JP5939140B2 - Particulate filter with catalyst - Google Patents
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- JP5939140B2 JP5939140B2 JP2012254596A JP2012254596A JP5939140B2 JP 5939140 B2 JP5939140 B2 JP 5939140B2 JP 2012254596 A JP2012254596 A JP 2012254596A JP 2012254596 A JP2012254596 A JP 2012254596A JP 5939140 B2 JP5939140 B2 JP 5939140B2
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- 239000003054 catalyst Substances 0.000 title claims description 130
- 239000002131 composite material Substances 0.000 claims description 92
- 239000000463 material Substances 0.000 claims description 74
- 238000011144 upstream manufacturing Methods 0.000 claims description 37
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 29
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 27
- 239000010948 rhodium Substances 0.000 claims description 21
- 229910052763 palladium Inorganic materials 0.000 claims description 11
- 229910052684 Cerium Inorganic materials 0.000 claims description 10
- 229910052697 platinum Inorganic materials 0.000 claims description 8
- 229910052726 zirconium Inorganic materials 0.000 claims description 7
- 229910052703 rhodium Inorganic materials 0.000 claims description 5
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 4
- 229910052779 Neodymium Inorganic materials 0.000 claims description 3
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 3
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims description 3
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 claims description 3
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 2
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 claims description 2
- 238000002485 combustion reaction Methods 0.000 description 95
- 239000007789 gas Substances 0.000 description 68
- 239000002245 particle Substances 0.000 description 31
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 29
- 229910052760 oxygen Inorganic materials 0.000 description 29
- 239000001301 oxygen Substances 0.000 description 29
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 22
- 229910052799 carbon Inorganic materials 0.000 description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 10
- 239000000243 solution Substances 0.000 description 10
- 230000000694 effects Effects 0.000 description 8
- 230000003647 oxidation Effects 0.000 description 8
- 238000007254 oxidation reaction Methods 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 239000011148 porous material Substances 0.000 description 6
- 239000002002 slurry Substances 0.000 description 6
- 239000000446 fuel Substances 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 229910052761 rare earth metal Inorganic materials 0.000 description 5
- 230000018044 dehydration Effects 0.000 description 4
- 238000006297 dehydration reaction Methods 0.000 description 4
- 238000005192 partition Methods 0.000 description 4
- 239000004071 soot Substances 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 230000000644 propagated effect Effects 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000000635 electron micrograph Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- VQVDTKCSDUNYBO-UHFFFAOYSA-N neodymium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Nd+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VQVDTKCSDUNYBO-UHFFFAOYSA-N 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 230000002688 persistence Effects 0.000 description 2
- 239000006228 supernatant Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 229910017493 Nd 2 O 3 Inorganic materials 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000010531 catalytic reduction reaction Methods 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 210000002421 cell wall Anatomy 0.000 description 1
- 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 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 229910052878 cordierite Inorganic materials 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000008021 deposition Effects 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
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000013618 particulate matter Substances 0.000 description 1
- YWECOPREQNXXBZ-UHFFFAOYSA-N praseodymium(3+);trinitrate Chemical compound [Pr+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O YWECOPREQNXXBZ-UHFFFAOYSA-N 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 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 1
- 230000036962 time dependent Effects 0.000 description 1
Landscapes
- Processes For Solid Components From Exhaust (AREA)
- Filtering Materials (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
- Exhaust Gas After Treatment (AREA)
Description
本発明は、エンジンから排出されるパティキュレートを捕集するとともに、捕集したパティキュレートを燃焼除去するのに用いられる触媒を備えた触媒付パティキュレートフィルタに関する。 The present invention relates to a particulate filter with a catalyst provided with a catalyst used for collecting particulates discharged from an engine and burning and removing the collected particulates.
ディーゼルエンジン等の希薄燃焼エンジンを搭載した自動車の排ガス通路には、排ガス中のパティキュレート（炭素質微粒子等のＰＭ：Particulate matter）を捕集するフィルタが設けられている。このフィルタのＰＭ堆積量が多くなると、フィルタの目詰まりを招く。そのため、フィルタの前後に設けられた圧力センサの圧力差等に基づいてＰＭ堆積量を推定し、その堆積量が所定値になった時点で、エンジンの燃料噴射制御（燃料増量や後噴射等）によって、フィルタに到達する排ガスの温度を高め、ＰＭを燃焼除去するようにされている。そして、このＰＭの燃焼を促進するために、フィルタの排ガス通路壁に触媒が担持されており、特に触媒金属として白金（Ｐｔ）を担持することが行われている。 A filter for collecting particulates (PM: Particulate matter) in exhaust gas is provided in an exhaust gas passage of an automobile equipped with a lean combustion engine such as a diesel engine. When the amount of PM deposited on the filter increases, the filter is clogged. Therefore, the PM accumulation amount is estimated based on the pressure difference of the pressure sensors provided before and after the filter, and when the accumulation amount reaches a predetermined value, engine fuel injection control (fuel increase, post-injection, etc.) Thus, the temperature of the exhaust gas reaching the filter is increased, and PM is burned and removed. In order to promote the combustion of PM, a catalyst is supported on the exhaust gas passage wall of the filter, and in particular, platinum (Pt) is supported as a catalyst metal.
例えば、特許文献１には、ＰＭの燃焼速度を向上するために、フィルタの排ガス通路壁に、ジルコニウム（Ｚｒ）と、ネオジム（Ｎｄ）と、セリウム（Ｃｅ）及びＮｄ以外の希土類元素とを含有する複合酸化物粒子にＰｔを担持又はドープした触媒材を設けることが開示されている。 For example, Patent Document 1 contains zirconium (Zr), neodymium (Nd), and rare earth elements other than cerium (Ce) and Nd in the exhaust gas passage wall of the filter in order to improve the PM combustion rate. It is disclosed to provide a catalyst material in which Pt is supported or doped on the composite oxide particles.
また、特許文献２には、ＰＭの燃焼のためでなく、三元触媒、選択的触媒還元（Selective Catalytic Reduction：ＳＣＲ）触媒、又はフィルタの上流若しくは下流に配設されるディーゼル酸化触媒として、Ｐｔではなくパラジウム（Ｐｄ）をＣｅ含有複合酸化物に担持した触媒材を用いることが開示されている。 Patent Document 2 discloses Pt as a three-way catalyst, a selective catalytic reduction (SCR) catalyst, or a diesel oxidation catalyst disposed upstream or downstream of a filter, not for combustion of PM. Instead, it is disclosed that a catalyst material in which palladium (Pd) is supported on a Ce-containing composite oxide is used.
ところで、従来の触媒付きパティキュレートフィルタでは、触媒層表面のＰＭ堆積量が少ないときは、そのＰＭが比較的効率良く燃焼除去されるが、ＰＭ堆積量が多くなると、ＰＭの燃焼除去に時間がかかる傾向がみられる。その理由は、本発明者の実験・研究に基づく知見によれば、次の通りである。 By the way, in the conventional particulate filter with catalyst, when the amount of PM deposited on the surface of the catalyst layer is small, the PM is combusted and removed relatively efficiently. However, when the amount of PM deposited is large, it takes time for the PM to be removed by combustion. This tendency is seen. The reason is as follows according to findings based on experiments and research by the present inventors.
すなわち、図１のグラフは触媒層に堆積したＰＭ（図１、図３及び図５では、ＰＭを「煤」と記載している。）が燃焼していくときのＰＭ残存割合の経時変化を模式的に示す。当初はＰＭの燃焼が急速に進むが、その急速燃焼領域（例えば、ＰＭ残存割合が１００％から５０％になるまでの燃焼前期）を経た後、ＰＭの燃焼が緩慢になる緩慢燃焼領域（ＰＭ残存割合が５０％から０％になるまでの燃焼後期）に移る。この点を以下詳述する。 That is, the graph of FIG. 1 shows the change over time in the PM remaining ratio when PM deposited on the catalyst layer (PM is described as “煤” in FIGS. 1, 3, and 5) burns. This is shown schematically. Initially, the combustion of PM proceeds rapidly, but after passing through the rapid combustion region (for example, the first combustion period until the PM remaining ratio becomes 100% to 50%), the combustion of PM becomes slow (PM) It shifts to the combustion late stage until the remaining ratio becomes 50% to 0%. This point will be described in detail below.
