JP5427443B2 - Composite oxide for exhaust gas purification catalyst, paint for exhaust gas purification catalyst and filter for diesel exhaust gas purification - Google Patents
Composite oxide for exhaust gas purification catalyst, paint for exhaust gas purification catalyst and filter for diesel exhaust gas purification Download PDFInfo
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- JP5427443B2 JP5427443B2 JP2009068698A JP2009068698A JP5427443B2 JP 5427443 B2 JP5427443 B2 JP 5427443B2 JP 2009068698 A JP2009068698 A JP 2009068698A JP 2009068698 A JP2009068698 A JP 2009068698A JP 5427443 B2 JP5427443 B2 JP 5427443B2
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- exhaust gas
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- gas purification
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- 239000002131 composite material Substances 0.000 title claims description 49
- 238000000746 purification Methods 0.000 title claims description 14
- 239000003973 paint Substances 0.000 title claims description 12
- 239000003054 catalyst Substances 0.000 title description 102
- 238000002485 combustion reaction Methods 0.000 claims description 63
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 35
- 239000006229 carbon black Substances 0.000 claims description 32
- 238000010438 heat treatment Methods 0.000 claims description 30
- 229910052684 Cerium Inorganic materials 0.000 claims description 29
- 230000000694 effects Effects 0.000 claims description 29
- 229910052726 zirconium Inorganic materials 0.000 claims description 25
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 19
- 230000006866 deterioration Effects 0.000 claims description 19
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 17
- 238000011156 evaluation Methods 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 229910052697 platinum Inorganic materials 0.000 claims description 11
- 229910001868 water Inorganic materials 0.000 claims description 11
- 238000001354 calcination Methods 0.000 claims description 7
- 238000004438 BET method Methods 0.000 claims description 6
- 239000011248 coating agent Substances 0.000 claims description 6
- 238000000576 coating method Methods 0.000 claims description 6
- 239000013618 particulate matter Substances 0.000 description 58
- 239000007789 gas Substances 0.000 description 47
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 41
- 229910052717 sulfur Inorganic materials 0.000 description 41
- 239000011593 sulfur Substances 0.000 description 41
- 238000000034 method Methods 0.000 description 36
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- 230000000052 comparative effect Effects 0.000 description 22
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- 230000015572 biosynthetic process Effects 0.000 description 17
- 238000003786 synthesis reaction Methods 0.000 description 17
- 230000003197 catalytic effect Effects 0.000 description 16
- 239000000243 solution Substances 0.000 description 15
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 12
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- 238000007254 oxidation reaction Methods 0.000 description 12
- 230000008569 process Effects 0.000 description 11
- 239000000203 mixture Substances 0.000 description 10
- 239000002243 precursor Substances 0.000 description 9
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 8
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 8
- 239000000463 material Substances 0.000 description 8
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- 238000003756 stirring Methods 0.000 description 6
- 230000002378 acidificating effect Effects 0.000 description 5
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- 239000001301 oxygen Substances 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- 239000006104 solid solution Substances 0.000 description 5
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- 239000001099 ammonium carbonate Substances 0.000 description 4
- 238000010304 firing Methods 0.000 description 4
- 239000011812 mixed powder Substances 0.000 description 4
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- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
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- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000015556 catabolic process Effects 0.000 description 3
- 229940044927 ceric oxide Drugs 0.000 description 3
- 229910000420 cerium oxide Inorganic materials 0.000 description 3
- QQZMWMKOWKGPQY-UHFFFAOYSA-N cerium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O QQZMWMKOWKGPQY-UHFFFAOYSA-N 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 230000009849 deactivation Effects 0.000 description 3
- 238000006731 degradation reaction Methods 0.000 description 3
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- 230000007246 mechanism Effects 0.000 description 3
- 239000004570 mortar (masonry) Substances 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 3
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- 229910052761 rare earth metal Inorganic materials 0.000 description 3
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- 229910004631 Ce(NO3)3.6H2O Inorganic materials 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- 229910010413 TiO 2 Inorganic materials 0.000 description 2
- 229910006219 ZrO(NO3)2·2H2O Inorganic materials 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 229910001854 alkali hydroxide Inorganic materials 0.000 description 2
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 2
- IXSUHTFXKKBBJP-UHFFFAOYSA-L azanide;platinum(2+);dinitrite Chemical compound [NH2-].[NH2-].[Pt+2].[O-]N=O.[O-]N=O IXSUHTFXKKBBJP-UHFFFAOYSA-L 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical group [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
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- 230000001747 exhibiting effect Effects 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
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- 238000004519 manufacturing process Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
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- YPJKMVATUPSWOH-UHFFFAOYSA-N nitrooxidanyl Chemical compound [O][N+]([O-])=O YPJKMVATUPSWOH-UHFFFAOYSA-N 0.000 description 2
- SJWFXCIHNDVPSH-UHFFFAOYSA-N octan-2-ol Chemical compound CCCCCCC(C)O SJWFXCIHNDVPSH-UHFFFAOYSA-N 0.000 description 2
- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 2
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 2
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 description 2
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- VXQBJTKSVGFQOL-UHFFFAOYSA-N 2-(2-butoxyethoxy)ethyl acetate Chemical compound CCCCOCCOCCOC(C)=O VXQBJTKSVGFQOL-UHFFFAOYSA-N 0.000 description 1
- 229910000505 Al2TiO5 Inorganic materials 0.000 description 1
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 101100224414 Caenorhabditis elegans dpf-1 gene Proteins 0.000 description 1
- 229910002492 Ce(NO3)3·6H2O Inorganic materials 0.000 description 1
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- 229910002651 NO3 Inorganic materials 0.000 description 1
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- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 230000010718 Oxidation Activity Effects 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- GWGQWFHTAOMUBD-UHFFFAOYSA-N [[3-[bis(phosphonomethyl)amino]-2-hydroxypropyl]-(phosphonomethyl)amino]methylphosphonic acid Chemical compound OP(=O)(O)CN(CP(O)(O)=O)CC(O)CN(CP(O)(O)=O)CP(O)(O)=O GWGQWFHTAOMUBD-UHFFFAOYSA-N 0.000 description 1
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
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- 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
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- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、自動車等のディーゼルエンジンから排出されるＰＭ（粒子状物質）を燃焼させるのに適した複合酸化物からなる排ガス浄化触媒、およびそれを用いた触媒用塗料とその塗料を基材上に塗布したディーゼル排ガス浄化用フィルタに関する。 The present invention relates to an exhaust gas purification catalyst composed of a composite oxide suitable for burning PM (particulate matter) discharged from a diesel engine such as an automobile, and a catalyst paint using the same and a paint on the substrate. The present invention relates to a filter for purifying diesel exhaust gas applied to a filter.
ディーゼルエンジンのもつ問題として、窒素酸化物（ＮＯx）とカーボンを主体とする微粒子（以後「ＰＭ」とも言う。）が排ガス中に含まれ、環境汚染の原因となる点が挙げられる。こうした問題の一つであるＰＭを除去する一般的な方法として、排気ガス流路に多孔質体セラミックスからなるディーゼル・パーティキュレート・フィルタ（ＤＰＦ）を設置してＰＭを捕集（トラップ）する方法がある。この方法では、ＤＰＦにはＰＭが蓄積されてゆき、排気が行われにくくなる。そのため、捕集されたＰＭを間欠的または連続的に燃焼処理することによりＰＭを除去し、ＤＰＦをＰＭ捕集前の状態に再生させることが通常行われている。 A problem with diesel engines is that particulates mainly composed of nitrogen oxides (NO x ) and carbon (hereinafter also referred to as “PM”) are contained in the exhaust gas, causing environmental pollution. As a general method for removing PM which is one of these problems, a diesel particulate filter (DPF) made of porous ceramics is installed in an exhaust gas flow path to trap PM. There is. In this method, PM is accumulated in the DPF, and exhaust is difficult to be performed. Therefore, it is a common practice to remove the PM by intermittently or continuously burning the collected PM to regenerate the DPF to the state before PM collection.
元来、このＤＰＦ再生処理には、電気ヒーターやバーナー等、外部からの強制加熱によりＰＭを燃焼させる方法、ＤＰＦよりもエンジン側に酸化触媒を設置し、排ガス中に含まれるＮＯを酸化触媒によりＮＯ2へと酸化した上で、ＤＰＦへと供給した後、ＮＯ2の酸化力を利用してＰＭを燃焼させる方法が一般的に用いられている。 Originally, in this DPF regeneration process, a method of burning PM by forced heating from the outside, such as an electric heater or a burner, an oxidation catalyst is installed on the engine side of the DPF, and NO contained in the exhaust gas is oxidized by the oxidation catalyst. A method is generally used in which PM is burned using the oxidizing power of NO 2 after being oxidized to NO 2 and supplied to DPF.
しかし、上述の方法では、外部に加熱するための機構（電気ヒーターやバーナーなど）が別途必要になるため排ガス浄化システムそのものが複雑化する。また、酸化触媒についてはもともと運転時に発生する排ガスの温度が低いため、触媒活性が十分に発揮されないことがあるとともに、ある一定の運転状況下でなければＮＯが不足して、ＰＭの燃焼が不十分となることもあることが問題点としてあげられていた。 However, the above-described method requires a separate mechanism (such as an electric heater or a burner) for heating to the outside, so that the exhaust gas purification system itself becomes complicated. In addition, since the temperature of exhaust gas generated during operation is originally low for an oxidation catalyst, the catalyst activity may not be fully exhibited, and NO is not sufficient unless PM is under certain operating conditions, and PM combustion is not possible. The problem was that it might be enough.
そこで、ＤＰＦそのものに触媒を担持させることで、その担持された触媒の作用によりＰＭの燃焼開始温度を低下させ、外部ヒーター等の加熱装置を必要とせずともＰＭを燃焼させることのできる方法が検討されている。そして究極的には排ガス温度にて連続的にＰＭを燃焼させる方法が最も望まれている。 Therefore, a method is considered in which the catalyst is supported on the DPF itself to lower the PM combustion start temperature by the action of the supported catalyst, and the PM can be combusted without the need for a heating device such as an external heater. Has been. Ultimately, a method of continuously burning PM at the exhaust gas temperature is most desired.
現在ではＤＰＦにトラップされたＰＭを燃焼除去させるための酸化触媒（ＰＭ燃焼触媒）として、高比表面積のアルミナ等に触媒金属のＰｔを担持させたものが使用されている。しかし、排ガス温度レベルではＰｔといえども、ＰＭを燃焼させるのに十分な触媒作用を発揮できない。すなわち、排ガスの熱を利用するだけでは、ＰＭを連続的に燃焼させることは困難であるので、外部からの強制加熱手段と併用することが必要不可欠となる。また、Ｐｔは希少金属であり高価であるため、わずかな使用であってもコスト増を招くという問題がある。 At present, an oxidation catalyst (PM combustion catalyst) for burning and removing PM trapped in the DPF is used in which a catalyst metal, Pt, is supported on alumina having a high specific surface area. However, even if it is Pt at the exhaust gas temperature level, it cannot exhibit a catalytic action sufficient for burning PM. That is, it is difficult to continuously burn PM only by using the heat of exhaust gas, so it is indispensable to use it together with a forced heating means from the outside. Further, since Pt is a rare metal and expensive, there is a problem that even a slight use causes an increase in cost.
