Preparation method of trimethyl borate

Abstract

The invention discloses a preparation method of trimethyl borate. The method comprises the following steps of: (1) heating and dehydrating a boric acid solid to prepare metaboric acid and pyroboric acid solids; (2) adding the metaboric acid and pyroboric acid solids which are obtained in the step (1) to methanol to make the mixture react under a stirring state; (3) heating and distilling the reaction solution obtained in the step (2) to obtain an azeotrope solution of the methanol and the trimethyl borate, distilling and cooling raffinate to obtain boric acid; and (4) separating the azeotrope solution of the methanol and the trimethyl borate, which is obtained in the step (3), to obtain a trimethyl borate product. In the invention, by firstly heating and dewatering the boric acid to prepare the metaboric acid and the pyroboric acid and then making the metaboric acid and the pyroboric acid react with the methanol to prepare trimethyl borate, the reaction speed is accelerated, the conversion per pass is improved, the reaction conditions are mild and no risks exist.

Description

technical field [0001] The invention relates to the technical field of borate preparation, in particular to a preparation method of trimethyl borate. Background technique [0002] Trimethyl borate is an important organic borate, mainly used in the synthesis of organic borides and the preparation of high-purity boron, and can also be used as organic solvents, plasticizers, catalysts, welding fluxes, flame retardants and polymerization Stabilizers etc. [0003] Trimethyl borate is a main raw material for the synthesis of boron-containing compounds, which can be used to produce sodium borohydride and higher esters; secondly, it is also widely used in olefin polymerization, wood preservation, oil and lubricant additives and other fields. In addition, trimethyl borate is also used in the preparation of special glass in optical devices and the preparation of boronic acid intermediates. [0004] The preparation method of trimethyl borate mainly contains following three kinds: ...

AI Technical Summary

Problems solved by technology

[0011] Wherein in the first method, due to the direct reaction of boric acid and methanol, the reaction generates a large amount of water, which will affect the reaction speed and conversion rate, and the removal of these water by distillation consumes a large amount of energy

The second method, for the defect of the first method, the water of boric acid is removed in advance to make boron oxide, so that the reaction speed and conversion rate are greatly improved, and the reflux ratio in the rectification process is only 3: 1, but this The method has two disadvantages: (1) It is very difficult to prepare boron oxide from boric acid, and boric acid is gradually dehydrated when heated to 70-100 ° C, and loses a part of water to form metaboric acid (HBO 2 ), when heated to 150-160°C, another 0.25 molecule of water will be lost to produce pyroboric acid (H 2 B 4 o 7 ), when heated to above 300°C, 0.25 molecular water will be lost to generate boron oxide (B 2 o 3 )

It can be seen that the process conditions for the preparation of boron oxide from boric acid are very harsh; (2) methanol reacts with boron oxide, and a violent reaction occurs at room temperature, which has a great safety risk

And the third method has the advantage that the raw material cost is relatively low, but there are still two disadvantages: (1) there is a large amount of water in the raw material itself. (2) In the reaction process, inorganic salt sodium bisulfate is produced, which makes it difficult to handle the water in the system after the reaction, which brings environmental problems