JP3881044B2 - Production method of glycolic acid aqueous solution - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a simple method for producing a high-concentration and high-purity glycolic acid aqueous solution.
Glycolic acid has a wide range of uses such as cleaning agents, metal treatment agents, and tanning agents, and in recent years, a product with a particularly high purity has been demanded as it has been approved for use in cosmetics.
[0002]
[Prior art]
Typical industrial production methods of glycolic acid include a method of coupling formaldehyde and carbon monoxide in the presence of a sulfuric acid catalyst (Japanese Patent Publication No. 6-501268), and a method of hydrolyzing monochloroacetic acid in the presence of a base (specialty). No. 62-77349), a method of treating a water-containing organic solvent containing glycolate ions with an ion exchange resin (Japanese Patent Laid-Open No. 57-192332), and the like.
Among the above representative glycolic acid production methods, the coupling method is produced under special reaction equipment and reaction conditions under high temperature and high pressure. In this method, formaldehyde harmful to the human body remains in the product, and by-product of methoxyacetic acid, which shows mutagenicity, is unavoidable, and much effort and energy are required to remove and purify these impurities. It is inefficient. Moreover, in this method, it is essential to use an anion exchange resin to remove sulfuric acid, live steam stripping to remove low boiling impurities, and a cation exchange resin to further remove metal impurities. Is extremely complicated.
[0003]
On the other hand, in the hydrolysis method using monochloroacetic acid as the raw material, the reaction rate is slow and there is a problem in productivity when the amount of alkali used is small, so it is necessary to use an alkali near the stoichiometric amount. As a by-product salt, the concentration of the slurry after concentration becomes high, the operability is poor and the loss is large, and there is a problem that the salt cannot be completely removed and remains.
In addition, the method of treating hydrous organic solvents containing glycolate ions with ion exchange resins is difficult with high-concentration solutions. Operation of deorganic solvent treatment after ion exchange resin treatment, resin degradation due to organic solvents, resin only In the case of desalting with, there is a problem that the capacity of the resin becomes very large.
Therefore, in the method of JP-A-62-77349, a stoichiometric by-product salt is efficiently removed by using a hydrophilic organic solvent such as acetone and an ion exchange resin in combination. However, this method has the following problems.
(B) The filtrate obtained by filtering and removing the inorganic salt precipitated as a by-product in the reaction needs to be concentrated to a high concentration, which is inefficient and may cause the resulting glycolic acid aqueous solution to be colored.
(B) In order to further remove the inorganic salt produced as a by-product in the reaction, it is necessary to add 2 to 7 times the amount of a very large excess of the hydrophilic organic solvent. A large excess of organic solvent must be distilled off by distillation.
(C) Since complete desalting cannot be achieved by the above operations (a) and (b), a large amount of cation exchange resin and anion exchange resin must be used in combination, which is extremely complicated. .
[0004]
[Problems to be solved by the invention]
The object of the present invention is to eliminate the need to concentrate the filtrate obtained by filtering and removing the inorganic salt deposited as a by-product in the reaction as described above to a high concentration, and it is not necessary to distill off a large amount of the organic solvent. And it is providing the simple manufacturing method of high concentration and highly purified glycolic acid aqueous solution which does not need to use ion exchange resin together at all.
[0005]
[Means for Solving the Problems]
The present invention is a method for producing glycolic acid by hydrolyzing monochloroacetic acid in water in the presence of an alkali metal base,
(1) Glycolic acid is selectively extracted from a reaction mother liquor containing an inorganic salt by bringing a water-insoluble organic solvent into contact with the reaction mother liquor from which inorganic salts precipitated as by-products have been removed by filtration;
(2) Contacting water with the resulting extract to back-extract glycolic acid from the organic solvent layer,
(3) A method for producing an aqueous glycolic acid solution, characterized by concentrating a back extract.
[0006]
According to the present invention, when monochloroacetic acid is hydrolyzed to obtain glycolic acid, desalting is performed by selectively extracting only glycolic acid from a reaction solution containing a by-product inorganic salt with a water-insoluble organic solvent. A high-purity glycolic acid aqueous solution can be obtained by a very simple, efficient and economical operation method that is achieved and then simply back-extracts the target product from the extract with water.