さらに、ＰＭを燃焼させる場合には、熱が発生することは避けられず、熱源に近接した触媒物質が曝される温度は大変高くなることが想定される。このため、ＰＭ燃焼触媒においては高温での熱履歴を受けた場合においても触媒性能の低下（熱劣化）ができるだけ少ない触媒物質であることも必要である。 Furthermore, when PM is burned, it is unavoidable that heat is generated, and it is assumed that the temperature at which the catalytic substance close to the heat source is exposed becomes very high. For this reason, it is also necessary for the PM combustion catalyst to be a catalyst material that has as little degradation in catalyst performance (thermal degradation) as possible even when it receives a thermal history at a high temperature.
ところで、酸化セリウムは酸素の保持・脱離能力に優れるため、助触媒として広く用いられてきた。ところが、セリウムは硫酸塩を形成しやすく、一度こうした化合物を形成してしまうと、容易に触媒作用を失活してしまう。このような状態を回避するため、特許文献１から４に記載されるように、触媒作用を有するセリウムに加えてジルコニウムを添加して、セリア・ジルコニア固溶体として使用することが行われてきた。ジルコニアを添加することは、上記のような効果とともに、耐熱性を高める効果もあることが知られている。 By the way, cerium oxide has been widely used as a co-catalyst because of its excellent ability to retain and desorb oxygen. However, cerium easily forms a sulfate, and once such a compound is formed, the catalytic action is easily deactivated. In order to avoid such a state, as described in Patent Documents 1 to 4, it has been performed to add zirconium in addition to cerium having a catalytic action to use as a ceria / zirconia solid solution. It is known that the addition of zirconia has an effect of improving heat resistance in addition to the above effect.
また、上記に加えて特許文献５には、セリア・ジルコニアの固溶体に対して、ランタン、ネオジウム、プラセオジウムから選択される少なくとも一種を添加して、ＢＥＴ比表面積が高く、また酸素吸蔵力の高い触媒も提案されている。また、特許文献６では、セリア・ジルコニア・希土類の複合酸化物を触媒として、カーボン燃焼速度を早める試みも提案されている。 In addition to the above, Patent Document 5 adds at least one selected from lanthanum, neodymium, and praseodymium to a solid solution of ceria and zirconia, and has a high BET specific surface area and a high oxygen storage capacity. Has also been proposed. Patent Document 6 also proposes an attempt to increase the carbon combustion rate using a ceria / zirconia / rare earth composite oxide as a catalyst.
酸化セリウムを成分として含み、触媒として使用する場合には、その含有量の多寡によらず硫黄による被毒による触媒活性の失活の問題が必ず生じる。そのため、先行文献では、ジルコニウムの配合割合を高め、失活の影響をできるだけ小さくすることが行われている。 When cerium oxide is used as a component and used as a catalyst, a problem of deactivation of catalytic activity due to sulfur poisoning inevitably occurs regardless of the content. For this reason, in the prior art, the proportion of zirconium is increased to reduce the influence of deactivation as much as possible.
一方、本願発明者らの検討によれば、特許文献５に記載されているような、セリア・ジルコニアの固溶体に対し、希土類成分、とりわけプラセオジウムを反応の初期段階で添加し、セリア・ジルコニア・希土類の固溶体とすることで、従来技術では見いだされていなかった、硫黄に対する耐性があることがわかってきた。しかしながら、特許文献５に記載されているような範囲であったとしても、必ずしも同様の効果が安定的に現れるわけではないこともわかってきた。 On the other hand, according to the study by the present inventors, a rare earth component, particularly praseodymium, is added to the solid solution of ceria and zirconia as described in Patent Document 5, at the initial stage of the reaction, and the ceria, zirconia and rare earth are added. As a solid solution, it has been found that there is resistance to sulfur, which has not been found in the prior art. However, even within the range described in Patent Document 5, it has been found that the same effect does not necessarily appear stably.
さらに、この組成系であれば、一旦硫黄が触媒に作用して被毒したとしても、簡単な操作を経るだけで容易に触媒作用が回復することがあることもわかってきたが、それも上記先行技術のような単純にセリウムの割合を高めるだけでは生じないこともわかってきた。 Furthermore, with this composition system, it has been found that even if sulfur acts on the catalyst and is poisoned, the catalytic action may be easily recovered by simple operation. It has also been found that simply increasing the proportion of cerium as in the prior art does not occur.
すなわち、上記特許文献５に記載の技術では、酸素吸蔵能に優れた燃焼を補助することに適した触媒を提供できているが、硫黄への耐性については検討されておらず、ディーゼルエンジンの排ガス用途に用いるには、まだ不十分であった。同様のことは特許文献６に記載の粒子にもいうことができ、硫黄酸性ガスに対する耐性がある場合と極端に悪くなる場合があり、硫黄酸性ガスに対する安定性に関しては検討すべき点が多い。 That is, in the technique described in Patent Document 5, a catalyst suitable for assisting combustion with excellent oxygen storage capacity can be provided, but resistance to sulfur has not been studied, and exhaust gas from a diesel engine has not been studied. It was still insufficient for use. The same can be said for the particles described in Patent Document 6, and there are cases where the resistance to sulfur acidic gas and the resistance to sulfur acidic gas are extremely poor, and there are many points to be examined regarding the stability to sulfur acidic gas.
そこで、本発明の解決すべき技術的課題は、触媒が備えておくべき耐熱性を確保しつつ、安定して硫黄による失活を抑制し、かつ容易に活性を回復しうる触媒を提供し、このような性質を有する触媒が分散された塗料ならびに、このような触媒が塗布されて形成されたディーゼルパティキュレートフィルターを提供することにある。 Therefore, the technical problem to be solved by the present invention is to provide a catalyst that stably suppresses deactivation by sulfur and can easily recover the activity while ensuring the heat resistance that the catalyst should have. An object of the present invention is to provide a paint in which a catalyst having such properties is dispersed, and a diesel particulate filter formed by applying such a catalyst.
本発明者らは、かかる目的を達成するため鋭意研究を重ねた結果、セリウムに所定元素を僅かに加えた複合酸化物であって、特定の結晶子径を有するものであれば、上記課題が解決できることを見出し、本発明を完成するに至った。 As a result of intensive studies to achieve such an object, the present inventors have found that the above-mentioned problem is solved if it is a complex oxide in which a predetermined element is slightly added to cerium and has a specific crystallite diameter. The inventors have found that this can be solved, and have completed the present invention.
即ち、本発明とは、セリウムとＰｒおよびＺｒを含み、
セリウム、ＰｒおよびＺｒの元素がモル比でＣｅ：Ｐｒ：Ｚｒ＝（１−ｘ−ｙ）：ｘ：ｙ（ただし、０＜ｘ＜０．３、０＜ｙ＜０．３、０＜ｘ＋ｙ≦０．３）であり、
ＣｅＯ２の（３１１）面で測定した結晶子径が１６ｎｍ以上であり、
８００℃で大気中２時間仮焼した後の酸化物のＢＥＴ法により算出される比表面積が５０ｍ ２ ／ｇ以上であり、８００℃で大気中１００時間仮焼した（耐熱安定性評価）後の酸化物のＢＥＴ法により算出される比表面積が２９ｍ ２ ／ｇ以上を保つ性質を有する複合酸化物である。
That is, the present invention includes cerium, Pr and Zr ,
The elements of cerium, Pr and Zr are in molar ratios Ce: Pr : Zr = (1-xy): x: y ( where 0 <x <0.3, 0 < y <0.3, 0 <x + y ≦ 0.3) der is,
Crystallite size measured by the CeO 2 (311) plane is Ri der least 16 nm,
The specific surface area calculated by the BET method of the oxide after calcining at 800 ° C. for 2 hours in the air is 50 m 2 / g or more, and after calcining at 800 ° C. for 100 hours in the air (heat stability evaluation) the specific surface area calculated by the BET method of the oxide is a composite oxide that have a property to keep more than 29m 2 / g.
また、熱処理前後の疑似ＰＭであるカーボンブラック（ＣＢ）燃焼活性評価において、次式（１）で示される、（燃焼活性）悪化率が１０％未満である酸化物である。
（燃焼活性）悪化率（％）＝１００×（熱処理後ＣＢ燃焼開始温度−合成直後ＣＢ燃焼開始温度）／合成直後ＣＢ燃焼開始温度・・・（１）
また、この複合酸化物が分散された塗料と、その塗料を多孔質フィルタに塗布することによって構成されたＤＰＦである。
Moreover, in the carbon black (CB) combustion activity evaluation which is pseudo PM before and after heat treatment, it is an oxide having a (combustion activity) deterioration rate of less than 10% represented by the following formula (1).
(Combustion activity) deterioration rate (%) = 100 × (post-heat treatment CB combustion start temperature−combination CB combustion start temperature) / combination CB combustion start temperature (1)
Moreover, it is DPF comprised by apply | coating the coating material in which this complex oxide was disperse | distributed, and the coating material to a porous filter.
さらには、上記の構成に加え、Ｐｄ、Ｐｔ、Ｒｈといった白金族を複合酸化物そのもの、あるいはフィルタに担持した、ＤＰＦである。 Furthermore, in addition to the above-described configuration, the DPF is one in which a platinum group such as Pd, Pt, and Rh is supported on a composite oxide itself or a filter.
本発明により提供される複合酸化物は、硫黄による被毒割合が小さいとともに、触媒性能の回復が容易であって、さらに耐熱性に富んだ触媒を提供することができる。さらには、この触媒が分散した塗料を塗布することによって、低温でも優れたＰＭ浄化性能を呈する触媒を提供することができるようになる。 The composite oxide provided by the present invention can provide a catalyst having a low poisoning ratio due to sulfur and easily recovering the catalyst performance and having further excellent heat resistance. Furthermore, by applying a paint in which the catalyst is dispersed, a catalyst exhibiting excellent PM purification performance even at a low temperature can be provided.
さらに、本発明に従う複合酸化物をＤＰＦに担持して使用することで、排ガス環境によらず低温でＰＭを除去できるようになるため、ＤＰＦそのものでＰＭを燃焼させることができるようになる。ひいては、上記従来行われていたＤＰＦのＰＭ捕集性能を回復するための大規模な外部加熱装置を設置することを必要としない、排ガス浄化システムも提供することも可能になる。 Further, by using the composite oxide according to the present invention supported on the DPF, it becomes possible to remove PM at a low temperature regardless of the exhaust gas environment, so that the DPF itself can combust PM. As a result, it is also possible to provide an exhaust gas purification system that does not require the installation of a large-scale external heating device for recovering the PM collection performance of the DPF that has been conventionally performed.
＜粒子の組成構成＞
本発明の排ガス浄化触媒用複合酸化物は、ＣｅにＰｒ、Ｚｒのうちの少なくとも２つの元素を含む複合酸化物である。このような構成とすることで、比較的低温で排ガス雰囲気が吸着した硫黄分を脱離させ、もとの触媒活性を回復することができる。
<Composition composition of particles>
Exhaust gas purifying catalyst composite oxide of the present invention is a composite oxide containing Pr, at least two elements of Z r to Ce. By setting it as such a structure, the sulfur content which the exhaust gas atmosphere adsorb | sucked by comparatively low temperature can be desorbed, and the original catalyst activity can be recovered | restored.
