以月桂酸(LA)和甲醇为原料,以离子液体(ILs)为催化剂,经酯化反应合成月桂酸甲酯。三种不同催化剂的效率,1-甲基咪唑硫酸氢盐([Hmim]HSO4),比较了1-甲基-2-吡咯烷酮硫酸氢铵([Hnmp]HSO4)和H2SO4。甲醇/LA摩尔比的影响,反应温度,通过单因素实验考察了反应时间和催化剂用量对LA酯化率的影响。在单因素实验的基础上,采用响应面法对LA与甲醇的酯化反应进行了优化。结果表明,最有效的催化剂是IL[Hnmp]HSO4。最佳条件为:[Hnmp]HSO4用量为5.23%,甲醇/LA摩尔比为7.68:1,反应时间为2.27h,反应温度为70°C。在这些条件下,酯化的LA转化率达到98.58%。动力学研究表明,酯化是二级反应,活化能和频率因子分别为68.45kJmol-1和1.9189×109min-1。[Hnmp]HSO4的催化活性在5次循环后仍然很高。
Methyl laurate was synthesized from lauric acid (LA) and methanol via an esterification reaction using ionic liquids (ILs) as catalysts. The efficiencies of three different catalysts, 1-methylimidazole hydrogen sulfate ([Hmim]HSO4), 1-methyl-2-pyrrolidonium hydrogen sulfate ([Hnmp]HSO4) and H2SO4, were compared. The effect of the methanol/LA molar ratio, reaction temperature, reaction time and catalyst dosage on the esterification rate of LA was investigated by single-factor experiments. Based on the single-factor experiments, the esterification of LA and methanol was optimized using response surface methodology. The results showed that the most effective catalyst was the IL [Hnmp]HSO4. The optimal conditions were as follows: [Hnmp]HSO4 dosage of 5.23%, methanol/LA molar ratio of 7.68 : 1, reaction time of 2.27 h and reaction temperature of 70°C. Under these conditions, the LA conversion of the esterification reached 98.58%. A kinetic
study indicated that the esterification was a second-order reaction with an activation energy and a frequency factor of 68.45 kJ mol-1 and 1.9189 × 109 min-1, respectively. The catalytic activity of [Hnmp]HSO4 remained high after five cycles.