図２の写真に示すように、燃焼当初はＰＭがフィルタの表面に担持された触媒層に接触している。このため、例えば触媒層がＣｅ含有酸化物粒子やＺｒ含有酸化物粒子を含んでいる場合、図３に模式的に示すように、それら酸化物粒子から放出される活性な内部酸素が触媒層に接触しているＰＭに高活性状態で供給される。その結果、触媒層表面のＰＭが急速に燃焼していく。 As shown in the photograph of FIG. 2, at the beginning of combustion, PM is in contact with the catalyst layer supported on the surface of the filter. For this reason, for example, when the catalyst layer contains Ce-containing oxide particles and Zr-containing oxide particles, as schematically shown in FIG. 3, active internal oxygen released from these oxide particles is generated in the catalyst layer. It is supplied in a highly active state to the contacting PM. As a result, the PM on the catalyst layer surface burns rapidly.
しかし、上述の如く、触媒層表面のＰＭが燃焼除去される結果、図４の写真に示すように、触媒層とＰＭ堆積層との間に数十μｍ程度の隙間を部分的に生ずる。そのため、図５に模式的に示すように、酸化物粒子内部から放出される活性酸素は、ごく短時間であれば活性を維持するが、ほとんどの活性酸素がＰＭに到達する前に活性が低下し、例えば、気相中の酸素と同じ通常の酸素となる。その結果、ＰＭの燃焼が緩慢になる。もちろん、図５左上及び左下に示すように排ガス中の酸素もＰＭの燃焼に寄与するが、上述の活性酸素による燃焼に比べると、その燃焼は緩慢である。 However, as described above, the PM on the surface of the catalyst layer is burned and removed. As a result, a gap of about several tens of μm is partially formed between the catalyst layer and the PM deposit layer as shown in the photograph of FIG. Therefore, as schematically shown in FIG. 5, the active oxygen released from the inside of the oxide particles maintains the activity for a very short time, but the activity decreases before most of the active oxygen reaches the PM. For example, it becomes the same normal oxygen as oxygen in the gas phase. As a result, the combustion of PM becomes slow. Of course, as shown in the upper left and lower left of FIG. 5, the oxygen in the exhaust gas also contributes to the combustion of PM, but the combustion is slower than the combustion by the active oxygen described above.
本発明は、前記の問題に鑑みてなされたものであり、その目的は、フィルタに堆積したＰＭの急速燃焼領域及び緩慢燃焼領域の双方において、その燃焼が効率良く進むようにすることにある。 The present invention has been made in view of the above problems, and an object of the present invention is to allow the combustion to proceed efficiently in both the rapid combustion region and the slow combustion region of PM deposited on the filter.
本発明者らは、前記の目的を達成するために、さらに実験・研究を進めた結果、ＰＭを燃焼するための触媒金属としてパラジウム（Ｐｄ）を用い、このＰｄを、Ｚｒと、Ｃｅ以外の希土類元素とを含むＺｒ含有複合酸化物に担持したＰｄ担持Ｚｒ含有複合酸化物を触媒材として用いることにより、白金（Ｐｔ）を担持した場合と比較して、特に急速燃焼領域におけるＰＭの燃焼速度を向上できることを見出した。さらに、緩慢燃焼領域におけるＰＭ燃焼速度をも向上できるようにするために、酸素過剰雰囲気において酸素を吸蔵し、酸素濃度が低下した際に酸素を放出する酸素吸蔵放出能を有し、反応活性が高い酸素を生成する酸素交換反応を起こすＣｅ及びＺｒを含む複合酸化物にロジウム（Ｒｈ）が含有された複合酸化物を含む触媒材を用いた。そして、フィルタの排ガス流れ方向の上流側における触媒層にＰｄ担持Ｚｒ含有複合酸化物を多く含有させ、下流側における触媒層にＲｈを含むＣｅＺｒ含有複合酸化物を多く含有させることにより、急速燃焼領域だけでなく緩慢燃焼領域におけるＰＭの燃焼性をも良好にできることを見出して本発明を完成した。 As a result of further experiments and researches to achieve the above object, the present inventors have used palladium (Pd) as a catalytic metal for burning PM, and this Pd is used in addition to Zr and Ce. Compared with the case where platinum (Pt) is supported, the Pd-supported Zr-containing composite oxide supported on a Zr-containing composite oxide containing rare earth elements is used as a catalyst material. It was found that can be improved. Furthermore, in order to improve the PM combustion rate in the slow combustion region, oxygen is stored in an oxygen-excess atmosphere, and has an oxygen storage / release capability of releasing oxygen when the oxygen concentration is reduced, and the reaction activity is high. A catalyst material containing a complex oxide containing rhodium (Rh) in a complex oxide containing Ce and Zr that causes an oxygen exchange reaction that generates high oxygen was used. The catalyst layer on the upstream side in the exhaust gas flow direction of the filter contains a large amount of Pd-supported Zr-containing composite oxide, and the catalyst layer on the downstream side contains a large amount of CeZr-containing composite oxide containing Rh, so that the rapid combustion region In addition, the present invention was completed by finding that not only the combustion property of PM in the slow combustion region can be improved.
すなわち、本発明に係る触媒付パティキュレートフィルタは、排ガス中のパティキュレートを捕集するフィルタの排ガス通路壁に、触媒層が設けられており、触媒層は、ジルコニウム（Ｚｒ）と、ネオジム（Ｎｄ）と、プラセオジム（Ｐｒ）とを含み且つセリウム（Ｃｅ）を含まないＺｒ含有複合酸化物にパラジウム（Ｐｄ）が担持された第１触媒材と、Ｃｅ及びＺｒを含むＣｅＺｒ含有複合酸化物にロジウム（Ｒｈ）が含有された第２触媒材とを含み、フィルタにおける排ガス流れ方向の上流側に設けられた触媒層は、第２触媒材よりも第１触媒材を多く含み、下流側に設けられた触媒層は、第１触媒材よりも第２触媒材を多く含むことを特徴とする。 That is, in the particulate filter with catalyst according to the present invention, a catalyst layer is provided on the exhaust gas passage wall of the filter that collects particulates in the exhaust gas, and the catalyst layer includes zirconium (Zr) and neodymium (Nd a) a first catalyst material palladium Zr-containing composite oxide not containing praseodymium (Pr) and unrealized and cerium (Ce) (Pd) is supported, in CeZr-containing composite oxide containing Ce and Zr The catalyst layer provided on the upstream side of the exhaust gas flow direction in the filter includes the first catalyst material more than the second catalyst material, and is provided on the downstream side, including the second catalyst material containing rhodium (Rh). The obtained catalyst layer contains a second catalyst material more than the first catalyst material.
