Patent ID: 7758832
Filing Date: 2010-07-20
Classification: B01D,F01N,Y02A,Y02T

Abstract:
1. A method of decomposing nitrogen dioxide (NO 2 ) to nitrogen monoxide (NO) in an exhaust gas of a lean-burn internal combustion engine, said method comprising the steps of contacting an acidic metal oxide selected from the group consisting of a zeolite, tungsten-doped titania, silica-titania, zirconia-titania, and mixtures of any two or more thereof, with a gas mixture comprising the exhaust gas; adjusting the composition of the gas mixture by injecting hydrocarbon therein at a rate that changes over the course of a duty cycle so that, on average over the duty cycle, the C1 hydrocarbon:nitrogen oxides (C1 HC:NO x ) ratio of the gas mixture contacting the acidic metal oxide is from 0.1 to 1.5; and passing the effluent gas directly to atmosphere or to atmosphere first via contacting the gas mixture with a hydrocarbon oxidation catalyst, wherein the hydrocarbon is diesel fuel, gasoline fuel, a gas-to-liquid (GTL)-based fuel or a liquid petroleum gas (LPG).