| 摘要 |
A catalyst comprises at least 80 wt.%, and preferably 91 or 95 wt.%, of ceria (cerium oxide, CeO2) and 0.1-20 wt.%, preferably 1-15, 1-5 or 0.1-9 wt.%, of niobia (niobium oxide, Nb2O5) or tantala (tantalum oxide, Ta2O5) doped on the ceria, and the catalyst is calcined (fired) at a temperature of 600-1000ºC, preferably 700-950°C. A process may comprise selectively reducing (SCR) a gaseous mixture comprising nitrogen oxides (NOx) in the presence of a reductant (e.g. ammonia) and the catalyst at a temperature of 100-650ºC. The catalyst may be provided on inlet and/or outlet surfaces of a diesel particulate filter (DPF). The catalyst may be prepared by impregnating ceria with an aqueous solution comprising a water-soluble niobium or tantalum salt before calcining. The catalyst may be prepared by co-precipitating a mixture comprising a cerium hydroxide and a niobium or tantalum hydroxide from an aqueous solution of soluble cerium and niobium or tantalum salts, and washing the resulting precipitate before calcining. |
