Exhaust gas purifying system

摘要

A vehicle-mounted exhaust gas purifying system includes at least a first threeway catalyst (21) and a plurality of HC adsorbing/purifying catalysts (10) downstream thereof on an exhaust gas passage (40). Each of the HC adsorbing/purifying catalysts (10) includes a monolithic carrier (1) having a plurality of cells (5), and includes HC adsorbent layer (2) and purifying catalyst layer (3), which are formed on the monolithic carrier. Moreover, the number of cells per unit areas of one HC adsorbing/purifying catalysts on an upstream side is larger than the number of cells per unit areas of another HC adsorbing/purifying catalyst on a downstream side.