CATALYST FOR PURIFYING EXHAUST GAS, ITS PRODUCTION AND EXHAUST GAS PURIFYING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a means capable of improving the NOx purifying performance at the time of high temp. of exhaust gas and the low temp. activity of a catalyst for purifying exhaust gas in an automobile engine of a type of excess air combustion at the time of normal operation. SOLUTION: In this catalyst 3 for purifying exhaust gas, a single catalyst layer 5 is formed (fixed) on a honeycomb carrier 4. In the catalyst layer 5, a catalyst A formed by carrying an active metal such a Pt on a zeolite by an ion exchange carrying method and a catalyst B formed by carrying an active metal such as Pt on the zeolite by a carrying form except ion exchange carrying such as a spray drying carrying method are coexisted. Then in the case that the exhaust gas has high temp., an olefin based HC in the exhaust gas is reformed into an aromatic based HC by the catalyst A and NOx in the exhaust gas is effectively purified with the use of the aromatic based HC by the catalyst B. And at the time that the exhaust gas has low temp., HC in the exhaust gas is cracked by the catalyst A and the low temp. activity of the catalyst for purifying exhaust gas is increased.