KR20190063662A - Isolation method of lactic acid - Google Patents

Abstract

The present invention relates to a method for separating lactic acid, capable of obtaining lactic acid with high purity, which comprises: a step (a) of recovering a lactic acid salt in a crystal; a step (b) of obtaining an alkyl lactic acid salt; a step (c) of hydrolyzing the alkyl lactic acid salt; and a step (d) of recovering lactic acid.

Description

{ISOLATION METHOD OF LACTIC ACID}

The present invention relates to a method for separating lactic acid from an organic acid salt solution containing a lactate.

Lactic acid has been widely used in various industries such as foods, medicines, and cosmetics. Recently, it has been used as a monomer of polylactic acid, and its demand has been greatly increased.

The production method of lactic acid can be classified into chemical synthesis and biological fermentation using carbohydrate as a substrate. Generally, the production of lactic acid by microbial fermentation is carried out while maintaining an optimum pH for microbial fermentation by adding an alkaline substance, for example, calcium hydroxide, or the like to the culture liquid. In the fermentation of microorganisms for the production of lactic acid, an unnecessary acidic substance, organic acid, may occur in addition to lactic acid as a target. These organic acids are present in the culture medium by an alkaline substance added for cultivation, for example, as an organic acid salt, for example, lactate, succinate, acetate and the like. In order to use lactic acid as a monomer for plastics, it is necessary to remove the organic acid salt as described above. To this end, after the completion of the cultivation, the organic acid salt is converted into the organic acid by adding an acidic substance such as sulfuric acid. At this time, the unnecessary organic acid can also be converted. Therefore, lactic acid fermentation broth obtained by microbial fermentation contains impurities such as organic acids other than lactic acid and its salts, proteins and amino acids, and it is necessary to remove such impurities when lactic acid is used as a monomer for plastics.

With regard to production of lactic acid, Korean Patent No. 10-1198866 relates to a method for recovering an alkyl lactate and lactic acid from a fermentation broth of lactic acid, comprising the steps of preparing a raw material liquid containing lactic acid or ammonium lactate, Removing the water and precipitating and removing the ammonium salt by sequentially adding alcohol and an acid solution to the raw material liquid from which the water has been removed, preparing an alkyllactate by esterification from the mixture, and separating the alkyllactate by separating the alkyllactate And recovering the lactic acid by hydrolyzing the alkyl lactate recovered by the recovering method. However, the method of the patent fails to disclose the separation of organic acid salts other than the ammonium lactate contained in the raw material liquid, and thus it is impossible to suggest a method of separating alkyl lactate and lactic acid with high purity in the presence of other impurities. In addition, PCT Laid-Open Publication No. 2015/152127 discloses a process for recovering lactic acid crystals through crystallization and using the mother liquor fed into the crystallization process as a lactic acid solution recovered on the vapor side through distillation. However, such a method requires a multistage distillation process for the recovery of lactic acid, so that not only a large amount of energy can be consumed for the operation but also the polymerization of lactic acid can take place during the recovery of lactic acid by the multistage distillation process, Due to the oligomer, it is not easy to supply high-purity lactic acid for the production of plastic monomers.

Therefore, there is a need for a method for efficiently removing lactic acid salts other than the lactic acid salt contained in the fermentation broth when lactic acid is produced for the production of plastic monomers.

Korean Patent No. 10-1198866 (2012.11.07) WO 2015152127 (Oct. 20, 2015)

An object of the present invention is to provide a method for separating lactic acid from an organic acid salt containing lactic acid and recovering lactic acid with high yield.

In order to solve the above problems,

(a) crystallizing an organic acid salt solution containing a lactate to recover a lactate as crystals;

(b) adding alcohol to the resulting lactate crystals and heating to obtain an esterification reaction to obtain an alkyl lactate;

(c) hydrolyzing the alkyl lactate salt; And

(d) removing the solvent from the hydrolysis solution to recover the lactic acid.

According to the method of separating lactic acid according to the present invention, lactic acid used as a monomer for plastics can be obtained with high purity, and multistage distillation is not required, so that the yield and productivity can be improved by simplifying the process.

