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

摘要

The present invention relates to a technology to purify nitrogen oxides contained in exhaust gas exhausted from lean combustion engines such as diesel engine with ammonia and a selective catalytic reduction type catalyst, and an object of the present invention is to provide a selective catalytic reduction type catalyst which can effectively purify nitrogen oxides even at a low temperature as well as inhibit leak of ammonia, and an exhaust gas purification equipment and a purifying process of exhaust gas using the same. The present invention is 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).