Patent ID: 8099951

Claim:
A method for reducing nitrogen oxides including NO and NO 2 in an exhaust stream also comprising oxygen, carbon monoxide and hydrocarbons at a temperature above about 150° C., the method comprising: oxidizing NO in the exhaust stream to NO 2 ; adding diesel fuel hydrocarbons and their oxygenates to the exhaust stream for the reduction of nitrogen oxides; and flowing the exhaust stream through a dual bed catalyst system comprising a front bed and a rear bed to reduce the nitrogen oxides to N 2 , wherein the front bed is a single layer catalyst bed and the rear bed is a double layer catalyst bed comprising a first layer including a first layer catalyst produced from the same materials as the single layer catalyst of the front bed and a second layer including a second layer catalyst, the single layer catalyst continuously forming NH 3 when the exhaust stream reacts with the single layer catalyst and the second layer catalyst of the rear bed reacts with the formed NH 3 to substantially eliminate the formed NH 3 to produce N 2 .