JP2007275709A - Wash coat slurry and method for manufacturing exhaust gas cleaning catalyst - Google Patents
Wash coat slurry and method for manufacturing exhaust gas cleaning catalyst Download PDFInfo
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- 239000002002 slurry Substances 0.000 title claims abstract description 71
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- 238000000034 method Methods 0.000 title abstract description 17
- 238000004140 cleaning Methods 0.000 title abstract description 5
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- 229910052751 metal Inorganic materials 0.000 claims description 32
- 239000002184 metal Substances 0.000 claims description 32
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- 230000003197 catalytic effect Effects 0.000 abstract description 2
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- 239000010948 rhodium Substances 0.000 description 10
- 210000002421 cell wall Anatomy 0.000 description 9
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- 238000002360 preparation method Methods 0.000 description 9
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- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 239000000243 solution Substances 0.000 description 7
- 229910052763 palladium Inorganic materials 0.000 description 6
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 5
- 239000000463 material Substances 0.000 description 5
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- 229910052703 rhodium Inorganic materials 0.000 description 5
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- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- 239000003929 acidic solution Substances 0.000 description 3
- 239000002585 base Substances 0.000 description 3
- 239000003637 basic solution Substances 0.000 description 3
- 239000002270 dispersing agent Substances 0.000 description 3
- 229930195733 hydrocarbon Natural products 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- 229910001510 metal chloride Inorganic materials 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
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- 238000004220 aggregation Methods 0.000 description 2
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- 238000000879 optical micrograph Methods 0.000 description 2
- NWAHZABTSDUXMJ-UHFFFAOYSA-N platinum(2+);dinitrate Chemical compound [Pt+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O NWAHZABTSDUXMJ-UHFFFAOYSA-N 0.000 description 2
- 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 2
- 239000012855 volatile organic compound Substances 0.000 description 2
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- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 1
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- GEIAQOFPUVMAGM-UHFFFAOYSA-N ZrO Inorganic materials [Zr]=O GEIAQOFPUVMAGM-UHFFFAOYSA-N 0.000 description 1
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- 238000001514 detection method Methods 0.000 description 1
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical compound [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 description 1
- 239000002612 dispersion medium Substances 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
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- 229920001249 ethyl cellulose Polymers 0.000 description 1
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- 238000007561 laser diffraction method Methods 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
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- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
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- 229920003169 water-soluble polymer Polymers 0.000 description 1
Landscapes
- Catalysts (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Abstract
Description
本発明は、ウォッシュコート用スラリー及びそれを用いた排ガス浄化用触媒の製造方法に関する。 The present invention relates to a slurry for washcoat and a method for producing an exhaust gas purification catalyst using the same.
自動車のエンジン等から排出される排ガスに含まれる有害物質を浄化するために、排ガス浄化用触媒が排ガス経路に配置される。排ガス浄化用触媒は、排ガスが通過する多数のセルを有するハニカム構造のモノリス基材のセル壁面に触媒層が配置されたものであり、セルを通過する排ガスと触媒とが広い接触面積で接触可能なようになっている。 In order to purify harmful substances contained in exhaust gas discharged from automobile engines and the like, an exhaust gas purification catalyst is disposed in the exhaust gas path. An exhaust gas purification catalyst is a honeycomb monolith substrate with a large number of cells through which exhaust gas passes. A catalyst layer is placed on the cell wall of the monolith substrate, and the exhaust gas passing through the cells and the catalyst can be contacted over a wide contact area. It is like that.
セル壁面の触媒層は、水を分散媒としたスラリーをウォッシュコート後、乾燥及び焼成の各工程を経て形成される。従来のウォッシュコート用スラリーは、触媒又は触媒を担持する担体としての微細な粉末（粒子径数μｍ以下）が均一に分散されたものである。例えば、平均粒子径が１〜１０μｍの担体粒子を含み粘度を１〜３００ｍＰａｓとしたスラリーを用いた排ガス浄化用触媒の製造方法が開示されている（例えば、特許文献１参照。）。
従来のウォッシュコート用スラリーでは微細な粉末を担体として用いるため、スラリー中で担体が凝集しやすく、この凝集を防ぐためにスラリーの粘度を高くする必要があった。ところが、粘度の高いスラリーを用いると、セルのコーナー部にスラリーの液だまりが形成され、コーナー部における触媒層が厚くなることがあった。触媒層が厚いと、浄化されるべき排ガスが触媒層中を拡散しにくくなるため触媒成分が有効に使われなくなり、その結果、排ガスの浄化率を向上させることが困難になる場合があった。 In conventional washcoat slurries, a fine powder is used as a carrier. Therefore, the carrier easily aggregates in the slurry, and the viscosity of the slurry needs to be increased to prevent this aggregation. However, when a slurry having a high viscosity is used, a slurry pool is formed at the corner of the cell, and the catalyst layer at the corner may be thick. If the catalyst layer is thick, the exhaust gas to be purified is less likely to diffuse through the catalyst layer, so that the catalyst component is not used effectively. As a result, it may be difficult to improve the exhaust gas purification rate.
一方、体積平均粒子径が２０〜１００μｍの大粒径の粒子状担体を用いる場合、大粒径の担体は凝集し難いので、高粘度スラリー中では粒子同士が離れてしまい、高粘度スラリーを用いて形成された触媒層中では担体粒子が不均一に配列し、安定した排ガス浄化性能を示す排ガス浄化用触媒を得ることが困難な場合があった。 On the other hand, when a large particle size carrier having a volume average particle size of 20 to 100 μm is used, the large particle size carrier is difficult to agglomerate. In some cases, it is difficult to obtain an exhaust gas purifying catalyst that shows a stable exhaust gas purifying performance because the carrier particles are non-uniformly arranged in the formed catalyst layer.