1 is a schematic diagram of a lactic acid recovery apparatus using separation of lactic acid according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the description. It should be understood, however, that the present invention is not intended to be limited to any particular embodiment, but is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, a method for separating lactic acid according to an embodiment of the present invention will be described in more detail.

The present invention relates to a method for recovering a lactate in a culture liquid through a crystallization process into crystals and then obtaining a lactic acid of high purity through an esterification reaction and a hydrolysis reaction. This method can be divided into a step of obtaining only lactate from the organic acid salt containing lactate through a crystallization process and a step of recovering lactic acid by esterification and hydrolysis reaction of the obtained lactate crystals.

Specifically, the present invention provides

(a) crystallizing an organic acid salt solution containing a lactate to recover a lactate as crystals;

(b) adding alcohol to the resulting lactate crystals and heating to obtain an esterification reaction to obtain an alkyl lactate;

(c) hydrolyzing the alkyl lactate salt; And

(d) removing the solvent from the hydrolysis solution to recover the lactic acid.

According to one embodiment, the method of the present invention comprises the crystallization tank 101, the esterification reaction tank 102, the distillation column 103, the hydrolysis reaction tank 104, and the evaporator 105 as shown in Fig. 1 May be carried out through the apparatus including.

1, the crystallization tank 101 is for separating only lactate from a feed, and the feed liquid injected thereinto is an organic acid salt solution containing a lactate, which is a solution formed by culturing or formed by mixing various compounds Lt; / RTI > The content of the lactate in the organic acid salt solution is 0.1 to 30% by weight, for example 1 to 20% by weight, based on the weight of the feed liquid, and the other organic acid salt except the lactate is 0.1 to 20% , For example from 1 to 10% by weight.

In one embodiment, the organic acid salt in the feed may be a calcium salt.

According to one embodiment, the lactate salt in the feed may be in the form of calcium lactate, potassium lactate, sodium lactate, and the like.

According to one embodiment, the temperature of the crystallization tank 101 may be between 2 and 25 占 폚, for example between 4 and 20 占 폚, for example between 4 and 10 占 폚. The lactate crystals obtained by these conditions have high purity and do not contain organic acid salts other than lactic acid salts. The lactate crystals obtained through the crystallization reaction are introduced into the esterification reaction tank 102, and alcohol is added under heating to undergo an esterification reaction of lactic acid and alcohol. According to one embodiment, an additional acid is added to the esterification reaction.

According to one embodiment, the alcohol may be an alcohol having from 2 to 8 carbon atoms, such as butanol, pentanol, hexanol or a combination thereof. The amount of the alcohol to be added may be a molar number of 0.5 to 20 times, for example, 1 to 10 times, the molar amount of the lactic acid crystal. Further, the temperature of the esterification reaction tank 102 may be 70 to 150 ° C, for example, 90 to 130 ° C, and the pressure may be 0.5 to 5 atm, for example, 1 to 3 atm.

According to one embodiment, the acid additionally introduced into the esterification reaction tank may be sulfuric acid, hydrochloric acid, nitric acid, or a combination thereof, and is not particularly limited.

According to one embodiment, the excess of alcohol and water generated by the vapor through the esterification reaction forms an azeotropy, but the vapor of the azeotrope through the upper condenser is cooled to separate into two layers And the layer containing the alcohol in the separated layers can be separated and easily refluxed into the reaction tank.

According to one embodiment, the salt generated by the reaction with the acid in the esterification reaction tank may be separated from the alkyl lactate produced by the esterification reaction through the distiller 103. The distiller 103 can be operated at a temperature of 50 to 210 ° C, for example, 70 to 190 ° C, under a pressure of 0.01 to 3 atm, for example, 0.05 to 1 atm.

