CN100345856C - Esterification and crystallizing process for producing glucose halfaldehyde lactone - Google Patents

Abstract

The invention relates to an esterification and crystallization process for preparing glucuronolactone. In this method, on the basis of traditional starch acid oxidation and hydrolysis procedures, the obtained oxidized starch hydrolyzate is subjected to primary concentration and dehydration, and the primary concentrate is subjected to secondary fine dehydration with a water-carrying agent. Esterification at ~70°C, the esterification reaction mixture is distilled to remove light acid for three-stage dehydration. The mixture after the three-stage dehydration starts from the esterification temperature, and undergoes dynamic gradient cooling crystallization at a rate of 1-2°C/hour, the crystallization termination temperature is 25±5°C, and the total crystallization time is ≤40 hours. The crystallization mixture is filtered to obtain a crude product with a glucuronolactone content of ≥90%, with a yield of ≥18%, which can be used in the refining process. The method improves the total yield and the final crystallization temperature of the glucuronolactone, greatly reduces the crystallization time and crystallization energy consumption, thereby reducing the production cost of the glucuronolactone.

Description

A kind of esterification and crystallization process method for preparing glucuronolactone

technical field

The invention relates to an esterification process for producing glucuronolactone by an acid method, and a crystallization and purification method for glucuronolactone obtained by the esterification process. The process is a further improvement of the existing process for preparing glucuronolactone esterification and crystallization.

Background technique

Glucuronolactone, referred to as glucuronolactone, has a molecular formula of C ₆ H ₈ O ₆ , and its chemical composition is: D(+)-furanoglucurono γ-lactone [D(+)-Glucofuranurono-6,3 -lactone]. As a liver detoxifier and immune function regulator, glucuronolactone is a conventional liver-protecting medicine; glucuronolactone and its follow-up products are also the main additives of functional beverages, foods, weight-loss drugs, cosmetics, etc., with The market demand for supplementing physical energy, improving hypoxia, nourishing skin, and delaying aging has exceeded the demand in the medical field in recent years.

Glucuronic acid and glucuronolactone have been discovered for nearly 80 years. In 1923, M.Bergmann and W.W.Wolff obtained and isolated glucuronic acid for the first time using glucose as a raw material; in 1939, Stacey published his method for synthesizing glucuronolactone. The main starting materials for the preparation of glucuronolactone are starch, trehalose or glucose, and the preparation principle is mainly to use the above-mentioned raw materials to prepare glucuronic acid first, and the glucuronic acid is lactonized to obtain glucuronolactone.

The main method of the current industrial production of glucuronolactone is the nitric acid oxidation method starting from starch. This method follows the production process of glucuronic acid and its lactones prepared by G.Serchi and L.Arcangeli in 1951 by oxidizing starch with nitric acid. The process is as follows: oxidize the mixture of starch and water with fuming nitric acid to obtain oxidized starch, heat and pressurize the starch oxidation solution under acidic conditions to obtain the hydrolyzate of oxidized starch, and concentrate the hydrolyzate under reduced pressure until the Baume degree is 44 At ~45 o'clock, directly add acetic acid for esterification, cool the esterified mixture to 45°C and let it stand for 16~20 hours, then gradually cool down to -4~-8°C, the total time for cooling and crystallization is generally 70~80 hours, and the crystallization is carried out at high speed. The crude product of glucuronolactone with a purity of 80-90% is obtained by centrifugal rejection filtration, the yield of the crude product is about 12-15%, and the total production cycle is about 5-6 days. The refined product can be obtained by decolorizing and recrystallizing the crude product, and the total yield after refining is generally about 10%. Japanese patents Sho 36-12114, Sho 38-14556, Sho 43-5882, etc. have also successively reported similar preparation methods. The main advantage of this method is that raw material starch has a wide source and low price, but this method has disadvantages such as poor reaction selectivity, incomplete esterification, long post-treatment cycle, difficult product separation, high energy consumption, and low product yield.

Contents of the invention

The technical problem to be solved by the present invention is to provide a kind of esterification and crystallization process method for preparing glucuronolactone by acid method for the deficiencies in the traditional acid method to produce glucuronolactone process, which can improve the The esterification reaction yield and the crystallization termination temperature simplify the crystallization process, thereby reducing production costs.

