Exhaust gas purification device in variable combination of absorbent and catalyst according to gas temperature

Claim 1

An exhaust gas purification device for purifying exhaust gas of an engine, comprising an absorbent trapper containing an absorbent absorptive of hydrocarbons in the exhaust gas, a catalytic converter containing a catalyst for purifying the hydrocarbons in the exhaust gas, a passage system means for selectively conducting the exhaust gas from the engine through said absorbent trapper and said catalytic converter, a temperature detection means for detecting temperature of the exhaust gas, and a change-over valve for controlling said passage system means so that the exhaust gas: (1) flows through at least said absorbent trapper when the temperature detected by said temperature detection means is not higher than a first temperature at which the absorptivity of said absorbent for the hydrocarbons substantially starts to decrease, (2) bypasses said absorbent trapper when the temperature detected by said temperature detection means is at or above said first temperature and not higher than a second temperature at which the purification of the hydrocarbons by said catalytic converter becomes substantially available, and (3) flows through said absorbent trapper and said catalytic converter in that order when the temperature detected by said temperature detection means is at or higher than said second temperature; wherein said absorbent is selected from the group consisting of mordenite, Y type zeolite and ZSM-5, and said absorbent has added there at least one material for retarding the accumulation of reaction products resulting from the contacting of said absorbent by said hydrocarbons and expediting the removal thereof, said material being selected from the group consisting of platinum, palladium, rhodium, iron and copper.