Method for directly preparing vitamin C with sodium gulonate

Abstract

The invention relates to a method for preparing ascorbic acid by using gulconic sodium to converse directly; the invention is importantly improved based on the existing two-step fermentation method for manufacturing VC: a 2KGA-Na crystal of high purity can be obtained by the techniques of hyperfiltration clarification, low temperature concentration and constant temperature crystallization, etc.; the completely novel method for separating the gulonic acid that are not converted into VC by the technique conditions of separating Na[2]SO[4] solid during the prophase of methyl reaction and optimizing and conversion reaction as well as by adopting an advanced chromatogram technology during the processes of acidification and refining leads to obtain the top-grade product from the crude VC by one-step crystallization, thereby leading the total yield for manufacturing VC by the two-step fermentation method to be improved to more than 86 percent; the waste water with high concentration is completely removed; and the energy consumption can be reduced by about 20 percent.

Description

technical field [0001] The present invention relates to a preparation method of ascorbic acid (abbreviated as VC), in particular to a method for preparing vitamin C from 2-keto-L-gulonic acid sodium (referred to as 2KGA-Na) through catalytic esterification, lactonization, acidification and other steps. new method. It belongs to the field of chemical synthesis. Background technique [0002] As we all know, two-step fermentation is currently used in industry to produce VC, and its subsequent conversion process mainly includes the following steps: [0003] (1) Isotransformation of clarified fermented mash and preparation of 2KGA crystals [0004] The 2KGA-Na solution (ultrafiltrate) containing 8-10% (W / V) obtained from two-step fermentation and ultrafiltration clarification is converted into 6-8% (W / V) 2-keto- L-gulonic acid (abbreviated as 2KGA) solution was concentrated, decolorized, crystallized, filtered and dried to obtain 2KGA crystals. [0005] (2) methyl esterificat...

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Problems solved by technology

[0021] ① During the methyl esterification reaction, the concentration of 2KGA-Na is too dilute, only 0.0855 (mol / ml), which not only makes the conversion process equipment very large, but also consumes too much solvent

[0022] ②Due to the constraints of process conditions and equipment, the purity of the prepared 2KGA-Na crystal is as low as about 90%, which brings difficulties to the transformation

The conversion rate of 2KGA-Na is limited below 92%, and the prepared 2KGA-CH 3 The purity of the solution is also affected to some extent by

[0024] ①The patent pursues the conversion rate of chemical synthesis too much, and raises the reaction temperature of the methyl esterification reaction and the lactonization reaction to above 65°C. The increase of the reaction temperature will inevitably lead to the decline of the conversion reaction selectivity, which will lead to the total VC pure product. drop in yield

[0025] ② The azeotropic performance of methanol and water is poor, and the water generated by the reaction is removed according to the discharge of methanol vapor. The efficiency is too poor, the energy consumption is too large, the investment is high, and the operation is also difficult

[0026] ③This process also fails to solve the problem of poor effect of removing impurities such as miscellaneous acids in step (4), and recrystallization is still required to produce pure VC

[0027] In a word, due to the defects in the above-mentioned patents, which affect its industrialization prospects, the method of directly converting sodium gulonic acid to produce ascorbic acid has not yet been industrially applied in production.

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