JP5094049B2 - Exhaust gas purification catalyst - Google Patents
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- JP5094049B2 JP5094049B2 JP2006164960A JP2006164960A JP5094049B2 JP 5094049 B2 JP5094049 B2 JP 5094049B2 JP 2006164960 A JP2006164960 A JP 2006164960A JP 2006164960 A JP2006164960 A JP 2006164960A JP 5094049 B2 JP5094049 B2 JP 5094049B2
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- 239000003054 catalyst Substances 0.000 title claims description 114
- 238000000746 purification Methods 0.000 title description 19
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 68
- 239000000463 material Substances 0.000 claims description 52
- 238000011144 upstream manufacturing Methods 0.000 claims description 48
- 239000007789 gas Substances 0.000 claims description 45
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 40
- 229910052760 oxygen Inorganic materials 0.000 claims description 40
- 239000001301 oxygen Substances 0.000 claims description 40
- 229910052697 platinum Inorganic materials 0.000 claims description 34
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims description 28
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims description 28
- 229910052703 rhodium Inorganic materials 0.000 claims description 25
- 239000010948 rhodium Substances 0.000 claims description 25
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 25
- 239000000758 substrate Substances 0.000 claims description 17
- 238000011068 loading method Methods 0.000 claims description 13
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 10
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 32
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 29
- 230000000052 comparative effect Effects 0.000 description 20
- 239000002002 slurry Substances 0.000 description 20
- 239000010410 layer Substances 0.000 description 19
- 229910000510 noble metal Inorganic materials 0.000 description 19
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 17
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 16
- 229910052759 nickel Inorganic materials 0.000 description 16
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 12
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 12
- 229910052717 sulfur Inorganic materials 0.000 description 10
- 239000011593 sulfur Substances 0.000 description 10
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 229910052684 Cerium Inorganic materials 0.000 description 7
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 229910052763 palladium Inorganic materials 0.000 description 6
- VXNYVYJABGOSBX-UHFFFAOYSA-N rhodium(3+);trinitrate Chemical compound [Rh+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VXNYVYJABGOSBX-UHFFFAOYSA-N 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 5
- 239000011247 coating layer Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 229910017604 nitric acid Inorganic materials 0.000 description 5
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 3
- 230000003197 catalytic effect Effects 0.000 description 3
- 238000006555 catalytic reaction Methods 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910000480 nickel oxide Inorganic materials 0.000 description 3
- 239000010970 precious metal Substances 0.000 description 3
- 229910002076 stabilized zirconia Inorganic materials 0.000 description 3
- 229910052726 zirconium Inorganic materials 0.000 description 3
- 229910000420 cerium oxide Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 2
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 2
- NWAHZABTSDUXMJ-UHFFFAOYSA-N platinum(2+);dinitrate Chemical compound [Pt+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O NWAHZABTSDUXMJ-UHFFFAOYSA-N 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000002336 sorption--desorption measurement Methods 0.000 description 2
- 229910004625 Ce—Zr Inorganic materials 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
- -1 Pr 6 O 11 Inorganic materials 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003426 co-catalyst Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 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
- 238000007598 dipping method Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000000796 flavoring agent Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000000383 hazardous chemical Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 150000002816 nickel compounds Chemical class 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- 150000003463 sulfur Chemical class 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
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- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
- Exhaust Gas After Treatment (AREA)
Description
本発明は、排ガス浄化触媒、詳細には、硫化水素の排出を低減しうる排ガス浄化用触媒に関する。 The present invention relates to an exhaust gas purification catalyst, and more particularly to an exhaust gas purification catalyst that can reduce the emission of hydrogen sulfide.
ガソリン等の自動車燃料には硫黄成分Sが含有されており、この硫黄成分は、燃焼に伴い二酸化硫黄SO2となる。この二酸化硫黄SO2は、排ガス浄化用触媒が還元雰囲気になった場合等に、触媒反応により水素H2と反応して硫化水素H2Sを発生させることがある。この硫化水素は異臭の原因となることがあるため、硫化水素の発生を抑制することが要望されている。 Automobile fuels such as gasoline contain a sulfur component S, and this sulfur component becomes sulfur dioxide SO 2 with combustion. This sulfur dioxide SO 2 may react with hydrogen H 2 by a catalytic reaction to generate hydrogen sulfide H 2 S when the exhaust gas purifying catalyst is in a reducing atmosphere. Since this hydrogen sulfide may cause off-flavors, it is desired to suppress the generation of hydrogen sulfide.
これまでに提案されている硫化水素の発生を抑制するための解決策としては、ニッケルを排ガス浄化用触媒に添加する手段が一般的であった(特開昭63−310637号、特開平1−242149号及び特開平8−290063号及びCatalysis Today, 9, (1991) 105-112を参照のこと)。 As a solution for suppressing the generation of hydrogen sulfide proposed so far, a means of adding nickel to the exhaust gas purifying catalyst has been generally used (Japanese Patent Laid-Open No. 63-310637, Japanese Patent Laid-Open No. 242149 and JP-A-8-290063 and Catalysis Today, 9, (1991) 105-112).
しかしながら、近年欧州を始めとする複数の国々はニッケル及びニッケル化合物を環境負荷物質として指定しており、これらを触媒に使用することができない。 However, in recent years, several countries including Europe have designated nickel and nickel compounds as environmentally hazardous substances, and these cannot be used as catalysts.
従って、本発明の目的は、ニッケルを用いずに排気ガス浄化性能を維持しつつ硫化水素排出量を低減する排ガス浄化用触媒を提供することにある。 Accordingly, an object of the present invention is to provide an exhaust gas purifying catalyst that reduces the amount of hydrogen sulfide emission while maintaining the exhaust gas purifying performance without using nickel.
