Composite, zoned oxidation catalyst for compression ignition internal combustion engine

Abstract

A composite oxidation catalyst (18, 20) for use in an exhaust system for treating an exhaust gas produced by a vehicular compression ignition internal combustion engine (30) and upstream of a particulate matter filter (44, 50) in the exhaust system comprises a substrate (5) having a total length L and a longitudinal axis and having a substrate surface extending axially between a first substrate end (I) and a second substrate end (O); and three or more catalyst washcoat zones (1, 2, 3; or 1, 2, 3, 4) arranged axially in series on and along the substrate surface, wherein a first catalyst washcoat zone (1) having a length L1, wherein L1 < L, is defined at one end by the first substrate end (I) and at a second end by a first end (19, 21) of a second catalyst washcoat zone (2) having a length L2, wherein L2 < L, wherein the first catalyst washcoat zone (1) comprises a first refractory metal oxide support material and two or more platinum group metal components supported thereon comprising both platinum and palladium at a weight ratio of platinum to palladium of >=1; the second catalyst washcoat zone (2) comprises a second refractory metal oxide support material and one or more platinum group metal components supported thereon; and a third catalyst washcoat zone (3) comprising a third refractory metal oxide support material and one or more platinum group metal components supported thereon is defined at a second end thereof by the second substrate end (O), wherein a total platinum group metal loading in the first catalyst washcoat zone (1) defined in grams of platinum group metal per cubic foot of substrate volume (g / l) (g / ft3) is greater than a total platinum group metal loading in the second catalyst washcoat zone (2), wherein a total platinum group metal loading in the third catalyst washcoat zone (3) defined in grams of platinum group metal per cubic foot of substrate volume (g / l) (g / ft3) is less than the total platinum group metal loading in the second catalyst washcoat zone (2) and wherein the first catalyst washcoat zone (1) comprises one or more first alkaline earth metal components supported on the first refractory metal oxide support material.

Description

technical field [0001] The present invention relates to a composite zoned oxidation catalyst for use in an exhaust system for treating exhaust gas produced by a compression ignition internal combustion engine of a vehicle, preferably for heavy duty diesel vehicles and located upstream of a particulate filter in the exhaust system . The invention also relates to an exhaust system or a vehicle comprising a composite zoned oxidation catalyst. The present invention also relates to the use of a composite zoned oxidation catalyst for generating an exotherm to regenerate a downstream particulate filter; and a method for preparing the composite zoned oxidation catalyst. Background technique [0002] Internal combustion engines produce pollutants such as carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NO x ) and particulate matter (PM) exhaust. Emission standards for pollutants in the exhaust gases produced by internal combustion engines, especially for vehicle ...

AI Technical Summary

Problems solved by technology

[0043] It is believed that two basic mechanisms by which catalysts used to treat exhaust gases from internal combustion engines may be poisoned are: (i) selective poisoning, in which pollutants react directly with active sites or catalyst supports, resulting in reduced or catastrophic loss of activity; and (ii) non-selective poisoning, which sterically hinders access to the active sites or pores in the catalyst support by contaminating (or masking) the surface of the support or active sites, resulting in loss of performance

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