Exhaust gas purification system

a technology of exhaust gas purification system and filter, which is applied in the direction of physical/chemical process catalysts, metal/metal-oxide/metal-hydroxide catalysts, and separation processes. it can solve the problems of reducing fuel economy, small amount of heat from hc combustion supplied to the catalyst to the filter, and low flow rate of exhaust gas in the downstream oxidation catalyst. , to achieve the effect of quick regenerating the filter and preventing an increase in fuel consumption

Inactive Publication Date: 2006-03-23
MAZDA MOTOR CORP
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Benefits of technology

[0022] As described above, in the exhaust gas purification system of the present invention, the oxidation catalyst for oxidizing HC in exhaust gas, which is disposed upstream of the particulate filter in an exhaust passage, has a structure that part of the catalyst downstream in the direction of flow of exhaust gas has a larger amount of support material than up

Problems solved by technology

Since, however, the flow rate of exhaust gas in the downstream oxidation catalyst is low, increase in HC in the exhaust gas produces a large amount of oxidation reaction heat of HC so that the downstream catalyst becomes likely to reach the necessary temperature for burning off soot.
Since in this case HC flows into the filter without being burned off by the oxidation catalyst, this means the amount of heat of HC combustion supplied from the catalyst to the filter is small, which is disadvantageous in the ignition of particulates deposited on the

Method used

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example 2

[0035] Both the upstream catalyst 3 and the downstream catalyst 4 are lean-NOx catalysts. The catalytic material is made of active alumina, CeO2, barium (Ba) serving as a NOx storage component and platinum (Pt) serving as a catalytic metal. Each catalyst was made by mixing active alumina and CeO2 in a mass ratio of 1:1 to prepare a support material and supporting Pt and Ba on the support material. As a support for each of the upstream and downstream catalysts 3 and 4 was used a cordierite honeycomb support of the same type as in Example 1.

[0036] Further, for the upstream catalyst 3, the support material obtained by mixing active alumina and CeO2 in a mass ratio of 1:1 was supported by 60 g / L on the honeycomb support. For the downstream catalyst 4, the same support material was supported by 180 g / L on the honeycomb support. Therefore, the downstream catalyst 4 contains a larger amount of support material per unit area of wall surfaces of each cell in the honeycomb support than the u...

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Abstract

An upstream catalyst (3) and a downstream catalyst (4) are disposed upstream of a particulate filter (5) in an exhaust passage of a diesel engine. The downstream catalyst (4) has a larger amount of support material for supporting catalytic metal than the upstream catalyst (3). This enhances the efficiency of oxidation reactions of HC in the catalysts to raise the temperature of exhaust gas flowing into the filter (5).

Description

CROSS-REFERENCES TO RELATED APPLICATIONS [0001] This application claims priority under 35 USC 119 to Japanese Patent Application No. 2004-275480, filed on Sep. 22, 2004, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] (a) Field of the Invention [0003] This invention relates to an exhaust gas purification system for a diesel engine. [0004] (b) Description of the Related Art [0005] Exhaust gas purification systems for diesel engines are generally known in which a filter for trapping particulates in exhaust gas is disposed in an exhaust passage and an oxidation catalyst is disposed upstream of the filter in the exhaust passage. These exhaust gas purification systems use reaction heat in the oxidation catalyst to raise the temperature of the filter up to a temperature at which particulates ignite and burn in order to regenerate the filter. The regeneration of the filter is implemented, for example, by increasing the amount of hydroca...

Claims

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Application Information

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IPC IPC(8): F01N3/00F01N3/10
CPCB01D53/9422Y02T10/22B01D53/9477B01D2251/208B01D2255/1021B01D2255/2042B01D2255/206B01D2255/407B01D2255/50B01D2255/908B01D2255/91B01D2255/912B01D2255/915B01J23/63B01J35/0006B01J37/0215B01J37/0242B01J37/0246B01D53/9454Y02T10/12
Inventor HARADA, KOICHIROTSUSHIO, YOSHINORITAKAMI, AKIHIDE
Owner MAZDA MOTOR CORP
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