本発明にかかる複合酸化物は、Ｃｅを基材とする複合酸化物であるので、ＰＭを低温から燃焼させることができる触媒活性の機構は、従来のセリウム系複合酸化物において考えられている機構と同様であると考えられる。 Since the complex oxide according to the present invention is a complex oxide based on Ce, the mechanism of catalytic activity capable of burning PM from a low temperature is the mechanism considered in conventional cerium-based complex oxides. It is thought that it is the same.
すなわち、本発明の複合酸化物は、酸化第二セリウム（ＣｅＯ2）の蛍石型構造を保ったまま、セリウムの位置の一部をジルコニウム等の添加元素が置換して固溶体となる。添加元素はセリウムより小さいことから、セリウムが酸素を排出して、４価から３価に変化し体積膨張が起こっても、ジルコニウムイオンの存在により、結晶格子の歪が緩和される性質を有する。 That is, the composite oxide of the present invention becomes a solid solution by substituting an additional element such as zirconium for a part of the position of cerium while maintaining the fluorite structure of ceric oxide (CeO 2 ). Since the additive element is smaller than cerium, even if cerium discharges oxygen and changes from tetravalent to trivalent and volume expansion occurs, the presence of zirconium ions has the property of relaxing the distortion of the crystal lattice.
従来このような組成で触媒を作成するには、セリウムの被毒を抑制し、触媒活性を維持する目的で、ジルコニウムをセリウムよりも多く混入することが広くなされてきた。しかし、本発明においては、ジルコニウムの含有量をより少なく設定し、セリウムの構成割合をより多くし、かつ触媒粒子における特定の物性値を特定の範囲とすることで、より触媒性能に優れた触媒粉末を得られることを見いだし、本発明を完成させた。ここで、ジルコニウムの添加量は、モル比で０＜Ｚｒ≦０．２５とするのが好ましい。さらに好ましくは０＜Ｚｒ≦０．１である。 Conventionally, in order to prepare a catalyst with such a composition, it has been widely practiced to incorporate more zirconium than cerium for the purpose of suppressing poisoning of cerium and maintaining the catalytic activity. However, in the present invention, by setting the zirconium content lower, increasing the cerium constituent ratio, and setting the specific physical property value in the catalyst particles within a specific range, a catalyst with more excellent catalyst performance. The inventors found that a powder can be obtained and completed the present invention. Here, the amount of zirconium added is preferably 0 <Zr ≦ 0.25 in terms of molar ratio. More preferably, 0 <Zr ≦ 0.1.
本発明では添加元素としてＰｒ、Ｚｒから選ばれた１種以上の元素）を添加した新規な複合酸化物を提供する。とりわけ、本発明の複合酸化物を構成する元素の割合は、ＣｅとＡ、Ｂ（ＡまたはＢは、Ｐｒ、Ｚｒから選ばれた１種以上の元素）のモル比をＣｅ：Ａ：Ｂ＝（１−ｘ−ｙ）：ｘ：ｙとするとき、０＜ｘ＋ｙ≦０．３であることが好ましい。 As an additive element in the present invention Pr, it provides a novel composite oxide doped with Z r or al least one selected of element). Especially, the ratio of elements constituting the composite oxide of the present invention, Ce and A, B (A or B, Pr, Z r or al least one selected of element) the molar ratio of Ce: A: When B = (1−xy): x: y, 0 <x + y ≦ 0.3 is preferable.
特にＡをＰｒ、ＢをＺｒで構成する場合は、Ｐｒの酸化物は酸化第二セリウム（ＣｅＯ２）と同様の蛍石型構造をとるため、ＰｒでＣｅ原子の一部を置換することにより蛍石型構造が維持され易く、一層耐熱性の向上した排ガス浄化触媒を得ることができる。そのときの元素割合のモル比は、Ｃｅ：Ｐｒ：Ｚｒ＝（１−ｘ−ｙ）：ｘ：ｙとするとき、０＜ｘ＜０．３、０＜ｙ＜０．３、０＜ｘ＋ｙ≦０．３を満たすものであるのがよい。 In particular, when A is composed of Pr and B is composed of Zr, the Pr oxide has a fluorite-type structure similar to ceric oxide (CeO 2 ). Therefore, by replacing part of the Ce atom with Pr, An exhaust gas purification catalyst having a fluorite structure that is easily maintained and having further improved heat resistance can be obtained. At that time, the molar ratio of the element ratios is 0 <x < 0.3, 0 <y < 0.3, 0 <x + y, where Ce: Pr: Zr = (1-xy): x: y. It is preferable to satisfy ≦ 0.3.
なお、本願発明のセリウム構造体においては、セリウムと複合酸化物を構成するために添加していた元素（Ｐｒ、Ｚｒ）が十分に酸化セリウムと複合酸化物を形成せずに、不純物相として存在する場合がある。これらの取り込まれなかった元素については、本発明の効果が阻害されない限りその不純物相の存在は許容される。許容される量の不純物相が存在する場合は、不純物相中のＣｅと添加元素を含めた複合酸化物全体としてのモル比が上記を満たしていればよい。 In the cerium structure of the present invention, the elements (Pr, Zr) added to form the composite oxide with cerium do not sufficiently form the composite oxide with cerium oxide, May exist. For these elements that have not been incorporated, the presence of the impurity phase is allowed unless the effect of the present invention is impaired. When an allowable amount of impurity phase exists, the molar ratio of the composite oxide as a whole including Ce and the additive element in the impurity phase should satisfy the above.
このような複合酸化物とともに白金族元素を共存させることも有効である。白金族元素は排気ガス中に含まれる未燃燃料、および、ＮＯ、ＣＯ等の未燃焼成分の酸化を促進させる作用を有する。また、ＰＭ燃焼開始温度をさらに低下させる効果も期待できる。白金族元素（Ｐｔ、Ｒｈ、Ｐｄ、Ｉｒ、Ｒｕ、Ｏｓ）のうち１種以上を使用することができ、特にＰｔ、Ｒｈ、Ｐｄが触媒効率を高める上で効果が大きい。白金族元素は例えば本発明の複合酸化物に含有させる形で共存させても、含浸して触媒表面に担持させてもよい。 It is also effective to allow a platinum group element to coexist with such a complex oxide. The platinum group element has an action of promoting oxidation of unburned fuel contained in the exhaust gas and unburned components such as NO and CO. In addition, an effect of further lowering the PM combustion start temperature can be expected. One or more of platinum group elements (Pt, Rh, Pd, Ir, Ru, Os) can be used. In particular, Pt, Rh, and Pd are highly effective in increasing the catalyst efficiency. For example, the platinum group element may be present in the form of being included in the composite oxide of the present invention, or may be impregnated and supported on the catalyst surface.
他方の構成として、Ａｌ2Ｏ3、ＴｉＯ2、ＳｉＯ2など一般に触媒担体として使用される物質に白金族元素を含有させ、その物質を本発明の複合酸化物とともに混合することによって、本発明の複合酸化物と白金族元素を共存させることも一つの構成である。白金族元素の量は、本発明の複合酸化物中、あるいはさらに上記触媒担体物質が混合される場合は本発明の複合酸化物と上記触媒担体物質の混合物中における白金族元素の含有量が例えば０．０５〜５質量％となるようにすればよい。 As another configuration, a platinum group element is contained in a substance generally used as a catalyst support such as Al 2 O 3 , TiO 2 , SiO 2 , and the substance is mixed with the composite oxide of the present invention. Coexistence of the complex oxide and the platinum group element is also one configuration. The amount of the platinum group element is, for example, the content of the platinum group element in the mixture of the composite oxide of the present invention and the catalyst support material when the catalyst support material is further mixed. What is necessary is just to make it become 0.05-5 mass%.
＜粒子の物理的特性＞
粒子の性質として粒子の組成比が上述の範囲内であり、かつ８００℃２時間の仮焼後に得られる粉体において、ＣｅＯ2（３１１）の回折線により算出される結晶子径が１６ｎｍ以上である複合酸化物であれば、合成直後に対して、長時間高熱に曝した後でもＰＭ燃焼活性が悪化しがたいことがわかった。この範囲を外れると硫黄の脱離性が低下し、触媒活性が回復しない、若しくは回復するとしても比較的高温の温度をかけなければ触媒活性が回復しない。
<Physical properties of particles>
As the properties of the particles, the composition ratio of the particles is in the above range, and the powder obtained after calcination at 800 ° C. for 2 hours has a crystallite diameter of 16 nm or more calculated by the diffraction line of CeO 2 (311). For some complex oxides, it was found that the PM combustion activity hardly deteriorates even after exposure to high heat for a long time compared to immediately after synthesis. If it is out of this range, the desorption property of sulfur is lowered and the catalytic activity is not recovered, or even if it is recovered, the catalytic activity is not recovered unless a relatively high temperature is applied.
この理由については不明確なところも多いが、本発明に従う粒子Ｃｅを含む三元系粒子）の構成を取る場合には、結晶子径が小さい場合、粒子としての反応活性が高く、硫黄酸性ガスと反応して難脱離性の硫黄化合物を形成しやすいため、再生処理を施しても触媒活性を容易な方法で回復させることが困難であることが判明した。発明者らの知見によれば、酸化第二セリウムの結晶方位（３１１）における結晶子径で１６ｎｍ未満の場合にこのような影響が顕著に現れる。この場合には、再生処理後の硫黄含有量の減少量は比較的小さい値を示す。 Although there are many unclear points about this reason, in the case of taking the configuration of a ternary particle containing particles Ce according to the present invention, when the crystallite size is small, the reaction activity as particles is high, and the sulfur acidic gas It has been found that it is difficult to recover the catalytic activity by an easy method even when regeneration treatment is performed because it is easy to form a sulfur compound that is difficult to desorb by reacting with NO. According to the knowledge of the inventors, such an effect appears remarkably when the crystallite diameter in the crystal orientation (311) of ceric oxide is less than 16 nm. In this case, the reduction amount of the sulfur content after the regeneration treatment shows a relatively small value.
本発明の粉体特性としては、８００℃２時間の仮焼後に得られる粉体において、ＢＥＴ法による比表面積が５０ｍ2／ｇ以上であることが好ましい。比表面積が５０ｍ2／ｇ未満であるとＰＭとの接触面積が少なくなるため、触媒作用が不十分になることがある。また、触媒表面に貴金属を担持する場合には、粒子表面における凹凸が少なくなっている状態であるため、担持できるサイトが少なくなることに起因し、貴金属を担持することそのものが難しくなる。 As the powder characteristics of the present invention, the powder obtained after calcination at 800 ° C. for 2 hours preferably has a specific surface area of 50 m 2 / g or more by the BET method. When the specific surface area is less than 50 m 2 / g, the contact area with the PM decreases, and the catalytic action may be insufficient. Further, when the noble metal is supported on the catalyst surface, since the unevenness on the particle surface is reduced, it is difficult to support the noble metal itself due to the reduction of the sites that can be supported.
