Method for preparing dimethyl maleate

Abstract

The invention relates to a method for preparing dimethyl maleate, which comprises the following steps of : (1) dehydration and impurity removal: methanol is mixed with alkaline-earth metal oxide to be dehydrated and removed impurity; (2) separation of solid and liquid; (3) monoesterification reaction: maleic anhydride is added in liquid-phase material which is obtained in the previous step; (4) vacuum distillation; (5) two-esterification reaction: acid catalyst and methanol are added in the material after the vacuum distillation in the previous step; (6) evaporation; (7) mixing of oil and water; (8) separation of oil and water; (9) re-esterification reaction; (10) evaporation; (11) mixing of oil and water; (12) separation of oil and water; (13) impurity removal and dehydration; (14) separation of solid and liquid: liquid-phase material enters the next step; (15) rectification separation: the product dimethyl maleate is obtained. The method is simple and has reasonable process, low preparation cost, high product purity and good product quality.

Description

technical field [0001] The invention relates to a method for preparing dimethyl maleate, in particular to a method for preparing dimethyl maleate by using maleic anhydride and methanol as raw materials, and belongs to the field of fine chemicals. Background technique [0002] Dimethyl Maleate (DMM), also known as dimethyl maleate (Maleic Acid Ester), CAS number 624-48-6, molecular formula C 6 h 8 o 4 , the molecular weight is 144.13, it is a colorless irritating liquid, the refractive index (n25D) is 1.4405, and the relative density of the phase material (d 4 25 ) 1.462, with a melting point of -19.0°C, a boiling point of 200.4°C, and a flash point (open cup) of 112°C. It is soluble in ether and miscible with various organic solvents. It is mainly used as a raw material for solvent and fine organic chemical synthesis, and can be used for the production of paints, coatings, pesticides, anti-rust additives, etc. It is an important organic chemical raw material. [0003] ...

AI Technical Summary

Problems solved by technology

[0013] In the prior art, the main problem in the synthesis of dimethyl maleate from maleic anhydride or maleic acid and methanol is that in the second step, the diesterification reaction between monomethyl maleate and methanol generates In the process of dimethyl maleate, because the reaction of monomethyl maleate and methanol is an equilibrium reversible reaction, and the by-product water in the reaction process, the prior art adopts methanol evaporation to take out water to achieve the effect of water removal. The purpose is very difficult, it is difficult to effectively remove the water of by-product in the reaction, so the reaction of monomethyl maleate is difficult to carry out thoroughly, the reaction conversion rate is low, the process reaction rate is slow, and the diesterification reaction product maleic acid di The selectivity and yield of methyl esters are reduced, and dimethyl maleate forms an azeotrope with water, which leads to difficulties in the separation and purification of materials after the diesterification reaction, and the product has low purity and poor quality

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