EXHAUST GAS CLEANING CATALYST

摘要

PROBLEM TO BE SOLVED: To efficiently clean HC in exhaust gas discharged from an internal combustion engine at the time of low temp. immediately after the start of the engine. SOLUTION: This exhaust gas cleaning catalyst having a monolithic structure is obtained by successively laminating a hydrocarbon adsorbing layer based n zeolite and a catalyst component layer containing a noble metal such as palladium or platinum on a monolithic carrier the cells of which have each a regular n-polygon (N; a natural number of 3 or more). The hydrocarbon adsorbing layer is bonded to each cell so as to leave a cavity forming a circle with a radius R centering around the center of gravity of the regular N-polygon shape in a cell cross section and the catalyst component layer is bonded to the hydrocarbon adsorbing layer in an almost annular shape so as to occupy a part of the cavity with the radius R in the cell cross section. A ratio (Rc/Rf) of the shortest distance Rc from the center of gravity to the hydrocarbon adsorbing layer bonded to the corners of each cell and the shortest distance Rf from the center of gravity to the hydrocarbon adsorbing layer bonded to the sides of the cell is (Rc/Rf)<=1.7.