Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2005-05-24
2005-05-24
Johnson, Christina (Department: 1725)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S303000, C502S304000, C502S328000, C502S330000, C502S339000, C502S340000, C502S344000
Reexamination Certificate
active
06897182
ABSTRACT:
A catalyst for purification of exhaust gases including (1) a catalysis-promoting coating comprising a noble metal catalyst and a NOx storage component loaded onto a carrier material, wherein the NOx storage component comprises an alkali metal and, (2) a ceramic substrate for supporting the catalysis-promoting coating, wherein the ceramic substrate exhibits resistance to alkali metal migration below 1000° C. and a coefficient of thermal expansion of less than about 25×10−7/° C. (25-800° C.). A second aspect of, the invention is a process for purifying an exhaust gas from a lean burn engine involving simultaneously removing carbon monoxide, hydrocarbons and nitrogen oxides by bringing the exhaust gas from a lean burn engine into contact with the exhaust gas purifying catalyst of the present invention disclosed above. In this process a majority of the nitrogen oxides in the exhaust gas are adsorbed to the NOx storage component on the porous support under a lean burn atmosphere in which oxidizing concentrations are above a stoichiometric point that is required for oxidizing components to be oxidized in the exhaust gas. Furthermore, when the exhaust gas is temporarily change from lean burn to fuel-rich, the adsorbed nitrogen oxides are released and chemically reduced by a reaction with the hydrocarbons and carbon monoxide in the exhaust gas under a stoichiometric atmosphere or a fuel-rich atmosphere in which oxygen concentrations are below stoichiometric point.
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Qian et al., “Effects of Excess Alumina on Microstructure of Aluminum Titanate Ceramics Prepared From Mixture of Alumina and Titania”, Yogyo-Kyokai Shi, 93(6), 1985, p. 1-12.
Cutler Willard A.
Day J. Paul
Lakhwani Shahid G.
Ogunwumi Steven B.
Corning Incorporated
Gheorghiu Anca C.
Johnson Christina
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