摘要：

The selective catalytic reduction(SCR) of nitrogen oxides by hydrocarbons is considered to be one of the most efficient ways to remove NO from lean burn automobile exhaust. The single noble metals Pt, Pd and Rh catalysts and two catalytic active components(Pt-Pd, Pt-Rh, Pd-Rh) based on the γ-alumina were prepared by the sol-gel and the selective catalytic reduction activity of NO with propene(C 3H 6) as reductant in the presence of excess oxygen was investigated in a fixed-bed microreactor. The results show that the order of activity for NO conversion and their optimal temperature is Rh (73%, 375℃)Pt(65%, 225℃)Pd(47%, 275℃), Pd and Rh have a higher activity for NO reduction to N 2 than that of Pt, while Pt-Al 2O 3 has a high activity for NO oxidation to NO 2, but the lowest selectivity for NO to N 2. The temperature ranges of the two catalytic active components catalysts for NO reduction have been broaden in comparison with the different temperature ranges of single catalytic component catalyst. The combined Pt-Rh catalyst is the most active among them. In different combination of Pt-Al 2O 3 and Rh-Al 2O 3 with physically mixed catalysts and packed with two-stage catalysts, it is found that the two-stage catalysts have a better activity than that of the other combinations in a wide temperature range(200—450 ℃) because the reductant C 3H 6 can be used efficiently, and this combined catalyst may be a potential candidates for practical use in the future.

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