Synthesis Of Benzimidazole Ionic Liquid And Catalytic Synthesis Of Paraben

Imidazole ionic liquid has many excellent properties.As its derivative,benzimidazole ionic liquid has good properties such as insensitivity to air and water,low melting point and high stability.In the past,people used concentrated sulfuric acid,solid acid,chitosan,enzymes,and ionic liquid to catalyze the esterification reaction.Among them,the ionic liquid catalyzed reaction yield was high,and it was environmentally friendly.Therefore,in this paper,benzimidazole ionic liquid is used to catalyze the synthesis of methyl paraben,with high yield,environmental protection,and the catalyst can be recycled many times.Compared with traditional catalysts,benzimidazole ionic liquid has many excellent characteristics.Catalytically synthesized methylparaben has the advantages of high chemical stability,non-volatile,antibacterial,low cost and no odor.It is often used as a preservative in cosmetics,medicine,food and beverages.In this paper,benzimidazole and benzyl chloride are used as rawmaterials,and dimethyl sulfoxide is used as a solvent.After reaction at room temperature for 3 hours,1-benzylbenzimidazole is synthesized with a yield of more than 90%.The compounds were characterized by FT-IR,1H NMR and 13C NMR,and the reaction conditions were optimized.Using 1-benzylbenzimidazole and acid(concentrated sulfuric acid,fluoboric acid,p-toluenesulfonic acid,hydrochloric acid,nitric acid,trifluoroacetic acid,methanesulfonic acid,phosphoric acid)as raw materials,ethanol as a solvent,react at room temperature for 8 h,synthesis Eight kinds of benzimidazole ionic liquids were obtained,and the yield was more than 70%.The compounds were characterized by FT-IR,1H NMR and 13C NMR,and the reaction conditions were optimized.In addition,the physical and chemical properties of benzimidazole ionic liquids such as solubility,water absorption,pH,TGA,SEM,etc.were also tested.Using 8 kinds of synthesized benzimidazole ionic liquids respectively to catalyze the reaction of p-hydroxybenzoic acid and methanol to synthesize methyl paraben,the yield is over 80%,and the melting point is tested.The compounds were characterized by FT-IR.Through orthogonal experiments,the effects of reaction temperature,reaction time,molar ratio of reactants and catalyst dosage on the yield of methyl paraben were studied.The results show that the optimal reaction conditions for the synthesis of methyl paraben are:reaction temperature 65?,reaction time 6 h,reactant molar ratio 1:3,catalyst dosage 15%(relative to the amount of acid substance)In addition,the recycling performance of the ionic liquid was also studied.The results showed that the ionic liquid was used for 5 times,and the catalytic activity was slightly reduced,indicating that the prepared benzimidazole ionic liquid is an excellent catalyst.