Exhaust gas purifying method

摘要

In order to improve a purification of exhaust gas from cold HC, it is provided an exhaust gas purifying method for an internal combustion engine (3) which uses an exhaust gas purifying system comprising a first catalyst (5), which contains a noble metal and reduces hydrocarbons contained in an exhaust gas, and a second catalyst (7), which is disposed downstream of the first catalyst (5) and contains ²-zeolite, wherein the method comprises the step of discharging the exhaust gas having an oxygen concentration of not less than 4% continuously or intermittently from the internal combustion engine at a time of engine cold start conditions.