Method for preparing tetramethyl ammonium bromide

Abstract

The invention discloses a method for preparing tetramethyl ammonium bromide. The method includes the steps that methyl aryl ether is subjected to demethylating reaction under the acid condition to generate gas containing methyl bromide, the gas containing methyl bromide is firstly introduced into an alkaline solution for adsorption, overflow gas then sequentially passes a particle activated carbon filler adsorption column and a particle anhydrous calcium chloride filler adsorption column, and pure dried methyl bromide gas is obtained; the methyl bromide gas is introduced into stirred absolute ethyl alcohol to obtain a methyl bromide and ethanol solution; dried trimethylamine gas is introduced into the methyl bromide and ethanol solution, and tetramethyl ammonium bromide precipitate is generated through reaction. The problem about recycle and use of the side product methyl bromide of the demethylating reaction of methyl aryl ether is solved through the simple method, the methyl bromide absorption rate is nearly 100%, the technology is simple and feasible, emission of three wastes meets requirements, methyl bromide recycle cost is low, and competitiveness is extremely good.

Description

technical field [0001] The invention relates to a method for preparing tetramethylammonium bromide, in particular to a method for preparing tetramethylammonium bromide by using methyl bromide, a by-product of methyl aryl ether hydrolysis and demethylation reaction, as a raw material. Background technique [0002] The acidic demethylation reaction of methyl aryl ether is a classic reaction, which takes acetic acid and hydrobromic acid or boron tribromide as the medium to remove the methyl group under acidic conditions, especially with acetic acid and hydrogen bromide Acid is the medium, and the methyl bromide is removed under the condition of reflux, and the reaction of forming the by-product methyl bromide is the most common. The reason is that the reaction has the lowest production cost and the reaction is well controlled. The disadvantage is that there are many side reactions, and the generated methyl bromide is difficult to handle. [0003] When methyl aryl ether and hy...

AI Technical Summary

Problems solved by technology

In this way, many chemicals synthesized with methyl bromide as the starting material also face the need to change the synthetic route to produce, which greatly increases the manufacturing cost of these chemicals

[0004] Although methyl aryl ether and hydrobromic acid carry out the demethylation reaction of methyl aryl ether and hydrobromic acid to produce methyl bromide under acidic conditions, the random discharge of methyl bromide is highly dangerous. extremely difficult to use

[0005] 1. The demethylation reaction of methyl aryl ether under acidic conditions is a batch reaction. Since the amount of methyl bromide produced by each batch of reaction is small, the gas storage cost is too high, and the problem of storage cannot be considered in industry. The methyl bromide produced by each batch of reaction must be used up in time

[0006] 2. The reaction time of each batch of demethylation reaction is about 2 to 6 hours, while the reaction time of the existing methyl bromide recycling process is more than 12 hours

This causes a serious mismatch between the generation rate of methyl bromide and the rate of recovery of methyl bromide, making the process impossible to achieve industrialization

[0007] 3. The conversion rate of methyl bromide absorbed by the existing methyl bromide recycling process is not ideal, that is to say, there is still a lot of residual methyl bromide in the exhaust tail gas after treatment, which will have an impact on the environment. Not high enough to be recycled further

[0008] 4. The equipment investment in the existing process of recycling methyl bromide gas is large, and the price of the product of the methyl aryl ether demethylation reaction is not too high. If the investment in the recovery process of methyl bromide is increased, the entire process will not have industrial application value

[0009] In summary, the existing methyl bromide recycling process cannot be applied to the industrial production of methyl aryl ether demethylation reaction