EXHAUST GAS PURIFYING CATALYST LAYER, EXHAUST GAS PURIFYING CATALYST COATED STRUCTURE AND EXHAUST PURIFYING PROCESS USING STRUCTURE

摘要

PROBLEM TO BE SOLVED: To provide an exhaust gas purifying catalyst layer and an exhaust gas purifying catalyst coated structure for removing efficiently NOx in lean combustion exhaust gas and also provide an exhaust gas purifying process using the catalyst layer and the structure and purifying Nox in lean combustion exhaust gas efficiently and with high reliability. SOLUTION: An exhaust gas purifying catalyst structure is provided dividedly with a catalyst A composed of a porous inorganic oxide carrier containing iridium alkali metal and/or alkali earth metal and disposed on its foregoing stage and a catalyst B composed of an alumina carrier containing silver and provided with a pore structure representing the relation between the pore diameter and the pore volume measured by the nitrogen adsorption process in which Y is 70% of X or more and Z is 20% or less of X is provided when the total value of the pore volume formed of pores of pore diameter of 300 angstroms or less is set as X, and the total value of the pore volume formed of pores of pore diameter of 25 angstroms to less than 100 angstroms is set as Y and the total value of the pore volume formed of pores of 100 angstroms to 300 angstroms or less is set as Z and disposed on the following stage. In an exhaust gas purifying process, the disposition of the catalyst is so divided as to dispose the catalyst A on the foregoing stage and the catalyst B on the following stage, and the catalyst structure is used.