Method for producing malic acid ester through direct esterification of malic acid aqueous solution

Abstract

The invention discloses a method for directly esterifying malic acid aqueous solution to produce malate. The method particularly includes mixing the malic acid aqueous solution, alcohol and inorganic acid with one another in a reaction vessel I; carrying out esterification reaction at the temperature of 80-120 DEG C under stirring conditions; generating steam mixtures with the malate, the alcohol and water in reaction procedures; cooling the steam mixtures and then filling a reaction vessel II with the steam mixtures; distilling the steam mixtures at the temperature of 50-90 DEG C under stirring conditions; allowing alcohol steam generated by means of distillation to flow back to spaces below a liquid surface of reaction liquid in the reaction vessel I; carrying out circular reaction for 2-10 hours, carrying out rotary evaporation on products in the reaction vessel II and removing the alcohol; extracting and drying residues to obtain the malate. The method has the advantages that the method is easy to implement, and conditions are controllable; catalysts do not need to be neutralized in downstream purification procedures, the malate is easy to extract, the production cost can be lowered to a great extent, and the malate yield can be greatly increased.

Description

technical field [0001] The invention belongs to the field of biochemical industry, and in particular relates to a method for directly esterifying malic acid aqueous solution to produce malic acid ester. Background technique [0002] Malate compounds include dimethyl malate, diethyl malate, dibutyl malate and other compounds, all of which have important uses. For example, dimethyl malate (Dimethyl malate, CAS NO: 617-55-0) is an important food, chemical raw material and pharmaceutical intermediate, with a molecular weight of 162.14 and a boiling point of 104-108°C. It can be used as a food sour agent and preservative , as well as coagulation inhibitors and fluorescent whitening agents in the chemical industry, have broad market prospects. [0003] The industrial preparation of malic acid esters is obtained by using concentrated sulfuric acid as a catalyst, and using anhydrous malic acid and alcohol as raw materials for esterification reaction. This method has serious equipme...

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Problems solved by technology

[0003] The industrial preparation of malic acid esters is obtained by using concentrated sulfuric acid as a catalyst, and using anhydrous malic acid and alcohol as raw materials for esterification reaction. This method has serious equipment corrosion and many side reactions. The catalyst must be neutralized to remove it. Environmental and catalyst can not be reused and other issues

In addition, due to the high solubility of malic acid, the preparation of finished malic acid needs to be crystallized in an 80% (m / v) supersaturated solution, resulting in high extraction and concentration costs

[0004] In the existing literature reports on malic acid esterification, most of the fossil-sourced D,L-malic acid products react with different esterifying agents to form malic acid esters under various catalysts, but the malic acid in the fermentation broth There is a lack of reports on the direct esterification of acid to produce malate

In existing patent reports, for example, Ren Xiaoqian et al. use the succinic acid solution produced by the fermentation method to directly esterify the succinic acid diester by adding alcohol, catalyst and extractant (invention patent application number 201410100605.8), but the immobilization method designed The sulfonic acid heteropolyacid ionic liquid is used as a catalyst, and the catalytic cost is high. At the same time, the addition of polychlorinated alkanes to extract the esterified product is beneficial to promote the forward reaction, but it further increases the cost of extraction and separation.