Method for extracting lactic acid by using organic solvent

Abstract

The invention belongs to the technical field of lactic acid extraction, and particularly relates to a method for extracting lactic acid by using an organic solvent. The method comprises the following steps: S1, adding concentrated hydrochloric acid into lactic acid fermentation liquor to adjust the pH value of the lactic acid fermentation liquor to 1.3-1.8; s2, mixing the lactic acid fermentation broth with an organic solvent, and fully mixing the lactic acid fermentation broth with the organic solvent to obtain a mixed solution I; s3, standing the mixed solution I to divide the mixed solution I into an upper-layer organic phase and a lower-layer water phase, and then separating out the water phase; s4, adding the lactic acid fermentation liquid into the organic phase again, and performing repeated experiments to obtain a saturated organic load phase containing lactic acid; s5, carrying out back extraction on the saturated organic load phase containing lactic acid by using deionized water to obtain a mixed solution II; s6, standing the mixed solution II to divide the mixed solution II into an upper-layer organic phase and a lower-layer water phase, separating after the organic phase is completely changed into a solid, collecting the lower-layer water phase, and repeating back extraction to obtain a back extraction solution; and S7, carrying out rotary evaporation concentration on the strip liquor to obtain a lactic acid finished product.

Description

Technical Field

[0001] The invention belongs to the technical field of lactic acid extraction, and particularly relates to a method for extracting lactic acid by utilizing an organic solvent. Background Art

[0002] Lactic acid, as one of the three major organic acids recognized in the world, is not only an important chemical raw material, but also an important fine chemical. It is widely used in food, medicine, agriculture, daily necessities, chemical industry and other fields. With the improvement of the quality of life, the demand for lactic acid by humans has increased year by year. At present, the fermentation method is mainly used in industrial production. However, the composition of lactic acid fermentation broth is complex. In addition to lactate, it also contains impurities such as bacterial fragments, proteins, pigments, residual sugars and fermentation byproducts. These impurities bring great burden to the subsequent separation and refining of lactic acid, and proteins will also undergo a series of complex reactions during heating and concentration, producing a large amount of pigments, which seriously affect the quality and extraction yield of the product. At present, the industrial extraction method of lactic acid is mainly based on the calcium salt method, which has many operating steps, low yield, and will produce a large amount of solid waste calcium sulfate, which is seriously polluting the environment. In comparison, the solvent extraction method is continuous, the equipment is simple and efficient, the operating cost is low, the obtained lactic acid product is of high quality, the process is cyclic, and the environment is friendly.

[0003] Extraction technology is widely welcomed by the industry due to its inherent characteristics of easy operation, easy scale-up, and strong equipment versatility. This technology is also used in the extraction and separation of lactic acid. The traditional solvent extraction method is a method of purifying or concentrating lactic acid by utilizing the different distribution coefficients of lactic acid in two immiscible phases. Due to unavoidable factors such as the contact tension between the oil phase and the water phase, the extraction process leads to problems such as incomplete separation of the water phase and incomplete recovery of the organic phase. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention discloses an organic solvent system for extracting lactic acid from lactic acid fermentation broth. During the standing process after extraction, due to the difference in melting points, the organic phase eventually becomes solid and is completely separated from the aqueous phase, while solving the problems of difficulty in recovering the organic solvent and incomplete recovery.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A method for extracting lactic acid using an organic solvent, the method comprising the following steps:

[0007] S1, adding concentrated hydrochloric acid to the lactic acid fermentation liquid to adjust the pH of the lactic acid fermentation liquid to 1.3-1.8 for later use;

[0008] S2, mixing the lactic acid fermentation broth and the organic solvent, so that the lactic acid fermentation broth and the organic solvent are fully mixed to obtain a mixed solution 1;

[0009] S3, allowing the mixed solution to stand to separate into an upper organic phase and a lower aqueous phase, and then separating the aqueous phase;

[0010] S4, adding lactic acid fermentation broth to the organic phase again, repeating the experiment to obtain an organic loading phase saturated with lactic acid;

[0011] S5, using deionized water to back-extract the saturated lactic acid-containing organic load phase to obtain a second mixed solution;

[0012] S6, leaving the mixed solution 2 to stand to separate the mixed solution into an upper organic phase and a lower aqueous phase, separating the organic phase after it completely turns into a solid, collecting the lower aqueous phase, and repeating the back extraction to obtain a stripping solution;

[0013] S7, concentrating the stripping solution by rotary evaporation to obtain finished lactic acid product.