Ｚｒ含有複合酸化物は、酸素吸蔵放出能を有し、イオン伝導性が高く、ＰＭ燃焼に有効に働く活性酸素を多く放出できると考えられている。このため、Ｚｒ含有複合酸化物にＰｄを担持させるとＰｄが活性の高い酸化状態に保たれ、上記の通り、特に急速燃焼領域における優れたＰＭ燃焼性能を有することとなる。また、ＣｅＺｒ含有複合酸化物は、高い酸素吸蔵放出能を有し、酸素交換反応を起こして反応活性が高い酸素を放出できると考えられている。このため、ＰＭの燃焼に伴ってその燃焼部位の酸素が局部的に消費されても、ＣｅＺｒ含有複合酸化物によって酸素が速やかに補われてＰＭ燃焼が維持される。また、Ｒｈを含むことにより酸素吸蔵放出及び酸素交換反応を促進できて、且つ、触媒と接触しないＰＭに対して、活性の持続性が高い脱離散素を供給する効果により、触媒層とＰＭとの間に隙間が形成された後の緩慢燃焼領域のＰＭ燃焼速度を特に向上できる。本発明に係る触媒付パティキュレートフィルタでは、そのフィルタの排ガス流れ方向上流側に設けられた触媒層にＰｄ担持Ｚｒ含有複合酸化物を、Ｒｈを含むＣｅＺｒ含有複合酸化物よりも多く含むように構成されている。また、下流側では、Ｒｈを含むＣｅＺｒ含有複合酸化物がＰｄ担持Ｚｒ含有複合酸化物よりも多く含まれるように構成されている。 The Zr-containing composite oxide has an oxygen storage / release ability, has high ionic conductivity, and is considered to be able to release a large amount of active oxygen that works effectively for PM combustion. For this reason, when Pd is supported on the Zr-containing composite oxide, Pd is kept in a highly active oxidation state, and as described above, it has excellent PM combustion performance particularly in the rapid combustion region. The CeZr-containing composite oxide has a high oxygen storage / release capability, and is considered to be capable of releasing oxygen having a high reaction activity by causing an oxygen exchange reaction. For this reason, even if oxygen of the combustion part is consumed locally with combustion of PM, oxygen is rapidly supplemented by CeZr containing complex oxide, and PM combustion is maintained. In addition, the inclusion of Rh can promote the oxygen storage / release and the oxygen exchange reaction, and the effect of supplying de-discrete elements with high activity persistence to PM that does not come into contact with the catalyst. In particular, the PM combustion rate in the slow combustion region after the gap is formed can be improved. In the particulate filter with catalyst according to the present invention, the catalyst layer provided upstream in the exhaust gas flow direction of the filter is configured to contain more Pd-supported Zr-containing composite oxide than CeZr-containing composite oxide containing Rh. Has been. Further, on the downstream side, the CeZr-containing composite oxide containing Rh is configured to be contained more than the Pd-supported Zr-containing composite oxide.
このため、燃焼初期に、上流では、多く含まれるＰｄ担持Ｚｒ含有複合酸化物によるＰＭの燃焼が促進され、その燃焼熱が下流にも伝播して良好な燃焼を可能とする。また、燃焼後半では、下流側に触媒と接触性が低いＰＭが残存するが、下流側はＲｈを含むＣｅＺｒ含有複合酸化物を多く含むため、持続性の高い活性酸素を多く放出できてＰＭの燃焼を促進できる。このとき、上流側では、触媒層との接触性が悪くなったＰＭが剥離して下流側に流れ込む場合もあるが、このようなＰＭもＲｈを含むＣｅＺｒ含有複合酸化物の働きにより燃焼することが可能となる。 For this reason, in the early stage of combustion, combustion of PM by the Pd-supported Zr-containing composite oxide contained in a large amount is promoted upstream, and the combustion heat is propagated downstream to enable good combustion. Further, in the latter half of combustion, PM having low contact with the catalyst remains on the downstream side, but the downstream side contains a large amount of CeZr-containing composite oxide containing Rh. Can promote combustion. At this time, the PM having poor contact with the catalyst layer may be separated on the upstream side and flow into the downstream side, but such PM is also burned by the action of the CeZr-containing composite oxide containing Rh. Is possible.
以上の通り、本発明に係る触媒付パティキュレートフィルタによると、燃焼初期の急速燃焼領域、及び燃焼後期の緩慢燃焼領域の両方で、ＰＭ燃焼速度を向上でき、その結果トータルのＰＭ燃焼速度を向上できる。そして、トータルのＰＭ燃焼速度を向上できるということは、上述したエンジン噴射制御が短時間となる、換言すると、燃料消費量が少なくなり、燃費性能が向上する。また、本発明では、触媒金属の１つとしてＰｄを用いるため、触媒金属として用いるＰｔの量を低減でき、その結果、コストの低減も可能となる。 As described above, according to the particulate filter with catalyst according to the present invention, the PM combustion rate can be improved in both the rapid combustion region in the early stage of combustion and the slow combustion region in the late stage of combustion, and as a result, the total PM combustion rate is improved. it can. The fact that the total PM combustion speed can be improved means that the engine injection control described above takes a short time, in other words, the fuel consumption is reduced, and the fuel efficiency is improved. In the present invention, since Pd is used as one of the catalyst metals, the amount of Pt used as the catalyst metal can be reduced, and as a result, the cost can be reduced.
本発明に係る触媒付パティキュレートフィルタにおいて、第１触媒材及び第２触媒材の少なくとも一方は、白金（Ｐｔ）を含むことが好ましい。このようにすると、触媒材のＰＭ燃焼性能をより向上できる。また、このとき、Ｐｔは、Ｚｒ含有複合酸化物及びＣｅＺｒ含有複合酸化物のうち少なくとも一方に担持されていることが好ましい。 In the particulate filter with catalyst according to the present invention, it is preferable that at least one of the first catalyst material and the second catalyst material contains platinum (Pt). If it does in this way, PM combustion performance of a catalyst material can be improved more. At this time, Pt is preferably supported on at least one of the Zr-containing composite oxide and the CeZr-containing composite oxide.
本発明に係るパティキュレートフィルタによると、急速燃焼領域及び緩慢燃焼領域におけるＰＭ燃焼性能を向上できるため、ＰＭの燃焼が効率良く進めることができ、燃費性能も向上できる。さらに、触媒金属として用いられるＰｔの量を低減できるため、コストを低減することも可能となる。 According to the particulate filter according to the present invention, the PM combustion performance in the rapid combustion region and the slow combustion region can be improved, so that the PM combustion can be advanced efficiently and the fuel efficiency can be improved. Furthermore, since the amount of Pt used as the catalyst metal can be reduced, the cost can also be reduced.
以下、本発明を実施するための形態を図面に基づいて説明する。以下の好ましい実施形態の説明は、本質的に例示に過ぎず、本発明、その適用物或いはその用途を制限することを意図するものでない。 Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or its application.
＜パティキュレートフィルタの構造＞
以下、ＰＭを捕集するためのパティキュレートフィルタの構造について説明する。
<Particulate filter structure>
Hereinafter, the structure of the particulate filter for collecting PM will be described.
図６はディーゼルエンジンの排ガス通路１１に配置されたパティキュレートフィルタ（以下、単に「フィルタ」という。）１０を示す。フィルタ１０よりも排ガス流の上流側の排ガス通路１１には、酸化物等からなるサポート材にＰｔ、Ｐｄ等に代表される触媒金属を担持した酸化触媒（図示省略）を配置することができる。配置される酸化触媒に、本実施形態に係る排ガス成分浄化触媒材を用いることができる。このような酸化触媒をフィルタ１０の上流側に配置するときは、該酸化触媒によって排ガス中のＨＣ、ＣＯを酸化させ、その酸化燃焼熱でフィルタ１０に流入する排ガス温度を高めてフィルタ１０を加熱することができ、ＰＭの燃焼除去に有利になる。また、ＮＯが酸化触媒でＮＯ２に酸化され、該ＮＯ２がフィルタ１０にＰＭを燃焼させる酸化剤として供給されることになる。 FIG. 6 shows a particulate filter (hereinafter simply referred to as “filter”) 10 arranged in the exhaust gas passage 11 of the diesel engine. In the exhaust gas passage 11 on the upstream side of the exhaust gas flow from the filter 10, an oxidation catalyst (not shown) in which a catalyst metal typified by Pt, Pd or the like is supported on an oxide or the like support material can be disposed. The exhaust gas component purification catalyst material according to the present embodiment can be used for the oxidation catalyst to be disposed. When such an oxidation catalyst is arranged on the upstream side of the filter 10, HC and CO in the exhaust gas are oxidized by the oxidation catalyst, and the temperature of the exhaust gas flowing into the filter 10 is increased by the oxidation combustion heat to heat the filter 10. This is advantageous for PM removal by combustion. Further, NO is oxidized to NO 2 by the oxidation catalyst, and the NO 2 is supplied to the filter 10 as an oxidant for burning PM.
