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Method for purifying dehydroacetic acid

A dehydroacetic acid, melt crystallizer technology, applied in the direction of organic chemistry, etc., can solve the problems of poor control of cooling temperature, equipment to be improved, low yield, etc., achieve good parallel reaction selectivity and safety, reduce costs and The effect of equipment investment and stable quality

Inactive Publication Date: 2016-01-06
张勇
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, the equipment for large-scale production of dehydroacetic acid at home and abroad is a general enamel reaction kettle. The mature process of the process is as follows: that is, toluene and diketene are condensed under the action of a catalyst, and then the enamel kettle is cooled and crystallized, dehydrated, Finished products are obtained through drying, packaging and other processes. However, due to the poor control of the cooling temperature of the enamel kettle, the material is easy to stick, the yield is not high, the purity is greatly affected, and the appearance is very bad.
Therefore existing technique and equipment of this dehydroacetic acid need to be improved

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0014] The process of purifying dehydroacetic acid by melting crystallizer is as follows:

[0015] (1) Crystallization: first pass calcium chloride solution at -8°C at the bottom of the outer jacket of the melting crystallizer, the calcium chloride solution flows evenly on the outer wall of the melting crystallizer in a falling film, and then put the condensed dehydroacetic acid solution into into the melting crystallizer, while passing through the melting crystallizer air duct at a distance of 4m 3 Inject compressed air into the dehydroacetic acid solution at a speed of 1 / min, so that it forms a slug-like flow bubble rising in the crystallization tube, causing turbulence of the melt, enhancing mass transfer and heat transfer performance, and the dehydroacetic acid solution is on the inner wall of the crystallizer The falling film flows down, gradually cools and crystallizes, and gradually grows a uniform crystal layer on the heat exchange surface. The concentration of the cry...

Embodiment 2

[0018] The process of purifying dehydroacetic acid by melting crystallizer is as follows:

[0019] (1) Crystallization: first pass -6°C sodium chloride solution at the bottom of the outer jacket of the melting crystallizer, and the sodium chloride solution uniformly flows in a falling film on the outer wall of the crystallizer, and then put the condensed dehydroacetic acid solution into the In the melting crystallizer, at the same time through the melting crystallizer air duct at a distance of 5m 3 Inject compressed air into the dehydroacetic acid solution at a speed of 1 / min, so that it forms a slug-like flow bubble rising in the crystallization tube, causing turbulence of the melt, enhancing mass transfer and heat transfer performance, and the dehydroacetic acid solution is on the inner wall of the crystallizer The falling film flows down, gradually cools and crystallizes, and gradually grows a uniform crystal layer on the heat exchange surface. The concentration of the crys...

Embodiment 3

[0022] The process of purifying dehydroacetic acid by melting crystallizer is as follows:

[0023] (1) Crystallization: first pass calcium chloride solution at -2°C at the bottom of the outer jacket of the melting crystallizer, and the calcium chloride solution flows uniformly in a falling film on the outer wall of the melting crystallizer, and then pour the condensed dehydroacetic acid solution Throw it into the melting crystallizer, and at the same time pass through the melting crystallizer air duct at a distance of 7m 3 Inject compressed air into the dehydroacetic acid solution at a speed of 1 / min, so that it forms a slug-like flow bubble rising in the crystallization tube, causing turbulence of the melt, enhancing mass transfer and heat transfer performance, and the dehydroacetic acid solution is on the inner wall of the crystallizer The falling film flows down, gradually cools and crystallizes, and gradually grows a uniform crystal layer on the heat exchange surface. The ...

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Abstract

The invention discloses a production process for preparing high purity dehydroacetic acid by virtue of melt crystallization. The process comprises the following steps of: firstly introducing frozen saline water into the bottom of an outer jacket of a melting crystallizer, wherein the frozen saline water uniformly flows in a falling film manner on the outer wall of the crystallizer; then inputting a concentrated dehydroacetic acid solution into the melting crystallizer, wherein the dehydroacetic acid solution flows in a falling film manner on the inner wall of the crystallizer and is gradually cooled to be crystallized; gradually growing a uniform crystal layer on a heat exchange face, wherein the concentration of the crystal layer is higher than that of a mixed solution, and impurities are gradually enriched in the mixture solution; and then adjusting the temperature of hot water by virtue of a heat exchanger to partly melt the crystal layer, namely a sweating operation, wherein low-melting-point impurities mingled in the crystal layer are partly melted and removed, so that the crystal is further purified. The process disclosed by the invention is simple, the equipment is compact in structure, and the energy is reduced in form of the falling film, and meanwhile, the cost and equipment investment are lowered; a product produced by the melting crystallizer is high in purity.

Description

technical field [0001] The invention relates to a method for purifying dehydroacetic acid, in particular to a method for purifying dehydroacetic acid with a melting crystallizer. Background technique [0002] Dehydroacetic acid is a broad-spectrum feed preservative that can inhibit the growth of mold, yeast and bacteria. The antibacterial effect is basically not affected by PH, but the antiseptic effect is the best under neutral conditions. It is also used as a food preservative. According to domestic regulations, it can be used for the preservation of fermented bean curd, pickles and orange juice, with a maximum usage of 0.3g / kg. At the same time, dehydroacetic acid is an organic synthesis intermediate and toughening agent, and it is also broad-spectrum. food preservatives. Since its antibacterial properties were discovered in 1940, it has been paid attention to by many countries, and has been allowed to be used for food preservation. As a food additive, dehydroacetic ac...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07D309/36
CPCC07D309/36
Inventor 张勇
Owner 张勇
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