| 摘要 |
PURPOSE:To purify exhaust gases in a region of a wide range from near stoichiometric to lean atmosphere by installing a specific catalyst on the upstream side and other specific catalyst on the downstream side in an exhaust gas passage of a lean burn engine. CONSTITUTION:The catalyst 1 formed by having a coating layer consisting of inorg. matter consisting essentially of zeolite contg. copper and phosphorus or the inorg. matter obtd. by further incorporating >=1 kinds of the metals selected from the group consisting of calcium, magnesium, lithium, strontium, cobalt, nickel, silver, iron, zinc, platinum and rhodium as other metals into this inorg. matter on a honeycomb carrier is placed in the exhaust gas passage of the leans burn engine. Further, the catalyst 2 which has the coating layer consisting essentially of active alumina contg. >=1 kinds of the noble metals selected from platinum, palladium and rhodium on a honeycomb carrier and simultaneously cracks hydrogen carbide, carbon monoxide and NOx near at a theoretical air-fuel ratio is placed on the downstream side. |