排ガス浄化用触媒が還元雰囲気で硫化水素を発生させる機構において、排ガス浄化用触媒中の白金(触媒成分)とセリア(酸素貯蔵放出材)は図1に示すようなメカニズムでSO2からH2Sを生成することがある。本発明者が上記メカニズムについて検討した結果、硫黄成分の吸着脱離反応に寄与する触媒成分としての貴金属と、酸素貯蔵放出材とを極力分離して基材上に配置することで、ニッケルを用いずに排気ガス浄化性能を維持しつつ硫化水素排出量を低減できることを見出した。更に、排ガス浄化用触媒中の酸素貯蔵放出材の比表面積を低減させて酸素貯蔵放出材への硫黄成分の吸着を抑制することにより、硫化水素排出量が更に低減することも明らかとなった。 In the mechanism in which the exhaust gas purifying catalyst generates hydrogen sulfide in a reducing atmosphere, platinum (catalyst component) and ceria (oxygen storage and release material) in the exhaust gas purifying catalyst are converted from SO 2 to H 2 S by the mechanism shown in FIG. May be generated. As a result of the study of the above mechanism by the present inventor, nickel was used by separating the noble metal as a catalyst component contributing to the adsorption / desorption reaction of the sulfur component and the oxygen storage / release material as much as possible on the substrate. It has been found that hydrogen sulfide emissions can be reduced while maintaining exhaust gas purification performance. Furthermore, it has also been clarified that the amount of hydrogen sulfide discharged is further reduced by reducing the specific surface area of the oxygen storage / release material in the exhaust gas purification catalyst and suppressing the adsorption of sulfur components to the oxygen storage / release material.
こうして、本発明によれば、基材上の触媒コート層において、排ガス上流部に含まれている貴金属の基材1L当たりの担持密度が排ガス下流部よりも多く、且つ前記下流部が前記上流部よりも酸素貯蔵放出材を基材1L当たり多く含む排ガス浄化用触媒、を提供する。 Thus, according to the present invention, in the catalyst coat layer on the base material, the loading density of the precious metal contained in the upstream portion of the exhaust gas per 1 L of the base material is larger than the downstream portion of the exhaust gas, and the downstream portion is the upstream portion. An exhaust gas purifying catalyst containing a larger amount of oxygen storage / release material per liter of base material.
本発明の排ガス浄化用触媒によれば、排ガス浄化用触媒において硫黄成分の吸着・脱離の窓口となる貴金属と酸素貯蔵放出材とを極力分離して配置することで、従来の排ガス浄化用触媒と同等の排気ガス浄化性能を維持しつつ硫化水素排出量を低減させることができる。貴金属の中でも特に白金は酸素貯蔵放出材との分離による硫化水素排出量の低減効果が大きい。このような硫化水素排出量の低減効果は、酸素吸蔵放出材の比表面積を低下させることで、当該酸素吸蔵放出材への硫黄の吸着が抑制されることにより更に向上する。本発明は、排ガス浄化性能を維持しつつ環境負荷の高いニッケルの使用を回避することができる点で従来の排ガス浄化用触媒と比較して望ましいものである。 According to the exhaust gas purifying catalyst of the present invention, the noble metal and the oxygen storage / release material, which serve as a window for adsorption / desorption of sulfur components in the exhaust gas purifying catalyst, are separated as much as possible to arrange the conventional exhaust gas purifying catalyst. As a result, the amount of hydrogen sulfide discharged can be reduced while maintaining the same exhaust gas purification performance. Among precious metals, platinum is particularly effective in reducing hydrogen sulfide emissions by separation from the oxygen storage / release material. Such an effect of reducing the amount of hydrogen sulfide emission is further improved by suppressing the adsorption of sulfur to the oxygen storage / release material by reducing the specific surface area of the oxygen storage / release material. The present invention is desirable in comparison with conventional exhaust gas purification catalysts in that the use of nickel having a high environmental load can be avoided while maintaining the exhaust gas purification performance.
本発明の排ガス浄化用触媒で使用する「基材」は、触媒成分及び酸素貯蔵放出材を含むスラリー状のコーティング溶液が担持されるものであり、排ガス浄化用触媒の製造に一般的に使用される担体を意味する。当該基材としては、コーディライト等の材料により形成されるハニカムなどの多孔質形態のものが触媒成分を分散担持させる観点から好ましい。 The “substrate” used in the exhaust gas purifying catalyst of the present invention carries a slurry-like coating solution containing a catalyst component and an oxygen storage / release material, and is generally used in the manufacture of exhaust gas purifying catalysts. Means a carrier. As the base material, a porous material such as a honeycomb formed of a material such as cordierite is preferable from the viewpoint of dispersing and supporting the catalyst component.
本発明においては、上記基材上には、触媒成分及び酸素貯蔵放出材を含む触媒コート層が形成される。ここで、本発明における触媒コート層は、貴金属と酸素貯蔵放出材とを極力分離して配置させるために排ガス上流部と排ガス下流部に分けられる。また、触媒コート層の態様としては、ニッケルを含まないものが好ましい。本明細書における「排ガス上流部」とは、上記基材上の触媒コート層における入りガス側を指し、一方、「排ガス下流部」とは上記基材上の触媒コート層における出ガス側を指す。排ガス上流部の長さは、限定しないが、基材の全長に対し、約10〜75%の比率となるように調節するのが好ましい。最も好ましくは、上流部長さは、浄化性能の向上の観点から基材の全長に対し約50%である。 In the present invention, a catalyst coat layer containing a catalyst component and an oxygen storage / release material is formed on the substrate. Here, the catalyst coat layer in the present invention is divided into an exhaust gas upstream portion and an exhaust gas downstream portion in order to separate and arrange the noble metal and the oxygen storage / release material as much as possible. Moreover, as an aspect of a catalyst coat layer, what does not contain nickel is preferable. In the present specification, the “exhaust gas upstream portion” refers to the inlet gas side of the catalyst coat layer on the substrate, while the “exhaust gas downstream portion” refers to the outlet gas side of the catalyst coat layer on the substrate. . Although the length of the exhaust gas upstream portion is not limited, it is preferably adjusted so that the ratio is about 10 to 75% with respect to the total length of the base material. Most preferably, the upstream length is about 50% of the total length of the substrate from the viewpoint of improving the purification performance.