図７及び図８に模式的に示すように、フィルタ１０は、ハニカム構造をなしており、互いに平行に延びる多数の排ガス通路１２、１３を備えている。すなわち、フィルタ１０は、下流端が栓１４により閉塞された排ガス流入路１２と、上流端が栓１４により閉塞された排ガス流出路１３とが交互に設けられ、排ガス流入路１２と排ガス流出路１３とは薄肉の隔壁１５を介して隔てられている。なお、図７においてハッチングを付した部分は排ガス流出路１３の上流端の栓１４を示している。 As schematically shown in FIGS. 7 and 8, the filter 10 has a honeycomb structure and includes a large number of exhaust gas passages 12 and 13 extending in parallel to each other. That is, in the filter 10, the exhaust gas inflow path 12 whose downstream end is blocked by the plug 14 and the exhaust gas outflow path 13 whose upstream end is blocked by the plug 14 are alternately provided. Is separated by a thin wall 15. In FIG. 7, hatched portions indicate the plugs 14 at the upstream end of the exhaust gas outflow passage 13.
フィルタ１０は、前記隔壁１５を含むフィルタ本体がコージェライト、ＳｉＣ、Ｓｉ３Ｎ４、サイアロン、ＡｌＴｉＯ３のような無機多孔質材料から形成されている。排ガス流入路１２内に流入した排ガスは図８において矢印で示したように周囲の隔壁１５を通って隣接する排ガス流出路１３内に流出する。すなわち、図９に示すように、隔壁１５は排ガス流入路１２と排ガス流出路１３とを連通する微小な細孔（排ガス通路）１６を有し、この細孔１６を排ガスが通る。ＰＭは主に排ガス流入路１２及び細孔１６の壁部に捕捉され堆積する。 In the filter 10, the filter main body including the partition wall 15 is formed of an inorganic porous material such as cordierite, SiC, Si 3 N 4 , sialon, or AlTiO 3 . The exhaust gas flowing into the exhaust gas inflow passage 12 flows out into the adjacent exhaust gas outflow passage 13 through the surrounding partition 15 as shown by the arrows in FIG. That is, as shown in FIG. 9, the partition wall 15 has minute pores (exhaust gas passages) 16 that connect the exhaust gas inflow passage 12 and the exhaust gas outflow passage 13, and the exhaust gas passes through the pores 16. PM is trapped and accumulated mainly in the exhaust gas inlet 12 and the walls of the pores 16.
上記フィルタ本体の排ガス通路（排ガス流入路１２、排ガス流出路１３及び細孔１６）を形成する壁面には触媒層１７が形成されている。なお、排ガス流出路１３側の壁面に触媒層を形成することは必ずしも要しない。 A catalyst layer 17 is formed on the wall surface forming the exhaust gas passage (exhaust gas inflow passage 12, exhaust gas outflow passage 13 and pore 16) of the filter body. It is not always necessary to form a catalyst layer on the wall surface on the exhaust gas outflow passage 13 side.
＜触媒材について＞
次に、本発明の実施形態に係るパティキュレートフィルタに設けられる触媒層の構成について説明する。
<About catalyst material>
Next, the configuration of the catalyst layer provided in the particulate filter according to the embodiment of the present invention will be described.
本発明者らは、Ｐｔ担持複合酸化物に代わるＰＭ燃焼性能が良好な触媒材について、実験・研究を進めた結果、Ｐｄを、Ｚｒと、Ｃｅ以外の希土類元素とを含むＺｒ含有複合酸化物に担持したＰｄ担持Ｚｒ含有複合酸化物を触媒材として用いることを見出した。ここで、Ｐｄ担持Ｚｒ含有複合酸化物と、上記Ｚｒ含有複合酸化物にＰｔを担持したＰｔ担持Ｚｒ含有複合酸化物とを用いて行ったカーボン燃焼試験及びその結果について以下に説明する。 As a result of advancing experiments and research on catalyst materials with good PM combustion performance instead of Pt-supported composite oxides, the present inventors have found that Zr-containing composite oxides containing Pd, Zr, and rare earth elements other than Ce. It was found that Pd-supported Zr-containing composite oxide supported on the catalyst was used as a catalyst material. Here, the carbon combustion test conducted using the Pd-supported Zr-containing composite oxide and the Pt-supported Zr-containing composite oxide in which Pt is supported on the Zr-containing composite oxide will be described below.
カーボン燃焼試験では、Ｐｄ担持Ｚｒ含有複合酸化物又はＰｔ担持Ｚｒ含有複合酸化物をそれぞれ触媒材として担持したサンプルフィルタを作製し、各サンプルフィルタにカーボン（カーボンブラック）を堆積させてカーボン燃焼速度を測定した。サンプルフィルタとしては、セル壁厚さ１６mil（４．０６４×１０−１ｍｍ）、１平方インチ（６４５．１６ｍｍ２）当たりのセル数１７８で、直径１７ｍｍ、長さ５０ｍｍの円筒状のＳｉＣ製ハニカム（容量１１．３ｃｃ）を用い、これに上流側と下流側とで交互になるように栓詰めしたフィルタを採用した。 In the carbon combustion test, sample filters each carrying a Pd-supported Zr-containing composite oxide or a Pt-supported Zr-containing composite oxide as a catalyst material are prepared, and carbon (carbon black) is deposited on each sample filter to increase the carbon combustion rate. It was measured. As a sample filter, a cylindrical SiC honeycomb having a cell wall thickness of 16 mil (4.064 × 10 −1 mm), 178 cells per square inch (645.16 mm 2 ), a diameter of 17 mm, and a length of 50 mm. (Capacity 11.3 cc) was used, and a filter plugged so as to alternate between the upstream side and the downstream side was adopted.
なお、カーボンの堆積は、担体容量１Ｌ当たり５ｇ／Ｌのカーボンが堆積するように行った。５ｇ／Ｌ相当のカーボンをイオン交換水中でスターラーを用いて撹拌した後、サンプルフィルタの入口側を浸漬させ、出口側からアスピレータを用いて吸引した。吸水性のシートの上に載せて余分な水分を除去した後、１５０℃、１時間の乾燥処理を行った。得られた各サンプルフィルタを模擬ガス流通反応装置に取り付け、Ｎ２ガスを流通させながらそのガス温度を上昇させた。フィルタ入口温度が５４０℃で安定した後、Ｎ２ガスから模擬排ガス（Ｏ２；７．５％，ＮＯ；３００ｐｐｍ，残Ｎ２）に切り換え、該模擬排ガスを空間速度４５０００／ｈで流した。そして、カーボンが燃焼することにより生じるＣＯ２のガス中濃度をフィルタ出口においてリアルタイムで測定した。 The carbon was deposited so that 5 g / L of carbon was deposited per 1 L of the carrier volume. After carbon equivalent to 5 g / L was stirred in ion-exchanged water using a stirrer, the inlet side of the sample filter was immersed and sucked from the outlet side using an aspirator. After removing excess water by placing on a water-absorbent sheet, a drying treatment was performed at 150 ° C. for 1 hour. Each of the obtained sample filters was attached to a simulated gas flow reactor, and the gas temperature was raised while flowing N 2 gas. After the filter inlet temperature was stabilized at 540 ° C., the simulated exhaust gas was switched from N 2 gas to simulated exhaust gas (O 2 ; 7.5%, NO; 300 ppm, remaining N 2 ), and flowed at a space velocity of 45000 / h. The concentration of CO 2 in the gas generated by the combustion of carbon was measured in real time at the filter outlet.
