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采用溶胶-凝胶法制备了Al_2O_3-Si O_2复合载体,采用等体积浸渍法在复合载体上负载Zn O制备固体碱催化剂,催化动物脂肪废油酯交换反应来制备生物柴油。研究了Zn O负载量以及复合载体中Al_2O_3/Si O_2质量比对催化剂活性的影响,并通过重复性实验对优化得到的催化剂稳定性进行考察。活性测试表明,当Zn O的负载量为20%,复合载体中Al_2O_3/Si O_2质量比为1∶9时催化剂的活性最佳,酯交换率达到95.2%。另外,对催化剂进行了BET、XRD、CO_2-TPD一系列表征。结果表明,Al_2O_3高度分散渗透于非晶相Si O_2中,形成催化剂的介孔结构。Zn O负载量为20%时催化剂碱性最强,这是导致催化剂高活性的重要原因。
Al 2 O 3 -SiO 2 composite support was prepared by sol-gel method. The solid support was prepared by loading Zn O on the composite support by the same volume impregnation method to catalyze the transesterification of animal fat waste oil to prepare biodiesel. The effects of ZnO loading, Al 2 O 3 / SiO 2 mass ratio on the catalyst activity were investigated. The stability of the catalyst was investigated by repeated experiments. The activity tests show that the catalyst has the best activity and the transesterification rate reaches 95.2% when the content of ZnO is 20% and the mass ratio of Al 2 O 3 / SiO 2 is 1: 9. In addition, a series of characterizations of catalysts were carried out by BET, XRD and CO_2-TPD. The results show that Al 2 O 3 is highly dispersed and permeates into the amorphous phase Si O 2, forming a mesoporous structure of the catalyst. When the loading of Zn O is 20%, the catalyst has the strongest basicity, which is an important reason for the high activity of the catalyst.