| abstract |
Nitrogen oxides are removed from the exhaust of an internal combustion engine which operates on a methane-containing fuel by reacting the nitrogen oxides and oxygen in the exhaust gas with a controlled amount of methane in the presence of a reducing catalyst. The catalyst preferably comprises a crystalline zeolite having a silicon to aluminum ratio of equal to or greater than about 2.5 which is prepared from a non-acid zeolite which is ion exchanged with a cation selected from the group consisting of cobalt, nickel, iron, chromium, and manganese. Methane for the reaction is provided as a portion of the methane-containing fuel. Carbon monoxide present in the exhaust gas is converted to carbon dioxide simultaneously with the reduction of nitrogen oxides. |