本発明は上記問題点に鑑みてなされたものであり、担体粒子の凝集を抑制できると共に担体粒子が緻密に配列した触媒層を形成可能なウォッシュコート用スラリー及びそれを用いた排ガス浄化性能に優れる排ガス浄化用触媒の製造方法を提供することを目的とする。 The present invention has been made in view of the above problems, and is capable of suppressing the aggregation of carrier particles and being excellent in exhaust gas purification performance using the slurry for wash coat capable of forming a catalyst layer in which carrier particles are densely arranged. It aims at providing the manufacturing method of the catalyst for exhaust gas purification.
即ち、本発明は、
＜１＞ 体積平均粒子径が２０〜１００μｍの担体粒子と、粘度調整剤と、溶剤と、を含有し、２５℃における粘度が５〜１０ｍＰａｓであるウォッシュコート用スラリーである。
That is, the present invention
<1> A slurry for washcoat containing carrier particles having a volume average particle diameter of 20 to 100 μm, a viscosity modifier, and a solvent, and having a viscosity at 25 ° C. of 5 to 10 mPas.
＜２＞ 前記担体粒子が、金属触媒を担持した＜１＞に記載のウォッシュコート用スラリーである。 <2> The washcoat slurry according to <1>, wherein the carrier particles carry a metal catalyst.
＜３＞ 体積平均粒子径が２０〜１００μｍの担体粒子と、粘度調整剤と、溶剤と、を含有し、２５℃における粘度が５〜１０ｍＰａｓであるウォッシュコート用スラリーをモノリス基材に導入する工程と、前記溶剤を除去して乾燥する工程と、前記担体粒子を焼成する工程と、を有する排ガス浄化用触媒の製造方法である。 <3> A step of introducing a slurry for washcoat containing carrier particles having a volume average particle diameter of 20 to 100 μm, a viscosity modifier, and a solvent and having a viscosity at 25 ° C. of 5 to 10 mPas into a monolith substrate. And a step of removing the solvent and drying, and a step of firing the carrier particles.
＜４＞ 前記担体粒子が、金属触媒を担持した＜３＞に記載の排ガス浄化用触媒の製造方法である。 <4> The method for producing an exhaust gas purifying catalyst according to <3>, wherein the carrier particles carry a metal catalyst.
本発明によれば、担体粒子が緻密に配列した触媒層を形成可能なウォッシュコート用スラリー及びそれを用いた排ガス浄化性能に優れる排ガス浄化用触媒の製造方法を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the catalyst for exhaust gas purification which is excellent in the exhaust gas purification | cleaning performance using the slurry for washcoat which can form the catalyst layer which the carrier particle arranged densely can be provided.
以下、本発明のウォッシュコート用スラリー及びそれを用いた排ガス浄化用触媒の製造方法について詳細に説明する。
＜ウォッシュコート用スラリー＞
本発明のウォッシュコート用スラリーは、体積平均粒子径が２０〜１００μｍの担体粒子と、粘度調整剤と、溶剤と、を含有し、２５℃における粘度が５〜１０ｍＰａｓのものである。
Hereinafter, the washcoat slurry of the present invention and the method for producing an exhaust gas purifying catalyst using the same will be described in detail.
<Slurry for washcoat>
The slurry for washcoat of the present invention contains carrier particles having a volume average particle diameter of 20 to 100 μm, a viscosity modifier, and a solvent, and has a viscosity at 25 ° C. of 5 to 10 mPas.
本発明者等は鋭意検討の結果、体積平均粒子径が２０〜１００μｍの担体粒子が緻密に配列された均一な触媒層を形成するには該担体粒子を含むウォッシュコート用スラリーの２５℃における粘度を５〜１０ｍＰａｓする必要があることを見いだした。ここで、本発明のウォッシュコート用スラリーの粘度が５ｍＰａｓ未満であるとスラリー中の粒子が少なく排ガス浄化用触媒の性能が低くなることがある。一方、粘度が１０ｍＰａｓよりも大きいと、モノリス基材中で粒子が密に配列せず、粒子が少なくなり排ガス浄化用触媒の性能が低くなることがある。 As a result of intensive studies, the inventors of the present invention have found that the viscosity at 25 ° C. of the slurry for washcoat containing the carrier particles in order to form a uniform catalyst layer in which carrier particles having a volume average particle diameter of 20 to 100 μm are densely arranged. It was found that 5 to 10 mPas was necessary. Here, when the viscosity of the slurry for the washcoat of the present invention is less than 5 mPas, the performance of the exhaust gas-purifying catalyst may be reduced due to a small amount of particles in the slurry. On the other hand, if the viscosity is higher than 10 mPas, the particles are not densely arranged in the monolith substrate, and the number of particles is reduced, and the performance of the exhaust gas purifying catalyst may be lowered.
本発明において、体積平均粒子径とはＪＩＳ Ｒ１６２９に準ずるレーザ回折・散乱法により測定された値をいう。また、本発明において、粘度とはＪＩＳ Ｒ１６５２に準ずるブルックフィールド形回転粘度計を用いて測定温度２５℃で測定された値をいう。 In the present invention, the volume average particle diameter is a value measured by a laser diffraction / scattering method according to JIS R1629. In the present invention, the viscosity is a value measured at a measurement temperature of 25 ° C. using a Brookfield rotary viscometer according to JIS R1652.
