Production method of lactic acid

Abstract

The invention belongs to the technical field of production of L-lactic acid, and particularly relates to a production method of lactic acid, which comprises the following steps: carrying out filter pressing on lactic acid fermentation liquor, filtering by a nanofiltration membrane, concentrating in a concentrator to obtain lactic acid concentrated liquor, evaporating the lactic acid concentrated liquor in a vacuum wiped-film drum evaporator, and distilling and purifying in a molecular distillation purifier to obtain the L-lactic acid. The separation of lactic acid and other trace impurities is realized, high-quality lactic acid is obtained, the optical purity of the L-lactic acid is 99.2% or above, a large amount of organic impurities and inorganic salts are removed firstly, then molecular distillation purification is used for further purification, the efficient purification of the L-lactic acid is realized, and the optical purity and the yield of the L-lactic acid product are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of L-lactic acid production, in particular to a method for producing lactic acid. Background Art

[0002] Lactic acid is an important organic acid, which was first recognized and used by humans. Nowadays, lactic acid is widely used in the fields of food, medicine and agriculture, and L-lactic acid is gradually replacing DL-lactic acid or racemic lactic acid, and is used in the fields of food, medicine and cosmetics. In recent years, with the development of poly L-lactic acid, a new type of highly biocompatible and fully degradable material, the demand for L-lactic acid in the international market has increased sharply, resulting in an increasingly prominent contradiction between supply and demand. At the same time, due to the influence of D-lactic acid on the biodegradability of polylactic acid, the market has higher and higher requirements for the optical purity of lactic acid. At present, the optical purity of lactic acid products is low, and the competitiveness in the market is insufficient, especially in the market of high optical purity L-lactic acid, the competitiveness of domestic products is even weaker. In order to solve the above problems, those skilled in the art are in urgent need of developing a production method of lactic acid to meet the existing market demand and performance requirements. Summary of the invention

[0003] In view of the above problems, the present invention aims to provide a process for purifying and refining L-lactic acid and its application.

[0004] A method for producing lactic acid comprises the following steps: 1. After the lactic acid fermentation liquid is filtered through a filter press, it is filtered through a nanofiltration membrane and then concentrated in a concentrator to obtain a lactic acid concentrate; 2. Evaporate the lactic acid concentrate in a vacuum scraped film drum evaporator for 3.5 to 5 minutes, and then send it to a molecular distillation purifier for distillation and purification for 30 to 50 seconds to obtain lactic acid.

[0005] Furthermore, the nanofiltration membrane filtration in the first step has the process conditions of pH 2-3, pressure 2-3 MPa, and temperature 25-30°C.

[0006] Furthermore, the vacuum scraped drum evaporator in the second step has a rotation speed of 15 r / min, a steam pressure of 0.1-0.3 MPa, a vacuum degree of 10-30 Pa, and an evaporation temperature of 50-70°C.

[0007] Furthermore, the feed rate of the second-step molecular distillation purifier is 40-50 L / h, the vacuum degree is 10-15 Pa, the condensation temperature is 30-35° C., the evaporation temperature is 55-60° C., and the scraping speed is 125-135 r / min.

[0008] Furthermore, the first step concentration temperature is 60-70° C. and the pressure is 0.02-0.04 MPa.

[0009] Furthermore, the mass concentration of the lactic acid concentrate is 25% to 35%.

[0010] Furthermore, the obtained lactic acid is polymerization-grade L-lactic acid with an optical purity of 99.2-99.9%.

[0011] Furthermore, the chromaticity of the lactic acid obtained in the second step after heating at 180° C. for two hours is ≤20 APHA.

