酯交换反应在制备生物柴油上的应用

Application of transesterification for the production of biodiesel

生物柴油因其环境友好且可再生作为矿物柴油的替代燃料而备受关注,生物柴油主要通过均相酸碱催化、脂肪酶催化、超临界法和固体酸碱催化的酯交换反应制备得到,但各种制备方法各有优劣,均相酸碱催化法反应迅速,转化率高但存在后续处理复杂,污染严重等问题;脂肪酶催化法反应条件温和,对原料中的水和游离脂肪酸不敏感,不需要过量的甲醇参与反应,后续处理工序简单,但酶的成本过高,这是制约其商业化发展的最大阻碍;超临界法是制备生物柴油的新技术,反应迅速,不需要催化剂,油脂转化率非常高,但其反应需要高温高压且能耗很大;固体酸碱催化剂腐蚀性小可以重复使用,后续分离工序简单,对环境的冲击较弱。其中负载型固体碱催化剂催化油脂酯交换反应将成为制备生物柴油的一个主要发展方向。

Biodiesel, an diesel alternative fuel. has attracted much attention because of its environmental benefits and renewability. Several transesterafication methods can be used to produce biodiesel, such as, homogeneous acid/base catalysis, lipase-catalyzed reaction, supercritical method and solid acid/base catalysis. However each method has its advantages and disadvantages. Homogeneous acid/base catalysis is very fast and with high efficiency, but down-stream product is difficult to purify and with significant pollution; Lipase-catalyzed reaction can take place in mild conditions and do not need excess methanol. It is not sensitive to water and free fatty acids, and the down-stream process is easy. But Lipase is too expensive which blocks its commercial use. Supercritical method is a new technology that is fast, and do not need catalyst. It has high conversion efficiency, but it requires high temperature and high pressure, and so high energy consumption, therefore is not cost effective. Solid acid/base catalyst, which can be recycled, has less causticity and without pollution. The down-stream product is easy to separate, which has less impaction on the environment. Supported solid base catalysis will be the main trend for biodiesel preparation by transesterification.