NO in the supplied exhaust model gas are purified by 50%. Temperature (NO conversion temperature, ° C.) (hereinafter referred to as “NO_T50”) was measured. The obtained results are shown in Table 1.
＜触媒活性評価試験の結果＞
表１に示した実施例１〜８の結果と比較例１〜１２の結果との比較から明らかなように、実施例１〜８の三元触媒は、酸化セリウム（ＣｅＯ２）を含む担体と該担体に担持された銅及びタングステンとを含んでおり、上記式（１）における「（５．７７×Ｃｕの担持量（質量％）＋３．６３×Ｗの担持量（質量％））／担体の比表面積（ｍ２／ｇ）」の値が０．０５〜０．５の範囲にあることにより、ＮＯ＿Ｔ１０及びＮＯ＿Ｔ５０が低いＮＯ転化温度であることから、高度に優れた触媒活性示す三元触媒が得られていることが確認された。
<Results of catalytic activity evaluation test>
As is clear from the comparison between the results of Examples 1 to 8 and the results of Comparative Examples 1 to 12 shown in Table 1, the three-way catalysts of Examples 1 to 8 are composed of a carrier containing cerium oxide (CeO 2 ) and Copper and tungsten supported on the support, and in the above formula (1), “(5.77 × Cu supported amount (mass%) + 3.63 × W supported amount (mass%)) / support Since the value of the specific surface area (m 2 / g) is in the range of 0.05 to 0.5, NO_T10 and NO_T50 have a low NO conversion temperature. It was confirmed that
なお、本発明と従来の卑金属酸化物触媒との比較のため、実施例１、比較例１及び２で得られた結果について、「ＮＯ＿Ｔ１０」（単に、Ｔ１０と示すことがある）及び「ＮＯ＿Ｔ５０」（単に、Ｔ５０と示すことがある）におけるＮＯ転化温度（℃）を図１に示す。 For comparison between the present invention and a conventional base metal oxide catalyst, the results obtained in Example 1, Comparative Examples 1 and 2 are “NO_T10” (sometimes simply indicated as T10) and “NO_T50”. FIG. 1 shows the NO conversion temperature (° C.) in (sometimes simply indicated as T50).
図１に示した実施例１の結果と比較例１及び２の結果との比較から明らかなように、実施例１の三元触媒は、従来の卑金属酸化物触媒を用いた比較例１及び２の比較用触媒に比較して、ＮＯ＿Ｔ１０及びＮＯ＿Ｔ５０がともに本実施例の方がＮＯ転化温度が低いことから、本発明の触媒は従来の卑金属酸化物触媒よりも高い活性を示すことが確認された。 As is clear from the comparison between the results of Example 1 shown in FIG. 1 and the results of Comparative Examples 1 and 2, the three-way catalyst of Example 1 is Comparative Examples 1 and 2 using conventional base metal oxide catalysts. Compared to the comparative catalyst, NO_T10 and NO_T50 both have a lower NO conversion temperature in this example, so that the catalyst of the present invention was confirmed to exhibit higher activity than the conventional base metal oxide catalyst. .
また、Ｃｕ及びＷの担持（添加）効果を調べるため、実施例１及び比較例３〜７で得られた結果について、「ＮＯ＿Ｔ１０」におけるＮＯ転化温度（℃）を図２に示す。 Moreover, in order to investigate the loading (addition) effect of Cu and W, FIG. 2 shows the NO conversion temperature (° C.) in “NO_T10” for the results obtained in Example 1 and Comparative Examples 3 to 7.