その結果、図１０に示すように、Ｐｄ担持Ｚｒ含有複合酸化物（Ｐｄ担持ＺｒＮｄＰｒＯｘ）は、Ｐｔ担持Ｚｒ含有複合酸化物（Ｐｔ担持ＺｒＮｄＰｒＯｘ）よりも燃焼初期における燃焼性能が極めて高いことが認められた。すなわち、触媒材として、Ｐｄ担持Ｚｒ含有複合酸化物を用いると、特に急速燃焼領域におけるＰＭ燃焼性能を向上できることが示唆された。そこで、本発明者らは、Ｐｄ担持Ｚｒ含有複合酸化物と、多量の酸素を改質（活性の持続性が高い脱離酸素を生成）できて、特に緩慢燃焼領域におけるＰＭ燃焼性能が高いＲｈを含むＣｅＺｒ含有複合酸化物とを組み合わせることにより、ＰＭ燃焼性能を向上できる触媒層を構成した。以下に、本実施形態に係る触媒層の構成について説明する。 As a result, as shown in FIG. 10, the Pd-supported Zr-containing composite oxide (Pd-supported ZrNdPrO x ) has an extremely high combustion performance at the initial stage of combustion than the Pt-supported Zr-containing composite oxide (Pt-supported ZrNdPrO x ). Admitted. That is, it was suggested that when a Pd-supported Zr-containing composite oxide is used as a catalyst material, PM combustion performance can be improved particularly in the rapid combustion region. Therefore, the present inventors can modify a large amount of oxygen with Pd-supported Zr-containing composite oxide (generate desorbed oxygen with high activity persistence), and have a high PM combustion performance particularly in a slow combustion region. In combination with a CeZr-containing composite oxide containing, a catalyst layer capable of improving PM combustion performance was constructed. Below, the structure of the catalyst layer which concerns on this embodiment is demonstrated.
図１１に示すように、本実施形態では、フィルタの排ガス通路壁における壁面（フィルタ担体２１）の表面に触媒層２２が形成されており、触媒層２２は、フィルタの排ガス流れ方向上流側に第１触媒材を含み、下流側に第２触媒材を含んでいる。上流側の第１触媒材には、Ｚｒと、Ｃｅ以外の希土類元素とを含むＺｒ含有複合酸化物２３が含まれており、Ｚｒ含有複合酸化物２３には、Ｐｄ２４が担持されている。なお、Ｚｒ含有複合酸化物２３はＣｅを含まない。一方、下流側の第２触媒材には、ＣｅとＺｒとを含むＣｅＺｒ含有複合酸化物２５が含まれており、ＣｅＺｒ含有複合酸化物２５には、Ｐｔ２６及びＲｈ２７が担持されている。 As shown in FIG. 11, in this embodiment, the catalyst layer 22 is formed on the surface of the wall surface (filter carrier 21) of the exhaust gas passage wall of the filter, and the catalyst layer 22 is disposed upstream of the filter in the exhaust gas flow direction. 1 catalyst material is included and the 2nd catalyst material is included downstream. The first catalyst material on the upstream side contains a Zr-containing composite oxide 23 containing Zr and a rare earth element other than Ce, and Pd 24 is supported on the Zr-containing composite oxide 23. The Zr-containing composite oxide 23 does not contain Ce. On the other hand, the downstream second catalyst material contains a CeZr-containing composite oxide 25 containing Ce and Zr, and Pt26 and Rh27 are supported on the CeZr-containing composite oxide 25.
なお、Ｐｔ２６は触媒層に必ずしも含まれている必要はないが、含まれている方が触媒層のＰＭ燃焼性能を向上できる。また、Ｐｔ２６は、ＣｅＺｒ含有複合酸化物２５でなく、Ｚｒ含有複合酸化物２３に担持されていてもよく、それら両方に担持されていても構わない。また、Ｒｈ２７は、ＣｅＺｒ含有複合酸化物２５に含まれていれば表面に担持されることに限らず、例えば固溶されてＣｅＺｒ含有複合酸化物２５に含まれていてもよい（ドープ型）。また、図１１では、上流側と下流側とで、第１触媒材と第２触媒材とが完全に分離しているように図示したが、上流側において第１触媒材が第２触媒材よりも多く、また、下流側において第２触媒材が第１触媒材よりも多く含まれていればよい。この条件を満たすならば、それぞれの触媒材の含有率に制限はない。また、上流側と下流側との境界は、フィルタ長に対して中間位置である必要はなく、中間位置よりも上流側又は下流側に位置していても構わない。後の実施例で示すが、上流側と下流側の境界を、例えばフィルタ上流側端面から下流側に向かってフィルタ長の１／４以上３／５以下の範囲に設定してもよい。 In addition, although Pt26 does not necessarily need to be contained in the catalyst layer, the one contained can improve the PM combustion performance of the catalyst layer. Further, Pt26 may be supported on the Zr-containing composite oxide 23 instead of the CeZr-containing composite oxide 25, or may be supported on both of them. Further, Rh27 is not limited to being supported on the surface as long as it is contained in CeZr-containing composite oxide 25, and may be, for example, dissolved in CeZr-containing composite oxide 25 (dope type). In FIG. 11, the first catalyst material and the second catalyst material are illustrated as completely separated on the upstream side and the downstream side, but the first catalyst material is more upstream than the second catalyst material on the upstream side. In addition, it is only necessary that the second catalyst material is included in the downstream side more than the first catalyst material. If this condition is satisfied, the content of each catalyst material is not limited. Further, the boundary between the upstream side and the downstream side does not have to be an intermediate position with respect to the filter length, and may be located upstream or downstream of the intermediate position. As shown in a later embodiment, the boundary between the upstream side and the downstream side may be set, for example, in a range from ¼ to 3/5 of the filter length from the upstream end face of the filter toward the downstream side.
このような触媒層２２は、多量の活性酸素を保持して放出できる第１触媒材がフィルタの排ガス流れ方向上流側に多く含まれるため、上流側で急速燃焼領域（燃焼初期）のＰＭ燃焼を促進できて、その燃焼熱が下流にも伝播して、下流のＰＭ燃焼をも促進できる。また、酸素交換反応により改質（活性の持続性が高い脱離酸素を生成）できる第２触媒材が排ガス流れ方向下流側に多く含まれるため、緩慢燃焼領域（燃焼後半）において触媒層との接触性が低いＰＭの燃焼を促進でき、さらに、上流側で触媒層との接触性が悪化したＰＭが剥離して下流側に流れ込んだものについても燃焼を促進できる。その結果、トータルのＰＭ燃焼速度を向上できる。 Since such a catalyst layer 22 contains a large amount of the first catalyst material that can hold and release a large amount of active oxygen upstream in the exhaust gas flow direction of the filter, PM combustion in the rapid combustion region (initial stage of combustion) is performed upstream. The combustion heat can be propagated downstream, and downstream PM combustion can be promoted. In addition, since the second catalyst material that can be reformed by oxygen exchange reaction (generates desorbed oxygen having a high activity sustainability) is contained in the downstream side in the exhaust gas flow direction, Combustion of PM with low contactability can be promoted, and combustion can also be promoted with respect to PM that has deteriorated contactability with the catalyst layer on the upstream side and flows into the downstream side. As a result, the total PM combustion rate can be improved.
＜触媒材の調製方法＞
次に、本発明の実施形態に係るパティキュレートフィルタに設けられる触媒材の調製方法について説明する。ここでは、Ｚｒと、Ｃｅ以外の希土類元素とを含むＺｒ含有複合酸化物として、ＺｒＮｄＰｒ複合酸化物の調製方法について説明する。
<Method for preparing catalyst material>
Next, a method for preparing a catalyst material provided in the particulate filter according to the embodiment of the present invention will be described. Here, a method for preparing a ZrNdPr composite oxide as a Zr-containing composite oxide containing Zr and a rare earth element other than Ce will be described.