本発明に用いられる担体粒子の体積平均粒子径が２０μｍよりも小さいと、粘度が５〜１０ｍＰａｓの範囲では該担体粒子が二次凝集してしまい、均一な触媒層を形成することが困難になる場合がある。一方、担体粒子の体積平均粒子径が１００μｍよりも大きいと、モノリス基材のセルの目詰まりを引き起こすことがある。本発明においては、担体粒子の体積平均粒子径は、セルサイズに合わせて適宜決定すればよいが、３０〜７０μｍが好ましく、４０〜６０μｍがさらに好ましい。 If the volume average particle diameter of the carrier particles used in the present invention is smaller than 20 μm, the carrier particles will be secondary agglomerated in the range of 5 to 10 mPas, making it difficult to form a uniform catalyst layer. There is a case. On the other hand, when the volume average particle diameter of the carrier particles is larger than 100 μm, the cells of the monolith substrate may be clogged. In the present invention, the volume average particle diameter of the carrier particles may be appropriately determined according to the cell size, but is preferably 30 to 70 μm, and more preferably 40 to 60 μm.
本発明のウォッシュコート用スラリーに用いられる担体粒子は、排ガス浄化用の触媒を担持することのできるものであれば特に限定されるものではないが、Ａｌ2Ｏ3、ＳｉＯ2、ＭｇＯ、ＣｅＯ2、ＺｒＯ2、ＴｉＯ2より選択される１種、１種以上の混合物、又は１種以上よりなる複合酸化物が使用できる。 The carrier particles used in the washcoat slurry of the present invention are not particularly limited as long as they can support a catalyst for exhaust gas purification, but Al 2 O 3 , SiO 2 , MgO, CeO 2. , ZrO 2 , TiO 2 , one kind, a mixture of one or more kinds, or a composite oxide composed of one or more kinds can be used.
本発明のウォッシュコート用スラリーに用いられる粘度調整剤の具体例としては、例えば、酸、アルカリ、無機粒子分散剤、有機高分子分散剤等が挙げられる。これらの中でも酸としては酢酸が、又は無機粒子分散剤としてはゾル等が好ましい。粘度調整剤の種類及び量を適宜調整することによりウォッシュコート用スラリーの粘度を上述の範囲にすることができる。 Specific examples of the viscosity modifier used in the washcoat slurry of the present invention include acid, alkali, inorganic particle dispersant, organic polymer dispersant and the like. Among these, acetic acid is preferable as the acid, and sol is preferable as the inorganic particle dispersant. By appropriately adjusting the type and amount of the viscosity modifier, the viscosity of the washcoat slurry can be adjusted to the above range.
本発明のウォッシュコート用スラリーに用いられる溶媒としては、水、アルコール類、ケトン類、アルデヒド類等及びこれらの混合溶媒等を用いることができるが、揮発性有機化合物（ＶＯＣ）削減の観点から水を用いることが好ましい。 As the solvent used in the washcoat slurry of the present invention, water, alcohols, ketones, aldehydes, and the like, and mixed solvents thereof can be used. From the viewpoint of reducing volatile organic compounds (VOC), water is used. Is preferably used.
本発明に係る担体粒子に担持させる触媒としては、Ｐｔ（プラチナ）、Ｐｄ（パラジウム）、Ｒｈ（ロジウム）等の金属触媒が挙げられるがこれらに限定されるものではない。なお、本発明のウォッシュコート用スラリーに含まれる担体粒子は金属触媒を担持していても担持していなくてもよい。なお、触媒を担持しない場合、後述の排ガス浄化用触媒の製造方法において該担体粒子に触媒金属を担持させる工程が必要になる。 Examples of the catalyst supported on the carrier particles according to the present invention include, but are not limited to, metal catalysts such as Pt (platinum), Pd (palladium), and Rh (rhodium). The carrier particles contained in the washcoat slurry of the present invention may or may not carry a metal catalyst. When no catalyst is supported, a step of supporting the catalyst metal on the carrier particles is required in the method for producing an exhaust gas purifying catalyst described later.
ここで、金属触媒を担持した担体粒子の製造方法の概略を、Ａｌ2Ｏ3の一種であるγ−Ａｌ2Ｏ3を用いた場合を例に説明する。まず、γ−Ａｌ2Ｏ3の一次粒子又は二次粒子（担体微粒子）に金属触媒を担持させる。担持には、金属の塩化物、硝酸系、アンミン系等の塩または錯体の酸性若しくは塩基性溶液等が用いられる。これらの溶液中に担体微粒子を浸漬させることにより金属触媒を担持させることができる。 Here, an outline of the manufacturing method of the carrier particles supporting a metal catalyst, a case of using one kind is a γ-Al 2 O 3 of Al 2 O 3 as an example. First, a metal catalyst is supported on primary particles or secondary particles (carrier fine particles) of γ-Al 2 O 3 . For supporting, an acid or basic solution of a metal chloride, nitric acid-based, ammine-based salt or complex is used. The metal catalyst can be supported by immersing the carrier fine particles in these solutions.
Ｐｔ、Ｐｄ、Ｒｈの担持量は排ガス浄化用触媒に求められる性能などに鑑みて適宜決定される。Ｐｔ、Ｐｄ及び／又はＲｈを担持したγ−Ａｌ2Ｏ3の一次粒子又は二次粒子を用いてスプレードライ法、流動層法、転動法等の公知の造粒方法により金属触媒を担持した担体粒子が製造される。また、金属触媒を担持しないγ−Ａｌ2Ｏ3の一次粒子又は二次粒子を用い、上述の造粒方法により金属触媒を担持しない担体粒子を製造し、これにＰｔ、Ｐｄ及び／又はＲｈを担持させるようにしてもよい。この場合、金属の塩化物、硝酸系、アンミン系等の塩または錯体の酸性若しくは塩基性溶液等の溶液中に金属触媒を担持しない担体粒子を浸漬させてもよいし、Ｐｔ、Ｐｄ及び／又はＲｈの担持されたγ−Ａｌ2Ｏ3の一次粒子又は二次粒子の分散液中に金属触媒を担持しない担体粒子を浸漬させて担体微粒子を付着させるようにしてもよい。 The amount of Pt, Pd, and Rh supported is appropriately determined in view of performance required for the exhaust gas purifying catalyst. A metal catalyst was supported by a known granulation method such as a spray drying method, a fluidized bed method, or a rolling method using primary particles or secondary particles of γ-Al 2 O 3 supporting Pt, Pd and / or Rh. Carrier particles are produced. Further, by using primary particles or secondary particles of γ-Al 2 O 3 that do not carry a metal catalyst, carrier particles that do not carry a metal catalyst are produced by the above granulation method, and Pt, Pd, and / or Rh are added thereto. You may make it carry | support. In this case, carrier particles not supporting the metal catalyst may be immersed in a solution such as an acid or basic solution of a salt or complex of a metal chloride, nitric acid, ammine, or the like, or Pt, Pd and / or The carrier particles not supporting the metal catalyst may be immersed in a dispersion of primary particles or secondary particles of γ-Al 2 O 3 supporting Rh to adhere the carrier particles.