上記触媒コート層は、触媒成分として1又は複数の種類の貴金属を含む。ここで、当該貴金属は、下流部に多く配置される酸素貯蔵放出材と極力分離して配置させるために、下流部と比較して上流部に多く配置される。上流部に使用する貴金属は、白金、パラジウムが好ましく、これらの中でも白金が特に好ましい。尚、ロジウムは、その高い水素化作用により上流部に配置すると触媒全体に付着している硫黄を還元して硫化水素を多量に発生させる恐れがあるため、好ましくない。下流部に使用する貴金属は、ロジウム、パラジウム及び/又は白金であることが好ましい。但し、これらの貴金属の中でも、白金は他の貴金属と比較して酸素貯蔵放出材との分離による硫化水素排出量の低減効果が大きいため、酸素貯蔵放出材とともに下流部に含まれる貴金属はロジウム又はパラジウムであることが更に好ましい。しかしながら、下流部の触媒コート層に白金を含める場合、基材1L当たりのその担持密度が低ければパラジウム又はロジウムと同様のH2S生成抑制効果を達成することができる。事実、下流部に担持される白金は、基材1L当たりの担持密度として0.3g以下に抑えることで従来の排ガス浄化用触媒よりもH2Sの生成を抑制できる。また、ロジウムは白金との組み合わせにより優れた排ガス浄化性能を発揮するため、上流部に白金を配置した場合には下流部に含まれる貴金属として特に好ましい。尚、ロジウムは上述のとおり上流部に配置すると硫化水素を多量に発生させる恐れがあるが、下流に配置することでかかる可能性を最小化することができる。上流部及び下流部の触媒成分は上記のものに限定されず、その他の貴金属元素等を含んでもよい。但しニッケルは除く。 The catalyst coat layer contains one or more kinds of noble metals as a catalyst component. Here, in order to separate the noble metal as much as possible from the oxygen storage / release material disposed in the downstream portion, the precious metal is disposed in the upstream portion in comparison with the downstream portion. The noble metal used in the upstream portion is preferably platinum or palladium, and platinum is particularly preferable among these. Note that rhodium is not preferable if it is arranged upstream due to its high hydrogenation action, because it may reduce sulfur adhering to the entire catalyst and generate a large amount of hydrogen sulfide. The noble metal used in the downstream portion is preferably rhodium, palladium and / or platinum. However, among these noble metals, platinum has a greater effect of reducing hydrogen sulfide emissions by separation from the oxygen storage / release material than other noble metals, so the noble metal contained in the downstream portion together with the oxygen storage / release material is rhodium or More preferably, it is palladium. However, when platinum is included in the catalyst coat layer in the downstream portion, the same H 2 S production suppressing effect as palladium or rhodium can be achieved if the supporting density per liter of the substrate is low. In fact, the platinum supported on the downstream portion can suppress the generation of H 2 S more than the conventional exhaust gas purifying catalyst by suppressing the supporting density per 1 L of the base material to 0.3 g or less. In addition, rhodium exhibits excellent exhaust gas purification performance in combination with platinum, and therefore is particularly preferable as a noble metal contained in the downstream portion when platinum is disposed in the upstream portion. As described above, rhodium may generate a large amount of hydrogen sulfide when arranged in the upstream portion, but the possibility can be minimized by arranging it in the downstream. The upstream and downstream catalyst components are not limited to those described above, and may include other noble metal elements. However, nickel is excluded.
上流部の触媒コート層に含まれる触媒成分としての貴金属担持密度(基材1L当たり)は、下流部よりも多ければ特に限定されない。一例を挙げると、下流部の触媒成分としてロジウム、パラジウム及び/又は白金を使用する場合、下流部中、ロジウムは基材1L当たりの担持密度として好ましくは0.1〜1g、更に好ましくは0.2〜0.6g、最も好ましくは0.4g、パラジウムは基材1L当たりの担持密度として好ましくは0.1〜10g、更に好ましくは0.1〜2.0g、最も好ましくは1.0g、白金は基材1L当たりの担持密度として0.3g以下、更に好ましくは0.1g以下含まれるのに対し、上流部の貴金属担持密度は上記下流部の貴金属担持密度を下回らないように適宜調節される。上流部に白金、そして下流部のロジウムを使用する場合、上流部の白金担持密度と下流部のロジウム担持密度との比率は1:1〜10:1であることが好ましく、5:1超であることが特に好ましい。尚、上記下流部中の貴金属担持密度は限定的に解釈されるべきではない。また、貴金属種により触媒活性が異なるため、使用する貴金属によっては、その担持密度だけでなく層ごとの全体の触媒活性を考慮して、上流部が下流部よりも高い触媒活性を有するように触媒成分の配置を検討する必要があることもある。 The noble metal supporting density (per 1 L of base material) as a catalyst component contained in the upstream catalyst coat layer is not particularly limited as long as it is higher than that of the downstream portion. For example, when rhodium, palladium and / or platinum is used as the catalyst component in the downstream portion, rhodium in the downstream portion is preferably 0.1 to 1 g, more preferably 0. 2 to 0.6 g, most preferably 0.4 g, palladium is preferably 0.1 to 10 g, more preferably 0.1 to 2.0 g, most preferably 1.0 g, platinum as the support density per liter of the base material. Is contained in an amount of not more than 0.3 g, more preferably not more than 0.1 g per 1 L of the base material, whereas the noble metal loading density in the upstream portion is appropriately adjusted so as not to fall below the noble metal loading density in the downstream portion. . In the case of using platinum in the upstream portion and rhodium in the downstream portion, the ratio of the platinum loading density in the upstream portion to the rhodium loading density in the downstream portion is preferably 1: 1 to 10: 1, and more than 5: 1. It is particularly preferred. In addition, the noble metal carrying density in the said downstream part should not be interpreted limitedly. In addition, since the catalytic activity differs depending on the type of the noble metal, depending on the noble metal used, the catalyst is such that the upstream portion has a higher catalytic activity than the downstream portion in consideration of not only the loading density but also the overall catalytic activity of each layer. It may be necessary to consider the placement of the components.
