Research In The Synthetic Technics Of Trimethyl Borate By Boric Acid And Methanol

Trimethyl borate, one of the important boron compound, has been mainly used for synthesis of boron hydride, senior boric acid ester and the preparation of high purity boron. In addition, it can be also used as plasticizer, anti-wear additives, flame retardants, lubricating oil and polymer stabilizer, etc. With the development of senior boric acid ester and new energy, there will be an increasing demand of trimethyl borate. Consequently, the study on synthesis and purifying of trimethyl borate is of great significance.In our study, Gas Chromatography—Mass Spectrometry, Gas chromatography, Titration analysis has been established for the qualitative and quantitative analysis of trimethyl borate. Trimethyl borate was prepared by direct reaction with raw materials of boric acid and methanol. The optimum reaction conditions have been determined with 1:21of the boric acid and methanol molar ratio, 54℃ of reflux temperature, 5 h of reflux time. After reaction, the method of fractional distillation and forerunning were adopted to obtain the trimethyl borate and methanol azeotropic system(70:30).Secondly, the separation of azeotrope of trimethyl borate and methanol has been investigated by extractive distillation using N,N-Dimethyl formamide as an extraction agent. The products could be separated under the following operation condition: The drip speed rate of extraction solvent is 2.8 m L/min, reflux ratio in extractive distillation 7, optimum temperature of solvent 55℃, total reflux time 35 min. The trimethyl borate with purity 98.19% and the yield of 72.03% has been obtained.At last, the separation of azeotrope of trimethyl borate and methanol has been investigated by the salt out agent of calcium chloride. The conditions of salt out are as follows: the mesh of calcium chloride is 20-80, temperature of oscillation 20℃, rotate speed 320 r/min, rotate time 10 min. The purity of trimethyl borate is 93.40%. Secondary salt out has been used for the further separation, and then the product trimethyl borate with purity 99% and the yield of 84.74% had been obtained.