γ−Ａｌ2Ｏ3以外の材料を用いて担体粒子を製造する場合にも、上述と同様の方法により担体粒子を得ることができる。 Even when carrier particles are produced using a material other than γ-Al 2 O 3 , carrier particles can be obtained by the same method as described above.
本発明のウォッシュコート用スラリーには、必要に応じて有機及び／又は無機のバインダーが含まれていてもよい。有機バインダーの具体例としては、例えば、ポリビニルアルコール、ポリアクリル酸、デンプン、エチルセルロース、樹脂系エマルジョン等の水溶性高分子化合物を用いることができる。また、無機バインダーの具体例としては、Ａｌ2Ｏ3、ＳｉＯ2、ＺｒＯ2等を用いることができる。 The washcoat slurry of the present invention may contain an organic and / or inorganic binder as necessary. Specific examples of the organic binder include water-soluble polymer compounds such as polyvinyl alcohol, polyacrylic acid, starch, ethyl cellulose, and resin emulsion. As specific examples of the inorganic binder, Al 2 O 3 , SiO 2 , ZrO 2 and the like can be used.
有機バインダーは接着剤の役目を果たすため、有機バインダーを含む本発明のウォッシュコート用スラリーをモノリス基材のセル壁面に塗布した際に担体粒子をセル壁面に安定して付着させることができる。また、無機バインダーは後述する焼成工程の際に担体粒子同士の結合及び担体粒子とセル壁面との結合を媒介するため、無機バインダーが存在しない場合と比較して担体粒子を強固にセル壁面に結合させることができる。 Since the organic binder serves as an adhesive, the carrier particles can be stably attached to the cell wall surface when the washcoat slurry of the present invention containing the organic binder is applied to the cell wall surface of the monolith substrate. In addition, since the inorganic binder mediates the bonding between the carrier particles and the bonding between the carrier particles and the cell wall surface in the firing step described later, the carrier particles are firmly bonded to the cell wall surface compared to the case where no inorganic binder is present. Can be made.
＜排ガス浄化用触媒の製造方法＞
本発明の排ガス浄化用触媒の製造方法は、本発明のウォッシュコート用スラリーをモノリス基材に導入する工程（以下、「導入工程」と称することがある。）と、前記溶剤を除去して乾燥する工程（以下、「乾燥工程」と称することがある。）と、前記担体粒子を焼成する工程（以下、「焼成工程」と称することがある。）と、を有する。
<Method for producing exhaust gas purifying catalyst>
The method for producing an exhaust gas purifying catalyst of the present invention comprises a step of introducing the washcoat slurry of the present invention into a monolith substrate (hereinafter sometimes referred to as “introduction step”), and drying by removing the solvent. And a step of firing the carrier particles (hereinafter also referred to as a “firing step”).
本発明の排ガス浄化用触媒の製造方法では２５℃における粘度が５〜１０ｍＰａｓである低粘度スラリー（本発明のウォッシュコート用スラリー）を用いるため、体積平均粒子径が２０〜１００μｍの担体粒子が緻密に配列した均一な触媒層を形成することができる。また、セルのコーナー部において触媒層が厚くなるのを防ぐことができる。その結果として排ガス浄化性能に優れる排ガス浄化用触媒を得ることが可能となる。 In the method for producing an exhaust gas purifying catalyst of the present invention, a low-viscosity slurry having a viscosity at 25 ° C. of 5 to 10 mPas (a slurry for washcoat of the present invention) is used, so that carrier particles having a volume average particle diameter of 20 to 100 μm are dense. A uniform catalyst layer can be formed. Moreover, it can prevent that a catalyst layer becomes thick in the corner part of a cell. As a result, it is possible to obtain an exhaust gas purification catalyst having excellent exhaust gas purification performance.
本発明に用いられるモノリス基材としては、例えば、コージェライト（２Ａｌ2Ｏ3・５ＳｉＯ2・２ＭｇＯ）等の耐熱性セラミックスを用いて押し出し成形及び焼成を経て形成された、高気孔なセル壁がハニカム構造を形成したセラミック構造体を用いることができるがこれらに限定されるものではない。 As the monolith substrate used in the present invention, for example, a highly porous cell wall formed by extrusion molding and firing using heat-resistant ceramics such as cordierite (2Al 2 O 3 .5SiO 2 .2MgO) is used. A ceramic structure in which a honeycomb structure is formed can be used, but is not limited thereto.
本発明に係る導入工程では、モノリス基材に本発明のウォッシュコート用スラリーが導入される。モノリス基材に導入されたスラリーは表面張力によりセル内に保持される。この状態でスラリーに含まれる溶剤を除去、乾燥する（乾燥工程）。乾燥工程を経ることにより、担体粒子がセル壁面に付着する。 In the introduction step according to the present invention, the slurry for washcoat of the present invention is introduced into the monolith substrate. The slurry introduced into the monolith substrate is held in the cell by surface tension. In this state, the solvent contained in the slurry is removed and dried (drying step). Through the drying process, the carrier particles adhere to the cell wall surface.