上記触媒コート層に含まれる酸素貯蔵放出材は、本明細書で使用する場合、酸化雰囲気下で酸素を吸蔵し、還元雰囲気下で吸蔵した酸素を放出するという性能(酸素吸蔵放出能(OSC))を有する材料を意味し、触媒成分を担持させる担体としての役割を果たす。しかしながら、本発明で触媒成分を担持するために使用する担体は酸素貯蔵放出材に限定されず、例えば、アルミナ、ジルコニア、及びこれらの複合酸化物等を一緒に使用してもよい。 The oxygen storage / release material contained in the catalyst coat layer, when used in the present specification, has the ability to occlude oxygen under an oxidizing atmosphere and release the oxygen occluded under a reducing atmosphere (oxygen storage / release capacity (OSC)). ) And serves as a carrier for supporting the catalyst component. However, the carrier used for supporting the catalyst component in the present invention is not limited to the oxygen storage / release material, and for example, alumina, zirconia, and composite oxides thereof may be used together.
酸素貯蔵放出材の例として、セリア(本明細書では酸化セリウムとも称する)、Pr6O11等の希土類金属酸化物、Fe2O3、CuO、Mn2O5などの遷移金属酸化物、Ce−Zr複合酸化物を挙げることができる。酸素貯蔵放出能力の観点からは、本発明における酸素貯蔵放出材としてはセリア若しくはCe−Zr複合酸化物が好ましい。 Examples of oxygen storage / release materials include ceria (also referred to herein as cerium oxide), rare earth metal oxides such as Pr 6 O 11 , transition metal oxides such as Fe 2 O 3 , CuO, and Mn 2 O 5 , Ce -Zr composite oxide can be mentioned. From the viewpoint of oxygen storage / release capability, the oxygen storage / release material in the present invention is preferably ceria or Ce-Zr composite oxide.
酸素貯蔵放出材は、その比表面積を低減させることで、硫黄成分が酸素貯蔵放出材の表面上に吸着するのを抑制することができ、延いては還元雰囲気のもとでの硫化水素への反応を抑制することができる。比表面積の低減は、例えば、所定の比表面積を有する酸素貯蔵放出材を高温で焼成することで行うことができる。本発明においては、硫化水素浄化性能を向上させる観点から30m2/g以下の比表面積を有する酸素貯蔵放出材を使用することが好ましい。更に好ましくは、上記比表面積は10m2/g以下である。ここで、本明細書で使用する「比表面積」とは触媒1g当たりの触媒のBET比表面積を表し、比表面積測定装置(カワチュウ社製マイクロデータ4232型)により測定する。 By reducing the specific surface area of the oxygen storage / release material, it is possible to suppress the sulfur component from adsorbing on the surface of the oxygen storage / release material, and thus to the hydrogen sulfide under a reducing atmosphere. The reaction can be suppressed. The specific surface area can be reduced, for example, by baking an oxygen storage / release material having a predetermined specific surface area at a high temperature. In the present invention, it is preferable to use an oxygen storage / release material having a specific surface area of 30 m 2 / g or less from the viewpoint of improving hydrogen sulfide purification performance. More preferably, the specific surface area is 10 m 2 / g or less. Here, the “specific surface area” used in the present specification represents the BET specific surface area of the catalyst per 1 g of the catalyst, and is measured by a specific surface area measuring device (Micro Data 4232 manufactured by Kawachu Corporation).
酸素貯蔵放出材は、触媒コート層において主に上流部に含まれる貴金属と極力分離するために、上流部よりも下流部に多く配置される。例えば、酸素貯蔵放出材としてセリアを使用し、且つ下流部のセリウム量を0.6モルとした場合、基材1L当たりの上流部のセリウム量は0.1モル以下とすればよい。しかし、H2S生成の抑制をより重視するならば、上流部の触媒コート層は酸素貯蔵放出材を含まないことが好ましい。 In order to separate as much as possible the noble metal mainly contained in the upstream part in the catalyst coat layer, the oxygen storage / release material is arranged more in the downstream part than in the upstream part. For example, when ceria is used as the oxygen storage / release material and the amount of cerium in the downstream portion is 0.6 mol, the amount of cerium in the upstream portion per 1 L of the substrate may be 0.1 mol or less. However, if importance is placed on the suppression of H 2 S generation, the upstream catalyst coat layer preferably does not contain an oxygen storage / release material.