また１００ｍ2／ｇを超えると本発明の効果以上に再生時の温度上昇による熱劣化が進行し触媒活性が低下しやすい。また、ＢＥＴ値が高い場合には、硫黄による被毒が生じた場合にも表面の凹凸に取り込まれて脱離し難くなるとも推測され、必ずしも好ましい形態ではない。 On the other hand, if it exceeds 100 m 2 / g, thermal deterioration due to temperature rise during regeneration proceeds more than the effect of the present invention, and the catalytic activity tends to decrease. Further, when the BET value is high, it is presumed that even when poisoning by sulfur occurs, it is assumed that it becomes difficult to be taken in and removed from the surface irregularities, which is not necessarily a preferable form.
８００℃で大気中１００時間仮焼した（耐熱安定性評価）後の酸化物の比表面積は２９ｍ2／ｇ以上であることが好ましい。耐熱安定化処理後の比表面積が２９ｍ2／ｇ未満となる場合では、ＰＭの燃焼性能が低下しやすくなる。さらに、表面に貴金属を担持している場合には、貴金属原子の移動が生じやすくなり、結果として貴金属が触媒層表面で塊状化することがある。かような場合には、貴金属の有する触媒性能を得ることができにくくなるので好ましくはない。 The specific surface area of the oxide after calcining at 800 ° C. for 100 hours in the atmosphere (evaluation of heat stability) is preferably 29 m 2 / g or more. In the case where the specific surface area after heat stabilization treatment is less than 29 m 2 / g, the PM combustion performance tends to decrease. Further, when a noble metal is supported on the surface, movement of noble metal atoms is likely to occur, and as a result, the noble metal may be agglomerated on the surface of the catalyst layer. In such a case, it is difficult to obtain the catalyst performance of the noble metal, which is not preferable.
また、粒度分布は、レーザー回折法による粒度分布測定によるＤ50径が０．０１〜１０μｍであることが好ましい。この算出法により得られる粒子径は、いわゆる粒子の凝集径を示すものであり、塗布時においては一つの粒子として振る舞う粒子の大きさを示す。Ｄ50径が０．０１μｍ未満であれば、ＤＰＦの内部まで浸透し、細孔の最深部まで浸透しやすいという意味では好ましい大きさではあるが、結果としてＰＭが入り込まない細孔にまで浸透してしまう。これは言い換えると、ＤＰＦに触媒粒子が埋没することになるので、触媒性能を発現させるために必要な量が多くなってしまうため好ましくない。１０μｍを超えるとＤＰＦの細孔を塞いでしまい、圧損が大きくなるため好ましくない。 The particle size distribution preferably has a D 50 diameter of 0.01 to 10 μm as measured by a particle size distribution by a laser diffraction method. The particle diameter obtained by this calculation method indicates the so-called particle aggregation diameter, and indicates the size of particles that behave as one particle during coating. If the D 50 diameter is less than 0.01 μm, it is a preferred size in the sense that it penetrates into the DPF and easily penetrates to the deepest part of the pores. As a result, it penetrates into the pores where PM does not enter. End up. In other words, the catalyst particles are buried in the DPF, which is not preferable because the amount necessary for developing the catalyst performance increases. If it exceeds 10 μm, the pores of the DPF are blocked and the pressure loss increases, which is not preferable.
＜粒子＞
ここで本願発明にかかる粒子についてさらに述べる。本願発明にかかる粒子はＣｅとＡ，Ｂからなる複合酸化物について、湿式法による沈殿粒子を８００℃にて２時間大気中で焼成する手法で合成し、粒子の物性と硫黄被毒後の再生性および耐熱処理後のＰＭ燃焼性能について調べたところ、Ａ、Ｂの添加によって、結晶子径の調整ができ、この三元系の下で、結晶子径を大きくすることが触媒の再生性やＰＭ燃焼性能に大きく関係することがわかった。
<Particle>
Here, the particles according to the present invention will be further described. The particles according to the invention of the present application are synthesized by a method in which precipitated particles by a wet method are baked in the air at 800 ° C. for 2 hours in a composite oxide composed of Ce, A, and B, and the physical properties of the particles and regeneration after sulfur poisoning. And PM combustion performance after heat treatment, the crystallite diameter can be adjusted by adding A and B. Under this ternary system, increasing the crystallite diameter It was found that the PM combustion performance is greatly related.
上記のような構成を取ることで、次のような性質が発現する。すなわち（イ）酸素の脱離が容易であり、ＰＭの燃焼を促進することができる（ロ）硫黄にさらされることより従来は劣化するとされていた触媒活性が維持される（ハ）触媒が硫黄にさらされて劣化したとしても、簡便な方法で吸着した硫黄分を放出し、触媒性能を回復させることができる、という性質である。 By taking the configuration as described above, the following properties are manifested. That is, (i) Oxygen can be easily desorbed and PM combustion can be promoted. (B) The catalytic activity that was previously deteriorated by exposure to sulfur is maintained. (C) The catalyst is sulfur. Even if it is deteriorated by exposure, it is possible to release the adsorbed sulfur content by a simple method and restore the catalyst performance.
続いて、本願にかかる粒子の製造方法について説明する。本発明の対象となる複合酸化物は、湿式法で得られた沈殿生成物質を焼成する方法により好適に合成することができる。Ｃｅの水溶性塩とＡ、Ｂ（例えばＰｒ、Ｚｒ）の水溶性塩を沈殿剤により沈殿させ、空気を吹き込んで酸化させる。その沈殿物を乾燥させることにより「前駆体」とし、その前駆体を熱処理することにより複合酸化物を合成する。 Then, the manufacturing method of the particle concerning this application is explained. The composite oxide which is the subject of the present invention can be suitably synthesized by a method of firing a precipitation product obtained by a wet method. A water-soluble salt of Ce and a water-soluble salt of A and B (for example, Pr and Zr) are precipitated with a precipitating agent, and are oxidized by blowing air. The precipitate is dried to obtain a “precursor”, and the precursor is heat treated to synthesize a composite oxide.
具体的には、Ｃｅの水溶性塩（例えば硝酸塩）、とＡおよびＢの水溶性塩を溶解させた水溶液に、沈殿剤としてアルカリを加えて反応させ、空気を吹き込み酸化させ酸化物の混合物を生成させる。得られた沈殿生成物を濾過、洗浄・乾燥することによって前駆体を得る。沈殿を生成させる液中のＣｅ、Ａ、Ｂのイオン濃度は、溶解度によって上限が決まる。しかし、あまり液中濃度が濃すぎると、撹拌時に均一に反応が生じず不均一になる可能性があり、また撹拌時に装置の負荷が過大になる場合があるので、好ましくない。 Specifically, an aqueous solution in which a water-soluble salt of Ce (for example, nitrate) and a water-soluble salt of A and B are dissolved is added with alkali as a precipitating agent to react, and air is blown to oxidize the mixture of oxides. Generate. The obtained precipitation product is filtered, washed and dried to obtain a precursor. The upper limit of the ion concentration of Ce, A, and B in the liquid that generates the precipitate is determined by the solubility. However, if the concentration in the liquid is too high, there is a possibility that the reaction does not occur uniformly at the time of stirring and there is a possibility of non-uniformity, and the load on the apparatus may become excessive at the time of stirring.
上記のような沈殿物を得るためには水酸化アルカリによる直接沈降、あるいは炭酸塩を経由した後アルカリを添加して沈降させる方法を用いることができる。具体的に例示すると、水酸化アルカリとしては水酸化ナトリウム、アンモニア水などが好適に用いられる。また、炭酸塩を経由する場合には炭酸水、炭酸ガス、炭酸ナトリウム、炭酸カリウム、炭酸水素ナトリウムなどといった、その構造中に炭酸基をもつものを使用した後、上記のアルカリを添加する方法や、あるいはその双方の機能を併せ持つ炭酸アンモニウム化合物、具体的には炭酸アンモニウム、炭酸水素アンモニウムなどを使用することができる。 In order to obtain the precipitate as described above, it is possible to use a method of direct sedimentation with an alkali hydroxide, or a method of sedimentation by adding an alkali after passing through a carbonate. Specifically, sodium hydroxide, aqueous ammonia and the like are suitably used as the alkali hydroxide. In the case of passing through a carbonate, after using a carbonate group in the structure, such as carbonated water, carbon dioxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, etc. Alternatively, an ammonium carbonate compound having both functions, specifically, ammonium carbonate, ammonium hydrogen carbonate, or the like can be used.
得られた沈殿物は必要に応じて濾過、水洗され、真空乾燥や通風乾燥などにより乾燥させ、前駆体とする。この際、乾燥による脱水効果を高めるため、濾過した直後の形態のまま乾燥処理するか、所定の形状に造粒した後に乾燥処理させることができる。その後、前駆体を、粉末形状あるいは造粒した状態のまま、例えば４００〜１０００℃、好ましくは５００〜１０００℃、さらに好ましくは８００〜９００℃で１時間以上、好ましくは２時間以上熱処理（焼成）することにより、目的とする複合酸化物を合成することができる。焼成時の雰囲気は複合酸化物が生成できるような条件であれば特に制限されず、例えば、空気中、窒素中、アルゴン中およびそれらに水蒸気を組み合わせた雰囲気を使用することができる。 The obtained precipitate is filtered, washed with water as necessary, and dried by vacuum drying or ventilation drying to obtain a precursor. At this time, in order to enhance the dehydration effect due to drying, it can be dried as it is immediately after filtering, or can be dried after granulating into a predetermined shape. Thereafter, the precursor is in a powder form or in a granulated state, for example, 400 to 1000 ° C., preferably 500 to 1000 ° C., more preferably 800 to 900 ° C. for 1 hour or longer, preferably 2 hours or longer. By doing so, the target composite oxide can be synthesized. The atmosphere during firing is not particularly limited as long as the complex oxide can be generated. For example, an atmosphere in air, nitrogen, argon, or a combination of water vapor and the like can be used.
白金族元素を本発明の複合酸化物に含有させる場合は、例えば、焼成後の複合酸化物に、目的量の白金族元素を含む塩あるいは錯体を含浸させた後、乾燥、焼成させる手法や、ロータリーエバポレーター等を使用し溶液中に浸漬させた後、蒸発乾固して得られた粉末を焼成する手法が採用できる。 When including the platinum group element in the composite oxide of the present invention, for example, impregnating the fired composite oxide with a salt or complex containing a target amount of the platinum group element, followed by drying and firing, A method of firing a powder obtained by evaporating to dryness after being immersed in a solution using a rotary evaporator or the like can be employed.
本発明の複合酸化物を排ガス浄化触媒として排ガス浄化触媒用塗料やそれを用いたＤＰＦを構築することができる。排ガス浄化触媒用塗料は、本発明の排ガス浄化触媒と、溶剤と無機バインダを含む塗料である。場合によって分散剤や粘度調整剤やｐＨ調整剤を含んでいても良い。 Using the composite oxide of the present invention as an exhaust gas purification catalyst, a paint for exhaust gas purification catalyst and a DPF using the same can be constructed. The exhaust gas purifying catalyst paint is a paint containing the exhaust gas purifying catalyst of the present invention, a solvent and an inorganic binder. In some cases, a dispersant, a viscosity modifier, and a pH adjuster may be included.