まず、オキシ硝酸ジルコニル溶液と硝酸ネオジム６水和物と硝酸プラセオジムとをイオン交換水に溶かす。この硝酸塩溶液に２８質量％アンモニア水の８倍希釈液を混合して中和させることにより、ＺｒＮｄＰｒ複合酸化物の前駆体（共沈体）を得る。この共沈物を遠心分離し、上澄み液を除去する脱水操作と、イオン交換水を加えて撹拌する水洗操作とを交互に必要回数繰り返す。最終的に脱水を行った後の共沈物を、大気中において１５０℃で一昼夜乾燥させた後、ボールミルにより平均粒子径１００ｎｍ程度まで粉砕した。その後、大気中において５００℃で２時間焼成することによりＺｒＮｄＰｒ複合酸化物粒子材を得ることができる。 First, a zirconyl oxynitrate solution, neodymium nitrate hexahydrate, and praseodymium nitrate are dissolved in ion-exchanged water. This nitrate solution is mixed with an 8-fold diluted solution of 28% by mass ammonia water for neutralization to obtain a ZrNdPr composite oxide precursor (coprecipitate). This coprecipitate is centrifuged, and the dehydration operation for removing the supernatant and the water washing operation for adding ion-exchanged water and stirring are repeated alternately as many times as necessary. The coprecipitate after the final dehydration was dried in the atmosphere at 150 ° C. for a whole day and night, and then pulverized to a mean particle diameter of about 100 nm by a ball mill. Then, a ZrNdPr composite oxide particle material can be obtained by firing at 500 ° C. for 2 hours in the air.
次に、ＣｅとＺｒとを含み、さらにＲｈを含有する複合酸化物として、ＲｈドープＣｅＺｒＮｄ複合酸化物の調製方法について説明する。 Next, a method for preparing an Rh-doped CeZrNd composite oxide as a composite oxide containing Ce and Zr and further containing Rh will be described.
まず、硝酸セリウム６水和物とオキシ硝酸ジルコニル溶液と硝酸ネオジム６水和物と硝酸ロジウム溶液とをイオン交換水に溶かす。この硝酸塩溶液に２８質量％アンモニア水の８倍希釈液を混合して中和させることにより、共沈物を得る。この共沈物を含む溶液を遠心分離器にかけて上澄み液を除去する脱水操作と、イオン交換水を加えて撹拌する水洗操作とを交互に必要回数繰り返す。最終的に脱水を行った後の共沈物を、大気中において１５０℃で一昼夜乾燥させた後、ボールミルにより平均粒子径１００ｎｍ程度まで粉砕した。その後、大気中において５００℃で２時間焼成することによりＲｈドープＣｅＺｒＮｄ複合酸化物粒子材を得ることができる。 First, cerium nitrate hexahydrate, zirconyl oxynitrate solution, neodymium nitrate hexahydrate, and rhodium nitrate solution are dissolved in ion-exchanged water. A coprecipitate is obtained by mixing and neutralizing this nitrate solution with an 8-fold diluted solution of 28% by mass ammonia water. A dehydration operation in which the solution containing the coprecipitate is centrifuged to remove the supernatant and a water washing operation in which ion-exchanged water is added and stirred are repeated alternately as many times as necessary. The coprecipitate after the final dehydration was dried in the atmosphere at 150 ° C. for a whole day and night, and then pulverized to a mean particle diameter of about 100 nm by a ball mill. Thereafter, the Rh-doped CeZrNd composite oxide particle material can be obtained by firing in the atmosphere at 500 ° C. for 2 hours.
次に、得られたＺｒＮｄＰｒ複合酸化物粒子材又はＲｈドープＣｅＺｒＮｄ複合酸化物に、Ｐｄ又はＰｔを担持する方法について説明する。 Next, a method for supporting Pd or Pt on the obtained ZrNdPr composite oxide particle material or Rh-doped CeZrNd composite oxide will be described.
まず、ＺｒＮｄＰｒ複合酸化物粒子材又はＲｈドープＣｅＺｒＮｄ複合酸化物粒子材にイオン交換水を加えてスラリー状にし、それをスターラー等により十分に撹拌する。続いて、撹拌しながらそのスラリーに所定量のジニトロジアミンＰｄ硝酸溶液、又はジニトロジアミンＰｔ硝酸溶液を滴下し、十分に撹拌する。その後、加熱しながらさらに撹拌を続けて、水分を完全に蒸発させる。蒸発後、大気中において５００℃で２時間焼成することにより、Ｐｄ又はＰｔがそれぞれの複合酸化物粒子材に担持される。 First, ion-exchanged water is added to a ZrNdPr composite oxide particle material or Rh-doped CeZrNd composite oxide particle material to form a slurry, which is sufficiently stirred with a stirrer or the like. Subsequently, a predetermined amount of dinitrodiamine Pd nitric acid solution or dinitrodiamine Pt nitric acid solution is dropped into the slurry while stirring, and sufficiently stirred. Thereafter, stirring is continued while heating to completely evaporate water. After evaporation, Pd or Pt is supported on each composite oxide particle material by firing at 500 ° C. for 2 hours in the air.
上記のようにして得られた複合酸化物粒子材に、イオン交換水及びバインダを加え、混合してスラリー状にする。このとき、フィルタの上流側及び下流側に設ける触媒材として各複合酸化物粒子材を所望の比で混合することができる。そして、フィルタの上流側に設けるためのスラリーに、フィルタの上流側を浸漬すると共に下流側からエアブローを行うことにより、スラリーが所望の長さ以上に進まないようにスラリー浸漬量を調整する。これにより、フィルタの上流側における所望の長さにのみフィルタをコーティングできる。一方、下流側へのフィルタのコーティングは、この逆を行えばよい。このようにして、フィルタに触媒材をコーティングし、乾燥させた後、５００℃で２時間焼成することにより、触媒付パティキュレートフィルタが得られる。 Ion exchange water and a binder are added to the composite oxide particle material obtained as described above and mixed to form a slurry. At this time, each composite oxide particle material can be mixed in a desired ratio as a catalyst material provided on the upstream side and downstream side of the filter. Then, by immersing the upstream side of the filter in the slurry to be provided on the upstream side of the filter and performing air blowing from the downstream side, the amount of slurry immersion is adjusted so that the slurry does not advance beyond a desired length. Thus, the filter can be coated only to a desired length on the upstream side of the filter. On the other hand, the filter coating on the downstream side may be reversed. In this way, the catalyst material is coated on the filter, dried, and then calcined at 500 ° C. for 2 hours to obtain a particulate filter with catalyst.
以下に、本発明に係る触媒付パティキュレートフィルタを詳細に説明するための実施例を示す。 Below, the Example for demonstrating in detail the particulate filter with a catalyst which concerns on this invention is shown.
本実施例では、触媒材としてＰｄ担持ＺｒＮｄＰｒ複合酸化物粒子材と、ＲｈドープＣｅＺｒＮｄ複合酸化物粒子材とを用いて、フィルタの排ガス流れ方向上流側と下流側とでそれらの含有率を変えた触媒層を用いてカーボン燃焼速度を検討した。また、比較例として、Ｐｄ担持ＺｒＮｄＰｒ複合酸化物粒子材とＲｈドープＣｅＺｒＮｄ複合酸化物粒子材とを含み、均一にコーティングされた触媒層について検討した。各実施例及び比較例の触媒層の組成について以下の表１に示す。 In this example, Pd-supported ZrNdPr composite oxide particle material and Rh-doped CeZrNd composite oxide particle material were used as the catalyst material, and their content rates were changed on the upstream side and the downstream side in the exhaust gas flow direction of the filter. Carbon burning rate was examined using the catalyst layer. As a comparative example, a uniformly coated catalyst layer including Pd-supported ZrNdPr composite oxide particle material and Rh-doped CeZrNd composite oxide particle material was examined. The composition of the catalyst layer of each example and comparative example is shown in Table 1 below.