That is, in the present invention, unlike the hydrophilic organic solvent used in the method of JP-A-62-77349, by using a water-insoluble organic solvent, the reaction was a disadvantage of the method of JP-A-62-77349. The filtrate obtained by filtering out the inorganic salts precipitated as a by-product is concentrated to a high concentration, a large amount of organic solvent is distilled off, and it is not necessary to use an ion exchange resin together. An extremely excellent effect is obtained that a high-purity glycolic acid aqueous solution is obtained.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Monochloroacetic acid used in the present invention may be a crystal or an aqueous solution. The concentration of monochloroacetic acid used for the hydrolysis reaction is not particularly limited as long as the by-product inorganic salt expresses the salting out effect and the generated glycolic acid is efficiently extracted into a water-insoluble organic solvent. Usually, 30 to 70% by weight is preferable. When it is lower than this concentration, the reactivity and extraction efficiency are lowered, and when it is higher, workability is lowered.
[0008]
The alkali metal base to be used is not particularly limited, but is preferably an alkali metal hydroxide such as sodium hydroxide, sodium carbonate, potassium hydroxide or potassium carbonate, carbonate or the like. These bases can be used individually by 1 type or in combination of 2 or more types. The amount of these bases used is not particularly limited, but is usually 0.9 to 1.8 times the stoichiometric amount, preferably 1.0 to 1.4 times the amount of monochloroacetic acid.
In the present invention, first, hydrolysis is carried out by bringing an alkali metal base into contact with monochloroacetic acid. The reaction temperature at this time is 70 to 130 ° C, preferably 100 to 120 ° C. If it is lower than this temperature, the reaction rate may be slow, and if it is higher, the selectivity of the reaction may be lowered.
[0009]
When the alkali metal salt of glycolic acid is contained in the hydrolyzed solution, the yield can be increased by converting the glycolate to glycolic acid by neutralization. The acid used for neutralization is not particularly limited, but hydrochloric acid, sulfuric acid and the like are preferable. The salt precipitated by the reaction and neutralization is preferably removed by a normal separation means such as filtration before subjecting the reaction solution to extraction with an organic solvent in the next step. If this operation is not performed, there is a possibility that workability in the extraction process is impaired.
In the present invention, by simply extracting the hydrolysis reaction solution with a water-insoluble organic solvent, the glycolic acid is selectively transferred to the solvent layer while utilizing the salting-out effect of the by-product inorganic salt, and extraction and desorption are performed. Salt can be achieved simultaneously.
[0010]
The water-insoluble organic solvent used for the extraction of the hydrolysis reaction solution has a solubility in water of 15% by weight or less at room temperature, preferably 10% by weight or less, does not react with glycolic acid, and is a hydrolysis reaction solution. There is no particular limitation as long as glycolic acid can be selectively extracted from, for example, acetate solvents such as ethyl acetate and butyl acetate, ether ethers such as diethyl ether, di-n-propyl ether, diisopropyl ether, and anisole. Examples thereof include solvents, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone, and halogenated hydrocarbons such as dichloromethane, chloroform, and tetrachloroethylene. The amount of the water-insoluble organic solvent used is usually 1 to 30 times, preferably 2 to 15 times the weight of the hydrolysis reaction solution, although it depends on the form of subjecting the hydrolysis solution to extraction. When it is less than this, the extraction efficiency of glycolic acid is low, and when it is more, the operability is lowered. The extraction form may be a so-called batch form or a continuous form.
[0011]
Subsequently, glycolic acid is moved from the water-insoluble organic solvent layer to the aqueous layer by simply back extracting the resulting extract with water. Originally, glycolic acid has extremely high solubility in water, so this back extraction can be easily achieved. The amount of water used for back extraction can be appropriately selected from a wide range according to the form to be subjected to back extraction, but is usually 0.1 to 20 times that of glycolic acid which is a solute in the water-insoluble organic solvent layer. The weight, preferably 0.7 to 3 times the weight. If the amount is less than this, the extraction efficiency is lowered, and if it is more, the concentration may take time. The form of back extraction may be a so-called batch format or a continuous format. The concentration of glycolic acid in water is not particularly limited, but it is usually preferably about 30 to 60% by weight.
[0012]
The aqueous glycolic acid solution thus obtained can be concentrated under normal pressure or reduced pressure as necessary, and the water-insoluble organic solvent mixed therein can be distilled off at the same time. The concentration of the resulting glycolic acid aqueous solution is not particularly limited and can be a desired concentration, but it is usually preferably 50 to 80% by weight.
[0013]
【Example】
The present invention will be specifically described with reference to examples.