According to one embodiment, the alkyl lactic acid salt obtained via the distillation step may be introduced into the hydrolysis reaction tank 104 and reacted with water to obtain lactic acid and alcohol. The temperature of the hydrolysis reactor may be 70-150 ° C., for example 90-130 ° C., and the pressure may be 0.5-5 atm, for example 1-3 atm. At this time, excess water and alcohol generated by the steam form an azeotropic mixture, but the vapor of the azeotropic composition can be cooled and separated into two layers, and water can be easily recovered to the reaction tank and used for the reaction.

According to one embodiment, the lactic acid solution obtained by the hydrolysis reaction may be recovered as lactic acid in a state suitable for being used as a plastic monomer after the solvent is evaporated and removed after being introduced into the evaporator 105. The temperature of the evaporator may be from 30 to 130 캜, for example from 50 to 100 캜, and the pressure may be from 0.01 to 3 atm, for example from 0.05 to 1 atm.

The present invention can simplify the process by proceeding to the single process.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Example 1 Crystallization Process

A lactic acid culture broth containing 242 g of calcium lactate, 10 g of calcium succinate and 1 g of calcium acetate was placed in a 1 L double jacket stirrer (heat resistant PYREX borosilicate glass material) And injected into the crystallization tank 101 equipped with The agitator was rotated at 300 rpm to agitate the culture solution.

The culture medium in the crystallization tank was preheated at 40 DEG C for 30 minutes. The temperature inside the crystallization tank was controlled through the temperature of the outer double jacket solvent (mixed solution of 60% water and 40% ethylene glycol), and the temperature was lowered by 1 ° C. per 3 minutes . When the crystallization temperature reached 30 ° C, 25 ° C, 20 ° C, 15 ° C, 10 ° C and 4 ° C, the mixture was kept for about 30 minutes each and then separated into solid phase particles and liquid phase through a filter (pore size 5 μm) Particles were obtained.

The crystallization yield was calculated by the following formula (1), and the crystallization yields according to the respective crystallization temperatures are shown in Table 1 below.

[Equation 1]

Crystallization yield (%) = (Amount of lactate in lactate crystals) / (Amount of lactate in the feed liquid supplied to the crystallization tank) 占 100

Crystallization temperature Culture solution 4 ℃ 10 ℃ 15 ℃ 20 ℃ 25 ℃ 30 ℃ Amount of calcium acetate (g) One - - - - - - Calcium succinate (g) 10 - - - - - - Amount of calcium lactate (g) 242 206 167 135 109 80 36 Crystallization yield (%) - 85.1 69 55.8 45 33 14.9

Example 2 : Esterification, distillation, hydrolysis and evaporation processes

300 ml of n-butanol and 1 g of sulfuric acid were added to 24 g of the lactate crystals obtained from the crystallization process of Example 1, and the esterification reaction was carried out at 110 ° C for 20 hours in the esterification reaction tank 102 at 1 atm. After the esterification reaction, the reaction mixture was distilled at 70 ° C and 0.05 atm, and 300 ml of water was added thereto. The hydrolysis reaction was carried out at 100 ° C for 18 hours at 1 atm in the hydrolysis reaction tank (104). After the hydrolysis reaction, the obtained solution was evaporated at 50 ° C under 0.05 atm to recover lactic acid.

Comparative Example 1

The lactic acid was recovered by using the culture liquid in which the crystallization process in Example 1 was not carried out as a raw material and the process after the crystallization process in Example 2 was carried out in the same manner.

The amount of the organic acid salt in the esterification reaction raw material according to the presence or absence of the crystallization process is shown in Table 2 below and the amount of the alkyllactate obtained after the subsequent esterification reaction and the distillation process is shown in Table 3 and the amount of the organic acid obtained after the subsequent hydrolysis and evaporation The amounts are shown in Table 4.

The amount of the organic acid was quantified by liquid chromatography (Dionex UHPLC 3000) - refractive index detector. In addition, the analysis of the alkyl lactate and the organic ester compound in the reaction solution was carried out by gas chromatography (Agilent 7890A) - flame ionization detector.

