Patent ID: 6941747

Claim:
A method of treating NOx emissions in the exhaust gas of an internal combustion engine having catalyst means including at least a first catalyst converter capable of treating NOx, said converter including a combination of Pt, Rh and Ba elements wherein the ratio of Pt to Rh is about 10:1 and the proportion of Ba is relatively low compared to the proportions of Pt and Rh, the method including operating the engine in a first mode to promote a first set of conditions and in a second mode to promote a second set of conditions, wherein the first set of conditions include exhaust gases at an exhaust gas temperature in the range of 200 to 400 degrees Celsius, and wherein the first mode of operation includes operating the engine with a lean air-fuel ratio, and the second mode of operation includes operating the engine with a stoichiometric air-fuel ratio, the method further including controlling the operation of the engine during the first mode so as to promote a selective catalyst NOx reduction process at the first catalytic converter, and controlling the temperature of the exhaust gas to be in the range of 200-400 degrees Celsius by operation of the engine to ensure effective operation of the first catalyst converter under the first mode of operation.