Study On The Synthesis Of Alkyl Gallate

Gallic acid alkyl esters possess strong antioxidant and antibacterial activity, which were widely utilized in food, medicine, cosmetic and feed industry etc. Based on this, studies on reaction rules, process conditions,separation and purification method of products with respect to the synthesis of methyl gallate(MG), dodecyl gallate(DG) and gallic acid stearyl ester(SG) via Fischer esterification were implemented, and the synthesis method of electronic grade methyl gallate was preliminarily discussed as well in this paper. The main content are as following:(1) In the study of synthesis of MG, the resin and sulfuric acid were used as catalysts. The rule of esterification reaction using resin as catalyst were explored, and also Thermodynamic characteristics and kinetic characteristics of the reaction were analyzed. Through orthogonal experiments, the ratio of acid to alcohol, the amount of sulfuric acid and reaction time were investigated. The optimal conditions of esterification:industrial grade gallic acid 0.05 mol, methanol 50 m L, catalyst amount0.6 m L, reflux reaction time 12 h, the yield of product was more than95%. In addition, a preliminary study on the synthesis of electronic grade MG was carried out.(2) In the study of synthesis of DG, selection of suitable catalyst,water-carrying agent and solvent were implemented through single factorexperiment. Besides, through orthogonal experiment, the optimal process parameters were obtained: industrial grade gallic acid 2.0 mol, lauryl alcohol 2.4 mol, solvent amount 500 m L, catalyst amount 20 g, reaction time 12~16 h under oil bath heating and stirring condition. The esterification rate was 97%. In addition, separation of the reaction product and purification of the crude ester were carried out. Isolation, recyle and analysis method of raw material and solvent were preliminarily investigated;(3) In the study of synthesis of SG, the preliminary conditions of the reaction were investigated by single factor experiment using non oxidizing organic solid acid as catalyst. The ratio of acid to alcohol, the amount of catalyst, the amount of solvent and reaction time were further optimized through orthogonal test, and the optimal condition of esterification were obtained: solvent adding quantity to gallic acid mole ratio 200 m L:1mol, alcohol-to-acid mole ratio 1:1.5, catalyst-to-gallic acid mole ratio 0.1:1, reaction time 16 h. The esterification rate was98.4%.The amplification test results demonstrated that proposed methods could be applied to industrial production.