Ceramic filter and ceramic filter with catalyst

Abstract

The present invention provides a catalyst-loaded ceramic filter that is made of a ceramic material capable of directly supporting a catalyst component thereon, and is capable of providing early activation of the catalyst with a low coefficient of thermal expansion and light weight, without compromising the high porosity of the filter substrate. According to the present invention, a catalyst-loaded ceramic filter is made of a ceramic material of which one or more kinds of element among the constituent elements thereof is substituted with element other than the constituent elements, for example a ceramic material with a part of Si or other elements included in cordierite is substituted with W or Co, as a filter substrate of honeycomb structure having a number of cells separated by porous walls, and supporting a catalyst such as a noble metal directly on the W. This constitution has advantages that there occurs no increase in the pressure loss, coefficient of thermal expansion or weight due to the formation of a coating layer, and that the heat capacity remains low.

Description

field of invention [0001] The present invention relates to a ceramic filter for trapping particulate matter contained in exhaust gas discharged from an automobile engine and a catalyst-loaded ceramic filter having a catalytic function to remove the particulate matter. Background technique [0002] It is practiced to trap fine particles such as soot (particulate matter) contained in the exhaust gas emitted from a diesel engine by a particulate trap filter (PDF) installed in the exhaust pipe. The particle trapping filter uses a honeycomb structure made of a porous ceramic material having a large number of cells in a direction parallel to the flow of exhaust gas as a filter base material. The interconnected cells are separated by porous walls, and the end face of each cell on the inlet or outlet side is staggeredly plugged so that the particulate matter was captured. [0003] The trapped particulate matter can be removed by periodic burning with, for example, an electric heat...

AI Technical Summary

Problems solved by technology

[0004] However, currently used DPF materials (cordierite, SiC, etc.) are not capable of directly supporting catalyst metals, and thus the catalyst-loaded DPF is usually wash-coated with gamma-alumina, etc. on the surface of the filter substrate. cloth so as to form a coating that supports the catalyst metal, resulting in an extremely high pressure loss (2-3 times that of a filter substrate with a porosity of 50% when the coating is formed) and a significant increase in weight ( When the coating is formed, it is 2-3 times the weight of the filter substrate with a porosity of 50%)

There are also problems where the coating reduces thermal shock resistance due to a higher coefficient of thermal expansion and prevents early manifestation of catalytic activity due to increased heat capacity

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