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NO.sub.x catalyst and method of suppressing sulfate formation in an exhaust purification system

United States Patent

7,235,221
June 26, 2007
View the Complete Patent at the US Patent & Trademark Office
The activity and durability of a zeolite lean-burn NOx catalyst can be increased by loading metal cations on the outer surface of the zeolite. However, the metal loadings can also oxidize sulfur dioxide to cause sulfate formation in the exhaust. The present invention is a method of suppressing sulfate formation in an exhaust purification system including a NO.sub.x catalyst. The NO.sub.x catalyst includes a zeolite loaded with at least one metal. The metal is selected from among an alkali metal, an alkaline earth metal, a lanthanide metal, a noble metal, and a transition metal. In order to suppress sulfate formation, at least a portion of the loaded metal is complexed with at least one of sulfate, phosphate, and carbonate.
Balmer-Millar; Mari Lou (Chillicothe, IL), Park; Paul W. (Peoria, IL), Panov; Alexander G. (Peoria, IL)
Caterpillar Inc. (Peoria, IL)
11/ 474,584
June 26, 2006
This invention was made with Government support under DOE Contract No. DE-FC05-97OR22579 awarded by the U.S. Department of Energy. The Government has certain rights to this invention.