[0012] Beneficial effects of the present invention: The process method for purifying and refining L-lactic acid disclosed in the present invention comprises the following steps: subjecting lactic acid fermentation liquor to pressure filtration, and then filtering through a nanofiltration membrane, and then concentrating the liquor in a concentrator to obtain a lactic acid concentrate; evaporating the lactic acid concentrate in a vacuum scraping drum evaporator, and then sending the lactic acid concentrate to a molecular distillation purifier for distillation and purification, so as to separate lactic acid from other trace impurities and obtain high-quality lactic acid, wherein the optical purity of L-lactic acid is above 99.2%. After removing a large amount of organic impurities and inorganic salts, the lactic acid is further purified by molecular distillation, so as to realize efficient purification of L-lactic acid and significantly improve the optical purity and output rate of L-lactic acid products. DETAILED DESCRIPTION

[0013] The present invention is described below with specific examples, but is not intended to be limiting of the present invention. Example 1

[0014] Raw materials and equipment: lactic acid fermentation liquid obtained from Bengbu Glatt after most of the bacteria, most of the protein and some residual sugar were removed, concentrated sulfuric acid was added to the filtered clarified liquid for acid hydrolysis, and the acid hydrolysis and neutralization were completely allowed to stand for 1 hour; belt filter PBF-19.2 / 1600, Haihua Drying HDZ-18 vacuum drum thin film evaporator; molecular distillation purifier FZL-24.

[0015] A method for producing lactic acid, comprising the following steps: 1. filtering the lactic acid fermentation liquid, filtering it through a PBF-19.2 / 1600 belt filter to remove calcium sulfate, filtering it through a nanofiltration membrane, and concentrating it in a concentrator. The process conditions of the DK8040C30 nanofiltration membrane filtration are pH 2, pressure 2MPa, temperature 25°C, concentration temperature 60°C, pressure 0.02MPa, and obtaining a lactic acid concentrate. The mass concentration of the lactic acid concentrate is 25%; 2. evaporating the lactic acid concentrate in a vacuum scraped film rotary drum evaporator for 3. After 5 minutes, the speed of the vacuum scraped drum evaporator is 15r / min, the steam pressure is 0.1Mpa, the vacuum degree is 10Pa, and the evaporation temperature is 50°C; then it is sent to the molecular distillation purifier for distillation and purification for 30s, the feed rate of the molecular distillation purifier is 40L / h, the vacuum degree is 10-15Pa, the condensation temperature is 30°C, the evaporation temperature is 55°C, and the scraping speed is 125r / min, to obtain lactic acid, which is polymerization-grade L-lactic acid with an optical purity of 99.9%, and the chromaticity after heating at 180°C for two hours is 15APHA. Example 2

[0016] Raw materials and equipment: lactic acid fermentation liquid obtained from Bengbu Glatt after most of the bacteria, most of the protein and some residual sugar were removed, concentrated sulfuric acid was added to the filtered clarified liquid for acid hydrolysis, and the acid hydrolysis and neutralization were completely allowed to stand for 1 hour; belt filter PBF-19.2 / 1600, Haihua Drying HDZ-12 vacuum drum thin film evaporator; molecular distillation purifier FZL-24.

[0017] A method for producing lactic acid, comprising the following steps: 1. filtering the lactic acid fermentation liquid, filtering it through a PBF-19.2 / 1600 belt filter to remove calcium sulfate, filtering it through a nanofiltration membrane, and then concentrating it in a concentrator. The process conditions of the DK8040C30 nanofiltration membrane filtration are pH 3, pressure 3MPa, temperature 30°C, concentration temperature 70°C, pressure 0.04MPa, and lactic acid concentrate. The mass concentration of the lactic acid concentrate is 35%; 2. evaporating the lactic acid concentrate in a vacuum scraped film rotary drum evaporator After 5 minutes, the speed of the vacuum scraped drum evaporator is 15r / min, the steam pressure is 0.3Mpa, the vacuum degree is 30Pa, and the evaporation temperature is 70°C; then it is sent to the molecular distillation purifier for distillation and purification for 50s. The feed rate of the molecular distillation purifier is 50L / h, the vacuum degree is 15Pa, the condensation temperature is 35°C, the evaporation temperature is 60°C, and the scraping speed is 135r / min. Lactic acid is obtained, which is a polymerization grade L-lactic acid with an optical purity of 99.2%. The chromaticity after heating at 180°C for two hours is 15APHA.