The technical scheme that the present invention adopts for solving the above-mentioned problem is:

First dehydrate the oxidized starch hydrolyzate: heat and reduce pressure to concentrate until no visible water distills out, and the Baume degree of the concentrate is 45-48Be;

Secondary dehydration of the oxidized starch hydrolyzate concentrate: by adding water-carrying agent and water to azeotropically separate the trace moisture remaining in the primary concentrate;

Add acetic acid to carry out esterification reaction in secondary concentrate;

Three-stage dehydration after the esterification reaction: distill light acetic acid at the same temperature as the esterification reaction and a vacuum degree ≥ 0.09MPa, and control the evaporated volume between 10% and 30% of the volume of the added acetic acid;

The mixture after three-stage dehydration starts from the esterification temperature, and undergoes dynamic gradient cooling crystallization at a rate of 1-2°C/hour. The crystallization termination temperature is 25±5°C, and the total crystallization time is ≤40 hours. The crystallization mixture is filtered to obtain glucose. The crude product with an aldolactone content ≥ 90% has a yield ≥ 18%, and is then refined in a subsequent process.

According to the above scheme, the temperature of the first-stage dehydration is 50-60°C, and the degree of vacuum is ≥0.093Mpa.

According to the above scheme, the water-carrying agent described in the secondary dehydration is selected from any one of butyl acetate, n-butanol, propyl acetate, ethyl acetate, cyclohexane, benzene, and the consumption of the water-carrying agent is by volume ( Volume: milliliters) is 0.5 to 1.2 times the weight of the concentrate (weight: grams), with water temperature ≤ 60°C, and vacuum between 0.06 and 0.09 MPa. Butyl acetate is the best water-carrying agent. Butyl acetate has a good azeotropic water-carrying effect, is almost insoluble in water, and has a recovery rate of more than 98%. The azeotropic components can be recycled after standing to separate water.

According to the above scheme, the temperature of the esterification reaction is 65-70°C, the reaction time is 1-2 hours, stirred under normal pressure, the amount of acetic acid added is the starch amount by volume (volume: milliliter) and the weight (weight: g ) of 0.8 to 1.2 times.

According to the above scheme, the three-stage dehydration is to steam off part of the light acetic acid under reduced pressure to take out the moisture generated by the reaction.

The mechanism of the present invention is that the conversion of glucuronic acid into glucuronolactone through intramolecular dehydration is a reversible reaction, water is generated in the reaction product, and glucuronic acid and glucuronolactone can be mutually converted in aqueous solution. According to the reaction equilibrium theory, effectively removing the water contained in the system before esterification and removing the water generated by the esterification reaction is conducive to the formation of esters, and at the same time removing the water before and after the reaction in time can reduce or avoid glucuronolactone The dissolution loss, thereby increasing the yield of glucuronolactone. The solubility of glucuronolactone in water varies greatly with temperature, and the solubility is relatively large in the high temperature zone (40-80°C), and although there is a certain difference in solubility in the low temperature zone (0-30°C), the difference is not large. Therefore, in the crystallization process, the relationship between energy consumption cost and yield increase should be comprehensively considered. At the same time, due to the high viscosity of the crystallization system at low temperature, it is not conducive to crystal precipitation and product separation, which increases the energy consumption of separation. Therefore, it is necessary to choose an appropriate final crystallization temperature.

The beneficial effects of the present invention are as follows: 1. The esterification process shortens the equilibrium time of the esterification reaction through three-stage dehydration operation before and after the esterification reaction, and improves the yield of the esterification reaction. 2. The esterification process reduces or avoids the dissolution loss of glucuronolactone in water through the three-stage dehydration operation before and after the esterification reaction, thereby increasing the crystallization yield of glucuronolactone. 3. The crystallization process improves the purity of the glucuronolactone product through dynamic gradient cooling crystallization. 4. The crystallization termination temperature of this crystallization process is 25±5°C, which not only greatly reduces the energy consumption of crystallization, but also can obtain crude crystals of glucuronolactone after suction filtration (without a large amount of centrifugal equipment), which simplifies the crystallization process , reducing production costs.

Detailed ways

Below in conjunction with example the present invention is described in further detail.

Example 1

Take 900ml of oxidized starch hydrolyzate (equivalent to 100g of raw starch) and concentrate the hydrolyzate under reduced pressure at a temperature of 60°C and a vacuum degree of ≥0.09MPa until no visible water distills out. For 48Be. Add 100ml of butyl acetate to the primary concentrate, azeotropically dehydrate at 60°C and a vacuum of 0.08MPa until no liquid distills out, and recover 99ml of butyl acetate. Add 100ml of glacial acetic acid to the secondary concentrate, stir the esterification reaction at 70°C for 1 hour, and then evaporate 20ml of light acetic acid under reduced pressure. The reaction mixture starts to cool down at a rate of 1°C/hour from 70°C and crystallizes under low-speed stirring , when the temperature was 30° C., the crystallization mixture was suction-filtered, the solid was washed with 2×10 ml of absolute ethanol, and dried in vacuo to obtain 20.4 grams of white crystalline powder with a glucuronolactone content of 92%.