尚、触媒コート層は、上記触媒成分及び酸素貯蔵放出材に限定されず、触媒を構成する上で基材上に担持されることが考えられるあらゆるものを包含する。例えば、前記触媒コート層は、H2S排出抑制に有効な物質であるネオジウム、鉄、プラセオジウム、ストロンチウム、バリウム等の酸化物を含んでもよい。これらの物質は硫黄を吸蔵する性質があり、その結果、H2S生成を抑制することができる。当該物質を触媒コート層に含めることで、本発明のH2S浄化性能は更に向上する。結果は示さないが、これらの物質の中でも酸化鉄はH2S排出量低減効果が優れているため特に好ましい。尚、これらのH2S排出抑制物質は、触媒成分等とともにスラリー状のコーティング溶液に含ませることで基材上にコーティングされる。好ましいH2S排出抑制物質量は、基材1L当たりの担持密度として0.2〜0.7モルであるが、これに限定されるものではない。当該H2S排出抑制物質は触媒コート層の上流部、下流部又はその両方に配置してもよい。 The catalyst coat layer is not limited to the catalyst component and the oxygen storage / release material, and includes any material that is considered to be supported on the base material in constituting the catalyst. For example, the catalyst coat layer may include an oxide such as neodymium, iron, praseodymium, strontium, and barium that is an effective material for suppressing H 2 S emission. These substances have a property of occluding sulfur, and as a result, H 2 S production can be suppressed. By including the substance in the catalyst coat layer, the H 2 S purification performance of the present invention is further improved. Although the results are not shown, iron oxide is particularly preferable among these substances because of its excellent effect of reducing H 2 S emission. Note that these H 2 S emissions material is coated on a substrate by including in the slurry-like coating solution together with the catalyst components and the like. A preferable amount of the H 2 S emission suppressing substance is 0.2 to 0.7 mol as a loading density per 1 L of the substrate, but is not limited thereto. The H 2 S emission suppressing substance may be disposed in the upstream portion, the downstream portion, or both of the catalyst coat layer.
本発明の触媒は、例えば、触媒成分、酸素貯蔵放出材、担体等を含むスラリー状のコーティング溶液中に基材を浸し、当該コーティング溶液を基材表面に吸着させ、乾燥、焼成する工程を繰り返すことで製造することができる。しかしながら、これらの方法に限定されるものではない。例えば、触媒成分を予め担体に担持した後、それらを含むスラリーを基材上にコーティングしてもよい。 In the catalyst of the present invention, for example, the substrate is immersed in a slurry-like coating solution containing a catalyst component, an oxygen storage / release material, a carrier and the like, the coating solution is adsorbed on the substrate surface, dried, and fired repeatedly. Can be manufactured. However, it is not limited to these methods. For example, after the catalyst components are previously supported on the support, a slurry containing them may be coated on the substrate.
以下の実施例を用いて、本発明の発明を更に具体的に説明する。尚、本発明はこれらの実施例に限定されるものではない。 The invention of the present invention will be described more specifically with reference to the following examples. The present invention is not limited to these examples.
(実施例1)
アルミナ45gとアルミナゾル(10wt%)50gとを混合し、スラリー1を調製した。別途、硝酸にロジウムを溶解させた液(以下硝酸ロジウム溶液と称する:ロジウム0.2g相当を含む)、アルミナ45g、約100m2/gの比表面積のセリア52g、アルミナゾル(10wt%)50g、純水50gを混合し、スラリー2を調製した。
Example 1
A slurry 1 was prepared by mixing 45 g of alumina and 50 g of alumina sol (10 wt%). Separately, a solution obtained by dissolving rhodium in nitric acid (hereinafter referred to as a rhodium nitrate solution: equivalent to 0.2 g of rhodium), 45 g of alumina, 52 g of ceria having a specific surface area of about 100 m 2 / g, 50 g of alumina sol (10 wt%), pure 50 g of water was mixed to prepare
容積1L(直径114mm×長さ98mm)のモノリスハニカム担体の上流より49mmの長さまでスラリー1でコートし、150℃で1時間乾燥させた後、500℃で1時間焼成した。続いて、当該担体のコートされている部分(担体長1/2)を、硝酸に白金を溶解させた液(以下硝酸白金系溶液と称する:当該担体が吸水可能な液量当たり白金1.0g相当を含む)に浸漬し、白金を担体0.5L当たり1.0g担持した。 The slurry 1 was coated from the upstream of a monolith honeycomb carrier having a volume of 1 L (diameter 114 mm × length 98 mm) to a length of 49 mm, dried at 150 ° C. for 1 hour, and then fired at 500 ° C. for 1 hour. Subsequently, the coated part of the carrier (carrier length 1/2) is a solution in which platinum is dissolved in nitric acid (hereinafter referred to as platinum nitrate solution: 1.0 g of platinum per liquid amount that the carrier can absorb water). In this case, 1.0 g of platinum was supported per 0.5 L of the carrier.
次に、上記担体の下流側より1/2の長さまでスラリー2でコートし、150℃で1時間乾燥させた後、500℃で1時間焼成し本発明の触媒を調製した(実施例1)。実施例1の触媒の最終組成は、以下のとおりである:
上流部:白金2.0g/L、アルミナ100g/L
下流部:ロジウム0.4g/L、アルミナ100g/L、セリア104g/L
Next, the
Upstream part: platinum 2.0 g / L, alumina 100 g / L
Downstream part: rhodium 0.4 g / L, alumina 100 g / L, ceria 104 g / L
(実施例2)
硝酸系白金溶液(白金1.0g相当を含む)、アルミナ35g、約25m2/gの比表面積の酸化セリウム安定化ジルコニア50g(セリウム:ジルコニウム(モル比)=10:90)、アルミナゾル(10wt%)50g、純水20gを混合し、スラリー3を調製した。別途、硝酸ロジウム溶液(ロジウム0.2g相当を含む)、アルミナ35g、約25m2/gの比表面積の酸化セリウム安定化ジルコニア60g(セリウム:ジルコニウム(モル比)=70:30)、アルミナゾル(10wt%)50g、純水40gを混合し、スラリー4を調製した。
(Example 2)
Nitric acid-based platinum solution (including platinum equivalent to 1.0 g), alumina 35 g, cerium oxide-stabilized zirconia 50 g (cerium: zirconium (molar ratio) = 10: 90) having a specific surface area of about 25 m 2 / g, alumina sol (10 wt% ) 50 g and 20 g of pure water were mixed to prepare slurry 3. Separately, a rhodium nitrate solution (including rhodium 0.2 g equivalent), 35 g of alumina, 60 g of cerium oxide-stabilized zirconia having a specific surface area of about 25 m 2 / g (cerium: zirconium (molar ratio) = 70: 30), alumina sol (10 wt. %) 50 g and 40 g of pure water were mixed to prepare slurry 4.
