稀土固体超强酸催化剂SO_4^(2-)/TiO_2/Ce^(4+)的制备及其性能研究

Preparation and Properties of SO_4^(2-)/TiO_2/Ce^(4+) Rare Earth Solid Super Acid Catalyst

采用X射线衍射(XRD),BET吸附,红外光谱(IR),差示扫描量热分析(DSC)表征了溶胶-凝胶法制备的稀土固体超强酸催化剂SO42-/TiO2/Ce4+的晶体结构、比表面积和表面结构.并以催化苯甲醛与乙二醇的缩合反应为指针,测试Ce掺杂对催化剂催化活性的影响.结果表明,掺杂Ce4+可以阻碍TiO2的晶型转变,减小催化剂的晶粒尺寸,比表面积增大.同时Ce4+的掺杂增强了催化剂Lewis酸性和提高催化剂表面与活性物种SO42-的配位能力从而增加催化剂表面活性中心的数目,这是提高催化剂活性的主要原因之一.掺杂Ce4+的摩尔分数x(Ce4+)=1.2%、焙烧温度为550℃时催化剂活性最高,此时催化剂为锐钛矿型.

The crystal pattern and parameter, the specific surface area, the surface structure of the rare earth solid superacid catalyst Ce^4＋ -doped SO4^2-/TiO2 prepared by the sol- gel method were characterized by means of X- ray diffraction （ XRD）, BET adsorption, infrared spectroscopy （IR） and differential scanning calorimetry （ DSC ） method respectively. The reaction for catalytic synthesis of benzaldehyde ethanedoil acetal was chosen to measure the effects of the Ce doping on catalytic activity. The results show that the Ce doping hinders the crystal transformation. The crystallite sizes of Ce^4＋ -doped SO4^2-/TiO2 catalyst decrease while their specific surface area increase owing to the Ce doping. The enhancement of catalytic activity of Ce^4＋ - doped SO4^2-/TiO2 catalyst increase because of the Lewis sourness and the number of active site of it increase owing to the Ce doping. The condensation reaction experiments show that the optimum molar content of Ce may be 1.2%, the optimum roasting temperature is 550℃. Then,the catalyst＇s crystalline state is anatase.