Patent ID: 6093377
Filing Date: 2000-07-25
Classification: B01D,F01N

Abstract:
A method of treating gas containing nitrogen oxides exhausted from an internal combustion engine for removing the nitrogen oxides from a gas flow by contacting a gas flow released from the internal combustion engine by lean burning and a gas flow released from the internal combustion engine by stoichiometric burning alternately with a catalyst; whereinsaid nitrogen oxides are reduced to nitrogen by contacting the gas flow with said catalyst in the presence of at least one of hydrocarbon and carbon monoxide, andsaid catalyst has a structure composed of an inorganic oxide supporter supporting active components; wherein said active components comprisenoble metals including both rhodium and platinum, the rare earth metal cerium, and magnesium, and, optionally, at least one other alkali earth metal; whereinsaid noble metals are contained in a range of 0.05-3.5 mol % per said inorganic oxide supporter 100 mol %,said rare earth metal cerium is contained in a range of 0.7-20 mol % per said inorganic oxide supporter 100 mol %,said alkali earth metals are contained in a range of 4-16 mol % per said inorganic oxide supporter 100 mol %,rhodium is less than 1.9 mol %,platinum is less than 2.6 mol %,said noble metals are contained in a form of metal or oxide,said rare earth metal cerium is contained in a form of oxide, andsaid alkali earth metals are contained in a form of oxide or carbonate.