以Brnsted-Lewis酸性离子液体为催化剂,用于催化生物柴油中不饱和脂肪酸甲酯聚合制备二聚酸甲酯反应,考察了催化剂种类、催化剂用量、反应温度和时间等因素对聚合反应性能的影响,得到较佳的反应条件.结果表明,当以1-(3-磺酸)-丙基-3-甲基咪唑氯锌酸盐[HO3S-(CH2)3-mim]Cl-ZnCl2(ZnCl2摩尔分数为0.67)为催化剂,生物柴油15g,m(生物柴油):m(离子液体)=15:1,于240oC下反应6h时,二聚酸甲酯收率为63.2%,其中三聚体含量小于5%.另外,该催化剂重复使用5次后,二聚酸甲酯收率仍超过63%,表明其具有较好的重复使用性能.离子液体的Brnsted和Lewis酸位的协同效应显著提高了其催化活性.
The polymerization of fatty acid methyl ester was investigated using biodiesel as the feed in the presence of a Brnsted-Lewis acidic ionic liquid (IL). A synergetic effect of Brnsted and Lewis acid sites enhanced the catalytic performance of the IL. 1-(3-Sulfonic acid)-propyl-3-methylimidazole chlorozincinate ([HO3S-(CH2)3-mim]Cl-ZnCl2,molar fraction of ZnCl2 was 0.67) was an efficient catalyst for the polymerization. The effects of catalyst amount,reaction temperature,and reaction time were investigated. The optimum conditions for the polymerization were:biodiesel 15 g,m(biodiesel):m(IL) = 15:1,reaction temperature 240 oC,and reaction time 6 h,which gave 63.2% yield of dimeric acid methyl ester. The reusability of the IL was good and after it was used five times,the dimeric acid methyl ester yield was still 63%.