Example 1
A 2-liter glass reactor equipped with a stirrer was charged with 520 g (5.50 mol) of monochloroacetic acid and 280 g of deionized water to obtain a uniform solution. When 578 g (7.08 mol) of a 49% aqueous sodium hydroxide solution was added to this solution and reacted at 100 ° C. for 2 hours, the raw material was completely consumed. The reaction solution was cooled to room temperature, and 170 g (1.66 mol) of 35% hydrochloric acid was added thereto to convert the glycolate salt to the free acid. The inorganic salt deposited at this time was filtered off by vacuum filtration. The obtained filtrate was placed in a separatory funnel A, 2400 ml of methyl isobutyl ketone was added and shaken, and then allowed to stand until it was completely separated into two layers (first extraction). Next, only the upper layer (organic layer) was transferred to a separatory funnel B previously charged with 480 ml of deionized water and shaken, and then allowed to stand until it was completely separated into two layers (first back extraction). Subsequently, only the upper layer (organic layer) was transferred to the separating funnel A, and the extraction and back-extraction cycles were repeated five times in the same manner as described above.
The obtained back-extracted aqueous solution was concentrated under reduced pressure to distill off about 320 ml of water. At this time, methyl isobutyl ketone mixed in a small amount in the aqueous solution was also azeotropically removed from the concentrated residue containing glycolic acid. The residue was treated with 10 g of activated carbon and filtered to obtain 526 g of a colorless and transparent 70% by weight glycolic acid aqueous solution (yield 88%). According to HPLC analysis, the purity of the solute was 99.6% or more, the residual ash content was 20 ppm or less, and the purity was so high that no further purification such as ion exchange resin treatment was required.
[0014]
Example 2
Hydrolysis and subsequent filtration were performed in the same manner as in Example 1 to obtain a filtrate containing glycolic acid. This was continuously supplied to a glass extraction tower having an inner diameter of 50 mm and a length of 1000 mm having ten Teflon vibrating shelves previously filled with 1.9 liters of methyl isobutyl ketone. On the other hand, 660 ml of deionized water was continuously supplied to a glass back-extraction column having an inner diameter of 50 mm and a length of 1000 mm having five Teflon vibrating shelves previously filled with 1.9 liters of methyl isobutyl ketone. The two extraction towers were connected by a metering pump, and methyl isobutyl ketone was circulated at a rate of 165 ml per minute. A schematic flow of the apparatus is shown in FIG. The shelf of each extraction tower was vibrated at a stroke length of 10 mm and 150 cycles per minute, and filtrate and deionized water were continuously supplied over 1 hour. The obtained back extracts were combined and about 500 ml of water was distilled off under reduced pressure. At this time, methyl isobutyl ketone mixed in a small amount in the aqueous solution was also azeotropically removed from the concentrated residue containing glycolic acid. The residue was treated with 10 g of activated carbon and then filtered to obtain 543 g of a colorless and transparent 70% by weight glycolic acid aqueous solution (yield 91%). According to HPLC analysis, the purity of the solute was 99.6% or more, the residual ash content was 20 ppm or less, and the purity was so high that no further purification such as ion exchange resin treatment was required.
[0015]
【The invention's effect】
According to the present invention, when monochloroacetic acid is hydrolyzed to obtain glycolic acid, desalting is performed by selectively extracting only glycolic acid from a reaction solution containing a by-product inorganic salt with a water-insoluble organic solvent. A high-purity glycolic acid aqueous solution can be obtained by a very simple, efficient and economical operation method that is achieved and then simply back-extracts the target product from the extract with water.
That is, unlike a hydrophilic organic solvent, by using a water-insoluble organic solvent, inorganic salts precipitated as a by-product in the reaction which was a drawback of the method of JP-A-62-77349 were removed by filtration. It is unnecessary to concentrate the filtrate to a high concentration, distill off a large amount of the organic solvent, and use an ion exchange resin in combination, and a high concentration and high purity glycolic acid aqueous solution can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic flowchart of an apparatus for performing extraction and back-extraction of the present invention in a continuous format.
[Explanation of symbols]
1 Metering pump for supplying filtrate 2 Metering pump for supplying deionized water 3 Metering pump for solvent circulation

Claims (1)

A process for producing glycolic acid by hydrolyzing monochloroacetic acid in water in the presence of an alkali metal base,
(1) Glycolic acid is selectively extracted from a reaction mother liquor containing an inorganic salt by bringing a water-insoluble organic solvent into contact with the reaction mother liquor from which inorganic salts precipitated as by-products have been removed by filtration;
(2) Contacting water with the resulting extract to back-extract glycolic acid from the organic solvent layer,
(3) A method for producing an aqueous glycolic acid solution, comprising concentrating a back extract.

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