金属复合氧化物催化制备生物柴油重复使用性能比较

Comparison of repetitive performance of metal composite oxide as catalyst for biodiesel synthesis

采用共沉淀及焙烧的方法制备了Mg-Al-O及Ca-Al-O固体碱催化剂。采用醇洗、干燥及焙烧的方法对用过的催化剂进行了活化处理。以一定条件下蓖麻油和甲醇的酯交换反应为模型反应,考察了催化剂重复使用次数对催化剂活性的影响并应用Hammett指示剂滴定法、XRD技术对新催化剂及使用后经活化处理的催化剂进行了表征,对催化过程碱溶解流失和析出的甘油量、总甘油量进行了测定。结果表明:两种金属复合氧化物固体碱均表现出了很好的重复使用性能,催化剂的碱强度均在7.2<H-<15.6范围;Mg-Al-O固体碱催化剂主要由Mg O晶体构成,Ca-Al-O固体碱催化剂由大量Ca O晶体和少量Al2O3晶体构成。两种固体碱催化剂的碱溶解流失均较小,生成的甘油量均较多。

The Mg-Al-O and Ca-Al-O solid base catalysts were prepared by co-precipitation and calcination process.Used catalyst was activated by alcohol washing, drying and calcination methods.The effects of repetitive use times of catalyst on catalyst activity were investigated with transesterification reaction of castor oil and methanol under certain conditions as a model reaction. The catalyst and activated catalyst were characterized using Hammett indicator titration and XRD technique. The alkali dissolution loss in the catalytic process, the amount of glycerol precipitated and total glycerol amount were determined. The results showed that two kinds of metal composite oxide solid base exhibited good repetitive performance. The base strength of the catalyst were 7.2 〈 H_ 〈 15.6, Mg - Al - O solid base catalyst consisted essentially of MgO crystal, and Ca - Al - O solid base catalyst consisted of a large amount of CaO crystal and a small amount of Al2O3 crystal. Alkali dissolution loss of the two solid base catalysts was small, and the amount of glycerol produced was more.