溶剤としては、極性溶剤や非極性溶剤のどちらを用いても良い。フィルタ上に塗布した後、すばやく乾燥させるためには、沸点の低い溶剤がよいが、取り扱いを考えると水系の溶剤でもよい。具体的には水、イソプロピルアルコール、テルピネオール、２−オクタノール、ブチルカルビトールアセテート等が好適に利用できる。 As the solvent, either a polar solvent or a nonpolar solvent may be used. A solvent having a low boiling point is preferable in order to dry quickly after coating on the filter, but an aqueous solvent may be used in consideration of handling. Specifically, water, isopropyl alcohol, terpineol, 2-octanol, butyl carbitol acetate and the like can be suitably used.
無機バインダとしては、Ａｌ2Ｏ3、ＴｉＯ2、ＳｉＯ2などの粉体が好適に用いられる。ＰＭ触媒は高温に曝されるため、高温でも安定した特性を示す材料が好ましい。 As the inorganic binder, powders such as Al 2 O 3 , TiO 2 , and SiO 2 are preferably used. Since the PM catalyst is exposed to a high temperature, a material exhibiting stable characteristics even at a high temperature is preferable.
本発明の複合酸化物を用いたＤＰＦは、構造は特に限定されない。例えば図２にＤＰＦの一例を示す。ＤＰＦ１は入り口側１０から見た断面がハニカム構造をした筒状の形態をしており、材質は多孔質なセラミックで構成されている。入り口側（「エンジン側」とも言う。）１０と出口側（「大気開放側」ともいう。）１１は直接的な貫通孔を有しておらず、多孔質セラミックがフィルタとなっている。多孔質セラミックには、具体的にはセラックス、コージェライト、炭化珪素、チタン酸アルミなどが好適に用いられる。また、形状は図２に示した構造のほか、発泡体、メッシュ、板状といった形状でもよい。 The structure of the DPF using the composite oxide of the present invention is not particularly limited. For example, FIG. 2 shows an example of the DPF. The DPF 1 has a cylindrical shape with a honeycomb structure as viewed from the entrance side 10 and is made of porous ceramic. The inlet side (also referred to as “engine side”) 10 and the outlet side (also referred to as “atmosphere release side”) 11 do not have direct through holes, and porous ceramics serve as filters. Specifically, ceramics, cordierite, silicon carbide, aluminum titanate, and the like are preferably used for the porous ceramic. In addition to the structure shown in FIG. 2, the shape may be a foam, a mesh, or a plate shape.
本発明の複合酸化物はＤＰＦのエンジン側１０に配置されるのがよい。また、白金系の触媒は本発明の触媒に担持させるだけでなく、別々に使用する方法も採用することができる。そういった構成にするために、本発明のＰＭ触媒から大気開放側に配置してもよい。例えば、ＤＰＦのエンジン側の壁面１２に白金系の触媒の層と本発明のＰＭ触媒の層をそれぞれ別々に塗布した多重層構造とすることなどが挙げられる。 The composite oxide of the present invention is preferably disposed on the engine side 10 of the DPF. In addition, the platinum-based catalyst can be supported not only on the catalyst of the present invention but also separately. In order to achieve such a configuration, the PM catalyst of the present invention may be disposed on the atmosphere opening side. For example, a multi-layer structure in which a platinum-based catalyst layer and a PM catalyst layer of the present invention are separately applied to the DPF engine-side wall surface 12 can be mentioned.
また本発明の排ガス浄化触媒用塗料をエンジン側の壁面１２に塗布し、大気開放側の壁面１４には白金系触媒の塗料を塗ってもよい。この場合は、エンジン側にＰＭ触媒３０があり、大気開放側に白金系の触媒４０が配置されることとなる。また、白金系の触媒粉を本発明の排ガス浄化触媒用塗料に混ぜて塗布してもよい。なお、白金系の触媒とは、白金族元素を用いた触媒をいう。 Further, the exhaust gas purifying catalyst paint of the present invention may be applied to the engine-side wall surface 12 and the atmosphere-side open wall surface 14 may be coated with a platinum-based catalyst paint. In this case, the PM catalyst 30 is on the engine side, and the platinum-based catalyst 40 is disposed on the atmosphere opening side. Alternatively, platinum-based catalyst powder may be mixed and applied to the exhaust gas purifying catalyst paint of the present invention. The platinum-based catalyst refers to a catalyst using a platinum group element.
次に本発明において、物性や触媒性能等を確認するため行う評価について詳述する。 Next, in the present invention, the evaluation performed for confirming physical properties, catalyst performance, etc. will be described in detail.
《ＢＥＴ比表面積の測定》
後述の方法で得られた耐熱処理前の試料、および上記耐熱処理後の試料（耐熱後と表示）について、メノウ乳鉢で解粒し、粉末とした後、ＢＥＴ法により比表面積を求めた。測定はユアサアイオニクス製の４ソーブＵＳを用いて行った。
<< Measurement of BET specific surface area >>
A sample before heat treatment and a sample after heat treatment (shown as after heat treatment) obtained by the method described below were pulverized with an agate mortar to form a powder, and then the specific surface area was determined by the BET method. The measurement was performed using a 4-sorb US manufactured by Yuasa Ionics.
《結晶子径の測定》
得られた耐熱処理前の試料、および上記耐熱処理後の試料（耐熱後と表示）について、メノウ乳鉢で解粒し、粉末とした後、粉末Ｘ線回折法による半価幅からＳｈｅｒｒｅｒの式を用いて算出した。使用するピークはＣｅＯ2（ＪＣＰＤＳカード：３４−０３９４）の（３１１）面に現れる回折線を使用した。
<Measurement of crystallite size>
The obtained sample before the heat treatment and the sample after the heat treatment (labeled after heat treatment) were pulverized in an agate mortar to form a powder, and then the Scherrer equation was calculated from the half width by the powder X-ray diffraction method. Used to calculate. As a peak to be used, diffraction lines appearing on the (311) plane of CeO 2 (JCPDS card: 34-0394) were used.
測定は、２θ＝６５〜６９度の範囲で行う。測定条件は、管球としてＣｏ管球を使用し、管電圧４０ｋＶ・管電流３０ｍＡとした。Ｘ線回折装置は、株式会社リガク製・自動Ｘ線回折装置ＲＩＮＴ−２１００、若しくはこの装置の同等品を使用できる。 The measurement is performed in the range of 2θ = 65 to 69 degrees. As measurement conditions, a Co tube was used as the tube, and the tube voltage was 40 kV and the tube current was 30 mA. As the X-ray diffractometer, an automatic X-ray diffractometer RINT-2100 manufactured by Rigaku Corporation or an equivalent product of this apparatus can be used.
《ＰＭ燃焼温度の評価》
後述の方法で得られた試料、および上記耐熱処理後の試料について、カーボンブラックとの混合粉を作り、その中の一部を規定量分取した上、ＴＧ／ＤＴＡ装置を用いてカーボンブラック燃焼温度を求めることによってＰＭ燃焼開始温度を測定した。具体的には以下のようにした。
<< Evaluation of PM combustion temperature >>
For the sample obtained by the method described below and the sample after the above heat-resistant treatment, a mixed powder with carbon black is prepared, and a part of the sample is taken out, and then a carbon black is burned using a TG / DTA device. The PM combustion start temperature was measured by determining the temperature. Specifically, it was as follows.
模擬ＰＭとして市販のカーボンブラック（三菱化学株式会社製、平均粒径２．０９μｍ）を用い、複合酸化物試料の粉体とカーボンブラックの質量比が６：１になるように秤量し、自動乳鉢機（石川工場製ＡＧＡ型）で２０分間混合し、カーボンブラックと各試料粉体の混合粉体を得た。この混合粉体２０ｍｇをＴＧ／ＤＴＡ装置（エスアイアイナノテクノロジー株式会社製、ＥｘｓｔａｒＴＧ／ＤＴＡ６３００型）にセットし、昇温速度１０℃／ｍｉｎにて常温から７００℃まで大気中で昇温し、重量減少量の測定を行った。カーボンブラックは燃焼により二酸化炭素として系外に排出されるので、初期重量からは減少傾向になるからである。 A commercially available carbon black (Mitsubishi Chemical Co., Ltd., average particle size 2.09 μm) was used as a simulated PM and weighed so that the mass ratio of the composite oxide sample powder to the carbon black was 6: 1. Mixing for 20 minutes using a machine (AGA type manufactured by Ishikawa Factory) to obtain a mixed powder of carbon black and each sample powder. 20 mg of this mixed powder was set in a TG / DTA apparatus (Exstar TG / DTA6300 type, manufactured by SII Nano Technology Co., Ltd.), heated in the atmosphere from room temperature to 700 ° C. at a heating rate of 10 ° C./min, and weight The amount of decrease was measured. This is because carbon black is discharged out of the system as carbon dioxide by combustion and tends to decrease from the initial weight.
図３に、重量変化曲線（ＴＧ曲線）と示差熱曲線（ＤＴＡ曲線）を模式的に示す。ＤＴＡ曲線において、発熱量が最大となる点をＰＭ燃焼温度とした。図３では符号５０の温度である。 FIG. 3 schematically shows a weight change curve (TG curve) and a differential heat curve (DTA curve). In the DTA curve, the point at which the calorific value is maximized was defined as the PM combustion temperature. In FIG. 3, the temperature is 50.
《耐熱性の評価》
ＰＭ燃焼触媒が高温・長時間の熱履歴を受けたときの耐熱性を評価する手法として、例えば焼成により合成された複合酸化物を大気中で高温・長時間加熱する処理（以下これを「耐熱処理」という）に供し、焼成された直後と、耐熱処理を受けた後とで、ＰＭ燃焼に対する触媒活性がどの程度変化するかを見る方法が有効である。本明細書での耐熱性を評価する試料は、電気炉により空気中８００℃で１００時間にわたって熱処理（耐熱処理）することによって得た。こうして得られた触媒粒子を、合成直後のＰＭ燃焼温度の評価と同じ手法を用いて評価した。
<Evaluation of heat resistance>
As a method for evaluating the heat resistance when the PM combustion catalyst is subjected to a high temperature / long time thermal history, for example, a process of heating a composite oxide synthesized by baking at a high temperature / long time in the atmosphere (hereinafter referred to as “heat resistance”). It is effective to observe how much the catalytic activity for PM combustion changes immediately after being fired and subjected to heat resistance treatment. A sample for evaluating heat resistance in the present specification was obtained by heat treatment (heat treatment) at 800 ° C. in air for 100 hours using an electric furnace. The catalyst particles obtained in this way were evaluated using the same method as the evaluation of the PM combustion temperature immediately after synthesis.
触媒の耐熱性は、絶対値自体を評価するほか、熱処理前後における燃焼温度の悪化度合を用いて評価することができる。具体的には、以下の（１）式によった。 In addition to evaluating the absolute value itself, the heat resistance of the catalyst can be evaluated using the degree of deterioration of the combustion temperature before and after the heat treatment. Specifically, the following equation (1) was used.