Example 2

Take 900ml of oxidized starch hydrolyzate (equivalent to 100g of raw starch) and concentrate the hydrolyzate under reduced pressure at a temperature of 60°C and a vacuum degree of ≥0.09MPa until no visible water distills out. It is 45Be. Add 120ml of butyl acetate to the primary concentrate, azeotropically dehydrate at 60°C and 0.08MPa vacuum until no liquid distills out, and recover 118ml of butyl acetate. Add 100ml of glacial acetic acid to the secondary concentrate, stir the esterification reaction at 70°C for 1 hour, and then evaporate 20ml of light acetic acid under reduced pressure. The reaction mixture starts from 70°C at a cooling rate of 1°C/hour and stirs at a low speed to cool down and crystallize. When the temperature was 30° C., the crystallization mixture was suction-filtered, the solid was washed with 2×10 ml of absolute ethanol, and dried in vacuo to obtain 23.4 g of white crystalline powder with a glucuronolactone content of 90%.

Example 3

Take 450ml of oxidized starch hydrolyzate (equivalent to 50g of raw starch) at a temperature of 55°C and a vacuum of 0.093MPa to concentrate the hydrolyzate under reduced pressure until no visible water distills out. For 48Be. Add 50ml of ethyl acetate to the primary concentrate, azeotropically dehydrate at 55°C and 0.07MPa vacuum until no liquid distills out, and recover 45ml of ethyl acetate. Add 50ml of glacial acetic acid to the residue (secondary concentrate), stir the esterification reaction at 68°C for 1.5 hours, and then evaporate 10ml of light acetic acid under reduced pressure. The temperature was lowered to crystallize, and the crystallization mixture was suction-filtered when the temperature was 20° C., the solid was washed with 2×10 ml of absolute ethanol, and dried in vacuo to obtain 9.6 grams of white crystalline powder with a glucuronolactone content of 93%.

Example 4

Take 900ml of the oxidized starch hydrolyzate (equivalent to 100 grams of raw starch), and concentrate the hydrolyzate under reduced pressure at 60°C and a vacuum of 0.093MPa until no visible water distills out. The Baume degree of the primary concentrate is 48Be. Add 100 ml of butyl acetate to the primary concentrate, azeotropically dehydrate at 55° C. and a vacuum of 0.09 MPa until no liquid distills out, and recover 98 ml of butyl acetate. Add 120ml of glacial acetic acid to the residue (secondary concentrate), stir the esterification reaction at 65°C for 2 hours, and then evaporate 20ml of light acetic acid under reduced pressure. Cool down to crystallize. Suction filter the crystallization mixture at 25° C., wash the solid with 2×10 ml of absolute ethanol, and dry in vacuo to obtain 22.5 grams of white crystalline powder with a glucuronolactone content of 92%.

Claims (5)

1. an esterification and a crystallization processes method for preparing Glucuronic acid lactone is characterized in that

Earlier the Sumstar 190 hydrolyzed solution is carried out the one-level dehydration: heating is evaporated to till no visible moisture distillates, and the enriched material degree Beaume is 45～48Be; Sumstar 190 hydrolyzed solution enriched material is done the secondary dehydration: tell micro-moisture residual in the one-level enriched material by adding band aqua and moisture content azeotropic; In the secondary enriched material, add acetic acid and carry out esterification; Do three grades of dehydrations after the esterification: with the esterification uniform temp and 〉=steam light acetic acid under the vacuum tightness of 0.09MPa, steam volume be controlled at add the acetic acid volume 10～30% between; Mixture after three grades of dehydrations begins from esterification temperature, carry out dynamic gradient cooling crystallization with 1～2 ℃/hour speed, the crystallization final temperature is 25 ± 5 ℃, crystallization total time≤40 hour, crystalline mixture obtains the crude product of Glucuronic acid lactone content 〉=90%, yield 〉=18% through suction filtration.

2. by described esterification of claim 1 and crystallization processes method, it is characterized in that described one-level dehydration temperaturre is 50～60 ℃, vacuum tightness 〉=0.093Mpa.

3. by claim 1 or 2 described esterifications and crystallization processes method, it is characterized in that the band aqua described in the secondary dehydration selects any in butylacetate, propyl carbinol, propyl acetate, ethyl acetate, hexanaphthene, the benzene for use.

4. by described esterification of claim 3 and crystallization processes method, it is characterized in that with the consumption of aqua by volume (milliliter) be 0.5～1.2 times of enriched material weight (gram), be with water temp≤60 ℃, vacuum tightness is between 0.06～0.09MPa.

5. by claim 1 or 2 described esterifications and crystallization processes method, it is characterized in that described esterification reaction temperature is 65-70 ℃, 1～2 hour reaction times, under normal pressure, stir, acetic acid add-on by volume (milliliter) is 0.8～1.2 times of amount of starch weight (gram).