従来の高粘度スラリーを用いた場合、高圧エアー吹き（１ＭＰａ以下）や吸引によりスラリーの液分除去を行っていたが、本発明のウォッシュコート用スラリーは従来のスラリーよりも低粘度であるため高圧エアー吹きや吸引ではセル内からほとんど排出されてしまうことがある。そこで、本発明においては１００℃以下のエアー（数ｍ3／ｍｉｎ.以下）をモノリス基材の端面に吹き付けるか、又は、吸水性の紙材をモノリス基材の端面に当接することによりスラリーの溶剤を除去することが好ましい。これにより、セル内に導入された担体粒子の量をモノリス基材に導入される担体粒子の量とすることができ、モノリス基材に担持される担体粒子の量を正確に調整することができる。また、金属触媒を担持した担体粒子を用いることにより、モノリス基材に担持される金属触媒の量を正確に調整することができる。 When conventional high-viscosity slurry is used, the slurry is removed by high-pressure air blowing (1 MPa or less) or suction. However, the washcoat slurry according to the present invention has a lower viscosity than the conventional slurry, and thus has a high pressure. When air is blown or sucked, it may be almost discharged from the cell. Therefore, in the present invention, air at a temperature of 100 ° C. or less (several m 3 / min. Or less) is blown onto the end surface of the monolith substrate, or a water-absorbing paper material is brought into contact with the end surface of the monolith substrate. It is preferable to remove the solvent. Thereby, the amount of carrier particles introduced into the cell can be made the amount of carrier particles introduced into the monolith substrate, and the amount of carrier particles carried on the monolith substrate can be adjusted accurately. . Moreover, the amount of the metal catalyst supported on the monolith substrate can be accurately adjusted by using the carrier particles supporting the metal catalyst.
セル壁面に担体粒子を付着させた後、該担体粒子を焼成させる（焼成工程）。焼成条件は、担体粒子、モノリス基材及び必要に応じて用いられる無機バインダーの種類により適宜決定される。 After the carrier particles are attached to the cell wall surface, the carrier particles are fired (firing step). Firing conditions are appropriately determined depending on the type of carrier particles, monolith substrate, and inorganic binder used as necessary.
金属触媒を担持しない担体粒子を用いた場合、焼成された担体粒子には、金属触媒が担持される（担持工程）。なお、金属触媒の担持された担体粒子を用いた場合には、当該担持工程は必要に応じて実施される。担体粒子への金属触媒の担持方法は金属触媒を担持した担体粒子の製造方法の場合と同様であり、金属の塩化物、硝酸系、アンミン系等の塩または錯体の酸性若しくは塩基性溶液等の溶液中及び／又はＰｔ、Ｐｄ及び／又はＲｈの担持された一次粒子又は二次粒子の分散液中に担体粒子が焼成されたモノリス基材を浸漬させればよい。 When carrier particles not supporting a metal catalyst are used, the metal catalyst is supported on the calcined carrier particles (supporting step). In addition, when the support particle | grains with which the metal catalyst was carry | supported is used, the said carrying | support process is implemented as needed. The method for supporting the metal catalyst on the carrier particles is the same as the method for producing the carrier particles supporting the metal catalyst, such as a metal chloride, nitric acid-based, ammine-based salt or complex acidic or basic solution, etc. What is necessary is just to immerse the monolith substrate by which the carrier particle was baked in the solution and / or the dispersion of the primary particle or the secondary particle carrying Pt, Pd and / or Rh.
以下、本発明について実施例に基づきさらに詳細に説明するが、本発明は下記実施例により限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited by the following Example.
［実施例１］
（１）金属触媒を担持した担体粒子の調製
γ−Ａｌ2Ｏ3粉末（体積平均粒子径＜０．１μｍ）をスプレードライヤーで造粒し、直径３０〜７０μｍにふるい等で分級して体積平均粒子径が５０μｍの担体粒子を得た。得られた担体粒子を、白金硝酸錯体水溶液及び硝酸ロジウム水溶液に浸漬させてＰｔ及びＲｈを各々１．０質量％及び０．５質量％該担体粒子に担持させて金属触媒を担持した担体粒子を調製した。
（２）スラリー調製
（１）の金属触媒を担持した担体粒子（以下、「触媒粒子」と称することがある。）１１０ｇ、イオン交換水８００ｇ、アルミナゾル（酢酸系、１０質量％）５ｇを混合してスラリーを調製した。このスラリーの粘度は２５℃において５ｍＰａｓであった。
（３）モノリス導入（導入工程）
モノリス基材（１Ｌ４００セル／ｉｎｃｈ2）の端面から（２）のスラリーを全量導入した。このとき、スラリーで約１００ｇ、触媒粒子で１０ｇ排出した。
（４）液分除去（乾燥工程）
次に、モノリス基材の流路方向を回転軸としてこのモノリス基材を数ｒｐｍの速さで回転させながら、８０℃のエアー（１ｍ3／ｍｉｎ．以下）をモノリス基材の端面に当ててセル内に導入し、液分を除去した。
（５）乾燥（乾燥工程）
液分除去後、１２０℃で５時間以上かけて乾燥した。
（６）焼成（焼成工程）
５００℃で２時間電気炉で焼成して排ガス浄化用触媒を得た。この排ガス浄化用触媒の触媒量は１００ｇであった。
[Example 1]
(1) Preparation of carrier particles carrying a metal catalyst γ-Al 2 O 3 powder (volume average particle diameter <0.1 μm) is granulated with a spray dryer, classified to a diameter of 30 to 70 μm with a sieve, etc., and volume average Carrier particles having a particle diameter of 50 μm were obtained. The obtained carrier particles are immersed in a platinum nitrate complex aqueous solution and a rhodium nitrate aqueous solution, and Pt and Rh are supported on 1.0% by mass and 0.5% by mass, respectively. Prepared.
