A method for separating 1,3-propanediol, butyric acid and acetic acid based on deep eutectic solvent extraction

Abstract

This invention discloses a method for separating 1,3-propanediol, butyric acid, and acetic acid using eutectic solvent extraction. In this method, trioctylamine or methyltrioctylammonium chloride is added to an aqueous solution containing 1,3-PDO as a eutectic solvent composed of long-chain fatty alcohols or long-chain fatty acids. After mixing, the mixture is allowed to stand and separate into two phases: an upper phase rich in butyric acid and acetic acid, and a lower phase rich in 1,3-propanediol. The lower phase is subjected to a second extraction to further extract butyric acid and acetic acid to the DES phase. The butyric acid and acetic acid in the upper phase are back-extracted using an alkaline solution or an alkaline inorganic salt solution, simultaneously recovering the DES. After multi-stage extraction, the lower phase rich in 1,3-propanediol is recovered by distillation. This invention solves the problems of poor selectivity, cumbersome separation steps, and high cost in the separation process of 1,3-propanediol production via fermentation. This method is simple, has a short separation time, high recovery rate, and low separation cost, providing a highly promising industrial solution for the efficient separation of bio-based 1,3-propanediol.

Description

Technical Field

[0001] This invention belongs to the field of bioseparation technology, specifically relating to a method for separating 1,3-propanediol, butyric acid and acetic acid based on eutectic solvent extraction. Background Technology

[0002] 1,3-Propanediol (1,3-PDO) is an important chemical raw material, primarily used in the synthesis of polypropylene terephthalate (PTT), a novel polyester material, with terephthalic acid. PTT fiber, as a new generation of high-performance polyester material, combines the softness of nylon, the bulkiness of acrylic fiber, the stain resistance of polyester, and unique elasticity and room-temperature dyeing properties, making it a popular new polyester material with optimal overall performance in the textile industry, boasting broad market prospects. In addition, 1,3-PDO can also be used as a solvent, adhesive, cosmetic ingredient, and preservative.

[0003] With the depletion of fossil fuels and increasing environmental awareness, the bioconversion fermentation method for producing 1,3-PDO has gradually replaced the chemical method as the main way to industrialize 1,3-PDO. The bioconversion method for producing 1,3-PDO mainly uses Klebsiella pneumoniae, Clostridium butyricum, or genetically engineered bacteria to convert 1,3-PDO into glycerol or glucose. It features mild reaction conditions, simple operation, low environmental pollution, and renewable raw materials. In recent years, researchers have made breakthroughs in strain selection, the construction of efficient cell factories, and large-scale fermentation using inexpensive raw materials; however, less investment has been made in the efficient extraction and separation of the product, making downstream separation technology a bottleneck restricting the large-scale production of 1,3-PDO. The fermentation broth of 1,3-PDO has a complex composition, typically containing large amounts of water, residual sugar / glycerol, bacterial protein, inorganic salts, and various metabolic byproducts. In typical fermentation systems, high concentrations of organic acid byproducts, especially butyric acid and acetic acid, are often generated. Due to its high boiling point and extreme hydrophilicity, the efficient separation and purification of 1,3-PDO from this complex aqueous system with low concentration and multiple components is the core bottleneck restricting its industrial production. Its separation cost usually accounts for more than 50% of the total production cost.

[0004] Invention patent CN200510047497.3 discloses a method for precipitating proteins by adding acid and heating (pH=1.5~5.5, 80~100℃), followed by concentration, crystallization, and vacuum distillation to extract 1,3-PDO; however, strong acids easily corrode equipment, resulting in high equipment investment; furthermore, this method is not thorough in desalination, requiring additional subsequent deep desalination processes. Invention patent CN200710009244.6 uses pretreatment combined with electrodialysis to thoroughly desalinate 1,3-PDO fermentation broth; however, the electrodialysis process consumes a large amount of electricity and generates a large amount of wastewater during operation, leading to excessively high energy consumption and operating costs for the overall separation system. Invention patent CN112920021B discloses a method for extracting 1,3-PDO from fermentation broth using a mixed alcohol solvent, wherein the mixed alcohol solvent is composed of two or more alcohols, and the carbon number difference between at least two alcohols is 3. Although mixed long-chain alcohols can improve the low extraction rate of single hydrophobic alcohols to some extent through synergistic extraction, they also have a high extraction rate for by-product organic acids (such as butyric acid and acetic acid) in 1,3-PDO fermentation broth, and the selective extraction and separation effect is not good.

