| 摘要 |
PURPOSE:To improve performance in purification of HC, CO and NOx even in an oxygen excessive atmosphere, particularly for NOx at high temperatures by causing a catalyst layer comprising zeolite to carry copper for ion-exchange and precious metals as well. CONSTITUTION:A zeolite layer is formed in advance over a heat-resisting carrier comprising cordierite, etc., wherein copper is carried by a part of said layer, while precious metals such as Pt, Pd, etc., are carried by the other parts thereof. Or copper and precious metals can be carried by the whole of the zeolite layer in a mixed state. Or a catalyst layer is formed by the use of zeolite powder by which copper and precious metals are carried in a mixed state in advance. Since various methods can be adopted as started above, catalysts suitable for specific requirements can be selected. Consequently, performance of catalysts to purify HC, CO and NOx, particularly NOx at high temperature, can be enhanced under conditions of high temperature ranging from about 200 deg.C to about 800 deg.C. |
