Patent ID: 8800270

Claim:
A method for reducing an amount of NO 2 in an exhaust gas mixture of an internal combustion engine, the exhaust gas mixture having a mixture of carbon monoxide, hydrocarbons, and NO 2 , the NO 2 being present in a first NO 2 concentration, the method comprising: contacting a first portion of the exhaust gas mixture with a first catalyst, the exhaust mixture being a diesel exhaust, the first catalyst including platinum in an amount from about 0.1 to 300 g/cubic foot, the first portion of the exhaust gas mixture being converted into a first oxidized exhaust mixture comprising NO 2 in a second NO 2 concentration, the second NO 2 concentration being greater than the first NO 2 concentration; passing a second portion of the exhaust gas mixture through a bypass; combining the second portion of the exhaust gas mixture with the first oxidized exhaust mixture at a position downstream of the first catalyst to produce a combined exhaust gas mixture; and contacting the combined exhaust gas mixture with a second catalyst positioned downstream of the first catalyst such that NO 2 is consumed in oxidizing the carbon monoxide and hydrocarbons from the second portion, the second catalyst including palladium in an amount from about 2 to 300 g/cubic foot, the second catalyst converting the combined exhaust gas mixture to a second combined exhaust gas mixture, the second combined exhaust gas mixture having NO 2 present in a third NO 2 concentration, the third NO 2 concentration being less that the second NO 2 concentration such that a portion of the NO 2 in the first oxidized exhaust mixture is converted to NO, a diameter and the positioning of the bypass determining an amount of unreacted gas and associated reductants delivered to the second catalyst.