DOC catalytic coating with high fuel oil ignition performance and preparation method thereof

Abstract

The invention discloses a DOC catalytic coating with high fuel oil ignition performance and a preparation method of the DOC catalytic coating. The catalytic coating comprises a bottom layer formed bycoating the surface of the carrier and drying and roasting and at least one upper layer coating the surface of the bottom layer, the upper layer is divided into a front section and a rear section, andnoble metals comprise Pt and Pd; the loading capacity of the noble metals on the bottom layer is 1-10g / ft < 3 >; the catalytic material is a Ce-containing material, the noble metal loading capacity of the rear section of the upper layer is 10-90g / ft3, the front section of the upper layer is a gradient coating prepared from a noble metal and a catalytic material, the noble metal content distribution of the gradient coating is gradually reduced along the circulation axial direction, and the noble metal loading capacity of the front section of the upper layer is 10-90g / ft3. According to the preparation method and the catalyst coating prepared by the preparation method, the synergistic effect of the noble metal and the catalytic material can be improved; the distribution gradient of the noblemetal on the catalyst carrier can be controlled according to a reaction functional area, so that the noble metal and the catalytic material are further well cooperated, the noble metal coating is more reasonably distributed on the carrier in a gradient manner, and the fuel ignition performance and durability of the catalyst are improved.

Description

technical field [0001] The invention belongs to the technical field of catalyst research, in particular to the field of environmental protection technology application of catalytic technology and air pollution emission control, and in particular to a DOC catalyst coating with high fuel light-off performance and a preparation method thereof. Background technique [0002] The mainstream national VI diesel vehicle exhaust after-treatment system adopts: diesel oxidation catalyst + catalytic diesel particulate filter + selective reduction catalyst + ammonia oxidation catalyst (DOC+CDPF+SCR+ASC) catalyst configuration. As the head of the system, the catalytic unit DOC, in addition to the traditional function of oxidizing HC, CO and SOF in the exhaust gas, also needs to assist the downstream CDPF passive regeneration and the rapid reaction of SCR, and oxidize NO to NO in a certain temperature range 2 ; In the National VI system, DOC assists the active regeneration of downstream CDP...

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Problems solved by technology

[0006] 1. Prior art route 1, single-layer coating with uniform distribution of noble metals: (1) noble metals are evenly distributed in the catalytic material, (2) the coating slurry is composed of one or several catalytic materials containing noble metals, (3) ) coating is evenly distributed on the catalytic carrier; its advantage is that the process is simple and can be completed in one coating, but the disadvantage is that the active elements are evenly distributed, but the exhaust gas composition and temperature are constantly changing with the radial and axial directions. Underutilized its catalytic effect

[0007] 2. Prior art route 2, layered coating: (1) noble metal is evenly distributed in the catalytic material, (2) coating slurry is composed of one or several catalytic materials containing noble metal, (3) coating 1 It is distributed on the first layer, coating 2 is distributed on the second layer, and coating 3 is distributed on the third layer...; its advantage is that the noble metal and catalytic material are combined according to the radial demand of the gas treated by the DOC, which can better play its role Catalysis, the disadvantage is that although the noble metal and the catalytic material have a gradient change in the radial direction, they have not yet fully exerted the full synergistic effect of the axial upstream and downstream catalysts

[0008] 3. Prior art route 3, segmented coating: (1) noble metals are uniformly distributed in the catalytic material, (2) coating slurry is composed of one or several catalytic materials containing noble metals, (3) coating 1 It is distributed at the front end, coating 2 is distributed at the middle end, and coating 3 is distributed at the rear end...; its advantage lies in the combination of noble metals and catalytic materials according to the axial requirements of the gas treated by DOC, which can better play its catalytic role, and its disadvantages The reason is that the concentration gradient of the noble metal presents a jumping distribution, which is quite different from the actual reactant concentration distribution trend, and its catalyst active center cannot be fully utilized.

[0009] 4. Prior art route 4, combining layered and segmented coatings: (1) noble metals are evenly distributed in the catalytic material, (2) the coating slurry is composed of one or several catalytic materials containing noble metals, (3) ) Coating 1 is distributed on the bottom layer, Coating 2 is distributed on the front end, and Coating 3 is distributed on the rear end...; its advantage is that it combines the advantages of Route 2 and Route 3, which can better play the catalytic performance of the catalyst. The disadvantage is that precious metals and The catalytic material has a large mutation gradient and cannot fully exert its catalytic effect

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