[0014] Furthermore, the organic solvent includes 30% tertiary amine extractant, 30% alcohol phase balance agent and 40% kerosene, and the melting point of the organic solvent is 28°C.

[0015] Furthermore, in step S2, the volume ratio of the lactic acid fermentation liquid and the organic solvent when mixed is 1:(1-10); the mixing conditions are: temperature of 40°C-60°C, and oscillation time of 5min-10min.

[0016] Furthermore, the temperature during standing in step S3 is 0°C-20°C, and the standing time is 1 to 3 hours.

[0017] Furthermore, the number of times the experiment is repeated in step S4 is at least 6 times.

[0018] Furthermore, in step S5, the volume ratio of the saturated lactic acid-containing organic load phase to deionized water is 1:(1-10); and the stripping temperature is 65°C-80°C.

[0019] Furthermore, the stripping in step S6 is repeated at least 20 times.

[0020] Furthermore, the conditions for rotary evaporation concentration in step S7 are 55° C. and 50 rpm.

[0021] The above-mentioned method of extracting lactic acid using an organic solvent is used to prepare lactic acid.

[0022] Beneficial effects of the present invention:

[0023] 1. In the organic solvent extraction adopted in the present invention, the separation temperature of the oil phase and the water phase is lower than the reaction temperature. After the organic phase becomes solid, it is directly separated from the water phase. After separation, the saturated loaded organic phase is directly stripped to reduce the residual oil phase in the water phase, and the recovery rate of the oil phase is improved.

[0024] 2. The oil phase during stripping is a saturated organic phase containing lactic acid. The lactic acid concentration is high and the stripping rate is improved simultaneously. The saturated adsorption experiment only needs to separate the water phase and repeatedly add the lactic acid fermentation liquid to maximize the utilization rate of the organic solution. At the same time, the operation process is simple and easy to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work. Figure 1 The figure is a specific flow chart of extracting lactic acid using an organic solvent in the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] Add concentrated HCL to the lactic acid fermentation liquid to adjust the pH to 1.5, add 300 ml of organic solvent to the separatory funnel, 100 ml of lactic acid fermentation liquid with pH 1.5, add 1 ml of dichloromethane and ethyl acetate to the mixed system; shake at 45 ° C for ten minutes, stand at 10 ° C for 1 hour, separate the water phase and the oil phase, the oil phase is recorded as Q1, add 100 ml of lactic acid fermentation liquid to Q1, repeat the above steps for 6 levels to obtain a saturated loaded organic phase containing lactic acid, recorded as Q6; add 150 ml of deionized water to Q6, shake at 70 ° C for 10 minutes, stand at 10 ° C for 1 hour, separate the water phase, add deionized water, repeat the above stripping steps to 20 levels, and the final stripping rate reaches 96.7%. Collect the water phase for distillation stripping to obtain lactic acid. At the same time, take samples of the finished lactic acid for HPLC testing.

[0029] Example 2

[0030] Add concentrated HCL to the lactic acid fermentation broth to adjust the pH to 1.7, add 500ml of organic solvent to the separatory funnel, add 500ml of lactic acid fermentation broth with pH 1.7, add 1ml of dichloromethane and ethyl acetate to the mixed system; shake at 45°C for ten minutes, stand at 45°C for 2h, separate the water phase and the oil phase, the oil phase is recorded as W1, add 500ml of lactic acid fermentation broth to W1, repeat the above steps for 6 levels to obtain a saturated loaded organic phase containing lactic acid, recorded as W6; add 500ml of deionized water to W6, shake at 70°C for 10min, stand at 70°C for 2h, separate the water phase, add deionized water, repeat the above stripping steps to 20 levels, and the final stripping rate reaches 99.3%. Collect the water phase for distillation stripping to obtain lactic acid. At the same time, sample the finished lactic acid for HPLC testing.

