CN1562942A - Malonic acid in high purity - Google Patents

Abstract

This invention relates prodn. of high pureness propane diacide, by ester exchange of diethyl malonate and acetic acid reacted in pure water content of diethyl malonate is not less than 99.8%, water is not more than 0.005%, chlorides=0.007%, sulfates are not more than 0.02%; and heavy metals are not more than 0.0001%. This invention solves the problems, in pharmaceutical prepn. and perfume prodn., of impurities, water content in prior art prodn.

Description

High purity malonic acid

The technical field is as follows:

the present invention relates to malonic acid, and is especially high purity malonic acid.

Background art:

malonic acid CH₂(COOH)₂Also named as caronic acid, beet acid, malic acid, etc., and the application is wide, and the product is mainly used in perfume, adhesive, resin additive, medical intermediate, electroplating polishing agent, explosion control agent, heat welding fluxing additive, etc. At present, the method for industrially producing the malonic acid in large quantities at home and abroad is mainly a hydrolysis method-a cyanoacetic acid hydrolysis method or a malonic acid diethyl ester hydrolysis method.

The hydrolysis process of cyanoacetic acid is to dissolve sodium cyanide in water, add it to chloroacetic acid solution, cool it, add calcium hydroxide to produce calcium malonate, add hydrochloric acid to hydrolyze it to obtain malonic acid and ammonium chloride as by-products. The invention discloses a preparation method of malonic acid and malonic ester, which is disclosed in publication No. CN1408697 on 19/4/2003, Chinese patent application is similar to the preparation method, calcium chloride is generated by reacting calcium hydroxide aqueous solution with monochloroacetic acid, hydrogen cyanide gas is introduced, calcium malonate solution is obtained by adding calcium oxide or calcium hydroxide, and the malonic acid is obtained by hydrolyzing the calcium malonate solution with hydrochloric acid.

The diethyl malonate hydrolysis method is characterized by that the diethyl malonate solution is hydrolyzed by sulfuric acid to produce malonic acid, and said method is simple, its production period is relatively shortened, and its three wastes are less. However, diethyl malonate can generate reversible reaction in the hydrolysis process, and the aqueous solution of malonic acid is subjected to high temperature to decarboxylate and decompose the malonic acid into water and carbon dioxide, so that the product yield is low, generally about 55%, and the production cost is increased.

The purity of the malonic acid prepared by the two industrial production methods is about 99 percent, the water content is high, and the impurities such as chloride or sulfate are high because of the hydrolysis treatment by using hydrochloric acid or sulfuric acid; in addition, the alloy also contains heavy metal elements harmful to human bodies, such as lead, and even the malonic acid with better quality produced by Thomas Baker at abroad accepted at present, the lead content is 0.001 percent. At present, malonic acid has low purity, high water content and high impurity content, particularly heavy metals, and cannot adapt to increasingly strict quality requirement situations of pharmaceutical and spice industries, and certain medicaments cannot be made to appear early due to the lack of high-purity malonic acid.

The invention content is as follows:

the invention aims to provide high-purity malonic acid, mainly solves the technical problem that the quality of malonic acid produced by the prior art in terms of purity, moisture and impurities cannot meet the technical requirements of pharmaceutical and spice manufacturing industries, and secondly solves the technical problem of low yield.

The technical scheme for solving the technical problems is as follows:

a high-purity malonic acid is prepared from diethyl malonate and acetic acid through ester exchange in pure water, and contains water (more than 99.8%), chloride (less than 0.005%), chloride (0.007%), sulfate (less than 0.02%) and heavy metal (less than 0.0001%).

The method for producing high-purity malonic acid comprises the following steps:

(1) stirring and heating diethyl malonate, acetic acid and pure water in a reaction kettle to 78-85 ℃, and preserving heat for 1-1.5 hours;

(2) distilling and separating ethyl acetate and ethanol water solution at the temperature under the reduced pressure of 0.01-0.06 Mpa for 4.5-5.2 hours;

(3) decoloring and filtering a malonic acid aqueous solution, and concentrating and crystallizing to obtain a crude malonic acid product;

(4) and (4) dehydrating and drying the crude malonic acid.

The invention has the advantages that:

1. the invention is prepared from malonic acid ethanediol CH₂(COOC₂H₅)₂And acetic acid CH₃COOH in pure water H₂Obtained by transesterification in O, according to the following reaction scheme:

as can be seen,high-purity malonic acid with large content, less impurities and low water content can be conveniently obtained by controlling the purity of the raw materials.

