Patent ID: 8105545

Claim:
An engine exhaust gas purifier comprising: a selective reduction catalyst, provided at an exhaust pipe of the diesel engine; a liquid injection nozzle which is provided at the exhaust pipe on the exhaust-gas upstream side of the selective reduction catalyst and can inject urea liquid toward the selective reduction catalyst; and an oxidation catalyst provided at the exhaust pipe on the exhaust-gas upstream, side of the selective reduction catalyst, wherein the selective reduction catalyst comprises a catalyst support in which a plurality of through holes are formed and partitioned by porous walls parallel to each other, the parallel porous walls carrying a first active component including metal zeolite or metal alumina, having a catalytic action, in which nitrogen oxide in an exhaust gas from an engine is reacted with ammonia for dissolution, wherein an inlet and an outlet, adjacent to each other, of the plurality of through holes partitioned by the parallel porous walls are sealed alternately; the parallel porous walls carrying the first active component have ventilation for the exhaust gas including ammonia and dissolved gas of nitrogen oxide and are formed so that the exhaust gas flowing in the inlet of a first through hole passes through the parallel porous walls and is emitted from the outlet of another through hole adjacent to the first through hole; a second active component including precious metal/zeolite or precious metal/alumina, having a catalytic action so as to oxidize ammonia having passed through the parallel porous walls is carried on the inner surface of the another through hole; the first and second active compounds are carried on the inner surfaces of all the through holes in 80 to 90 percent of the through holes in the longitudinal direction; the parallel porous walls carrying the first active component is formed so that ammonium nitrate in the particle-state of solid matter cannot pass through the parallel porous walls; and the ammonium nitrate deposited on the parallel porous walls is configured so as to be dissolved and pass through the parallel porous walls by heat of the exhaust gas whose temperature has been raised to a temperature of 210° C. or above by oxidation reaction in the oxidation catalyst, so that the selective reduction catalyst can be regenerated.