Diesel oxidation catalyst

摘要

The invention relates to a catalyst for purifying the exhaust gases from diesel engines, in particular an oxidation catalyst which is particularly well suited for the purification of exhaust gases from heavy goods vehicles when further exhaust gas purification units such as a particle filter and/or a nitrogen oxide reduction catalyst are installed downstream thereof. The catalyst contains two catalytically active coatings which have different compositions and of which only one is in direct contact with the outflowing exhaust gas. The coating (1) which is in direct contact with the outflowing exhaust gas is platinum-rich and contains a total amount of noble metal (platinum and palladium) which is greater than that in the coating (2) which is not in direct contact with the outflowing exhaust gas. The platinum-rich coating (1) displays an extremely high oxidizing power, in particular in the NO oxidation, while the coating (2) which is not in direct contact with the outflowing exhaust gas ensures a good “heat-up performance” of the catalyst.

主权项

1. A catalyst for purifying an outflowing exhaust gas of a diesel engine, comprising
a support body and two catalytically active coatings which have different compositions, with only a first coating of the two catalytically active coatings in direct contact with the outflowing exhaust gas, and with both coatings containing the platinum group metals platinum (Pt) and palladium (Pd) as catalytically active components, with the first coating containing more Pt than Pd, wherein the first coating contains a greater amount of total platinum group metal than a second coating of the two catalytically active coatings that is not in direct contact with the outflowing exhaust gas, and the second coating contains one or more zeolite compounds selected from beta-zeolites, X-zeolites, Y-zeolites, mordenites and ZSM-5 zeolites.