PURPOSE: To provide a hydrocarbon adsorbent having satisfactory hydrocarbon adsorbing ability over a wide temp. range of exhaust gas from low temp. at the time of starting an internal-combustion engine at which moisture exists to high temp. and capable of adsorbing a large amt. of hydrocarbon from exhaust gas under high diffusion.
CONSTITUTION: A coating layer of a mixture of two or more kinds of zeolites adsorbing hydrocarbon and different from each other in crystal structure is formed on a honeycomb carrier. Powder of a mixture of at least one among mordenite, Y type zeolite, USY zeolite and β-zeolite with ZSM-5 zeolite is preferably used as the zeolites. The coating layer may be formed by coating the honeycomb carrier with a slurry of a mixture of two or more kinds of ZSM-5 zeolites different from each other in the ratio of silica to alumina.
IKEDA TAKUYA
KAMIKUBO MASANORI