| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust gas purifying method which spray-supplies a selective reduction catalyst with urea water as a reduction component, so that nitrogen oxide included in an exhaust gas from a lean combustion engine can effectively be purified particularly when the temperature is low.SOLUTION: In the exhaust gas purifying method, a hydrocarbon component, carbon monoxide, and nitrogen monoxide in the exhaust gas are oxidized by an oxidation catalyst which includes platinum or palladium as a noble metal component, and in which the amount of this noble metal component is 0.1-3 g/L in terms of metal, and the platinum content in the noble metal component is 50-100 wt% in terms of metal to increase the nitrogen dioxide concentration, then an urea solution is spary-supplied to the selective reduction catalyst including specific zeolite (A) and a hydrolytic accelerating component (B) for urea as main components and they are made contact with each other at 150-600°C to generate ammonia at a ratio of ammonia to NOin the exhaust gas of 0.5-1.5 in terms of ammonia [NH/NO=0.5-1.5] to thereby decompose nitrogen oxide to nitrogen and water. |