[0018] The L-lactic acid obtained in Examples 1 and 2 was tested for performance. The test results are shown in Table 1 Table 1 L-lactic acid performance test results of Examples 1 to 2

[0019] Note: The determination of lactic acid content refers to the method specified in A.3 of Appendix A of GB1886.173-2016. Optical purity determination: Reagents and materials: Grade 1 water specified in GB / T6682; Instruments and equipment: High performance liquid chromatograph. Reference chromatographic conditions (1) Chromatographic column: Chirex3126 (D) -Penicillamine (4.6Φ × 150mm). (2) Mobile phase: 0.002mol / L copper sulfate solution. (3) Detection wavelength: 254nm. (4) Column temperature: 35℃; (5) Flow rate: 0.5ml / min. (6) Injection volume: 10μl. (7) Separation requirement: Separation between type D and type L ≥ 1.0. Analysis steps Weigh 0.05g of sample (accurate to 0.0001g), dilute with water or mobile phase to 100mL, and filter with a 0.45um microporous membrane before chromatographic analysis. The determination was carried out under the reference chromatographic conditions in A.4.3, and the peak areas of D-lactic acid and L-lactic acid in the sample were obtained by analysis (D-lactic acid retention time 10min, L-lactic acid retention time 12min), and quantified by area normalization method. Result calculation X1=A L / (A L +A D )×100%, where the optical purity of L-lactic acid is X1; where: X1—is the optical purity of L-lactic acid; A L —peak area value of L-lactic acid in the sample; A D —Peak area value of D-lactic acid in the sample. The determination of heavy metals (in terms of Pb) shall be carried out in accordance with the method specified in GB5009.75 or GB5009.12. The determination of chromaticity shall be carried out in accordance with GB / T605-2006; the chromaticity at 180°C is determined by heating at 180°C for two hours and carried out in accordance with GB / T605-2006. The determination of ignition residue shall be carried out in accordance with the method specified in A.5 of Appendix A of GB1886.173-2016. The determination of chloride (in terms of Cl) shall be carried out in accordance with the method specified in A.6 of Appendix A of GB1886.173-2016. The determination of mercury shall be carried out in accordance with the atomic fluorescence analysis method of GB5009.17-2014; the determination of arsenic shall be carried out in accordance with the flame atomic absorption spectrometry of GB5009.76. The determination of sulfate (in terms of SO4) shall be carried out in accordance with the method specified in A.7 of Appendix A of GB1886.173-2016. The determination of iron salt (expressed as Fe) shall be in accordance with the method specified in A.8 of Appendix A of GB1886.173-2016.

Claims

1. A method for producing lactic acid, characterized in that: The following steps are involved:

1. The lactic acid fermentation liquid is filtered through a filter press, then filtered through a nanofiltration membrane, and then concentrated in a concentrator to obtain a lactic acid concentrate; 2. Evaporate the lactic acid concentrate in a vacuum scraped film drum evaporator for 3.5 to 5 minutes, and then send it to a molecular distillation purifier for distillation and purification for 30 to 50 seconds to obtain lactic acid.

2. The method for producing lactic acid according to claim 1, characterized in that: The nanofiltration membrane filtration in the first step has the process conditions of pH 2-3, pressure 2-3 MPa, and temperature 25-30°C.

3. The method for producing lactic acid according to claim 1, characterized in that: The vacuum scraped film drum evaporator in the second step has a rotation speed of 15 r / min, a steam pressure of 0.1-0.3 MPa, a vacuum degree of 10-30 Pa, and an evaporation temperature of 50-70°C.

4. The method for producing lactic acid according to claim 1, characterized in that: The second step molecular distillation purifier has a feed rate of 40-50 L / h, a vacuum degree of 10-15 Pa, a condensation temperature of 30-35° C., an evaporation temperature of 55-60° C., and a scraping speed of 125-135 r / min.

5. The method for producing lactic acid according to claim 1, characterized in that: The first step of concentration has a temperature of 60-70° C. and a pressure of 0.02-0.04 MPa.

6. The method for producing lactic acid according to claim 1, characterized in that: The mass concentration of the first step lactic acid concentrate is 25% to 35%.

7. The method for producing lactic acid according to claim 1, characterized in that: The lactic acid obtained in the second step is polymerization-grade L-lactic acid with an optical purity of 99.2-99.9%.

8. The method for producing lactic acid according to claim 1, characterized in that: The color of the lactic acid obtained in the second step after heating at 180° C. for two hours is ≤20 APHA.

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