[0005] In recent years, eutectic solvents (DES) have been dubbed "designable green solvents" due to their advantages such as ease of preparation, good chemical stability, non-volatility, biodegradability, and good biocompatibility. They have demonstrated their advantages in fields such as biomass pretreatment, extraction and separation, organic synthesis, gas capture, and electrochemistry. Eutectic solvents are typically solvent systems formed by complexing eutectic mixtures of Lewis or Brønsted acids and / or bases, and can contain various cations and / or anions. Compared with traditional organic solvents, DES can achieve efficient extraction of specific hydrophilic substances by controlling the composition of its components. Currently, there are few reports on the extraction and separation of 1,3-PDO, butyric acid, and acetic acid from fermentation broth using eutectic solvents. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a method for separating 1,3-propanediol, butyric acid and acetic acid based on eutectic solvent extraction, thereby achieving efficient and selective separation of 1,3-PDO from metabolic byproduct organic acids.

[0007] To achieve the objectives of this invention, the technical solution is as follows:

[0008] In a first aspect, the present invention provides a method for separating 1,3-PDO, butyric acid, and acetic acid based on eutectic solvent extraction, comprising the following steps: S1: Preparation of eutectic solvent: Trioctylamine (TOA) and long-chain fatty alcohol are mixed in a molar ratio of 1:0.25 to 1:4 or methyltrioctylammonium chloride (TOMAC) and long-chain fatty acids are mixed in a molar ratio of 1:0.25 to 1:4 and stirred at 50 to 70°C to prepare eutectic solvent (DES). S2: First step extraction: The eutectic solvent obtained in step S1 is mixed with an aqueous solution containing 1,3-PDO at a volume ratio of 1:5 to 5:1. The mixture is vortexed, stirred or shaken to separate the phases, resulting in an extract phase and a raffinate phase. The raffinate phase is an aqueous phase rich in 1,3-PDO. S3: Multi-stage extraction: Add the eutectic solvent described in step S1 to the raffinate phase obtained in step S2, vortex, stir or shake, separate the phases to obtain the extract phase and the raffinate phase, and perform multi-stage extraction. S4: Back-extraction and DES recovery: Add an alkaline aqueous solution to the extract phase obtained in steps S2 and S3 for back-extraction. The raffinate of the lower phase is concentrated and dried to obtain a mixture of butyrate and acetate. At the same time, the eutectic solvent of the upper phase is recovered and used for extraction in steps S2 and S3. S5: Separation and purification of 1,3-PDO: The raffinate obtained in step S3 is separated and purified to obtain 1,3-PDO.

[0009] Furthermore, in the above technical solution, the long-chain fatty alcohol mentioned in step S1 is one or a combination of two or more of n-octanol, n-nonanol, n-decanol, undecylol, dodecanol, tridecanol, tetradecanol or octadecylol, preferably n-octanol.

[0010] Furthermore, in the above technical solution, the molar ratio of trioctylamine to long-chain fatty alcohol in step S1 is 1:0.25 to 1:3, preferably 1:2.

[0011] Furthermore, in the above technical solution, the long-chain fatty acid mentioned in step S1 is one or a combination of two or more of nonanoic acid, decanoic acid, lauric acid, myristic acid or stearic acid, and the molar ratio of methyltrioctylammonium chloride to long-chain fatty acid is 1:0.25~1:2.

[0012] Furthermore, in the above technical solution, the 1,3-PDO aqueous solution mentioned in step S2 is an aqueous solution mainly containing 1,3-PDO, butyric acid and acetic acid, untreated 1,3-PDO fermentation broth, 1,3-PDO fermentation membrane liquid or 1,3-PDO fermentation concentrate; the concentration of 1,3-PDO is 85~425 g / L, the concentration of butyric acid is 15~75 g / L, and the concentration of acetic acid is 8~40 g / L.

[0013] Furthermore, in the above technical solution, in step S2, when the 1,3-PDO aqueous solution is an untreated 1,3-PDO fermentation broth, 1,3-PDO fermentation membrane liquid, or 1,3-PDO fermentation concentrate, the extraction phase is an organic phase rich in butyric acid and acetic acid, and the intermediate phase is a solid phase layer rich in cells and / or proteins.

[0014] Furthermore, in the above technical solution, in step S2, before extraction, the pH of the aqueous solution containing 1,3-PDO is adjusted to 2.7~7.0, preferably pH 2.7~4.0.

[0015] Furthermore, in the above technical solution, the vortexing, stirring or oscillation time in step S2 is 0.5~10 min, preferably 0.5~5 min.

[0016] Furthermore, in the above technical solution, the extraction temperature in step S2 is 20~60℃, preferably 20~40℃.

[0017] Furthermore, in the above technical solution, the number of stages of multi-stage extraction in step S3 is 1 to 4, preferably 2 stages.

