铈锆比率及过渡金属掺杂对Pd/Ce_xZr_(1-x)O_2催化剂性能的影响

Effects of Ce/Zr molar ratio and transition metal doping on performance of Pd / Ce_xZr_(1-x)O_2 catalyst

采用均相共沉淀法制备了不同铈锆比率的复合氧化物,并用等体积浸渍法制备了其负载的Pd/CexZr1-xO2催化剂。考察了铈锆比率对复合氧化物性质及其负载单Pd催化剂催化氧化柴油机尾气性能的影响。在此基础上,掺杂Mn、Ni和Cu对催化剂进行改性并考察反应活性。利用XRD、BET、H2-TPR和TEM等技术对样品进行表征。结果表明,Ce/Zr为1/1时Pd/CZ催化剂抗烧结性能最佳;过渡金属和铈锆协同作用一定程度上提高了柴油机氧化催化剂(DOC)的催化活性;Cu和Mn的掺杂能有效降低CO、碳氢化合物(HC)和NO的起燃温度,提高柴油机尾气催化氧化性能;Ni对催化性能的改善不明显。

A series of ceria-zirconia composite oxides with different Ce / Zr molar ratios were prepared by homo-precipitation. And corresponding Pd / CexZr1-xO2 catalysts were prepared by impregnation using the oxides.The effects of Ce / Zr molar ratio on properties of ceria-zirconia oxides and the catalytic oxidation performance of Pd / CexZr1-xO2 catalysts for diesel emissions were investigated systematically. Besides,the effects of doping Mn,Ni and Cu on the catalytic activity in the oxidation of diesel exhaust were studied in detail. The supports and catalysts were characterized by BET,H2-TPR,XRD,TEM. The results showed that supported Pd catalyst with the Ce /Zr ratio of 1 /1 has the highest resistance towards sintering during the reaction. The synergism of transition metal and Ce / Zr improved the activity of DOC. Doping of Cu,Mn reduced the ignition temperature of Pd / CexZr1-xO2 catalyst for the oxidation of diesel exhaust containing CO,HC and NO effectively. Improvement on the catalytic activity of Ni doped sample is not obvious.