| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method of reducing NOx with high durability over a wide temperature range without deterioration of an NOx occluded catalyst or production of the harmful ammonia even in the presence of oxygen, sulfur oxides and/or water, especially deterioration of the NOx catalyst in the coexistence of sulfur oxides and production of ammonia under rich conditions, which have so far been serious problems of the catalyst. <P>SOLUTION: The method comprises burning a fuel with the burning atmosphere for the fuel switched alternately under rich and lean conditions, introducing the produced exhaust gas into a catalyst device and bringing the gas in contact with the catalyst to reduce nitrogen oxides in the exhaust gas catalytically. The catalyst contains, as catalyst ingredients, (A) an oxide catalyst ingredient A comprising (a) ceria, (b) praseodymium oxide or (c) a mixture and/or a compound oxide of oxides of two or more elements selected from cerium, zirconium, praseodymium, neodymium, terbium, samarium, gadolinium and lanthanum and (B) a noble metal catalyst ingredient B comprising one or more selected from platinum, rhodium and palladium and oxides of the elements. The concentration of oxygen at the outlet of the catalyst device under rich conditions is 0.1-1.0%. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