図２に示した実施例１の結果と比較例３〜７の結果との比較から明らかなように、実施例１の三元触媒は、ＮＯ＿Ｔ１０（ＮＯ転化温度）が２６７℃と優れた低温ＮＯ活性が発現していることが確認された。一方、比較例では、同じＣｅＯ２担体とＷ源試薬を用いてＦｅ又はＣｏを含浸担持した触媒（比較例４、６）、Ｗを添加せずにＣｅＯ２担体にＣｕ，Ｆｅ又はＣｏを含浸した触媒（比較例３、５、７）のいずれもＮＯ＿Ｔ１０（ＮＯ転化温度）が高く（３８９〜４１７℃）、触媒活性が低いことが確認された。この結果から、ＣｅＯ２担体にＣｕとＷを担持したときのみ、２００℃近傍からのＮＯ還元反応が発現することが確認された。 As is clear from the comparison between the results of Example 1 shown in FIG. 2 and the results of Comparative Examples 3 to 7, the three-way catalyst of Example 1 has an excellent low temperature NO_T10 (NO conversion temperature) of 267 ° C. It was confirmed that the activity was expressed. On the other hand, in the comparative example, the same CeO 2 carrier and the W source reagent were used to impregnate and support Fe or Co (Comparative Examples 4 and 6), and the CeO 2 carrier was impregnated with Cu, Fe or Co without adding W. It was confirmed that all of the catalysts (Comparative Examples 3, 5, and 7) had high NO_T10 (NO conversion temperature) (389 to 417 ° C.) and low catalytic activity. From this result, it was confirmed that the NO reduction reaction from around 200 ° C. was developed only when Cu and W were supported on the CeO 2 carrier.
次に、ＣｕとＷの組成範囲を調べるため、実施例１〜８及び比較例８〜１２で得られた結果について、「ＮＯ＿Ｔ５０」におけるＮＯ転化温度（℃）と数値Ａとの関係を、図３に示す。図３に示した実施例１〜７の結果と比較例８〜１１の結果との比較から明らかなように、実施例１〜７の三元触媒は数値Ａが０．０５〜０．５の範囲にある場合において、ＮＯ＿Ｔ５０及びＮＯ＿Ｔ１０がともに低いＮＯ転化温度であることが確認された。したがって、２００℃から６００℃の温度範囲において高度に優れた触媒活性示す三元触媒とするためには、数値Ａが０．０５〜０．５の範囲にあることが好ましいことが確認された。 Next, in order to investigate the composition range of Cu and W, the relationship between the NO conversion temperature (° C.) and the numerical value A in “NO_T50” is shown for the results obtained in Examples 1 to 8 and Comparative Examples 8 to 12. 3 shows. As is clear from the comparison between the results of Examples 1 to 7 shown in FIG. 3 and the results of Comparative Examples 8 to 11, the three-way catalysts of Examples 1 to 7 have a numerical value A of 0.05 to 0.5. When in the range, it was confirmed that NO_T50 and NO_T10 are both low NO conversion temperatures. Therefore, it was confirmed that the numerical value A is preferably in the range of 0.05 to 0.5 in order to obtain a three-way catalyst exhibiting highly excellent catalytic activity in the temperature range of 200 ° C. to 600 ° C.
なお、上記式（１）は、ＣｕとＷがＣｕＯとＷＯ３の状態でＣｅＯ２表面上にモノレイヤーを形成していると仮定し、各酸化物の密度と各成分の担持量から担体単位表面積当りのＣｕとＷの合計表面積を算出する式と見ることができる。このような観点でみると、数値Ａは、担体単位表面積当たりのＣｕ及びＷの合計表面積に相当するものと見ることができ、したがって、図３を「ＮＯ＿Ｔ５０」におけるＮＯ転化温度（℃）と担体単位表面積当たりのＣｕ及びＷの合計表面積との関係と見ることができる。このような関係から、図３に示した実施例１〜７の三元触媒は、担体の表面積１ｍ２当たりのＣｕ及びＷの合計表面積（酸化物換算）が０．０５〜０．５ｍ２の範囲にある場合において、ＮＯ＿Ｔ５０及びＮＯ＿Ｔ１０がともに低いＮＯ転化温度であることが確認された。これより、２００℃から６００℃の温度範囲において高度に優れた触媒活性示す三元触媒とするためには、担体の表面積１ｍ２当たりのＣｕ及びＷの合計表面積（酸化物換算）が０．０５〜０．５ｍ２の範囲にあることが好ましいことが確認された。 The above formula (1) assumes that a monolayer is formed on the CeO 2 surface with Cu and W being in the state of CuO and WO 3 , and the carrier unit is determined from the density of each oxide and the amount of each component supported. It can be seen as an equation for calculating the total surface area of Cu and W per surface area. From this point of view, the numerical value A can be regarded as corresponding to the total surface area of Cu and W per unit surface area of the support. Therefore, FIG. 3 shows the NO conversion temperature (° C.) in “NO_T50” and the support. It can be seen as a relationship with the total surface area of Cu and W per unit surface area. From such a relationship, the three-way catalysts of Examples 1 to 7 shown in FIG. 3 have a total surface area (in terms of oxide) of Cu and W per 1 m 2 of the support surface area of 0.05 to 0.5 m 2 . When in the range, it was confirmed that NO_T50 and NO_T10 are both low NO conversion temperatures. Thus, in order to obtain a three-way catalyst exhibiting a highly excellent catalytic activity in a temperature range of 200 ° C. to 600 ° C., the total surface area (as oxide) of Cu and W per 1 m 2 of the surface area of the support is 0.05. It was confirmed that it is preferable to be in the range of ˜0.5 m 2 .
