Patent ID: 7163661

Claim:
An exhaust gas purifying system for a vehicle, comprising: a) an exhaust gas passage; b) a first three-way catalyst disposed on the exhaust gas passage to form a first three-way catalytic converter; and c) a plurality of HC adsorbing/purifying catalysts disposed in series downstream of the first three-way catalyst on the exhaust gas passage, the plurality of HC adsorbing/purifying catalysts including a first HC adsorbing/purifying catalyst disposed downstream of the first three-way catalyst to form a first HC catalytic converter and a second HC adsorbing/purifying catalyst disposed downstream of the first HC adsorbing/purifying catalyst to be distant therefrom to form a second HC catalytic converter, wherein the first three-way catalyst comprises a monolithic carrier having a plurality of cells, wherein each of the HC adsorbing/purifying catalysts comprises: a monolithic carrier having a plurality of cells; a HC adsorbent layer on the monolithic carrier; and a purifying catalyst layer on the HC adsorbent layer, wherein a number of cells per unit area of the first HC adsorbing/purifying catalyst is larger than a number of cells per unit area of the second HC adsorbing/purifying catalyst, and a number of cells per unit area of the first three-way catalyst is larger than the number of cells per unit area of the first HC adsorbing/purifying catalyst and the second HC adsorbing/purifying catalyst, and wherein a heat capacity per unit volume of the first HC adsorbing/purifying catalyst is larger than a heat capacity per unit volume of the second HC adsorbing/purifying catalyst.