(2) Preparation of slurry 110 g of carrier particles carrying the metal catalyst of (1) (hereinafter sometimes referred to as “catalyst particles”), 800 g of ion-exchanged water, and 5 g of alumina sol (acetic acid-based, 10 mass%) are mixed. A slurry was prepared. The slurry had a viscosity of 5 mPas at 25 ° C.
(3) Monolith introduction (introduction process)
The whole amount of the slurry (2) was introduced from the end face of the monolith substrate (1 L400 cell / inch 2 ). At this time, about 100 g of slurry and 10 g of catalyst particles were discharged.
(4) Liquid removal (drying process)
Next, air at 80 ° C. (1 m 3 / min. Or less) is applied to the end face of the monolith substrate while rotating the monolith substrate at a speed of several rpm with the flow direction of the monolith substrate as the rotation axis. The solution was introduced into the cell and the liquid was removed.
(5) Drying (drying process)
After removing the liquid, it was dried at 120 ° C. over 5 hours.
(6) Firing (firing process)
The catalyst for exhaust gas purification was obtained by firing in an electric furnace at 500 ° C. for 2 hours. The catalyst amount of this exhaust gas purification catalyst was 100 g.
［実施例２］
実施例１の（４）液分除去において、液分除去を吸水性の紙材（吸引用ろ紙、アドバンテック東洋製）をモノリス基材の両端面に当接させて行った以外は実施例１と同様の操作で排ガス浄化用触媒を得た。この排ガス浄化用触媒の触媒量は１００ｇであった。
[Example 2]
In Example 1 (4) liquid removal, liquid removal was performed in the same manner as in Example 1 except that water-absorbing paper material (suction filter paper, manufactured by Advantech Toyo) was brought into contact with both end faces of the monolith substrate. A catalyst for exhaust gas purification was obtained in the same manner. The catalyst amount of this exhaust gas purification catalyst was 100 g.
［実施例３］
実施例１の（４）液分除去において、液分除去をモノリス基材の流路方向を回転軸としてモノリス基材を数ｒｐｍの速さで回転させながら、吸水性の紙材をモノリス基材の両面に当てて行った以外は実施例１と同様の操作で排ガス浄化用触媒を得た。この排ガス浄化用触媒の触媒量は１００ｇであった。
[Example 3]
In (4) liquid removal in Example 1, liquid removal is carried out by rotating the monolith substrate at a speed of several rpm with the flow path direction of the monolith substrate as the rotation axis. Exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that it was carried out on both sides. The catalyst amount of this exhaust gas purification catalyst was 100 g.
［実施例４］
（１）金属触媒を担持した担体粒子の調製
実施例１と同様にして金属触媒を担持した担体粒子を調製した。
（２）スラリー調製
（１）の金属触媒を担持した担体粒子１５０ｇ、イオン交換水８００ｇ、アルミナゾル（酢酸系、１０質量％）１０ｇを混合してスラリーを調製した。このスラリーの粘度は２５℃において１０ｍＰａｓであった。
（３）モノリス導入（導入工程）
モノリス基材（１Ｌ４００セル／ｉｎｃｈ2）の端面から（２）のスラリーを全量導入した。このとき、スラリーで約１５０ｇ、触媒粒子で３０ｇ排出した。
（４）液分除去（乾燥工程）
次に、モノリス基材の流路方向を回転軸としてこのモノリス基材を数ｒｐｍの速さで回転させながら、８０℃のエアー（１ｍ3／ｍｉｎ．以下）をモノリス基材の端面に当ててセル内に導入し、液分を除去した。
（５）乾燥（乾燥工程）
液分除去後、１２０℃で５時間以上かけて乾燥した。
（６）焼成（焼成工程）
５００℃で２時間電気炉で焼成して排ガス浄化用触媒を得た。この排ガス浄化用触媒の触媒担持量は１２０ｇであった。
[Example 4]
(1) Preparation of carrier particles carrying a metal catalyst Carrier particles carrying a metal catalyst were prepared in the same manner as in Example 1.
(2) Slurry preparation A slurry was prepared by mixing 150 g of carrier particles carrying the metal catalyst of (1), 800 g of ion-exchanged water, and 10 g of alumina sol (acetic acid-based, 10% by mass). The slurry had a viscosity of 10 mPas at 25 ° C.
(3) Monolith introduction (introduction process)
The whole amount of the slurry (2) was introduced from the end face of the monolith substrate (1 L400 cell / inch 2 ). At this time, about 150 g of slurry and 30 g of catalyst particles were discharged.
(4) Liquid removal (drying process)
Next, air at 80 ° C. (1 m 3 / min. Or less) is applied to the end face of the monolith substrate while rotating the monolith substrate at a speed of several rpm with the flow direction of the monolith substrate as the rotation axis. The solution was introduced into the cell and the liquid was removed.
(5) Drying (drying process)
After removing the liquid, it was dried at 120 ° C. over 5 hours.
(6) Firing (firing process)
The catalyst for exhaust gas purification was obtained by firing in an electric furnace at 500 ° C. for 2 hours. The catalyst carrying amount of this exhaust gas purifying catalyst was 120 g.
