Study On Synthesis Of Isopropyl Palmitate Catalyzed By Br?nsted Acidic Task-specific Ionic Liquids

Isopropyl palmitate is an important organic compound and intermediate of chemical raw materials,which is widely used in cosmetics,medicine and other fields.The conventional method for the synthesis of isopropyl palmitate has several drawbacks:1.Using a large amount of acid or base catalyst will cause serious equipment corrosion;2.Extensive use of toxic and harmful organic reagents may cause pollution to the environment;3.The reaction time is long and the yield is not high;4.The catalyst can not be recycled.In recent years,task-specific ionic liquids?TSILs?have developed rapidly.Due to its excellent physical and chemical properties,it is widely used in the research work of green chemistry.In this paper,isopropanol and palmitic acid were used as raw materials to synthesize isopropyl palmitate in the presence of solvent-free and acidic task-specific ionic liquids,which highlighted the role and advantages of task-specific ionic liquids in green synthesis.In this paper,a series of acidic task-specific ionic liquids with different numbers of-SO₃H were synthesized,including conventional acidic ionic liquid[Hmim][HSO₄],single-SO₃H task-specific ionic liquids[MIM-PS][HSO₄],[MIM-BS][HSO₄],[TEA-PS][HSO₄],double-SO₃H task-specific ionic liquids[2?IM-PS?-C₃][HSO₄]₂,[DA-2PS][HSO₄]₂andquadruple-SO₃Htask-specificionicliquid[HMA-4PS][HSO₄]₄,and the catalysts were characterized by FT-IR,NMR,TGA and other techniques.It is found that[HMA-4PS][HSO₄]₄ has the highest catalytic activity in the reaction of synthesizing isopropyl palmitate.Subsequently,the related reaction conditions were optimized by univariate analysis:isopropanol:palmitic acid:ionic liquid=5:1:0.04?molar ratio?,the reaction time was 8 hours,the reaction temperature was 90?,the esterification rate was 87.89%.At the same time,the cyclic performance was investigated.The catalytic effect was almost unchanged when the catalyst had been reused 6 times.In order to solve the problems of acidic task-specific ionic liquids,such as high viscosity,large application amount,high cost,and uneasily separation.Ionic liquids were immobilized.Two kinds of immobilized acidic task-specific ionic liquids were synthesized,and the reaction was catalyzed by silica-supported ionic liquid[HMA-4PS][HSO₄]₄.The optimum conditions under the water separator were determined by orthogonal experiments:isopropanol:palmitic acid=4:1?molar ratio?,the reaction temperature was 100°C,the reaction time was 5 hours,the amount of catalyst was 10 wt.%of palmitic acid,the reaction esterification was 98.37%.In addition,the catalysts were characterized by FT-IR,NMR.And the cyclic performance was investigated,the reaction esterification could still reach a level of92%after the catalyst had been reused 6 times.The study in this paper shows that acidic task-specific ionic liquids can be used in the catalytic synthesis of isopropyl palmitate,which provides a new way of environment-friendly synthesizing ester products.