Selective catalytic reduction type catalyst, and exhaust gas purification equipment and purifying process of exhaust gas using the same

Abstract

The present invention is an exhaust gas purification catalyst equipment, and a method of use thereof, formed by arranging a selective catalytic reduction type catalyst for purifying nitrogen oxides in exhaust gas exhausted from lean combustion engines using ammonia or urea as a reducing agent, it is provided with a selective catalytic reduction type catalyst, characterized in that said catalyst comprises a lower-layer catalyst layer (A) having an oxidative function for nitrogen monoxide (NO) in exhaust gas and an upper-layer catalyst layer (B) having an adsorbing function for ammonia on the surface of a monolithic structure type carrier (C), and that the lower-layer catalyst layer (A) comprises a noble metal component (i), an inorganic base material constituent (ii) and zeolite (iii), and the upper-layer catalyst layer (B) comprises substantially none of component (i) but the component (iii), in a flow path of exhaust gas, characterized in that a spraying means to supply an urea aqueous solution or an aqueous ammonia solution is arranged in the downstream of the aforementioned oxidation catalyst and in the upstream of aforementioned selective catalytic reduction type catalyst.