Zeolite/catalyst wall-flow monolith adsorber

摘要

An exhaust system for an internal combustion engine having a primary catalytic converter located downstream of the engine and a hydrocarbon adsorber located downstream of the primary converter. The adsorber comprises a ceramic wall-flow substrate having a zeolite coating, having the ability to selectively adsorb hydrocarbon molecules from exhaust gas, applied to the interior surfaces of the inlet passages of the substrate and a catalytic coating applied to the adjacent surfaces of the walls of the outlet passages of the substrate. The catalyst preferably has a light-off temperature below the desorption temperature of the zeolite. In operation, hydrocarbon is adsorbed by the zeolite following a cold engine start and is held until the zeolite reaches its desorption temperature at which time the hydrocarbon is released and passes through the porous walled substrate for conversion by the catalyst.