Study On Synthesis Of Acidic Functional Ionic Liquids And Their Applications In Esterification As Catalysts

As traditional catalysts for esterification reaction,concentrated sulfuric acid might erode equipment and pollute environment.As kind of new green catalyst,acidic ionic liquids are characterized by high catalytic activity,environmentally friendly,recyclable,etc.Acidic ionic liquids were reported as catalyst in the esterification reaction in recent years.Acidic ionic liquids have significant shortcomings in efficient separation of reactants and catalyst as well as recycling,so heterogeneous esterification reaction catalyzed with ionic liquids becoming focus of study.Lewis acidic ionic liquids were designed and prepared using [Bmim]Br and metal chlorides.The thermal stability,acidity,and catalytic properties were studied,and used for the synthesis of succinic acid diisopropyl ester.It was found that [Bmim]Br-Fe2Cl6 had the best catalytic activity and the stronger the Lewis acidic ionic liquids,esterification activity is higer.The optimal reaction condition was confirmed,and the yield was 81.9%.The yield of the product decreased by 1.7% after [Bmim]Br-Fe2Cl6 was repeated used for 6 times.However,the structure of Lewis acidic ionic liquids acid is not stable,and they react easily with water,there is high requirement for water content in materials and reaction system.Comparing with Lewis acidic ionic liquids,Br?nsted acidic ionic liquids have advantages in providing hydrogen proton intrinsically.Moreover,Br?nsted acidic ionic liquids have fine water-stability,which is a unique nature of Br?nsted acidic ionic liquids.In this paper,a series of Br?nsted acidic ionic liquids were designed and synthesized.The influence of anion-cation on the acidity of ionic liquids was investigated by FTIR and Hammett acidity.Solubility experiments were done to study the intersolubility,and the catalytic activity was tested too.The relationship of catalytic activity of ionic liquid and its acidity and solubility was studied.The optimum technological condition of the synthesis of carboxylic acid esters was determined.The yield of the product decreased slightly after [HSO3-Bmim]HSO4 was used as catalytic for 7 times.To solve the problem of acidic ionic liquids homogeneous catalysis esterification reaction,grafted ionic liquids and the binuclear ionic liquids as the catalyst of heterogeneous catalytic reaction system was constructed in the paper.Firstly,the catalytic acidic ionic liquid [HSO3-Pmim]HSO4 supported on silicon gel was prepared by sol gel method and two-step method,and used for synthesis of n-butyl acetate.The productivity was 69.10%.During repeated use of grafted ionic liquids,the loss of ionic liquids from the supporter was inevitable.The binuclear ionic liquids as the catalyst to build heterogeneous catalytic reaction system that can solve above problem.In this paper,four kinds of binuclear ionic liquid,Im-PTSA,Im-HSO4,Py-PTSA,and Py-HSO4 were synthetized,and were used in the synthesis of diethyl succinate.The catalytic ability order was Im-HSO4 > Py-HSO4 > Im-PTSA > Py-PTSA.Catalytic Im-HSO4 showed the best catalytic ability,and the production yield was 93.6%.The paper put forward the dual-core ionic liquid catalytic esterification of in situ reaction separation coupling mechanism,which was validated by cold-state experiment.