金属氧化物掺杂对锡锆固溶体催化剂的一氧化氮选择性还原性能的影响

Effect of Doped Metal Oxides on Performance of Sn_xZr_(1-x)O_2 Solid Solution Catalysts for NO Selective Reduction

锡锆固溶体催化剂Sn0 55Zr0 45O2 具有较好的NO选择性还原性能 .本文在此基础上对其进行金属氧化物掺杂 ,发现用浸渍法掺入碱性金属元素Y ,La ,Ba和Zn以及用研磨法加入α Mn2 O3 可以提高Sn0 55Zr0 45O2 的NO选择性还原性能 ,用浸渍法掺入过渡金属元素Ce,Ag ,Cu ,Mn及Ni降低了母体催化剂的活性 ,而浸渍硫酸镓由于在表面引入B酸位使催化剂严重积碳而大大降低了催化剂的NO选择性还原性能 .文中给出了活性改善体系的最佳掺杂量 ,并测定了其抗水性能 .在反应气中不含水的条件下 ,添加 2 %Ba的样品活性最高 ,而掺杂 1%Zn样品具有最好的抗水性能 .对丙烯氧化反应和NO氧化反应的研究表明 ,抑制还原剂丙烯的完全燃烧或促进NO氧化为NO2

Several doped Sn 0 55 Zr 0 45 O 2 solid solution catalysts were prepared by impregnation of Sn Zr hydrous oxide with aqueous solution of respective metal salts and their catalytic properties for the selective reduction of NO under lean burn conditions were investigated. Among the samples tested, Sn 0 55 Zr 0 45 O 2 doped with Y, La, Ba, or Zn by impregnation followed by calcination at 500 ℃, and the mechanical mixture of Sn 0 55 Zr 0 45 O 2 and α Mn 2O 3 showed better activity than Sn 0 55 Zr 0 45 O 2 for NO selective reduction under lean burn conditions. Ga doped Sn 0 55 Zr 0 45 O 2 having strong B acid sites on the surface and the catalysts doped with transition metal elements such as Ce, Ag, Cu, Mn, and Ni showed poor catalytic performance. Further experiments found that Sn Zr hydrous oxide prepared by homogeneous precipitation is a better precursor than that prepared by co current precipitation. The best loading for each dopant is 6%Y, 3%La, 2%Ba, 1%Zn and 8%Mn 2O 3 respectively. Among these catalysts, 2%Ba doped Sn 0 55 Zr 0 45 O 2 showed the highest NO conversion with dry gas feed, and 1%Zn doped Sn 0 55 Zr 0 45 O 2 had the best NO reduction activity with steam. Studies on the reaction process of propene oxidation with O 2 indicated that the combustion of propene was restrained over the Sn x Zr 1- x O 2 solid solution catalysts doped with Y, La, Ba and Zn. Meanwhile, the oxidation of NO to NO 2 can be enhanced over the Y and La doped samples or the mixture with α Mn 2O 3. The suppressing of propene complete combustion and the enhancement of NO oxidation to NO 2 may be beneficial to NO selective reduction.