（燃焼活性）悪化率（％）＝１００×（熱処理後ＣＢ燃焼開始温度−合成直後ＣＢ燃焼開始温度）／合成直後ＣＢ燃焼開始温度・・・（１）
《硫黄被毒の評価》
ＰＭ燃焼触媒が硫黄酸化物に曝された場合の耐被毒性を評価する方法としては、合成したＰＭ燃焼触媒を微量の硫黄含有ガスに所定時間曝して、触媒活性の変化を見るのが有効である。試料については下記のようにして調製したものを用いた。
(Combustion activity) deterioration rate (%) = 100 × (post-heat treatment CB combustion start temperature−combination CB combustion start temperature) / combination CB combustion start temperature (1)
<Evaluation of sulfur poisoning>
As a method of evaluating the poisoning resistance when the PM combustion catalyst is exposed to sulfur oxides, it is effective to expose the synthesized PM combustion catalyst to a small amount of sulfur-containing gas for a predetermined time and observe the change in catalyst activity. is there. A sample prepared as follows was used.
金型プレスを用いて、複合酸化物を１００ｋｇ／ｃｍ2で圧縮成形後、粉砕して、粒子径１．０〜２．０ｍｍの粒状試料を作製する。当該粒状試料３ｇを縦型管状炉に配置し、３００℃×１０時間の処理条件下で、２００ｐｐｍのＳＯ2、１０％のＯ2、１０％のＨ2Ｏ、残部Ｎ2のガスを５００ｃｃ／ｍｉｎの流量で流し、硫黄被毒処理を実施し硫黄被毒処理材を得た。硫黄被毒処理材は、乳鉢にて解粒する。その後それぞれの試料とカーボンブラックとの混合粉を作り、その中の一部を規定量分取した上、ＴＧ／ＤＴＡ装置を用いてカーボンブラック燃焼温度を求めることによってＰＭ燃焼温度を測定した。条件としては、上述の昇温速度１０℃／ｍｉｎにて常温から７００℃まで大気中で昇温し、重量減少量の測定を行うことにより求めた。 Using a mold press, the composite oxide is compression molded at 100 kg / cm 2 and then pulverized to prepare a granular sample having a particle size of 1.0 to 2.0 mm. 3 g of the granular sample was placed in a vertical tubular furnace, and 200 ppm SO 2 , 10% O 2 , 10% H 2 O, and the balance N 2 gas at 500 cc / day under processing conditions of 300 ° C. × 10 hours. It flowed with the flow volume of min, the sulfur poisoning process was implemented, and the sulfur poisoning processing material was obtained. The sulfur poisoning treatment material is pulverized in a mortar. Thereafter, a mixed powder of each sample and carbon black was prepared, a part of the powder was taken out, and a PM combustion temperature was measured by obtaining a carbon black combustion temperature using a TG / DTA apparatus. The conditions were determined by raising the temperature in the atmosphere from room temperature to 700 ° C. at the above-described temperature rise rate of 10 ° C./min and measuring the weight loss.
評価は、絶対値自体を評価するほか、硫黄被毒処理前後における燃焼温度の悪化度合を用いて評価することができる。具体的には、以下の（２）式によった。 In addition to evaluating the absolute value itself, the evaluation can be performed using the degree of deterioration of the combustion temperature before and after the sulfur poisoning treatment. Specifically, the following equation (2) was used.
（燃焼活性）悪化率（％）＝１００×（硫黄被毒処理後ＣＢ燃焼開始温度−合成直後ＣＢ燃焼開始温度）／合成直後ＣＢ燃焼開始温度・・・（２）
《触媒再生処理（硫黄パージ性）の評価》
ＰＭ燃焼触媒の硫黄脱離性を評価する手法としては、最初にＰＭ燃焼温度を測定しておき、Ｓの含有ガスに触媒を所定時間接触させる。次に短時間の間所定温度に曝すＳ脱離処理を行い、その後再度ＰＭ燃焼温度を測定し、最初のＰＭ燃焼温度と比較する方法が有効である。以下この方法を触媒再生処理という。
(Combustion activity) Deterioration rate (%) = 100 × (CB combustion start temperature after sulfur poisoning treatment−CB combustion start temperature immediately after synthesis) / CB combustion start temperature immediately after synthesis (2)
<< Evaluation of catalyst regeneration treatment (sulfur purge) >>
As a method for evaluating the sulfur desorption property of the PM combustion catalyst, first, the PM combustion temperature is measured, and the catalyst is brought into contact with the S-containing gas for a predetermined time. Next, it is effective to perform an S desorption process of exposing to a predetermined temperature for a short time, and then measuring the PM combustion temperature again and comparing it with the initial PM combustion temperature. Hereinafter, this method is referred to as catalyst regeneration treatment.
得られた試料について、上述の通り硫黄被毒処理を実施した後、５８０ｐｐｍのＮＯと２００００ｐｐｍのＣＯと１６％のＣＯ2と６２００ｐｐｍのプロピレンと１．９５％のＯ2と１０％のＨ2Ｏで残部Ｎ2のガスを流量３Ｌ／ｍｉｎの環境で６００℃の温度にて３分間処理し、触媒再生処理を行った。その後上述の方法でＰＭ燃焼温度を測定した。 The obtained sample was subjected to sulfur poisoning as described above and then 580 ppm NO, 20000 ppm CO, 16% CO 2 , 6200 ppm propylene, 1.95% O 2 and 10% H 2 O. Then, the remaining N 2 gas was treated for 3 minutes at a temperature of 600 ° C. in an environment with a flow rate of 3 L / min to perform catalyst regeneration treatment. Thereafter, the PM combustion temperature was measured by the method described above.
評価は、絶対値自体を評価するほか、硫黄被毒処理によって悪化した悪化率が、触媒再生処理によってどの程度回復するかを用いて行うこともできる。触媒再生処理後の合成直後の触媒に対する活性悪化率をまず（３）式で算出する。
（燃焼活性）悪化率（％）＝１００×（触媒再生処理後ＣＢ燃焼開始温度−合成直後ＣＢ燃焼開始温度）／合成直後ＣＢ燃焼開始温度・・・（３）
そうしたのち、硫黄被毒により悪化した悪化率がどの程度回復したかを示す再生利率を次の（６）式のように定義し算出した。
In addition to evaluating the absolute value itself, the evaluation can be performed by using how much the deterioration rate deteriorated by the sulfur poisoning treatment is recovered by the catalyst regeneration treatment. First, the activity deterioration rate for the catalyst immediately after the synthesis after the catalyst regeneration treatment is calculated by the equation (3).
(Combustion activity) Deterioration rate (%) = 100 × (CB combustion start temperature after catalyst regeneration treatment−CB combustion start temperature immediately after synthesis) / CB combustion start temperature immediately after synthesis (3)
After that, the regeneration rate indicating how much the deterioration rate deteriorated due to sulfur poisoning recovered was defined and calculated as the following equation (6).
再生率（％）＝１００×｛（２）−（３）｝／（２）・・・（４）
《吸着硫黄量の評価》
各実施例、比較例で得られた試料について、上述硫黄被毒処理、Ｓパージ処理を実施したものについて吸着硫黄量の定量分析を行った。当該定量分析には炭素・硫黄分析装置（株式会社堀場製作所製ＥＭＩＡ−２２０Ｖ）を用いることができる。
Regeneration rate (%) = 100 × {(2) − (3)} / (2) (4)
<Evaluation of adsorbed sulfur amount>
About the sample obtained by each Example and the comparative example, the quantitative analysis of the amount of adsorption | suction sulfur was performed about what implemented the above-mentioned sulfur poisoning process and S purge process. A carbon / sulfur analyzer (EMIA-220V manufactured by Horiba, Ltd.) can be used for the quantitative analysis.
《測定結果について》
実施例１〜４および比較例１〜３について、元素モル比、比表面積、結晶子径、ＣＢ燃焼温度および吸着硫黄量の結果を表１に示す。
About measurement results
Tables 1 to 4 show the results of element molar ratio, specific surface area, crystallite diameter, CB combustion temperature, and adsorbed sulfur amount for Examples 1 to 4 and Comparative Examples 1 to 3.
以下実施例について詳細に説明する。 Examples will be described in detail below.
《複合酸化物の作製》
各実施例、比較例の複合酸化物を以下のようにして作製した。
<Production of composite oxide>
The composite oxide of each example and comparative example was produced as follows.
〔実施例１〕ＣｅＰｒＺｒ（０．９０：０．０５：０．０５）の系
Ｃｅ源として硝酸セリウム六水和物（Ｃｅ（ＮＯ3）3・６Ｈ2Ｏ）、Ｐｒ源として硝酸プラセオジム六水和物（ＰｒＮＯ3）3・６Ｈ2Ｏ）、Ｚｒ源としてオキシ硝酸ジルコニウム二水和物（ＺｒＯ（ＮＯ3）2・２Ｈ2Ｏ）を用意した。
[Example 1] CePrZr (0.90: 0.05: 0.05) system Cerium nitrate hexahydrate (Ce (NO 3 ) 3 .6H 2 O) as a Ce source, praseodymium nitrate hexahydrate as a Pr source Japanese (PrNO 3 ) 3 · 6H 2 O) and zirconium oxynitrate dihydrate (ZrO (NO 3 ) 2 · 2H 2 O) were prepared as Zr sources.
これらを、Ｃｅ、Ｐｒ、Ｚｒのモル比が０．９０：０．０５：０．０５となる配合割合で混合し、Ｃｅ、Ｐｒ、Ｚｒの合計が０．８ｍｏｌ／Ｌとなるようにイオン交換水を加えて原料溶液を得た。沈澱剤として原料溶液中硝酸根の１．７当量分のＮＨ4ＯＨを原料溶液の３倍量の水溶液とし、攪拌しながら反応溶液中のＣｅ、Ｐｒ、Ｚｒの合計が０．２ｍｏｌ／Ｌとなるように（すなわち、合計液量は４Ｌであり、Ｃｅ、Ｐｒ、Ｚｒは、Ｃｅ：０．７２ｍｏｌ、Ｐｒ：０．０４ｍｏｌ、Ｚｒ：０．０４ｍｏｌ溶解している）上記原料溶液を添加し水酸化物の沈殿を得た。 These are mixed at a blending ratio of Ce, Pr, Zr of 0.90: 0.05: 0.05, and ion exchange is performed so that the total of Ce, Pr, Zr is 0.8 mol / L. Water was added to obtain a raw material solution. As a precipitant, NH 4 OH equivalent to 1.7 equivalents of the nitrate radical in the raw material solution is made into an aqueous solution three times the amount of the raw material solution, and the total of Ce, Pr, and Zr in the reaction solution is 0.2 mol / L while stirring. (That is, the total liquid volume is 4L, Ce, Pr, Zr are dissolved in Ce: 0.72 mol, Pr: 0.04 mol, Zr: 0.04 mol) An oxide precipitate was obtained.
その後、撹拌しながら５０℃で空気を充分に吹き込み、水酸化物を酸化物にして安定化させた。得られた沈殿物をろ過、水洗し、１２５℃で大気中１２時間乾燥して、乾燥粉末を得た。この乾燥粉末が「前駆体」である。次に、この前駆体を大気雰囲気下８００℃で２時間焼成してＣｅとＰｒとＺｒを主成分とする複合酸化物を得た。Ｘ線による構造解析によれば、本粉末の回折線は、ＣｅＯ2のピークに合致するものであった。 Thereafter, air was sufficiently blown at 50 ° C. with stirring to stabilize the hydroxide into an oxide. The obtained precipitate was filtered, washed with water, and dried in the air at 125 ° C. for 12 hours to obtain a dry powder. This dry powder is the “precursor”. Next, this precursor was calcined at 800 ° C. for 2 hours in an air atmosphere to obtain a composite oxide containing Ce, Pr, and Zr as main components. According to the structural analysis by X-ray, the diffraction line of the present powder coincided with the peak of CeO 2 .
