水和游离脂肪酸对DBU催化制备生物柴油的影响

Effects of water and free fatty acids on biodiesel production using DBU as catalyst

以低品质油脂作为生产生物柴油的原料可以有效降低产品的成本。催化剂对原料油中主要杂质游离脂肪酸和水分的耐受程度决定了该工艺对原料油的适应性。本文采用有机碱1,8-二氮杂双环[5,4,0]十一碳-7-烯(DBU)催化酯交换反应制备生物柴油,研究了不同水和游离脂肪酸含量下酯交换反应的转化率、反应后产物两相的组成以及各组分在两相的分配。结果表明,DBU作为催化剂时,对水和游离脂肪酸具有较强的耐受性:水含量小于2%(质量分数,下同),游离脂肪酸含量小于5%;1.5%左右的水对反应具有促进作用,水含量为1.5%时,酯交换转化率最高可达93.7%。此外,水和游离脂肪酸会降低甲醇、DBU在甲酯相中的分布,这使得甲酯相中甲酯的纯度有所上升。

It is an effective way to decrease the cost of biodiesel using low-quality fats and oils as feedstock.The choice of feedstock however is dependent on the tolerance of the catalyst to the impurities(such as free fatty acids and moisture).In this paper,an organic base 1,8-diazabicyclo-[5.4.0]-undec-7-ene(DBU)was used to catalyze the transesterification reaction to produce biodiesel.The effects of water and free fatty acid content on the conversion of transesterification,the phase composition and the distribution of the components after the reaction were studied.It showed that the DBU catalyst has an excellent tolerance to water and free fatty acid(water<2%or FFA<5%).Furthermore,the presence of about 1.5%water can improve the conversion of the reaction.The highest conversion of 93.7%was obtained when the water content was 1.5%.In addition,the distribution of methanol and DBU in the biodiesel-rich phase decreased with the increase of water and FFA content.As a result,the purity of biodiesel in the biodiesel-rich phase increased.