実施例１、２及び比較例１の触媒材に含まれるＰｄ担持ＺｒＮｄＰｒ複合酸化物粒子材と、ＲｈドープＣｅＺｒＮｄ複合酸化物粒子材とは、上述の通りに調製した。実施例１では、フィルタの排ガス流れ方向上流側端部から下流側に向かってフィルタ長の４分の１の領域に、Ｐｄ担持ＺｒＮｄＰｒ複合酸化物粒子材とＲｈドープＣｅＺｒＮｄ複合酸化物粒子材とを３：２の質量比で含む触媒材をフィルタにコーティングした。さらにその下流側の４分の３の領域にＰｄ担持ＺｒＮｄＰｒ複合酸化物粒子材とＲｈドープＣｅＺｒＮｄ複合酸化物粒子材とを７：８の質量比で含む触媒材をフィルタにコーティングすることにより、サンプルフィルタ（触媒付パティキュレートフィルタ）を得た。実施例２では、フィルタの排ガス流れ方向上流側端部から下流側に向かってフィルタ長の５分の３の領域に、Ｐｄ担持ＺｒＮｄＰｒ複合酸化物粒子材とＲｈドープＣｅＺｒＮｄ複合酸化物粒子材とを２：１の質量比で含む触媒材をフィルタにコーティングした。さらにその下流側の５分の２の領域にＰｄ担持ＺｒＮｄＰｒ複合酸化物粒子材とＲｈドープＣｅＺｒＮｄ複合酸化物粒子材とを１：３の質量比で含む触媒材をフィルタにコーティングすることにより、サンプルフィルタを得た。 The Pd-supported ZrNdPr composite oxide particle material and the Rh-doped CeZrNd composite oxide particle material contained in the catalyst materials of Examples 1 and 2 and Comparative Example 1 were prepared as described above. In Example 1, the Pd-supported ZrNdPr composite oxide particle material and the Rh-doped CeZrNd composite oxide particle material are disposed in a region of a quarter of the filter length from the upstream end portion in the exhaust gas flow direction of the filter toward the downstream side. A catalyst material containing a mass ratio of 3: 2 was coated on the filter. Further, a sample containing a Pd-supported ZrNdPr composite oxide particle material and a Rh-doped CeZrNd composite oxide particle material at a mass ratio of 7: 8 is coated on the filter in a three-quarter region downstream thereof. A filter (particulate filter with catalyst) was obtained. In Example 2, the Pd-supported ZrNdPr composite oxide particle material and the Rh-doped CeZrNd composite oxide particle material are disposed in the region of three-fifths of the filter length from the upstream end portion in the exhaust gas flow direction of the filter toward the downstream side. The filter was coated with a catalyst material containing a 2: 1 mass ratio. Further, a sample containing a Pd-supported ZrNdPr composite oxide particle material and a Rh-doped CeZrNd composite oxide particle material in a mass ratio of 1: 3 is coated on the filter in a two-fifth region downstream thereof. A filter was obtained.
一方、比較例では、Ｐｄ担持ＺｒＮｄＰｒ複合酸化物粒子材と、ＲｈドープＣｅＺｒＮｄ複合酸化物粒子材とを１：１で混合してフィルタに均一にコーティングすることによりサンプルフィルタを得た。 On the other hand, in the comparative example, a sample filter was obtained by uniformly mixing the Pd-supported ZrNdPr composite oxide particle material and the Rh-doped CeZrNd composite oxide particle material at a ratio of 1: 1.
各実施例及び比較例において、サポート材（貴金属を除くＺｒ含有複合酸化物）の総量は２０ｇ／Ｌとして、ＺｒＮｄＰｒ複合酸化物とＣｅＺｒＮｄ複合酸化物との質量比は１：１とした。なお、ＺｒＮｄＰｒ複合酸化物の組成は、ＺｒＯ２：Ｎｄ２Ｏ３：Ｐｒ２Ｏ３＝７０：１２：１８（モル比）とし、ＣｅＺｒＮｄ複合酸化物の組成は、ＣｅＯ２：ＺｒＯ２：Ｎｄ２Ｏ３＝２４：７２：４（モル比）とした。また、各実施例及び比較例において、Ｐｄ及びＲｈの総貴金属量は、０．１ｇ／Ｌとし、Ｐｄ：Ｒｈを０．０９：０．０１とした。 In each example and comparative example, the total amount of the support material (Zr-containing composite oxide excluding noble metals) was 20 g / L, and the mass ratio of the ZrNdPr composite oxide and the CeZrNd composite oxide was 1: 1. The composition of the ZrNdPr composite oxide is ZrO 2 : Nd 2 O 3 : Pr 2 O 3 = 70: 12: 18 (molar ratio), and the composition of the CeZrNd composite oxide is CeO 2 : ZrO 2 : Nd 2. O 3 = 24: 72: I was 4 (molar ratio). In each example and comparative example, the total noble metal amount of Pd and Rh was 0.1 g / L, and Pd: Rh was 0.09: 0.01.
カーボンの堆積は、担体容量１Ｌ当たり５ｇ／Ｌのカーボンが堆積するように行った。５ｇ／Ｌ相当のカーボンをイオン交換水中でスターラーを用いて撹拌した後、サンプルフィルタの入口側を浸漬させ、出口側からアスピレータを用いて吸引した。吸水性のシートの上に載せて余分な水分を除去した後、１５０℃、１時間の乾燥処理を行った。 The carbon was deposited so that 5 g / L of carbon was deposited per liter of the carrier volume. After carbon equivalent to 5 g / L was stirred in ion-exchanged water using a stirrer, the inlet side of the sample filter was immersed and sucked from the outlet side using an aspirator. After removing excess water by placing on a water-absorbent sheet, a drying treatment was performed at 150 ° C. for 1 hour.
得られた各サンプルフィルタを模擬ガス流通反応装置に取り付け、Ｎ２ガスを流通させながらそのガス温度を上昇させた。フィルタ入口温度が５４０℃で安定した後、Ｎ２ガスから模擬排ガス（Ｏ２；７．５％，ＮＯ；３００ｐｐｍ，残Ｎ２）に切り換え、該模擬排ガスを空間速度４５０００／ｈで流した。そして、カーボンが燃焼することにより生じるＣＯ及びＣＯ２のガス中濃度をフィルタ出口においてリアルタイムで測定し、それらの濃度から、下記の計算式を用いて、所定時間毎に、カーボン燃焼速度（単位時間当たりのＰＭ燃焼量）を計算した。 Each of the obtained sample filters was attached to a simulated gas flow reactor, and the gas temperature was raised while flowing N 2 gas. After the filter inlet temperature was stabilized at 540 ° C., the simulated exhaust gas was switched from N 2 gas to simulated exhaust gas (O 2 ; 7.5%, NO; 300 ppm, remaining N 2 ), and flowed at a space velocity of 45000 / h. Then, the CO and CO 2 gas concentrations produced by the combustion of carbon are measured in real time at the filter outlet, and from these concentrations, the carbon combustion rate (unit time) is determined at predetermined intervals using the following formula. Per PM combustion amount) was calculated.