上流側より容積1Lのモノリスハニカム担体の1/2の長さまでスラリー3でコートし、150℃で1時間乾燥させた後、500℃で1時間焼成した。次に、上記担体の下流側より1/2の長さまでスラリー4でコートし、150℃で1時間乾燥させた後、500℃で1時間焼成し本発明の触媒を調製した(実施例2)。実施例2の触媒の最終組成は、以下のとおりである:
上流部:白金2.0g/L、アルミナ80g/L、セリア14g/L、ジルコニア86g/L
下流部:ロジウム0.4g/L、アルミナ80g/L、セリア92g/L、ジルコニア28g/L
The slurry 3 was coated from the upstream side to 1/2 the length of a monolith honeycomb carrier having a volume of 1 L, dried at 150 ° C. for 1 hour, and then fired at 500 ° C. for 1 hour. Next, the slurry 4 was coated to a length ½ from the downstream side of the carrier, dried at 150 ° C. for 1 hour, and then calcined at 500 ° C. for 1 hour to prepare the catalyst of the present invention (Example 2). . The final composition of the catalyst of Example 2 is as follows:
Upstream part: platinum 2.0 g / L, alumina 80 g / L, ceria 14 g / L, zirconia 86 g / L
Downstream part: rhodium 0.4 g / L, alumina 80 g / L, ceria 92 g / L, zirconia 28 g / L
(実施例3)
硝酸系白金溶液(白金1.0g相当を含む)、アルミナ35g、ジルコニア50g、アルミナゾル(10wt%)50g、純水20gを混合し、スラリー5を調製した。別途、硝酸ロジウム溶液(ロジウム0.2g相当を含む)、アルミナ35g、酸化セリウム安定化ジルコニア67.5g(セリウム:ジルコニウム(モル比)=70:30)、アルミナゾル(10wt%)50g、純水50gを混合し、スラリー6を調製した。
(Example 3)
A slurry 5 was prepared by mixing a nitrate-based platinum solution (including platinum equivalent to 1.0 g), 35 g of alumina, 50 g of zirconia, 50 g of alumina sol (10 wt%), and 20 g of pure water. Separately, rhodium nitrate solution (including rhodium 0.2 g equivalent), alumina 35 g, cerium oxide stabilized zirconia 67.5 g (cerium: zirconium (molar ratio) = 70: 30), alumina sol (10 wt%) 50 g, pure water 50 g Were mixed to prepare slurry 6.
上流側より容積1Lのモノリスハニカム担体の1/2の長さまでスラリー5でコートし、150℃で1時間乾燥させた後、500℃で1時間焼成した。次に、上記担体の下流側より1/2の長さまでスラリー6でコートし、150℃で1時間乾燥させた後、500℃で1時間焼成し本発明の触媒を調製した(実施例3)。実施例3の触媒の最終組成は、以下のとおりである:
上流部:白金2.0g/L、アルミナ80g/L、ジルコニア100g/L
下流部:ロジウム0.4g/L、アルミナ80g/L、セリア103g/L、ジルコニア32g/L
The slurry 5 was coated from the upstream side to 1/2 the length of a monolith honeycomb carrier having a volume of 1 L, dried at 150 ° C. for 1 hour, and then fired at 500 ° C. for 1 hour. Next, the slurry 6 was coated to a length ½ from the downstream side of the carrier, dried at 150 ° C. for 1 hour, and then calcined at 500 ° C. for 1 hour to prepare a catalyst of the present invention (Example 3). . The final composition of the catalyst of Example 3 is as follows:
Upstream part: platinum 2.0 g / L, alumina 80 g / L, zirconia 100 g / L
Downstream part: rhodium 0.4 g / L, alumina 80 g / L, ceria 103 g / L, zirconia 32 g / L
(実施例4)
実施例1と同様の方法で、スラリー1を用いてコーティングを実施した後、硝酸白金系溶液に浸漬することで上流部を調製した。硝酸ロジウム溶液(ロジウム0.2g相当を含む)、アルミナ45g、約10m2/gの比表面積のセリア52g、酸化鉄(Fe2O3)24g、アルミナゾル(10wt%)50g、純水60gを混合してスラリー7を調製した後、担体の下流側より1/2の長さまでスラリー7でコートし、150℃で1時間乾燥させた後、500℃で1時間焼成し本発明の触媒を調製した(実施例4)。実施例4の触媒の最終組成は、以下のとおりである:
上流部:白金2.0g/L、アルミナ100g/L
下流部:ロジウム0.4g/L、アルミナ100g/L、セリア104g/L、酸化鉄48g/L
Example 4
In the same manner as in Example 1, the slurry 1 was used for coating, and then the upstream part was prepared by dipping in a platinum nitrate solution. A rhodium nitrate solution (including 0.2 g of rhodium), 45 g of alumina, 52 g of ceria having a specific surface area of about 10 m 2 / g, 24 g of iron oxide (Fe 2 O 3 ), 50 g of alumina sol (10 wt%), and 60 g of pure water are mixed. Then, slurry 7 was prepared, and coated with slurry 7 to a length ½ from the downstream side of the carrier, dried at 150 ° C. for 1 hour, and then calcined at 500 ° C. for 1 hour to prepare the catalyst of the present invention. (Example 4). The final composition of the catalyst of Example 4 is as follows:
Upstream part: platinum 2.0 g / L, alumina 100 g / L
Downstream part: rhodium 0.4 g / L, alumina 100 g / L, ceria 104 g / L, iron oxide 48 g / L
(比較例1)