［比較例１］
（１）金属触媒を担持した担体粒子の調製
実施例１と同様にして金属触媒を担持した担体粒子を調製した。
（２）スラリー調製
（１）の金属触媒を担持した担体粒子３００ｇ、イオン交換水６００ｇ、アルミナゾル（酢酸系、１０質量％）１００ｇを混合してスラリーを調製した。このスラリーの粘度は２５℃において３００ｍＰａｓであった。
（３）モノリス導入（導入工程）
実施例１と同様のモノリス基材を用い、該モノリス基材の端面から（２）のスラリーを全量導入した。
（４）余剰スラリーの除去
高圧エアー（０．５ＭＰａ）でブローした。このとき、スラリーで約８００ｇ、触媒粒子で２６０ｇ排出した。
その後、実施例１と同様の操作で排ガス浄化用触媒を得た。この排ガス浄化用触媒の触媒量は４０ｇであった。
[Comparative Example 1]
(1) Preparation of carrier particles carrying a metal catalyst Carrier particles carrying a metal catalyst were prepared in the same manner as in Example 1.
(2) Slurry preparation A slurry was prepared by mixing 300 g of carrier particles carrying the metal catalyst of (1), 600 g of ion-exchanged water, and 100 g of alumina sol (acetic acid-based, 10% by mass). The slurry had a viscosity of 300 mPas at 25 ° C.
(3) Monolith introduction (introduction process)
The same monolith substrate as in Example 1 was used, and the entire amount of the slurry (2) was introduced from the end surface of the monolith substrate.
(4) Removal of excess slurry Blowed with high-pressure air (0.5 MPa). At this time, about 800 g of slurry and 260 g of catalyst particles were discharged.
Thereafter, an exhaust gas purifying catalyst was obtained in the same manner as in Example 1. The catalyst amount of this exhaust gas purifying catalyst was 40 g.
［比較例２］
γ−Ａｌ2Ｏ3粉末（体積平均粒子径＜０．１μｍ）を白金硝酸錯体水溶液及び硝酸ロジウム水溶液に浸漬させてＰｔ及びＲｈを各々１．０質量％及び０．５質量％担持させた。Ｐｔ及びＲｈを担持したγ−Ａｌ2Ｏ3粉末を３０質量％、アルミナゾル（酢酸系、１０質量％）を１０質量％となるようにイオン交換水に分散させてスラリーを作成した。
このスラリーの粘度は２５℃において５００ｍＰａｓだった。このスラリーを用いた以外は比較例１と同様の操作で排ガス浄化用触媒を得た。この排ガス浄化用触媒の触媒量は１００ｇであった。なお、（４）余剰スラリーの除去では、スラリーを約６００ｇ、触媒粒子で２００ｇ排出した。
[Comparative Example 2]
γ-Al 2 O 3 powder (volume average particle diameter <0.1 μm) was immersed in an aqueous platinum nitrate complex solution and an aqueous rhodium nitrate solution to carry 1.0% by mass and 0.5% by mass of Pt and Rh, respectively. A slurry was prepared by dispersing γ-Al 2 O 3 powder supporting Pt and Rh in ion-exchanged water so as to be 30% by mass and alumina sol (acetic acid type, 10% by mass) to 10% by mass.
The viscosity of this slurry was 500 mPas at 25 ° C. Exhaust gas purification catalyst was obtained by the same operation as in Comparative Example 1 except that this slurry was used. The catalyst amount of this exhaust gas purification catalyst was 100 g. In (4) removal of surplus slurry, about 600 g of slurry and 200 g of catalyst particles were discharged.
［比較例３］
（１）金属触媒を担持した担体粒子の調製
実施例１と同様にして金属触媒を担持した担体粒子を調製した。
（２）スラリー調製
（１）の触媒粒子２００ｇ、イオン交換水７００ｇ、アルミナゾル（酢酸系、１０質量％）４０ｇを混合してスラリーを調製した。このスラリーの粘度は２５℃において２０ｍＰａｓであった。
（３）モノリス導入
モノリス基材（１Ｌ４００セル／ｉｎｃｈ2）の端面から（２）のスラリーを全量導入した。このとき、スラリーで約３００ｇ、触媒粒子で１４０ｇ排出した。
（４）液分除去
次に、モノリス基材の流路方向を回転軸としてこのモノリス基材を数ｒｐｍの速さで回転させながら、８０℃のエアー（１ｍ3／ｍｉｎ．以下）をモノリス基材の端面に当ててセル内に導入し、液分を除去した。
その後、実施例１と同様の操作で排ガス浄化用触媒を得た。この排ガス浄化用触媒の触媒量は６０ｇであった。
[Comparative Example 3]
(1) Preparation of carrier particles carrying a metal catalyst Carrier particles carrying a metal catalyst were prepared in the same manner as in Example 1.
(2) Slurry preparation A slurry was prepared by mixing 200 g of the catalyst particles of (1), 700 g of ion-exchanged water, and 40 g of alumina sol (acetic acid-based, 10% by mass). The viscosity of this slurry was 20 mPas at 25 ° C.
(3) Monolith introduction The entire amount of the slurry (2) was introduced from the end face of the monolith substrate (1L400 cell / inch 2 ). At this time, about 300 g of slurry and 140 g of catalyst particles were discharged.
(4) Liquid removal Next, air at 80 ° C. (1 m 3 / min. Or less) is supplied to the monolith base while rotating the monolith base at a speed of several rpm with the flow path direction of the monolith base as the rotation axis. The material was introduced into the cell against the end face of the material to remove the liquid.
Thereafter, an exhaust gas purifying catalyst was obtained in the same manner as in Example 1. The catalyst amount of this exhaust gas-purifying catalyst was 60 g.