The amount of the organic acid salt in the esterification reaction raw material Esterification reaction raw material Example 2
(Crystallization step O) Comparative Example 1
(Crystallization step x) Lactate (g) 24 24 Acetate (g) - 0.23 The succinic acid salt (g) - 2.3 Reaction yield (%) -

Amount of alkyllactate after esterification and distillation Esterification reaction distillation Example 2 Comparative Example 1 Example 2 Comparative Example 1 Butyl lactate (g) 29.7 29.7 28.81 28.81 Butyl acetate (g) - 0.45 - - Butyl succinate (g) - 3.39 - 3.29 Reaction yield (%) 94 97

Amount of organic acid after hydrolysis and evaporation process Hydrolysis reaction evaporation Example 2 Comparative Example 1 Example 2 Comparative Example 1 Lactic acid (g) 17.75 17.75 17.44 17.44 Acetic acid (g) - - - - Succinic acid (g) - 2.30 - 2.25 Reaction yield (%) 100 98

As shown in Tables 3 and 4, it was confirmed that the purity of lactic acid from Example 2 after the crystallization process was higher than the purity of lactic acid from Comparative Example 1 which had not undergone the crystallization process. This is because the product from Example 2 after the crystallization process does not contain acetic acid and succinic acid after the hydrolysis and evaporation process, while the product from Comparative Example 1 which has not undergone the crystallization process is the acetate and succinate And can be identified from the inclusion of succinic acid after the hydrolysis process.

In the case of Comparative Example 1, esterification reaction and hydrolysis reaction proceeded with the same yield for lactic acid, but it can be confirmed that succinic acid having a boiling point higher than lactic acid is not removed during purification through distillation. In this respect, it can be seen that the removal of the organic acid salt through crystallization is necessary to increase the purity of lactic acid.

As described above, according to the present invention, the lactate can be selectively recovered from the organic acid salt solution containing the lactate through the crystallization process. That is, through the crystallization process, other organic acid salts other than lactic acid can selectively crystallize only the objective lactate while keeping the liquid state, and thus, lactate crystals of high purity can be obtained. These lactic acid crystals can be obtained as a high purity alkyl lactate through an esterification reaction and a distillation step. After the hydrolysis step and the evaporation step, ultrapure lactic acid, which can finally be used as a monomer for plastics, Can be recovered.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (12)

(a) crystallizing an organic acid salt solution containing a lactate to recover a lactate as crystals;
(b) adding alcohol to the resulting lactate crystals and heating to obtain an esterification reaction to obtain an alkyl lactate;
(c) hydrolyzing the alkyl lactate salt; And
(d) removing the solvent from the hydrolysis solution to recover the lactic acid. The method of separating lactic acid according to claim 1, wherein the organic acid salt further comprises a lactate selected from an acetate, a succinate and a combination thereof. The method for separating lactic acid according to claim 2, wherein the organic acid salt is a calcium salt. The method of separating lactic acid according to claim 1, wherein the crystallization of the organic acid salt solution is carried out at 2 to 25 캜. The method of separating lactic acid according to claim 1, wherein the alcohol is an alcohol having 2 to 8 carbon atoms. 6. The method of separating lactic acid according to claim 5, wherein the alcohol is butanol, pentanol, hexanol or a combination thereof. The method of separating lactic acid according to claim 1, wherein the amount of the alcohol is 0.5 to 20 times the molar amount of the lactic acid crystal. The method of separating lactic acid according to claim 1, wherein an acid which is sulfuric acid, hydrochloric acid, nitric acid or a combination thereof is further added to the esterification reaction. The process according to claim 1, wherein the esterification reaction is carried out at a temperature of 70 to 150 캜 and a pressure of 0.5 to 5 atm. The method of claim 1, further comprising distilling lactate at a temperature of from 50 to 210 < 0 > C and a pressure of from 0.01 to 3 atmospheres prior to hydrolysis. The process according to claim 1, wherein the hydrolysis is carried out at a temperature of 70 to 150 캜 and a pressure of 0.5 to 5 atm. The method of separating lactic acid according to claim 1, wherein the solvent removal is carried out by evaporating the solvent at a temperature of 30 to 130 DEG C and a pressure of 0.01 to 3 atm.

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