硝酸系白金溶液(白金1.0g相当を含む)、硝酸ロジウム溶液(ロジウム0.2g相当を含む)、アルミナ90g、約100m2/gの比表面積のセリア52g、アルミナゾル(10wt%)100g、純水30gを混合し、スラリー8を調製した。当該スラリーで容積1Lのモノリスハニカム担体をコートし、150℃で1時間乾燥させた後、500℃で1時間焼成して、ニッケルを含まない、上流部と下流部に分かれていない触媒コート層から成る触媒を調製した(比較例1)。比較例1の触媒の最終組成は、以下のとおりである:
白金1.0g/L、ロジウム0.2g/L、アルミナ100g/L、セリア52g/L
(Comparative Example 1)
Nitric acid-based platinum solution (including platinum equivalent to 1.0 g), rhodium nitrate solution (including rhodium equivalent to 0.2 g), alumina 90 g, ceria 52 g with a specific surface area of about 100 m 2 / g, alumina sol (10 wt%) 100 g, pure 30 g of water was mixed to prepare
Platinum 1.0g / L, Rhodium 0.2g / L, Alumina 100g / L, Ceria 52g / L
(比較例2)
硝酸系白金溶液(白金1.0g相当を含む)、硝酸ロジウム溶液(ロジウム0.2g相当を含む)、アルミナ90g、約100m2/gの比表面積のセリア52g、ニッケル酸化物4.5g、アルミナゾル(10wt%)100g、純水30gを混合し、スラリー9を調製した。当該スラリーで容積1Lのモノリスハニカム担体をコートし、150℃で1時間乾燥させた後、500℃で1時間焼成して、ニッケルを含む、上流部と下流部に分かれていない触媒コート層から成る触媒を調製した(比較例2)。比較例2の触媒の最終組成は、以下のとおりである:
白金1.0g/L、ロジウム0.2g/L、アルミナ100g/L、セリア52g/L、ニッケル酸化物(NiO)4.5g/L
(Comparative Example 2)
Nitric acid-based platinum solution (including platinum equivalent to 1.0 g), rhodium nitrate solution (including rhodium equivalent to 0.2 g), alumina 90 g, ceria 52 g having a specific surface area of about 100 m 2 / g, nickel oxide 4.5 g, alumina sol (10 wt%) 100 g and pure water 30 g were mixed to prepare slurry 9. The slurry is coated with a monolithic honeycomb carrier having a volume of 1 L, dried at 150 ° C. for 1 hour, and then fired at 500 ° C. for 1 hour to comprise a catalyst coating layer containing nickel and not separated into an upstream portion and a downstream portion. A catalyst was prepared (Comparative Example 2). The final composition of the catalyst of Comparative Example 2 is as follows:
Platinum 1.0g / L, Rhodium 0.2g / L, Alumina 100g / L, Ceria 52g / L, Nickel oxide (NiO) 4.5g / L
1.H2S排出量測定
直列4気筒1.5Lエンジン車を用い、時速40kmで走行して上記触媒に硫黄を吸着させた後、WOT(ワイドオープンスロットル)の状態で加速することにより時速100kmに達した際のH2S排出量を測定した。結果を図2に示す。
1. H 2 S emission measurement Using an inline 4-cylinder 1.5L engine vehicle, running at 40km / h, adsorbing sulfur to the catalyst, and accelerating in the state of WOT (wide open throttle), the speed reaches 100km / h The amount of H 2 S emitted was measured. The results are shown in FIG.
図2に示すとおり、実施例1〜4の触媒は、上流部と下流部に分かれておらず、且つニッケルを含まない触媒コート層から成る触媒(比較例1)と比較してH2S排出量がはるかに低下した。更に、実施例1〜3の触媒は、上流部と下流部に分かれておらず且つニッケルを含む触媒コート層から成る触媒(比較例2)とほぼ程度のH2S浄化性能を示した。一方、下流部に助触媒として酸化鉄を添加した実施例4の触媒は比較例2の触媒と比較して約40%H2S排出量が低かった。 As shown in FIG. 2, the catalysts of Examples 1 to 4 are not divided into an upstream portion and a downstream portion, and H 2 S emissions are compared with a catalyst composed of a catalyst coat layer that does not contain nickel (Comparative Example 1). The amount was much lower. Furthermore, the catalysts of Examples 1 to 3 showed almost the same H 2 S purification performance as the catalyst (Comparative Example 2) which was not divided into the upstream part and the downstream part and was composed of a catalyst coating layer containing nickel. On the other hand, the catalyst of Example 4 in which iron oxide was added as a co-catalyst in the downstream portion had a lower amount of about 40% H 2 S emission than the catalyst of Comparative Example 2.
2.浄化性能測定
上記触媒を排気量4Lのエンジンにて、触媒入りガス温度800℃で5時間耐久させた後、排気量2.2Lのエンジンを有する実機車両へ搭載した。運転モードをLA♯4モードに設定して当該車両を走行させ、当該触媒のNOx、HC、COエミッション効果を測定した。NOxエミッションについての結果を表1及び図3に示す。
2. Purification performance measurement The catalyst was endured for 5 hours at a catalyst-containing gas temperature of 800 ° C. with an engine with a displacement of 4 L, and then mounted on a real vehicle having an engine with a displacement of 2.2 L. The vehicle was driven with the operation mode set to the LA # 4 mode, and the NOx, HC, and CO emission effects of the catalyst were measured. The results for NOx emissions are shown in Table 1 and FIG.
