Method for producing vitamin C by esterification reaction-infiltration evaporation barrier separation integral process

Abstract

The present invention provides a method of synthesizing the vitamin C (V _C ) through the esterification, the pervaporation (PV) membrane separation and integration technology, comprising the process of the methyl esterification between the methanol and the 2-ketone-L-gulonic acid (2-KLG) to produce the 2-ketone-L-gulonic methyl ester (2-Me-KLG). The process comprises the following steps: (1) the solid or liquid 2-KLG is dissolved in the methanol; the temperature is then raised and the catalyst is added; (2) the reaction solution prepared in the first step is pumped into the PV membrane separation device; the reaction solution after the membrane dehydration circulates into the esterification reactor; (3) the product 2-Me-KLG or the reaction solution is directly provided for the later production of the V_C. In the method of the present invention, the area of the used membrane is small; the ratio between the alcohol and acid of the raw material liquid and the reaction temperature are relatively low; the invention greatly improves the purity and collection rate of the 2-Me-KLG; the technology is simple and the process is stable; the present invention is suitable for the industrial production-line.

Description

technical field [0001] The invention relates to the application of pervaporation membrane technology in the esterification industry, in particular to a method for producing vitamin C by adopting an esterification reaction-pervaporation membrane separation integration process. Background technique [0002] V C V C The production scale and output are constantly expanding. [0003] V C One of the important links in the production process of methanol is the methyl esterification reaction of methanol and 2-keto-L-gulonic acid (hereinafter referred to as: 2-KLG) to generate 2-keto-L-gulonic acid methyl ester (hereinafter referred to as: 2-KLG) -Me-KLG). Currently, traditional processes for V C Most of the produced esterification reactions are maintained in a liquid system in which the weight ratio of methanol to 2-KLG is 1-1.5. Its reaction formula is as follows: [0004] [0005] The 2-Me-KLG obtained by the above methylation reaction reacts with sodium bicarbonate to g...

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Problems solved by technology

[0009] M.T.Sanz and Jurgen Gmehling successively in "Esterification of acetic acid with isopropanol coupled with pervaporation Part I: Kinetics and pervaporationstudies" ("Chemical Engineering Journal". 2006, 123: 1-8) and "Esterification of acetic acid with isopropanol coupled with pervaporation Part II : Study of apervaporation reactor" ("Chemical Engineering Journal" 2006, 123: 9-14) shows that the use of PERVAP  The 2201 membrane selectively removes the water produced in the isopropanol / acetic acid esterification reaction. With the increase of the molar ratio of isopropanol / acetic acid, the ratio of the membrane area to the volume of the reaction solution, the operating temperature and the amount of catalyst added, The yields of esters were all increased to varying degrees, but the reaction time was too long, and the equilibrium of the conventional esterification reaction was not broken until 10 hours later.

[0010] The esterification reaction-pervaporation membrane integration technology mentioned in the above-mentioned documents is all used for either n-butyl acetate or ethyl lactate at a higher reaction temperature or under the condition of a high membrane area to reaction liquid volume ratio. The esterification reaction of liquid raw materials such as esters or isopropyl acetate has not yet involved the esterification synthesis reaction of solid raw materials in the reactants, let alone V C Application of Esterification Reaction Combined Membrane Technology in Production Process

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