离子液体催化合成食用香料乙酸辛酯的研究

Study on catalytic synthesis of n-octyl acetate in ionic liquid

乙酸辛酯是一种无色透明液体具有橙花、茉莉花和苹果香气的食用香料。实验利用微波辅助制备了离子液体1-丁基-3-甲基咪唑对甲苯磺酸盐([pmim]PTSA),并用红外光谱对其结构进行了分析表征。将[pmim]PTSA用于催化合成乙酸辛酯的反应中,考察了[pmim]PTSA的催化活性和离子液体用量、醇酸物质的量比、反应时间、离子液体重复使用等因素对酯化率的影响。结果表明:离子液体对该酯化反应有较好的催化活性。乙酸辛酯最佳合成条件为:离子液体用量15mL,n(辛醇):n(乙酸)=1.5:1.0,反应时间2.5h,酯化率达91.5%。反应结束后,产物乙酸辛酯与离子液体分层,倾倒即可分离。分离后的[pmim]PTSA蒸馏除水能重复使用,连续使用6次,催化活性不变。[pmim]PTSA是合成乙酸辛酯的良好催化剂。

The n-octyl acetate is one kind of achromatic color transparent liquid has the orange flower,the jasmine and the apple fragrance edible spice.A ionic liquid／[pmim／]PTSA was preparated by microwave radiation,and its structures was characterized by FT-IR.N-octyl acetate was synthesized from acetic acid and n-octanol with ionic liquid／[bmim／]PTSA as catalyst.The influences of the amount of ionic liquid,the reaction time,and the mole ratio between alcohol and acid on the esterification yield,and the catalyst properties of ／[pmim／]PTSA were discussed.The optimized condition are follow：／[bmim／]PTSA 15mL,the mole ratio of alcohol to acid 1.5：1.0,the reaction time 2.5h,The esterification yield is 91.5%.The n-octyl acetate and the ionic liquid could be easily separated from the reaction system via simple phase separation.After used 6 times under the esterification the ／[pmim／]PTAS keeps high catalyst.The ionic liquid is good catalyst of the esterification.