表1及び図3に示すとおり、実施例1〜4の触媒は、上流部と下流部に分かれておらず、且つニッケルを含まない触媒コート層から成る触媒(比較例1)及び上流部と下流部に分かれておらず且つニッケルを含む触媒コート層から成る触媒(比較例2)と比較して同等又はそれ以下にまでNOxエミッションが低下した。中でも、実施例2及び実施例3の触媒は、最もNOxエミッションが低かった。また、結果は示さないが、HC,COエミッション効果についても、実施例1〜4の触媒は比較例のものと比べて浄化性能の悪化は見られなかった。 As shown in Table 1 and FIG. 3, the catalysts of Examples 1 to 4 are not divided into an upstream portion and a downstream portion, and are composed of a catalyst coating layer containing no nickel (Comparative Example 1), and an upstream portion and a downstream portion. Compared with the catalyst (Comparative Example 2) which is not divided into parts and is composed of a catalyst coat layer containing nickel, the NOx emission was reduced to the same level or lower. Among them, the catalysts of Example 2 and Example 3 had the lowest NOx emission. Moreover, although a result is not shown, also about the HC and CO emission effect, the catalyst of Examples 1-4 did not show deterioration of purification performance compared with the thing of a comparative example.
3.上流に対し添加可能な酸素貯蔵放出材量の検討
上流に添加することができる酸素貯蔵放出材量の上限を決定するために、下流部に基材1L当たりの担持密度として0.6モル(103g)のセリアを含有する実施例1の触媒の上流部に種々の量のセリアを含有する触媒を調製し、これらのH2S浄化性能を上述のように測定した。比較例2の触媒(セリア担持密度約0.3モル/L)を対照(100%)として比較した結果、上流のセリアの基材1L当たりの担持密度が低いほどH2S排出量が低減し、セリアが含まれていない場合(0モル/L)には、上流と下流に分かれていない従来技術のニッケルを含む比較例2の触媒と比較して同程度のH2S排出量を示した(表2及び図4を参照のこと)。
3. Examination of the amount of oxygen storage / release material that can be added to the upstream In order to determine the upper limit of the amount of oxygen storage / release material that can be added upstream, 0.6 mol (103 g) The catalyst containing various amounts of ceria in the upstream portion of the catalyst of Example 1 containing ceria was prepared, and their H 2 S purification performance was measured as described above. As a result of comparison using the catalyst of Comparative Example 2 (ceria loading density of about 0.3 mol / L) as a control (100%), the lower the loading density per 1 L of the upstream ceria substrate, the lower the H 2 S emission. In the case where ceria is not contained (0 mol / L), the same amount of H 2 S emission was shown as compared with the catalyst of Comparative Example 2 containing nickel of the prior art that is not divided into upstream and downstream. (See Table 2 and FIG. 4).
4.酸素貯蔵放出材の比表面積の検討
続いて、触媒コート層に使用した酸素貯蔵放出材の比表面積とH2S排出量の関係を検討した。最初に、100m2/gの比表面積を有するセリアを種々の温度で5時間電気炉焼成することにより、75、45、25m2/gの比表面積に低減させた。次に、これらの比表面積を有するセリアを用い、実施例1と同様の触媒成分組成を有する上流部及び下流部とに分かれた触媒を調製した。異なる比表面積のセリアを用いて調製したこれらの触媒のH2S浄化性能を上述のように測定した結果、セリアの比表面積が低下するほどH2S排出量が低減した。更に、比較例2の触媒、すなわち、100m2/gの比表面積を有する、上流と下流に分かれていない従来技術のニッケルを含む触媒と比較した場合、45m2/gの比表面積を有する本発明の触媒は同程度までH2S排出量が低減し、そして25m2/gの比表面積を有する触媒はより低いH2S排出量を示した。結果を表3及び図5に示す。
4). Examination of specific surface area of oxygen storage / release material Subsequently, the relationship between the specific surface area of the oxygen storage / release material used in the catalyst coating layer and the H 2 S emission amount was examined. First, ceria having a specific surface area of 100 m 2 / g was reduced to a specific surface area of 75, 45, 25 m 2 / g by firing in an electric furnace at various temperatures for 5 hours. Next, a catalyst separated into an upstream portion and a downstream portion having the same catalyst component composition as in Example 1 was prepared using ceria having these specific surface areas. As a result of measuring the H 2 S purification performance of these catalysts prepared using ceria having different specific surface areas as described above, the amount of H 2 S emission decreased as the specific surface area of ceria decreased. In addition, the present invention has a specific surface area of 45 m 2 / g when compared to the catalyst of Comparative Example 2, ie, a prior art nickel-containing catalyst that has a specific surface area of 100 m 2 / g and is not divided upstream and downstream. Of the catalyst reduced H 2 S emissions to the same extent, and catalysts with a specific surface area of 25 m 2 / g showed lower H 2 S emissions. The results are shown in Table 3 and FIG.
以上の結果より、本発明の排ガス浄化用触媒は、環境負荷物質であるニッケルを用いることなく、従来の触媒よりも優れたH2S浄化性能を示し、且つNOx等その他の排気ガス浄化性能も維持できることが明らかとなった。 From the above results, the exhaust gas purifying catalyst of the present invention exhibits H 2 S purification performance superior to that of the conventional catalyst without using nickel which is an environmental load substance, and other exhaust gas purification performance such as NOx. It became clear that it could be maintained.
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