纳米CeO_2及其复合催化剂的制备及对CO氧化的催化性能

Preparation and catalytic performance for CO oxidation of nano-CeO_2 and its composite catalysts

以硝酸铈和氢氧化钠为原料,使用超声雾化工艺实现微区反应制备纳米CeO2粉体和掺铜CeO2复合粉体;再以硝酸铈为铈源,氨水为沉淀剂,用凹凸棒石为载体合成凹凸棒石负载CeO2纳米复合材料。利用XRD、TEM、HRTEM和BET-N2等手段对所得产物的成分、物相结构和形貌进行表征,研究所制备的纳米CeO2及其复合催化剂对CO氧化的催化性能。结果表明:所制备的纳米CeO2粉体和掺铜CeO2复合粉体呈球形,粒径均为4～5nm,且单分散性好;所合成的CeO2/凹凸棒石纳米复合材料中,CeO2颗粒均匀包覆在凹凸棒石表面。催化实验结果表明:CeO2颗粒越小、比表面积越大,对CO氧化的催化活性就越高;凹凸棒石负载CeO2纳米复合催化剂具有很强的协同催化效应,可提高其催化活性;Cu(5%)-Ce-O催化剂对CO氧化具有最好的催化活性,表明铜的掺入有利于提高CeO2在CO催化氧化反应中的低温活性,降低起燃温度。

CeO2 and Cu-doped CeO2 nano-particles were prepared by ultrasonic automization method using cerium nitrate, copper nitrate and sodium hydroxide as raw materials, and the palygorskite supported with CeO2 composite nanocatalyst was synthesized by liquid phase precipitation process using cerium nitrate as cerium resource and ammonia as precipitating agent. The as-prepared samples were characterized by X-ray diffractometry（XRD）, transmission electron microseopy（TEM）, high resolution TEM and Brunauer-Emmett-Teller procedure（BET-N2）. The catalytic performances of samples for CO oxidation were examined. The results show that the well dispersed and uniformly distributed CeO2 and Cu-doped CeO2 particles with size of about 4-5 nm are obtained, and the nano-CeO2 particles are coated on the surface of palygorskite homogeneously and densely by the above methods. The results of catalytic tests exhibit that the supported-catalyst has a positive synergistic catalytic effect, thus shows excellent catalytic activity for CO oxidation. The catalytic activity for CO oxidation obviously depends on the size of CeO2 particles, and Cu dopant significantly enhances the catalytic efficiency.