| 摘要 |
PROBLEM TO BE SOLVED: To provide a catalyst for purification of exhaust gas containing HC adsorbents which have excellent adsorption efficiency of cold HC of various kinds of molecular diameters and hardly desorb the adsorbed HC. SOLUTION: This catalyst for purification of exhaust gas contains two or more kinds of hydrocarbon adsorbents having different medians in the pore diameter distributions in the catalyst component layers, and the hydrocarbon adsorbents have 4 to 9 Å distribution of the pore diameters. The catalyst has a multilayered structure comprising each layer of two or more kinds of hydrocarbon adsorbents having different medians in the pore diameter distributions. The uppermost layer consists of a hydrocarbon adsorbent having a larger median in the pore diameter distribution, and from the uppermost layer, layers of adsorbents with smaller medians in the pore diameter distributions are successively formed. The hydrocarbon adsorbents are preferably arranged in such a manner that an exhaust gas is successively brought into contact with the hydrocarbon adsorbent having a larger median in the pore diameter distribution and then successively into contact with hydrocarbon adsorbents having smaller medians in the pore diameter distributions. Two or more catalysts for purification of exhaust gas are disposed in series along the exhaust gas stream. |