〔実施例２〕ＣｅＰｒＺｒ（０．８５：０．０５：０．１０）の系
Ｃｅ、Ｐｒ、Ｚｒのモル比が０．８５：０．０５：０．１０となる配合割合で混合した以外は、実施例１と同様の操作を繰り返して、本例の複合酸化物を得た。
[Example 2] CePrZr (0.85: 0.05: 0.10) system Except that the molar ratio of Ce, Pr, Zr was mixed at a blending ratio of 0.85: 0.05: 0.10. The same operation as in Example 1 was repeated to obtain a composite oxide of this example.
〔実施例３〕ＣｅＰｒＺｒ（０．８０：０．１０：０．１０）の系
Ｃｅ、Ｐｒ、Ｚｒのモル比が０．８０：０．１０：０．１０となる配合割合で混合した以外は、実施例１と同様の操作を繰り返して、本例の複合酸化物を得た。
[Example 3] CePrZr (0.80: 0.10: 0.10) system Except that the molar ratio of Ce, Pr and Zr was mixed at a blending ratio of 0.80: 0.10: 0.10. The same operation as in Example 1 was repeated to obtain a composite oxide of this example.
〔実施例４〕ＣｅＰｒＺｒ（０．７０：０．２０：０．１０）の系
Ｃｅ、Ｐｒ、Ｚｒのモル比が０．７０：０．２０：０．１０となる配合割合で混合した以外は、実施例１と同様の操作を繰り返して、本例の複合酸化物を得た。
[Example 4] System of CePrZr (0.70: 0.20: 0.10) Except that the molar ratio of Ce, Pr and Zr was mixed at a blending ratio of 0.70: 0.20: 0.10. The same operation as in Example 1 was repeated to obtain a composite oxide of this example.
〔比較例１〕
Ｃｅ源として硝酸セリウム六水和物（Ｃｅ（ＮＯ3）3・６Ｈ2Ｏ）を用い、溶液中のＣｅ量が０．２ｍｏｌ／Ｌとなるようにイオン交換水を加えて原料溶液を得た。この溶液を撹拌しながら沈殿剤として炭酸アンモニウム水溶液を添加した。その後、３０分間撹拌を継続することにより、沈殿反応を十分に進行させた。得られた沈殿物をろ過、水洗し、１２５℃で大気中１２時間乾燥して、乾燥粉末を得た。得られた粉末を前駆体という。次に、この前駆体を大気雰囲気下８００℃で２時間焼成してＣｅＯ2を得た。
[Comparative Example 1]
Using cerium nitrate hexahydrate (Ce (NO 3 ) 3 .6H 2 O) as a Ce source, ion exchange water was added so that the amount of Ce in the solution was 0.2 mol / L to obtain a raw material solution. . While this solution was stirred, an aqueous ammonium carbonate solution was added as a precipitant. Then, precipitation reaction was fully advanced by continuing stirring for 30 minutes. The obtained precipitate was filtered, washed with water, and dried in the air at 125 ° C. for 12 hours to obtain a dry powder. The obtained powder is called a precursor. Next, this precursor was calcined at 800 ° C. for 2 hours in an air atmosphere to obtain CeO 2 .
〔比較例２〕
Ｃｅ、Ｚｒのモル比が０．７１：０．２９のＣｅＺｒ酸化物を使用した。具体的にはＣｅ源として硝酸セリウム六水和物（Ｃｅ（ＮＯ3）3・６Ｈ2Ｏ）、Ｚｒ源としてオキシ硝酸ジルコニウム二水和物（ＺｒＯ（ＮＯ3）2・２Ｈ2Ｏ）を用意した。
[Comparative Example 2]
A CeZr oxide having a Ce: Zr molar ratio of 0.71: 0.29 was used. Prepared cerium nitrate hexahydrate (Ce (NO 3) 3 · 6H 2 O), oxy zirconium nitrate dihydrate as Zr source (ZrO (NO 3) 2 · 2H 2 O) in particular as a Ce source did.
これらを、Ｃｅ、Ｚｒのモル比が０．７１：０．２９となる配合割合で混合し、Ｃｅ、Ｚｒの合計が０．８ｍｏｌ／Ｌとなるようにイオン交換水を加えて原料溶液を得た。沈澱剤として原料溶液中硝酸根の１．７当量分のＮＨ4ＯＨを原料溶液の３倍量の水溶液とし、攪拌しながら反応溶液中のＣｅ、Ｚｒの合計が０．２ｍｏｌ／Ｌとなるように上記原料溶液を添加し水酸化物の沈殿を得た。その後の工程は実施例１と同じであった。 These are mixed at a blending ratio such that the molar ratio of Ce and Zr is 0.71: 0.29, and ion-exchanged water is added so that the total of Ce and Zr is 0.8 mol / L to obtain a raw material solution. It was. As a precipitant, NH 4 OH equivalent to 1.7 equivalents of the nitrate radical in the raw material solution is made into an aqueous solution three times the amount of the raw material solution, and the total of Ce and Zr in the reaction solution is 0.2 mol / L while stirring. The above raw material solution was added to obtain a hydroxide precipitate. Subsequent steps were the same as in Example 1.
〔比較例３〕ＣｅＰｒＺｒ（０．６０：０．１０：０．３０）の系
Ｃｅ、Ｐｒ、Ｚｒのモル比が０．６０：０．１０：０．３０となる配合割合で混合した以外は、実施例１と同様の操作を繰り返して、本例の複合酸化物を得た。
[Comparative Example 3] CePrZr (0.60: 0.10: 0.30) system Except that the molar ratio of Ce, Pr and Zr was mixed at a blending ratio of 0.60: 0.10: 0.30. The same operation as in Example 1 was repeated to obtain a composite oxide of this example.
ここで、Ｃｅ／Ｐｒ＋Ｚｒは組成比をそれぞれ組み込んで計算した。例えば、実施例１ではＣｅ：０．９０、Ｐｒ：０．０５、Ｚｒ：０．０５なので、Ｃｅ／Ｐｒ＋Ｚｒ＝０．９０／（０．０５＋０．０５）＝９．０となる。また結晶子の変化率は空気中８００℃で１００時間にわたって熱処理（耐熱処理）することによって得た粉末における結晶子径と合成直後の結晶子径の比較により算出した。熱処理により結晶子径は大きくなると推定されたので、以下の計算から結晶子変化率（％）を求めた。 Here, Ce / Pr + Zr was calculated by incorporating the respective composition ratios. For example, in Example 1, since Ce: 0.90, Pr: 0.05, and Zr: 0.05, Ce / Pr + Zr = 0.90 / (0.05 + 0.05) = 9.0. Moreover, the change rate of the crystallite was calculated by comparing the crystallite diameter in the powder obtained by heat treatment (heat treatment) at 800 ° C. in air for 100 hours and the crystallite diameter immediately after synthesis. Since it was estimated that the crystallite diameter was increased by the heat treatment, the crystallite change rate (%) was obtained from the following calculation.
結晶子変化率（％）＝１００×（（熱処理後の結晶子径（ｎｍ）−合成直後の結晶子径（ｎｍ））／熱処理前の結晶子径（ｎｍ） Crystallite change rate (%) = 100 × ((crystallite diameter after heat treatment (nm) −crystallite diameter immediately after synthesis (nm)) / crystallite diameter before heat treatment (nm)
次に、比較例２では、触媒の再生率は９２．８％と高いものの、合成直後のＰＭ燃焼温度も４０３．０℃と最も高く、また熱安定性の悪化率も２１．８％と最も高い。これより、比較例２で示したＰｒといった第三成分の添加されていないＣｅ0.7Ｚｒ0.3Ｏ2は、触媒の再生率は高い値を示すものの、元々の初期活性が低いとともに、熱に対する安定性が良くないことがわかる。また、本願発明の範囲から外れるＰｒ添加量である比較例３であれば、硫黄被毒処理後の再生が十分でなく、再生率が５８．２％と最も小さい値を示し、一度劣化した触媒性能は回復しづらいことを示す。 Next, in Comparative Example 2, although the catalyst regeneration rate was as high as 92.8%, the PM combustion temperature immediately after synthesis was the highest at 403.0 ° C., and the deterioration rate of thermal stability was the highest at 21.8%. high. Accordingly, Ce 0.7 Zr 0.3 O 2 to which no third component such as Pr shown in Comparative Example 2 is added shows a high value of the catalyst regeneration rate, but has a low initial initial activity and stability to heat. It turns out that is not good. Further, in Comparative Example 3 in which the amount of Pr added is out of the scope of the present invention, regeneration after sulfur poisoning treatment is not sufficient, and the regeneration rate shows the smallest value of 58.2%, and once deteriorated catalyst Performance indicates that it is difficult to recover.
表１に示した結晶子径の値を見ると、比較例２，３は合成直後の結晶子径が小さく、実施例は比較的大きい値を示している。比較的組成系の近接した実施例４と比較例３を対比すると、熱処理前後の変化率が比較例３の方が大きくなっており、粒子内における結晶成長が進んでいることを示唆する結果になっている。この二者間において、大きく触媒の再生性能に違いが出ており、このわずかな組成間で触媒の性質が劇的に変化していることがわかる。 Looking at the crystallite diameter values shown in Table 1, Comparative Examples 2 and 3 have small crystallite diameters immediately after synthesis, and the Examples show relatively large values. When Example 4 and Comparative Example 3 having relatively close compositional systems are compared, the rate of change before and after the heat treatment is larger in Comparative Example 3, which suggests that crystal growth is progressing in the grains. It has become. There is a large difference in the regeneration performance of the catalyst between the two, and it can be seen that the properties of the catalyst change dramatically between these slight compositions.
絶対値の比較において本発明の複合酸化物のＰＭ燃焼温度特性は、合成直後のＣＢ燃焼温度が３５０℃程度と低く、かつ耐熱処理後のＣＢ燃焼温度の上昇が２０℃以下と小さくなっている。すなわち、初期の活性が高く、かつ耐熱処理による劣化が抑えられていると言える。一方、比較例はどれも耐熱処理後のＣＢ燃焼温度は合成直後より２０℃以上高く、耐熱性に劣っていることがわかる。 In the comparison of absolute values, the PM combustion temperature characteristics of the composite oxide of the present invention are as follows: the CB combustion temperature immediately after synthesis is as low as about 350 ° C., and the increase in CB combustion temperature after heat treatment is as low as 20 ° C. or less. . That is, it can be said that the initial activity is high and the deterioration due to the heat-resistant treatment is suppressed. On the other hand, in all of the comparative examples, the CB combustion temperature after the heat treatment is 20 ° C. or higher immediately after the synthesis, indicating that the heat resistance is poor.
次に、硫黄含有ガスに１０時間曝された後のＣＢ燃焼温度（「硫黄劣化処理後」参照）は、合成処理直後と比較して、実施例では、１１０℃以下の悪化に抑制されているのに対して、比較例は１３０℃以上悪化している。 Next, the CB combustion temperature after being exposed to a sulfur-containing gas for 10 hours (see “after sulfur degradation treatment”) is suppressed to a deterioration of 110 ° C. or less in the examples as compared to immediately after the synthesis treatment. On the other hand, the comparative example has deteriorated 130 degreeC or more.
