CATALYST FOR PURIFYING EXHAUST GAS

摘要

PURPOSE:To efficiently remove nitrogen oxides and the like by contacting catalysts comprising Co, alkaline earth metals and rare earth metals carried by zeolite having the ratio SiO2/Al2O3 of 15 or more with exhaust gas in an oxygen excessive atmosphere. CONSTITUTION:Co, alkaline earth metals and rare earth metals are carried by zeolite having the mole ratio SiO2/AL2O3 of 15 or more by an ion-exchange method or impregnation method to provide catalysts for purifying exhaust gas. As zeolite, ZSM-5,Y having the mole ratio SiO2/Al2O3 of 20-200 or one having mordent structure are preferable. High ion-exchange rate of Co is desirable and conventional methods can be used for ion-exchange of the alkaline earth metals and rare earth metals. The catalysts thus provided can efficiently remove nitrogen oxides, hydrocarbons and carbon monoxides within a wide temperature range of 80 deg.C or lower in an oxygen excessive atmosphere.