また、実施例６、８及び比較例３、１２で得られた結果について表２に示す。これら結果、上記関係式Ａより算出される数値Ａ、及び一般的に使用されるＣｅＯ２担体の比表面積から、Ｗの担持量（含有量）が触媒の全質量に対して酸化物換算で１〜２５質量％の範囲にあることが好ましいことが、Ｃｕの担持量（含有量）が触媒の全質量に対して酸化物換算で０．３〜１５質量％の範囲にあることが好ましいことが確認された。 The results obtained in Examples 6 and 8 and Comparative Examples 3 and 12 are shown in Table 2. As a result, from the numerical value A calculated from the above relational expression A and the specific surface area of the commonly used CeO 2 carrier, the supported amount (content) of W is 1 in terms of oxide with respect to the total mass of the catalyst. It is preferable that it is in the range of ˜25 mass%, and it is preferable that the supported amount (content) of Cu is in the range of 0.3 to 15 mass% in terms of oxide with respect to the total mass of the catalyst. confirmed.
以上説明したように、本発明によれば、貴金属を用いない場合であっても、優れた排ガス浄化性能（高度に優れた触媒活性）を示す三元触媒及びそれを用いた排ガス浄化方法を提供することが可能となる。 As described above, according to the present invention, a three-way catalyst exhibiting excellent exhaust gas purification performance (highly excellent catalytic activity) even when no precious metal is used, and an exhaust gas purification method using the same are provided. It becomes possible to do.
このように本発明の三元触媒及びそれを用いた排ガス浄化方法は、貴金属を用いない場合であっても、排ガス中に含まれるＨＣ、ＣＯ及びＮＯｘを効率よく浄化することが可能であるため、特に、自動車等の内燃機関から排出される排ガス中に含まれるＨＣ、ＣＯ及びＮＯｘを効率よく浄化するために有用である。 As described above, the three-way catalyst of the present invention and the exhaust gas purification method using the same can efficiently purify HC, CO, and NOx contained in the exhaust gas even when noble metal is not used. In particular, it is useful for efficiently purifying HC, CO and NOx contained in exhaust gas discharged from an internal combustion engine such as an automobile.
Claims (5)
酸化セリウム（ＣｅＯ２）を含む担体と、該担体に担持された銅（Ｃｕ）及びタングステン（Ｗ）とを含んでおり、
前記担体におけるＣｅＯ ２ の含有量が、該担体中の金属元素に対するＣｅの比率が７０モル％以上となる量であり、
前記担体の比表面積とＣｕの担持量（ＣｕＯ換算）及びＷの担持量（ＷＯ３換算）が下記式（１）：
A support containing cerium oxide (CeO 2 ), and copper (Cu) and tungsten (W) supported on the support,
The content of CeO 2 in the support is such an amount that the ratio of Ce to metal elements in the support is 70 mol% or more,
The specific surface area of the carrier, the supported amount of Cu (in terms of CuO), and the supported amount of W (in terms of WO 3 ) are expressed by the following formula (1):
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