稀土氧化物掺杂对SO_4^(2-)/ZrO_2/Al_2O_3催化剂催化性能的影响

Effect of Rare Earth Doping on Property of SO_4^(2-)/ZrO_2/Al_2O_3 Catalyst

采用浸渍-沉淀法在具有较大比表面积的Al2O3上直接合成纳米ZrO2制备负载型纳米ZrO2/Al2O3复合载体,并将氧化钪、氧化钕、氧化镨等稀土氧化物(RExOy)分别掺杂到负载型纳米ZrO2/Al2O3复合载体中以改善ZrO2的表面性能。同时以此复合载体负载SO42-制备SO24-/RExOy-ZrO2/Al2O3催化剂。运用XRD,BET,NH3-TPD,原位红外等技术与方法对催化剂的晶相结构、比表面积、孔径分布、酸中心种类等进行表征,并以α-蒎烯异构化反应为探针考察了催化剂的催化性能。结果表明,掺杂的稀土氧化物没有改变ZrO2的晶相结构,但ZrO2粒度有所减小,催化剂的比表面积增加,同时稀土氧化物的存在还会改变催化剂表面SO24-的配位方式,提高表面酸中心数和酸强度,增强催化剂的活性。催化剂的孔结构对选择性有较大的影响。

Impregnation-precipitation method was applied to support the nano ZrO2 onto the Al2O3 with bigger surface area to prepare the supported nano-ZrO2/ Al2O3 composite supports. A series of rare earth oxides such as scandium oxide and praseodymium oxide, neodymium oxide were doped into ZrO2/Al2O3 composite supports to improve the surface properties of ZrO2. The SO4^2- /RExOy-ZrO2/Al2O3 catalysts were obtained by supporting SO4^2- onto the composite supports doped by rare earth oxides. Crystalline structures, surface area, pore diameter distribution and acid properties of the catalysts were characterized by XRD, BET, in-suit FTIR, and TPD. The α-pinene isomerization reaction was chosen to investigate the catalytic properties of the catalysts. The results indicated that there was no change in the crystalline structures of the ZrO2. And the grain size of the ZrO2 was decreased and the surface area of the catalysts was increased. The existence of the rare earth oxide changed the coordination mode of SO4^2- which had the directive influence on the acid site number and acid strength to increase the activity of the catalysts. The pore structure had great influence on the selectivity of the catalysts.