CATALYST,ITS PREPARATION AND USE

PURPOSE: To obtain a catalyst having an excellent stability to waste gas components and particularly a good cleaning property in NOx by containing a support material comprising zeolite, mixing spinel with the support material or coating the spinel on the support material. CONSTITUTION: The catalyst formed of spinel containing copper, zinc and aluminum contains a support material comprising zeolite, and the spinel is mixed with the support material, or coated on the support material. Consequently, the catalyst is substantially stable to waste gas components, for example H2 O, NOx , CO2 or SO2 , works for oxidation of hydrocarbon, and works for catalytic reduction of NOx . The reduction of NOx is executed in a gas containing oxygen, for example, in existence of such a reducing agent as hydrocarbon. An existence of hydrocarbon with enough concentration in the waste gas of the combustion engine is advantageous.