摘要
用溶胶 -凝胶 ( Sol-gel)法制备了以 γ-Al2 O3 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( 4 7% ) ,最高活性对应的温度分别为 Pt( 2 2 5℃ ) ,Pd( 2 75℃ )和 Rh( 3 75℃ ) ,N2 选择性顺序为 Rh,Pd( >80 % ) >Pt( 4 8% ) ,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/ Al2 O3 和 Pt/ Al2 O3 两种催化剂分层有序填装时 ,可提高 C3 H6的利用率 ,在 2 0 0～ 45 0℃范围内 ,可有效地催化净化 NO.
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.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2003年第11期2060-2064,共5页
Chemical Journal of Chinese Universities
基金
国家"八六三"计划 (批准号 :2 0 0 1AA 64 3 0 3 0 )资助
关键词
富氧条件
贵金属
催化剂
丙烯
选择性还原
NO
协同效应
分子筛
稀燃车尾气
Lean-burn automobile exhaust
Noble metal catalyst
NO reduction
Selective catalytic reduction
Synergistic effect