カーボン燃焼速度(g/h)
＝{ガス流速(L/h)×[(CO+CO２)濃度(ppm)/(1×10６)]}×12(g/mol)/22.4(L/mol)
上記所定時間毎のカーボン燃焼速度に基づいてカーボン燃焼量積算値の経時変化を求め、カーボン燃焼率が０％から５０％、５０％から９０％及び０％から９０％に達するまでに要した時間とその間のカーボン燃焼量の積算値とからカーボン燃焼速度（フィルタ１Ｌでの１分間当たりのＰＭ燃焼量(mg／min-L)）を求めた。その結果を図１２に示す。
Carbon burning rate (g / h)
= {Gas flow rate (L / h) x [(CO + CO 2 ) concentration (ppm) / (1 x 10 6 )]} x 12 (g / mol) /22.4 (L / mol)
The time required for the carbon combustion rate to reach 0% to 50%, 50% to 90%, and 0% to 90% is obtained based on the carbon combustion rate for each predetermined time. The carbon combustion rate (PM combustion amount per minute (1 mg / min-L) in the filter 1 L) was obtained from the integrated value of the carbon combustion amount in the meantime. The result is shown in FIG.
図１２に示すように、実施例１及び２と比較例１とを比較すると、触媒層の組成が全領域で同一である比較例１よりも、触媒層の組成がフィルタの排ガス流れ方向上流側と下流側とで異なる実施例１及び２の方が、明らかにＰＭ燃焼性能が優れている。これは、上述の通り、多量の活性酸素を保持して放出できるＰｄ担持ＺｒＮｄＰｒ複合酸化物がフィルタの排ガス流れ方向上流側に多く含まれるため、上流側で燃焼初期のＰＭ燃焼を促進できて、その燃焼熱が下流にも伝播して、下流のＰＭ燃焼をも促進できたためであると考えられる。また、酸素交換反応により改質できるＲｈドープＣｅＺｒＮｄ複合酸化物が排ガス流れ方向下流側に多く含まれるため、燃焼後半において触媒層との接触性が低いＰＭの燃焼を促進でき、さらに、上流側で触媒層との接触性が悪化したＰＭが剥離して下流側に流れ込んだものについても燃焼を促進でき、その結果、トータルのＰＭ燃焼速度を向上できたと考えられる。 As shown in FIG. 12, when Examples 1 and 2 and Comparative Example 1 are compared, the composition of the catalyst layer is upstream of the filter in the exhaust gas flow direction, compared to Comparative Example 1 in which the composition of the catalyst layer is the same in all regions. The first and second embodiments, which are different from each other on the downstream side, clearly have better PM combustion performance. This is because, as described above, a large amount of Pd-supported ZrNdPr composite oxide capable of holding and releasing a large amount of active oxygen is contained on the upstream side in the exhaust gas flow direction of the filter. This is considered to be because the combustion heat propagated downstream and promoted downstream PM combustion. In addition, since a large amount of Rh-doped CeZrNd composite oxide that can be modified by oxygen exchange reaction is contained on the downstream side in the exhaust gas flow direction, combustion of PM having low contact with the catalyst layer can be promoted in the latter half of combustion, Combustion can also be promoted with respect to PM in which the contact property with the catalyst layer has deteriorated and separated into the downstream side, and as a result, it is considered that the total PM combustion rate can be improved.
なお、実施例１と２とでは大きな差は認められないため、上流側と下流側との境界位置、及び上流側と下流側とにおける触媒層に含まれるＰｄ担持ＺｒＮｄＰｒ複合酸化物とＲｈドープＣｅＺｒＮｄ複合酸化物との割合を比較的自由に設定できることが認められた。 In addition, since a big difference is not recognized by Example 1 and 2, the Pd carrying | support ZrNdPr complex oxide and Rh dope CeZrNd which are contained in the catalyst layer in the upstream and downstream boundary position and the upstream and downstream sides are not seen. It was recognized that the ratio with the composite oxide can be set relatively freely.
一方、比較例１は、実施例１及び２と同等の触媒材を含むものの上流側及び下流側に同一の組成の触媒層が均一に設けられており、その結果、実施例１及び２と比較して、トータルのカーボン燃焼速度が実施例１及び２よりも低い結果を示した。 On the other hand, Comparative Example 1 contains a catalyst material equivalent to that in Examples 1 and 2, but the catalyst layers having the same composition are uniformly provided on the upstream side and the downstream side, and as a result, compared with Examples 1 and 2. As a result, the total carbon burning rate was lower than those in Examples 1 and 2.
以上の結果から、フィルタの排ガス流れ方向上流側においてＰｄ担持Ｚｒ含有複合酸化物がＲｈを含むＣｅＺｒ含有複合酸化物よりも多く含まれ、下流側においてＲｈを含むＣｅＺｒ含有複合酸化物がＰｄ担持Ｚｒ含有複合酸化物よりも多く含まれる触媒層が設けられたフィルタは、等量のＰｄ担持Ｚｒ含有複合酸化物と、Ｒｈを含むＣｅＺｒ含有複合酸化物とを含む触媒層が均一にコーティングされたフィルタよりも、ＰＭ燃焼性能を向上できることが認められた。 From the above results, the Pd-supported Zr-containing composite oxide is contained more in the upstream side in the exhaust gas flow direction of the filter than the CeZr-containing composite oxide containing Rh, and the CeZr-containing composite oxide containing Rh is downstream in the Pd-supported Zr. A filter provided with a catalyst layer containing more than the contained composite oxide is a filter in which a catalyst layer containing an equal amount of Pd-supported Zr-containing composite oxide and a CeZr-containing composite oxide containing Rh is uniformly coated It was confirmed that the PM combustion performance can be improved.
１０ フィルタ
１１ 排ガス通路
１２ 排ガス流入路（排ガス通路）
１３ 排ガス流出路（排ガス通路）
１４ 栓
１５ 隔壁
１６ 細孔（排ガス通路）
１７ 触媒層
２１ フィルタ担体
２２ 触媒層
２３ Ｚｒ含有複合酸化物
２４ パラジウム（Ｐｄ）
２５ ＣｅＺｒ含有複合酸化物
２６ 白金（Ｐｔ）
２７ ロジウム（Ｒｈ）
10 Filter 11 Exhaust gas passage 12 Exhaust gas inflow passage (exhaust gas passage)
13 Exhaust gas outflow passage (exhaust gas passage)
14 plug 15 partition 16 pore (exhaust gas passage)
17 Catalyst layer 21 Filter carrier 22 Catalyst layer 23 Zr-containing composite oxide 24 Palladium (Pd)
25 CeZr-containing composite oxide 26 Platinum (Pt)
27 Rhodium (Rh)
Claims (3)
前記触媒層は、ジルコニウム（Ｚｒ）と、ネオジム（Ｎｄ）と、プラセオジム（Ｐｒ）とを含み且つセリウム（Ｃｅ）を含まないＺｒ含有複合酸化物にパラジウム（Ｐｄ）が担持された第１触媒材と、Ｃｅ及びＺｒを含むＣｅＺｒ含有複合酸化物にロジウム（Ｒｈ）が含有された第２触媒材とを含み、
前記フィルタにおける排ガス流れ方向の上流側に設けられた前記触媒層は、前記第２触媒材よりも前記第１触媒材を多く含み、下流側に設けられた前記触媒層は、前記第１触媒材よりも前記第２触媒材を多く含むことを特徴とする触媒付パティキュレートフィルタ。 A particulate filter with a catalyst in which a catalyst layer is provided on an exhaust gas passage wall of a filter that collects particulates in exhaust gas,
The catalyst layer includes a zirconium (Zr), neodymium and (Nd), praseodymium (Pr) and the first catalyst of palladium (Pd) on Zr-containing composite oxide containing no unrealized and cerium (Ce) is supported And a second catalyst material in which rhodium (Rh) is contained in a CeZr-containing composite oxide containing Ce and Zr,
The catalyst layer provided on the upstream side in the exhaust gas flow direction of the filter contains more of the first catalyst material than the second catalyst material, and the catalyst layer provided on the downstream side includes the first catalyst material. A particulate filter with catalyst, wherein the particulate filter contains a larger amount of the second catalyst material.
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