负载型Au-Pd双金属催化剂的制备及其对CO氧化的催化活性

采用改性的等体积浸渍法制备了SiO2负载的Au-Pd双金属催化剂,考察了催化剂的焙烧温度对CO氧化反应活性的影响.与623,723和773K的条件下焙烧的催化剂相比,673K焙烧的催化剂具有良好的催化CO氧化活性,CO完全转化温度低于398K.应用N2物理吸附、X射线衍射、程序升温还原、CO程序升温脱附及X射线光电子能谱等技术对催化剂进行了表征.结果表明,673K焙烧的催化剂具有最大的比表面积和最小的孔径,存在Au0,Pd0和PdO相,AuxPdy合金相很少;而773K焙烧的催化剂上除了含有Au0,Pd0和PdO相外,还存在明显的AuxPdy合金相.具有大比表面积,小孔径,Au0,Pd0和PdO多相共存的催化剂可使CO的吸附量增加,催化活性提高;而AuxPdy合金相的生成并不能提高催化剂的催化活性.

Preparation of Supported Au-Pd Bimetallic Catalyst and Its Catalytic Activity for CO Oxidation

The Au-Pd/SiO2 catalyst was prepared by impregnation of SiO2 with an alkaline HAuCl4 solution by an incipient wetness method.The effect of calcination temperature on the catalytic activity for CO oxidation was evaluated.The Au-Pd/SiO2 catalyst calcined in air at 673 K shows higher catalytic activity compared with the catalysts calcined at 623,723,or 773 K.The catalyst was characterized by N2 adsorption-desorption isotherms,X-ray diffraction,temperature-programmed reduction,CO temperature-programmed desorption,and X-ray photoelectron spectroscopy.The results indicate that the catalyst calcined at 673 K has the largest surface area and the smallest pore volume,and there exist Pd0,PdO,and Au0 phases on it.The formation of AuxPdy alloy does not favor the catalyst activity.