次に１０時間硫黄含有ガスで被毒された状態からの触媒再生性（「触媒再生処理後」参照）では、上述の６００℃３分の触媒再生処理で、実施例は合成処理直後のＣＢ燃焼温度に対してほぼ３０℃高くなる程度の水準にまで回復した。一方、比較例１および３は、約６０℃高くなる程度の水準までしか回復しなかった。これはより低い触媒再生温度で、しかもより効果的に触媒活性を回復することができることを示している。なお、比較例２は、合成処理直後より１０℃高い劣化まで回復したが、合成処理直後のＣＢ燃焼温度がそもそも高く、もともと初期における活性が低いものである。 Next, for catalyst regeneration from a state poisoned with sulfur-containing gas for 10 hours (see “After catalyst regeneration process”), the catalyst regeneration process is performed at 600 ° C. for 3 minutes, and the example is CB combustion immediately after the synthesis process. It recovered to a level of about 30 ° C. higher than the temperature. On the other hand, Comparative Examples 1 and 3 recovered only to a level of about 60 ° C. higher. This indicates that the catalyst activity can be recovered more effectively at a lower catalyst regeneration temperature. In Comparative Example 2, the deterioration was recovered to 10 ° C. higher immediately after the synthesis process, but the CB combustion temperature immediately after the synthesis process was originally high, and originally the activity at the initial stage was low.
次に本発明の複合酸化物へ貴金属を担持したときの効果についてＣＯガスの酸化性能のＣＯ2への転化率で確認を行った。 Next, the effect of loading a noble metal on the composite oxide of the present invention was confirmed by the conversion rate of CO gas oxidation performance to CO 2 .
〔実施例５〕
実施例３で得られた複合酸化物１０ｇを、濃度４．８４質量％硝酸パラジウム溶液０．８３ｇと純水８９．２ｇとを混合した硝酸パラジウム水溶液へ、２５℃にて６０分浸漬し、Ｐｄを含浸させた。その後減圧下８０℃にて蒸発乾固した後、１２５℃で１２時間、通風乾燥を行い、更に大気雰囲気下で８００℃、２時間熱処理して実施例５に係るＰｄ含有量０．４質量％のＰｄ担持ＣｅＰｒＺｒ複合酸化物（０．４質量％Ｐｄ／ＣｅＰｒＺｒ）を得た。
Example 5
10 g of the composite oxide obtained in Example 3 was immersed in a palladium nitrate aqueous solution obtained by mixing 0.83 g of a palladium nitrate solution with a concentration of 4.84% by mass and 89.2 g of pure water at 25 ° C. for 60 minutes, and Pd Was impregnated. Then, after evaporating to dryness at 80 ° C. under reduced pressure, it was dried by ventilation at 125 ° C. for 12 hours, and further heat-treated at 800 ° C. for 2 hours in an air atmosphere, so that the Pd content according to Example 5 was 0.4% by mass. Of Pd-supported CePrZr composite oxide (0.4 mass% Pd / CePrZr) was obtained.
〔比較例４〕
市販のγ−アルミナ（比表面積２５０ｍ2／ｇ）（ＳＡＳＯＬ社製ＰＵＲＡＬＯＸ ＳＣＦａ１４０）３０ｇを、濃度８．５質量％ジニトロジアンミン白金水溶液（田中貴金属工業（株）社製）３．６ｇと純水２８５ｇとを混合したジニトロジアンミン白金水溶液へ、２５℃にて１５時間浸漬し、γアルミナにＰｔを含浸させた。当該γアルミナを回収した後、９０℃で１２時間、通風乾燥を行い、更に大気雰囲気下で５００℃、１時間熱処理して比較例４に係るＰｔ含有量１．０質量％のＰｔ担持アルミナ（１質量％Ｐｔ／Ａｌ2Ｏ3）を得た。
[Comparative Example 4]
30 g of commercially available γ-alumina (specific surface area: 250 m 2 / g) (PURALOX SCFa140 manufactured by SASOL), 3.6 g of dinitrodiammine platinum aqueous solution (produced by Tanaka Kikinzoku Kogyo Co., Ltd.) and 285 g of pure water. Was immersed in an aqueous solution of dinitrodiammine platinum mixed at 25 ° C. for 15 hours to impregnate γ alumina with Pt. After collecting the γ-alumina, it was air-dried at 90 ° C. for 12 hours, and further heat-treated at 500 ° C. for 1 hour in an air atmosphere, and a Pt-supported alumina having a Pt content of 1.0 mass% according to Comparative Example 4 ( 1 mass% Pt / Al 2 O 3 ) was obtained.
《ガス酸化性能の測定》
ガス酸化性能としてのＣＯの酸化活性は以下のようにして測定した。実施例５、比較例４について固定床流通系反応器に０．５〜１ｍｍのペレット状にしたサンプルをそれぞれ０．４１９７ｃｃ充填した。
<Measurement of gas oxidation performance>
The oxidation activity of CO as gas oxidation performance was measured as follows. About Example 5 and Comparative Example 4, 0.4197 cc of each sample in the form of pellets of 0.5 to 1 mm was packed in a fixed bed flow system reactor.
次に２０００ｐｐｍのＣＯガス、１０％のＯ2ガス、残部Ｎ2ガスの組成のディーゼル排ガスの模擬混合ガスを室温において全ガス流量１Ｌ／分で流通させた。固定床流通系反応器の出口側では、ＣＯ濃度をＦＴ−ＩＲ（Ｔｈｅｒｍｏ ＥＬＥＣＴＲＯＮ ＣＯＲＰＯＲＡＴＩＯＮ 製 Ｎｉｃｏｌｔｅ ４７００ＦＴ−ＩＲ）によってモニタリングした。触媒充填層の温度を室温から５００℃まで昇温し、測定温度におけるＣＯ濃度からＣＯ転化率（％）を以下の（５）式により求めた。入口ＣＯ濃度は２０００ｐｐｍを用いた。
ＣＯ転化率（％）＝（入口ＣＯ濃度−出口ＣＯ濃度）×１００／入口ＣＯ濃度・・（５）
ＣＯ転化率は、入流したＣＯガスが全てＣＯ2へ転化されると１００％となる。図４の縦軸はＣＯ転化率（％）を示し、横軸は触媒温度を（℃）を示す。図４の結果から本発明の複合酸化物に少量のＰｄを担持することでＰｔ担持アルミナ以上のＣＯ酸化性能が得られること結果となった。また低温での酸化性能もあることからエンジン始動直後のＣＯ酸化性能の向上効果も期待できる。すなわち酸化触媒としての応用も見込める。さらに少量で効果が得られることよりコスト面での効果も大きい。
Next, a simulated mixed gas of diesel exhaust gas having a composition of 2000 ppm CO gas, 10% O 2 gas, and the balance N 2 gas was circulated at room temperature at a total gas flow rate of 1 L / min. On the outlet side of the fixed bed flow system reactor, the CO concentration was monitored by FT-IR (Nicolte 4700FT-IR manufactured by Thermo ELECTRON CORPORATION). The temperature of the catalyst packed bed was raised from room temperature to 500 ° C., and the CO conversion rate (%) was determined from the CO concentration at the measurement temperature by the following equation (5). The inlet CO concentration was 2000 ppm.
CO conversion rate (%) = (inlet CO concentration−outlet CO concentration) × 100 / inlet CO concentration (5)
The CO conversion rate becomes 100% when all of the incoming CO gas is converted to CO 2 . The vertical axis in FIG. 4 indicates the CO conversion (%), and the horizontal axis indicates the catalyst temperature (° C.). From the results of FIG. 4, it was found that CO oxidation performance higher than that of Pt-supported alumina was obtained by supporting a small amount of Pd on the composite oxide of the present invention. In addition, since there is an oxidation performance at low temperature, an effect of improving the CO oxidation performance immediately after starting the engine can be expected. In other words, it can be used as an oxidation catalyst. Furthermore, since the effect can be obtained in a small amount, the cost effect is also great.
以上のように本発明の排ガス浄化触媒用複合酸化物は、耐熱性が高くＳ被毒によって低下した触媒活性を低温で、しかもより効果的に復活させることができる。 As described above, the composite oxide for exhaust gas purification catalyst of the present invention has high heat resistance and can recover the catalytic activity reduced by S poisoning at a low temperature and more effectively.
本発明は、ディーゼルエンジンの排ガス浄化用フィルタ（ＤＰＦ）に好適に利用することができる。 The present invention can be suitably used for an exhaust gas purification filter (DPF) of a diesel engine.
１ ＤＰＦ
１０ エンジン側
１１ 大気開放側
１２ エンジン側壁面
１４ 大気開放側壁面
３０ エンジン側壁面に塗布されたＰＭ触媒
４０ 大気開放側壁面に塗布された白金系触媒
1 DPF
DESCRIPTION OF SYMBOLS 10 Engine side 11 Atmosphere release side 12 Engine side wall surface 14 Atmosphere release side wall surface 30 PM catalyst apply | coated to engine side wall surface 40 Platinum-type catalyst apply | coated to atmosphere open side wall surface
Claims (7)
セリウム、ＰｒおよびＺｒの元素がモル比でＣｅ：Ｐｒ：Ｚｒ＝（１−ｘ−ｙ）：ｘ：ｙ（ただし、０＜ｘ＜０．３、０＜ｙ＜０．３、０＜ｘ＋ｙ≦０．３）であり、
ＣｅＯ２の（３１１）面で測定した結晶子径が１６ｎｍ以上であり、
８００℃で大気中２時間仮焼した後の酸化物のＢＥＴ法により算出される比表面積が５０ｍ ２ ／ｇ以上であり、８００℃で大気中１００時間仮焼した（耐熱安定性評価）後の酸化物のＢＥＴ法により算出される比表面積が２９ｍ ２ ／ｇ以上を保つ性質を有する複合酸化物。 Containing cerium and Pr and Zr ,
The elements of cerium, Pr, and Zr are molar ratios of Ce: Pr : Zr = (1-xy): x: y (where 0 <x <0.3, 0 < y <0.3, 0 <x + y ≦ 0.3),
Crystallite size measured by the CeO 2 (311) plane is Ri der least 16 nm,
The specific surface area calculated by the BET method of the oxide after calcining at 800 ° C. for 2 hours in the air is 50 m 2 / g or more, and after calcining at 800 ° C. for 100 hours in the air (heat stability evaluation) composite oxide specific surface area calculated by the BET method of oxides that have a property to keep more than 29m 2 / g.
（燃焼活性）悪化率（％）＝１００×（熱処理後ＣＢ燃焼開始温度−合成直後ＣＢ燃焼開始温度）／合成直後ＣＢ燃焼開始温度・・・（１） 2. The composite oxide according to claim 1, wherein, in carbon black (CB) combustion evaluation, which is pseudo-PM before and after heat treatment, a (combustion activity) deterioration rate represented by the following formula (1) is less than 10%.
(Combustion activity) deterioration rate (%) = 100 × (post-heat treatment CB combustion start temperature−combination CB combustion start temperature) / combination CB combustion start temperature (1)
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