EXHAUST GAS CLEANING METHOD, EXHAUST GAS CLEANING CATALYST AND EXHAUST GAS CLEANING DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PURPOSE: An apparatus provides a method, device and catalyst to remove nitrogen oxides contained in the exhaust gas of lean-burn automobiles at a high efficiency. CONSTITUTION: NOx and CO adsorbent components are contained in the exhaust gas cleaning catalyst which captures NOx when the air-fuel ratio of exhaust gas is higher than theoretical air-fuel ratio and reduces said captured NOx when the air-fuel ratio of exhaust gas is equal to or smaller than theoretical air-fuel ratio. Said catalyst is placed in the exhaust gas path; said catalyst characterized in that the maximum CO desorption temperature reaches 200 to 220°C when the temperature is raised in He gas flow at the rate of 5 to 10°C/min after CO has been adsorbed by saturation at 100°C wherein exhaust gas having an air-fuel ratio higher than theoretical air-fuel and exhaust gas having an air-fuel ratio equal to or smaller than theoretical air-fuel ratio are alternately made to flow to said catalyst.