EXHAUST GAS PURIFYING CATALYST AND ITS PREPARATION

摘要

PURPOSE: To efficiently remove NOx even when the air-fuel ratio is within a lean combustion zone and prepare an exhaust gas purifying catalyst of superior heat resistance and durability by carrying a fluorine component and a copper component on a specified ZSM-5 and/or mordenite on a catalyst carrier. CONSTITUTION: A fluorine component and copper component are carried on a ZSM-5 and/or mordenite having SiO2 /Al2 O3 molar ratio in the range of 20-60 on a catalyst carrier of an exhaust gas purifying catalyst. Also the detailed mechanism of the exhaust gas purifying catalyst is not clarified, and it is considered that copper is stabilized efficiently by fluorine and also zeolite itself is stabilized. It is essential that the SiO2 /Al2 O3 molar ratio of zeolite should be in the range of 20-60. When the molar ratio is less than 20, the aluminum removing phenomenon is very easily generated and durability is lowered, while the molar ratio is beyond 60, the carrying amount of an active metal component in ZSM-5 or mordenite lowers and the catalyst activities become insufficient.