Gm Global Technolgoy Operations, Inc.

Chih-Hao M Tsang

Raymond E Bedford

Richard F Beckmeyer

A preferred catalytically active solid acid material, zeolite, forms the basis of a washcoat effective for treating diesel-fueled engine exhaust to reduce emission of particulate. In a preferred method, hydrocarbon in exhaust is cracked and oxidized in the presence of a zeolite/silica washcoat mixture catalyzed with precious metal. A preferred Y-type zeolite provides acidic (cationic) sites having releasable cations which are exchanged with precious metal to form catalyzed zeolite. A preferred method of making the catalyzed zeolite/silica washcoat is provided, whereby colloidal silica is disposed as a barrier over the catalyzed washcoat, limiting exposure of catalyst to sulfur constituents in the exhaust.

Catalyst for treatment of diesel exhaust particulate

In a preferred method, particles of amorphous silica are used to provide a silica coating suitable for carrying dispersed catalyst particles for the treatment of diesel engine exhaust emissions. The silica coating is formed from a mixture consisting essentially of two groups of the fine silica particles of respective average sizes and size ranges which are virtually non-overlapping. The particles of the first of the two groups have a first average size sufficient to permit the particles of the first group (smaller group) to occupy voids between the particles of the second group (larger group) in a packed arrangement, and preferably the second group has a second average size which is at least 20 times greater than the first average size. Although particles of amorphous silica are preferred for use in forming a coating with improved adherence suitable for the treatment of diesel exhaust, the method of the invention is also useful to improve the adherence of coatings formed of other ceramics, such as alumina, titania, zirconia and zeolite.

Ceramic coating for a catalyst support

A high surface area ceria-alumina washcoat is disclosed in which the ceria is prepared from cerium acetate.

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Davison, MI, United States of America

Chih-Hao M Tsang