2. The quality of the invention is far superior to the strict requirements of the pharmaceutical and spice industries on the quality, so that the invention not only can meet the production requirements of the existing products in the pharmaceutical and spice industries, but also has good application prospect for developing new products.

3. The diethyl malonate is a non-toxic liquid, is used as a raw material, is easy to obtain, and is convenient to operate and use.

4. The ester exchange is an irreversible reaction, so the yield of the product is as high as more than 95 percent.

5. The reaction speed of ester exchange is fast, the production cycle is short, and the continuous production can be realized, thereby improving the work efficiency and the energy utilization rate.

6. No three wastes are generated, and the ethyl acetate and ethanol byproducts generated after ester exchange can be sold as commodities.

The specific implementation mode is as follows:

reacting malonic acid diethyl ester CH₂(COOC₂H₅)₂Acetic acid CH₃COOH and pure water (i.e., deionized or distilled) H₂Placing the O into an enamel or glass lining reaction kettle, stirring and heating to 78-85 ℃, and preserving heat for 1-1.5 hours to enable the O to perform ester exchange reaction in the kettle according to the following reaction formula:

during the ester exchange process, diethyl malonate loses ester to generate malonic acid, acetic acid is used for generating ethyl acetate, and an ethanol byproduct is obtained, wherein a reaction formula shows that 1 mol of diethyl malonate and 1 mol of acetic acid are needed for producing 1 mol of malonic acid, so that the input amount of the diethyl malonate and the acetic acid can be conveniently calculated by combining the component content of the diethyl malonate and the acetic acid; to improve efficiency, diethyl malonate and acetic acid are used in amounts greater than 99%. Even if the feeding is not in the proportion calculated according to the reaction formula, the ester exchange reaction still proceeds as usual, and only a certain more fed raw material does not participate in the ester reaction; in general, more acetic acid may be added as a result of calculation. In order to facilitate the ester exchange reaction process, the consumption of pure water can be increased, the consumption is generally more than 1 time of that of diethyl malonate, and the redundant pure water can be recycled.

And then, under the temperature, the reaction kettle is kept at the pressure of 0.01-0.06 Mpa for ester exchange reaction for 4.5-5.2 hours, simultaneously, the ethyl acetate and the ethanol water solution generated by the reaction are separated by distillation, and the malonic acid water solution generated by the reaction is left in the reaction kettle.

Then discharging the malonic acid aqueous solution from the reaction kettle to a filter for decolorization and filtration, and feeding the reaction kettle for the next round of ester exchange reaction. Pumping the filtered malonic acid aqueous solution into a crystallizing pan for concentration and crystallization to form crude malonic acid. In order to accelerate the crystallization process, the crystallization can be carried out at a temperature of 50-70 ℃ and a pressure of 0.07-0.12 MPa. And finally, dehydrating and drying the crystallized crude product, wherein the temperature is generally controlled to be about 80 ℃ and the time is about 10 hours, so that the high-purity malonic acid can be obtained. The quality indexes of the high-purity malonic acid are determined as follows:

the content is more than or equal to 99.85;

the melting point is 135.8-137.3 ℃;

the burning residue is less than or equal to 0.04 percent;

chloride (CL) is less than or equal to 0.007 percent;

sulfate (SO4) is less than or equal to 0.02 percent;

the heavy metal (Pb) is less than or equal to 0.0001 percent;

water content is less than or equal to 0.005 percent;

density (20 ℃ C. g/ml) 1.63;

flash point 338F.

Claims (2)

1. A high-purity malonic acid is prepared from diethyl malonate and acetic acid through ester exchange in pure water, and contains water (more than 99.8%), chloride (less than 0.005%), chloride (0.007%), sulfate (less than 0.02%) and heavy metal (less than 0.0001%).

2. The process for producing high-purity malonic acid according to claim 1, comprising:

(1) stirring and heating diethyl malonate, acetic acid and pure water in a reaction kettle to 78-85 ℃, and preserving heat for 1-1.5 hours;

(2) distilling and separating ethyl acetate and ethanol water solution at the temperature under the reduced pressure of 0.01-0.06 Mpa for 4.5-5.2 hours;

(3) decoloring and filtering a malonic acid aqueous solution, and concentrating and crystallizing to obtain a crude malonic acid product;

(4) and (4) dehydrating and drying the crude malonic acid.