［比較例４］
実施例１の（２）スラリー調製において触媒粒子の量を減らし、スラリー粘度を２５℃において２ｍＰａｓにした以外は実施例１と同様の操作で排ガス浄化用触媒を得た。この排ガス浄化用触媒の触媒量は３０ｇであった。
[Comparative Example 4]
An exhaust gas purifying catalyst was obtained in the same manner as in Example 1 except that the amount of catalyst particles was reduced in Example 2 (2) slurry preparation and the slurry viscosity was 2 mPas at 25 ° C. The catalyst amount of the exhaust gas-purifying catalyst was 30 g.
［評価］
−エージング処理−
排気量２．５Ｌのガソリンエンジンに上述の方法により得た排ガス浄化用触媒を装着し、排ガス浄化用触媒の入りガス温度６００℃で５０時間運転した。
[Evaluation]
-Aging process-
The exhaust gas purification catalyst obtained by the above-described method was mounted on a 2.5 L gasoline engine and operated at an inlet gas temperature of 600 ° C. for 50 hours.
−触媒性能−
上述のようにエージング処理後、排気量２．５Ｌのガソリンエンジンの運転条件（回転数、出力など）を制御して、排ガス浄化用触媒の入りガス温度を変化させ、排ガス出口側での炭化水素濃度が排ガス入り口側の半分になる温度（ＨＣ−Ｔ５０）を求めた。なお、炭化水素濃度はエンジン排ガス装置を用い、水素炎イオン化検出法により測定した。得られた結果を図１に示す。ＨＣ−Ｔ５０が低いほど、排ガス浄化性能に優れる。
-Catalyst performance-
After the aging treatment as described above, the operating conditions (rotation speed, output, etc.) of the gasoline engine with a displacement of 2.5L are controlled to change the inlet gas temperature of the exhaust gas purification catalyst, and the hydrocarbons on the exhaust gas outlet side The temperature (HC-T50) at which the concentration becomes half of the exhaust gas inlet side was determined. The hydrocarbon concentration was measured by a flame ionization detection method using an engine exhaust gas apparatus. The obtained results are shown in FIG. The lower the HC-T50, the better the exhaust gas purification performance.
−触媒層表面観察−
実施例４及び比較例３で得られた排ガス浄化用触媒の触媒層の表面を光学顕微鏡により撮影した。得られた結果を図２（実施例４）及び図３（比較例３）に示す。
-Catalyst layer surface observation-
The surface of the catalyst layer of the exhaust gas purifying catalyst obtained in Example 4 and Comparative Example 3 was photographed with an optical microscope. The obtained results are shown in FIG. 2 (Example 4) and FIG. 3 (Comparative Example 3).
図１から、実施例１乃至４の排ガス浄化用触媒は、比較例１乃至３の排ガス浄化用触媒と比較して触媒性能（排ガス浄化性能）に優れることがわかる。なお、比較例４の排ガス浄化用触媒については温度を上げても排ガス出口側での炭化水素濃度が排ガス入り口側の半分になることはなかった。これは、モノリス基材にコートされた触媒粒子が少ないためと推察される。 1 that the exhaust gas purifying catalysts of Examples 1 to 4 are superior in catalytic performance (exhaust gas purifying performance) as compared with the exhaust gas purifying catalysts of Comparative Examples 1 to 3. For the exhaust gas purifying catalyst of Comparative Example 4, the hydrocarbon concentration on the exhaust gas outlet side did not become half of the exhaust gas inlet side even when the temperature was raised. This is presumed to be because there are few catalyst particles coated on the monolith substrate.
図２及び図３から、比較例３に係る排ガス浄化用触媒の表面と比較して、実施例４に係る排ガス浄化用触媒の表面は触媒粒子が緻密に配列していることがわかる。 2 and 3, it can be seen that the catalyst particles are densely arranged on the surface of the exhaust gas purifying catalyst according to Example 4 as compared with the surface of the exhaust gas purifying catalyst according to Comparative Example 3.
また、実施例１乃至４では排出される触媒粒子の量が比較例１乃至３と比較して少なく、触媒粒子の使用効率が高い。 Further, in Examples 1 to 4, the amount of catalyst particles discharged is small compared to Comparative Examples 1 to 3, and the use efficiency of the catalyst particles is high.
Claims (4)
前記溶剤を除去して乾燥する工程と、
前記担体粒子を焼成する工程と、
を有する排ガス浄化用触媒の製造方法。 A step of introducing a slurry for washcoat containing carrier particles having a volume average particle diameter of 20 to 100 μm, a viscosity modifier, and a solvent and having a viscosity at 25 ° C. of 5 to 10 mPas into a monolith substrate;
Removing the solvent and drying;
Firing the carrier particles;
A method for producing an exhaust gas purifying catalyst.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013108756A1 (en) | 2012-01-20 | 2013-07-25 | トヨタ自動車株式会社 | Production method for base metal catalyst for exhaust gas purification |
| JP2014105222A (en) * | 2012-11-22 | 2014-06-09 | San Nopco Ltd | Viscosity-reducing agent, slurry for exhaust emission control catalyst and method of producing the same, and internal combustion engine |
| JP2020192524A (en) * | 2019-05-27 | 2020-12-03 | 東京濾器株式会社 | Processing method |
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2006
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2013108756A1 (en) | 2012-01-20 | 2013-07-25 | トヨタ自動車株式会社 | Production method for base metal catalyst for exhaust gas purification |
| US9050584B2 (en) | 2012-01-20 | 2015-06-09 | Toyota Jidosha Kabushiki Kabushiki Kaisha | Production method of base metal catalyst for exhaust gas purification |
| JP2014105222A (en) * | 2012-11-22 | 2014-06-09 | San Nopco Ltd | Viscosity-reducing agent, slurry for exhaust emission control catalyst and method of producing the same, and internal combustion engine |
| JP2020192524A (en) * | 2019-05-27 | 2020-12-03 | 東京濾器株式会社 | Processing method |
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