Patent ID: 9061245
Filing Date: 2015-06-23
Classification: B01D,F01N,Y02T

Abstract:
1. A method for purifying diesel engine exhaust gases containing hydrocarbons, carbon monoxide, soot particles, and nitrogen oxides consisting of NO and NO 2 , the method comprising the following steps in the direction of the exhaust gas flow: a.) introducing into the exhaust gas to be cleaned ammonia or a precursor compound capable of decomposing to liberate ammonia under operating conditions; b.) passing the exhaust gas resulting from a.) through a first SCR catalyst under conditions effective for converting less than or at most 50% of the nitrogen oxides that are present in the exhaust gas upstream of the first SCR catalyst into nitrogen; c.) passing the exhaust gas resulting from b.) through a catalytically activated particulate filter, in which soot particles are collected and at least partially oxidized with NO d.) introducing into the exhaust gas resulting from c.) ammonia or a precursor compound capable of decomposing to liberate ammonia under operating conditions; e.) passing the exhaust gas resulting from d.) through a second SCR catalyst under conditions effective for converting substantially all of the nitrogen oxides present upstream of the second SCR catalyst into nitrogen.