Synthesis Of Medium And Long Structure Lipids Catalyzed By Ionic Liquids

Medium-and long-chain triglycerides (MLCT) were low-calorie fats whichcontained both medium-chain fatty acids (MCFA) and long-chain fatty acids (LCFA)in the same glycerol backbones. They were widely used in clinical nutrition support,base oil fat emulsion, infant foods and low-calorie foods because of their specialmetabolic pathway. Ionic liquids were new green catalyst and solvent which werecomposed of ions and were low temperature molten salt which was liquid at roomtemperature. In this paper, homemade ionic liquids were used as catalyst in the acidhydrolysis of soybean oil and caprylic acid. The results showed that the ionic liquid[AAMIM][HSO4] had a good catalytic effect. Meanwhile, the effects of differentionic liquid structure on the catalytic properties were studied through6differentpurchased ionic liquids containing6different structures.Through the study of6ionic liquids containing different structures, we canconcluded that: the catalytic activity of the ionic liquids containing different cationsunder the same anion were as following: Pyrrolidine> Pyridine>Imidazole>Piperidine; the catalytic activity of ionic liquids containing differentanions under the same cation were as following: P-toluenesulfonate>Sulfate>Dihydrogen phosphate. This provided a theoretical basis for further designand screening efficient ionic liquids catalytic grease acid hydrolysis reactions.By the contrast of catalytic activity of three homemade acidic ionic liquids andthree homemade neutral ionic liquids, we could draw the following conclusions:neutral ionic liquids had very low catalytic activity. Under the experimental condition,the [PSMIM][BF4] had highest catalytic activity among3neutral ionic liquids andthe highest binding rate of carbon-chain fatty acid was3.67%under the substratemolar ratio8:1, reaction temperature130℃,4.0wt%ionic liquid load, reaction time10h, while the acidic ionic liquid had a very good catalytic activity. The acid hydrolysis reaction of soybean was catalyzed by homemade acidic ionicliquid [AAMIM][HSO4]. Based on the univariate experiment, we took an orthogonaltest. The orthogonal variance analysis showed the following three factors affectedsignificantly: time, temperature and catalyst, the optimum reaction conditions were asfollowing: reaction time6h, reaction temperature140℃,4wt%ionic liquid load(relative to the weight of total substrates), substrate molar ratio (fatty acids/soybeanoil) of10:1. Under the optimum conditions, the medium-chain acids binding rate were51.49%. We could draw conclude that the homemade ionic liquid had a good activity.The ionic liquid immobilized by Sol-gel method was used as catalyst onacidolysis of soybean oil and medium-chain acids. According to the single factorexperiment and response surface experiment, we could get the optimization of processconditions: substrate molar ratio (fatty acids/soybean oil) of8.30/1,12.22wt%ionicliquid load (relative to the weight of total substrates), reaction temperature131.49℃,reaction time9.00h, under these conditions, the MCFAbinding rate was51.24%.Using the ionic liquid immobilized before and after as catalyst, we tookexperiments under the optimal conditions. The MCFA bingding rates were51.49%and51.23%, respectively. This demonstrated that the ionic liquids immobilized or nothad the same catalytic activity. But the ionic liquid immobilized was easy to separatewith product and lighter in color.In order to explored the selectivity between caprylic and capric caused by theionic liquid immobilized, we took the experiment under the following condition:reaction temperature140℃,4.0wt%ionic liquid load, caprylic: capric: soybean oil=5:5:1(molar ratio), reaction time were2h,4h,6h,8h. The final MCFA binding rate was55.75%, capric binding rate was1.66~1.80times as that caprylic. When the substratewas caprilic: soybean oil=10:1and capric: soybean oil=10:1, respertively, the finalcapric binding rates was61.41%, and48.67%as that of caprylic. The binding rate ofcapric was1.19~1.26times than caprylic. So we could draw a conclusion from abovethat capric was easier to react than caprylic, and they competed with each other in the reaction, and capric was dominant.We found the MLCT crystallization peak was single by using DSC for acrystallization kinetics study. With the rate of decrease temperature increases, thecrystallization peak was wider and move towards to low temperature. The time ofcomplete crystallization was shorter. The higher crystallinity, the bigger decrease rateof temperature was needed.