Br (?) Nsted Acidic Ionic Liquid In The Esterification Reaction

This dissertation consists of two parts: (1) The preparation of methyl acetate of ultra purity in acidic ionic liquids; (2) The study of esterifaction reactions in Br0nsted acidic ionic liquids.1. The preparation of methyl acetate of ultra purity in acidic ionic liquidsPreparation of methyl acetate in ionic liquids was studied for the first tune. Under optimized reaction conditions, methyl acetate of purity over 99% was obtained.Three Brensted acidic ionic liquids were synthesized: [Hmim]+CH3COO-, [Hmim]+TsO- and [Hmim]+BF4-, and the catalytic capacity in the preparation of methyl acetate was studied. Experiments showed that all of the three ionic liquids can catalyze the esterification of acetic acid with methanol, and the conversions of methanol were high after reaching equibrilium. Through evaluating reaction rate, conversion of methanol and yield of the product, ionic liquid [Hmim]+BF4- was selected as the catalyst for the reaction.The conversion of methanol was above 99.5% when the reaction was carried out at 100℃ for 6 hours, and the molar ratio of ionic liquid to acetic acid to methanol was 0.7:3:1. By rectifying the product was obtained with the highest purity of 99.18% and the yield of 94.3%.Ionic liquid [Hmim]+BF4- is very stable. When the product and the excess of acetic acid have been distilled off, the ionic liquid can be reused after drying under vacuum, and recycled for 6 runs without appreciable change in catalytical capacity.2. The study of esterification reaction in Br0nsted acidic ionic liquidsThe esterification in several Br0nsted acidic ionic liuqids based on organic acid was studied. Ionic liquid functioned as reactant, catalyst and solvent, and the resultsof esterification were compared and explained.In ionic liquid [Hmim]+HCOO- and [Hmim]+CH3COO-, the conversions of most alcohols were high. Without sulfuric acid, there was no elimination or dehydration reactions and envioment pollutions. In ionic liquids, the conversions of alcohols were related to the structure of the acids and alcohols, as well as the boiling points of the alcohols. Generally speaking, primary alcohols were esterified most easily, and their conversions were the highest during the same time, followed by secondary alcohols, then tertiary alcohols due to the increase in the steric interaction. However, if the boiling point of an alcohol was below the reaction temperature, there would be a decrease in the conversion as there was part of the reactant refluxing. To allyl alcohol and benzyl alcohol, the paired electrons of oxygen can be conjugated with double bond and thus the electron cloud density decreased, so the nucleophilicity was decreased. For a particular alcohol, the structure of the acid influenced the result.The esterification with aromatic acids was the most difficult, because the positive charge of the carbon anion formed during reaction delocalized to benzene.Ionic liquid [Hmim]+TsO- can hardly be used for an esterification reagent, but it can catalyze esterification of other acids and alcohols. The ionic liquid is very stable and not decomposable, is a promising catalyst for esterification.