LaMnO_3催化剂制备及用于氯乙烯催化燃烧研究

Preparation of LaMnO_3 Catalysts and Their Application for Catalytic Combustion of Vinyl Chloride

采用柠檬酸溶胶凝胶法制备了LaMnO_3钙钛矿氧化物用于氯乙烯催化燃烧模型反应,考察了催化剂制备条件包括焙烧温度、焙烧时间、柠檬酸用量以及操作参数如空速、氯乙烯浓度等对其催化活性的影响,并采用XRD、低温氮气吸附和H_2-TPR技术对相关催化剂的结构、晶体尺寸及氧化还原性能进行表征。实验结果发现,当柠檬酸与镧锰金属离子摩尔比为1.0,焙烧温度为800℃,焙烧时间为2 h时制备的LaMnO_3催化剂表现出最优的催化活性;该催化剂的催化活性随空速或氯乙烯浓度的增加逐渐降低,在72 h的连续反应后氯乙烯转化率仍高于90%,说明其具有良好的催化稳定性;同时材料表征结果表明比表面积、晶粒尺寸以及低温可还原性能是影响LaMnO_3催化剂催化活性的重要因素。

LaMnO3 perovskite-type oxides were prepared by citric sol-gel method for the model reaction of vinyl chloride （VC） catalytic combustion. The effects of preparation conditions including calcination temperature, calcination period, citric acid （CA） amounts and operation parameters such as space velocity, VC concentration on the catalytic activities of LaMnO3 catalysts were investigated. The structure, crystalline size and redox ability of LaMnO3 catalyst were characterized by XRD, low-temperature N2 sorption and H2-TPR techniques. It was found that the LaMnO3 catalyst prepared with the molar ratio of （La＋Mn）/CA=1.0 and under the calcination at 800℃ for 2 h exhibited the optimum catalytic activity for VC combustion. The catalytic activity of this catalyst gradually decreased with the increase in space velocity or VC concentration, and VC conversion remained above 90% over this catalyst after 72 h time-on-stream reaction, indicating its good catalytic stability. Addi- tionally, characterization results revealed that specific surface area, crystalline size and low-temperature reducibility were the important factors for influencing the catalytic activity of LaMnO3 catalyst.