CATALYST FOR PURIFYING EXHAUST GAS AND PROCESS FOR PURIFYING EXHAUST GAS

摘要

A catalyst for purifying exhaust gas, comprising a mixture of a first powder comprising at least platinum supported on a first carrier with a second powder comprising at least rhodium supported on a second carrier and a NOx occluding material supported at least on the first carrier, wherein the second carrier is zirconia stabilized with either an alkaline earth metal or a rare earth element or both. Since the second carrier is made basic by the alkaline earth metal and/or the rare earth element and therefore is excellent in adsorption of steam (H2O), steam reforming with rhodium proceeds so sufficiently that the hydrogen thus formed greatly contributes to the reduction of NOx and the prevention of the NOx occluding material from being poisoned with sulfur. Further, the catalyst has advantages in that the oxidizing power of platinum can be kept at a high level, that the steam reforming activity of rhodium is exerted sufficiently, and that the poisoning of the NOx occluding material with sulfur is inhibited.