[0031] Example 3

[0032] Add concentrated HCL to the lactic acid fermentation liquid to adjust the pH to 1.7, add 500ml of organic solvent to the separatory funnel, add 500ml of lactic acid fermentation liquid with pH 1.7, add 1ml of dichloromethane and ethyl acetate to the mixed system; shake at 45°C for ten minutes, stand at 45°C for 2h, separate the water phase and the oil phase, the oil phase is recorded as S1, add 500ml of lactic acid fermentation liquid to S1, repeat the above steps for 6 levels to obtain a saturated loaded organic phase containing lactic acid, recorded as S6; add 500ml of deionized water to S6, shake at 70°C for 10min, stand at 10°C for 2h, separate the water phase, add deionized water, repeat the above stripping steps to 20 levels, and the final stripping rate reaches 96.7%. Collect the water phase for distillation stripping to obtain lactic acid. At the same time, take samples of the finished lactic acid for HPLC testing.

[0033] The experimental results of comparative example 1, example 2 and example 3 are shown in Table 1 below.

[0034] Example Stripping rate Is dichloromethane residue detected? Is ethyl acetate detected? Example 1 96.7％ no no Example 2 99.3％ yes yes Example 3 98.7％ no no

[0035] Combining the data of Example 1, Example 2 and Example 3, it can be seen that the method used to extract lactic acid from lactic acid fermentation broth can completely recover the extractant, and the extractant does not remain in the stripping solution. Comparing Example 1 and Example 2, it can be seen that the extraction rate is higher than that of 1:1. Comparing Example 2 and Example 3, it can be seen that when the standing temperature is higher than the melting point of the extractant, even if the standing time is longer, the extractant and the stripping solution cannot be completely separated. Compared with conventional melting point organic solvents, the separation process is simple and the organic solvent is recovered more completely. In addition, the process uses a saturated organic load phase containing lactic acid for stripping, and the stripping rate is high. During the experiment, only the stripping solution needs to be tested, which is convenient to operate and has fewer monitoring points. At the same time, the utilization rate of organic solvents is improved, reducing costs.

[0036] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0037] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for extracting lactic acid using an organic solvent, characterized in that: The method comprises the following steps: S1, adding concentrated hydrochloric acid to the lactic acid fermentation liquid to adjust the pH of the lactic acid fermentation liquid to 1.3-1.8 for later use; S2, mixing the lactic acid fermentation broth and the organic solvent, so that the lactic acid fermentation broth and the organic solvent are fully mixed to obtain a mixed solution 1; S3, allowing the mixed solution to stand to separate into an upper organic phase and a lower aqueous phase, and then separating the aqueous phase; S4, adding lactic acid fermentation broth to the organic phase again, repeating the experiment to obtain an organic loading phase saturated with lactic acid; S5, using deionized water to back-extract the saturated lactic acid-containing organic load phase to obtain a second mixed solution; S6, leaving the mixed solution 2 to stand to separate the mixed solution into an upper organic phase and a lower aqueous phase, separating the organic phase after it completely turns into a solid, collecting the lower aqueous phase, and repeating the back extraction to obtain a stripping solution; S7, concentrating the stripping solution by rotary evaporation to obtain finished lactic acid product.

2. The method for extracting lactic acid using an organic solvent according to claim 1, characterized in that: The organic solvent comprises 30% of a tertiary amine extractant, 30% of an alcohol phase balancer and 40% of kerosene, and the melting point of the organic solvent is 28°C.

3. The method for extracting lactic acid using an organic solvent according to claim 1, characterized in that: In step S2, the volume ratio of the lactic acid fermentation liquid and the organic solvent when mixed is 1:(1-10); the mixing conditions are: temperature of 40°C-60°C, and oscillation time of 5min-10min.

4. The method for extracting lactic acid using an organic solvent according to claim 1, characterized in that: The temperature during the standing in step S3 is 0°C-20°C, and the standing time is 1 to 3 hours.

5. The method for extracting lactic acid using an organic solvent according to claim 1, characterized in that: The number of times the experiment is repeated in step S4 is at least 6 times.

6. The method for extracting lactic acid using an organic solvent according to claim 1, characterized in that: In step S5, the volume ratio of the saturated lactic acid-containing organic load phase to deionized water is 1:(1-10); the stripping temperature is 65°C-80°C.

7. The method for extracting lactic acid using an organic solvent according to claim 1, characterized in that: The stripping in step S6 is repeated at least 20 times.

8. The method for extracting lactic acid using an organic solvent according to claim 1, characterized in that: The conditions for rotary evaporation concentration in step S7 are 55° C. and 50 rpm.

9. A method for extracting lactic acid using an organic solvent as claimed in any one of claims 1 to 8 for preparing lactic acid.

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