富氧条件下贵金属催化剂上丙烯选择性还原NO研究

用溶胶-凝胶(Sol-gel)法制备了以γ-Al₂O₃为载体,以Pt,Pd和Rh等为活性组分的单组分及双组分催化剂,在稀燃汽油机条件下评价了丙烯对NO的选择性催化还原活性.结果表明,在单组分催化剂中,催化剂的活性及顺序为Rh(73%)>Pt(65%)>Pd(47%),最高活性对应的温度分别为Pt(225℃),Pd(275℃)和Rh(375℃),N₂选择性顺序为Rh,Pd(>80%)>Pt(48%),氧化性顺序为Pt>Rh>Pd.Sol-gel制备的双组分催化剂中的不同贵金属活性位具有一定的协同效应,可明显拓宽活性温度范围,其中以Pt-Rh组合活性最好.Rh/Al₂O₃和Pt/Al₂O₃两种催化剂分层有序填装时,可提高C₃H₆的利用率,在200～450℃范围内,可有效地催化净化NO.

Selective Catalytic Reduction of Nitrogen Oxide by Propene over Noble Catalysts in the Pressence of Exess Oxygen

The selective catalytic reduction(SCR) of nitrogen oxides by hydrocarbonSIs 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(C₃H₆) as reductant in the presence of excess oxygen waSInvestigated 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 N₂than that of Pt, while Pt-Al₂O₃has a high activity for NO oxidation to NO₂, 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-Al₂O₃and Rh-Al₂O₃with 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 combinationSIn a wide temperature range(200-450 ℃) because the reductant C₃H₆can be used efficiently, and this combined catalyst may be a potential candidates for practical use in the future.