[0018] Furthermore, in the above technical solution, the extraction step of the multi-stage extraction in step S3 is the same as that in step S2, with a volume ratio of 1:5 to 5:1, a vortexing, stirring or shaking time of 0.5 to 10 min, preferably 0.5 to 5 min, and an extraction temperature of 20 to 60°C, preferably 20 to 40°C.

[0019] Furthermore, in the above technical solution, the alkaline aqueous solution mentioned in step S4 is one of sodium hydroxide aqueous solution, sodium carbonate aqueous solution, or sodium bicarbonate aqueous solution, preferably sodium hydroxide aqueous solution.

[0020] Furthermore, in the above technical solution, the concentration of the alkaline aqueous solution in step S4 is 10~100 g / L, preferably 40~60 g / L.

[0021] Furthermore, in the above technical solution, the volume ratio of the alkaline aqueous solution to the extraction phase in step S4 is 1:1 to 1:5, preferably 1:1.

[0022] Furthermore, in the above technical solution, the separation and purification described in step S5 includes vacuum distillation.

[0023] Furthermore, in the above technical solution, the reduced pressure distillation in step S5 adopts a vacuum distillation method with a vacuum degree of 0.094~0.096 MPa. Glycerol is added to the bottom of the column before distillation, and the amount added is 10~30% (v / v) of the volume of the raffinate.

[0024] In this invention, the extraction of 1,3-PDO, acetic acid, and butyric acid can be performed intermittently or continuously.

[0025] In this invention, the microbial fermentation broth containing 1,3-PDO refers to a 1,3-PDO fermentation broth produced using conventional microbial fermentation methods. The microorganisms used are not particularly limited and can be common strains used for fermentation production of 1,3-PDO, such as *Clostridium butyricum*, *Klebsiella pneumoniae*, and *Citrobacter freundii*. Furthermore, the method in this invention is not limited to isolating 1,3-PDO from microbial fermentation broths; it can also be applied to the isolation of 1,3-PDO contained in aqueous mixed solvents.

[0026] In this invention, the 1,3-PDO fermentation broth can be pretreated by flocculation, microfiltration or centrifugation to remove cells and some proteins; if extraction is performed directly without pretreatment, cells and proteins will be distributed in the intermediate phase.

[0027] Secondly, the present invention provides a 1,3-PDO solution obtained by the above method, wherein the residual amount of eutectic solvent in the 1,3-PDO solution is lower than the instrument detection limit.

[0028] Compared with the prior art, the present invention has the following beneficial effects: This invention presents a method for separating 1,3-PDO, butyric acid, and acetic acid from fermentation broth using eutectic solvent extraction. This method effectively overcomes the technical bottleneck of separating 1,3-PDO from organic acids in complex fermentation broths. The system exhibits excellent separation selectivity; diethyl ether extract (DES) efficiently extracts butyric acid and acetic acid byproducts, while the highly hydrophilic 1,3-PDO is enriched in the lower aqueous phase, with no DES residue remaining. Furthermore, the DES phase rich in organic acids can be back-extracted with an alkaline solution or alkaline inorganic salt solution, achieving not only efficient recovery of organic acid salts but also simultaneous DES recovery with minimal loss, allowing for recycling. Simultaneously, the raffinate aqueous phase can be distilled to obtain high-purity 1,3-PDO. In summary, this separation method is simple, simultaneously achieving efficient and selective separation and resource recovery of main and byproducts, significantly reducing separation costs, and possessing broad prospects for industrial application. Attached Figure Description

[0029] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.

[0030] Figure 1 Effects of trioctylamine (TOA) / long-chain fatty alcohols on the extraction and separation of 1,3-PDO, butyric acid and acetic acid, where A is the partition coefficient and ratio, B is the extraction recovery rate, and C is the selectivity coefficient.

[0031] Figure 2Effect of methyltrioctylammonium chloride (TOMAC) / long-chain fatty acids on the extraction and separation of 1,3-PDO, butyric acid and acetic acid, where A is the partition coefficient and ratio, B is the extraction recovery rate, and C is the selectivity coefficient.

[0032] Figure 3 Effects of different TOA / n-octanol (OCT) ratios on the extraction partitioning behavior of 1,3-PDO, butyric acid and acetic acid, where A is the partition coefficient and ratio, B is the extraction recovery rate and C is the selectivity coefficient.

[0033] Figure 4 Effect of vortexing time on the partition behavior of 1,3-PDO, butyric acid and acetic acid separated by TOA / OCT extraction, where A is the partition coefficient and ratio, B is the extraction recovery rate and C is the selectivity coefficient.

[0034] Figure 5 The effect of concentration factor on the partition behavior of 1,3-PDO, butyric acid and acetic acid separated by TOA / OCT extraction, where A is the partition coefficient and ratio, B is the extraction recovery rate and C is the selectivity coefficient.

[0035] Figure 6 Effect of pH on the partition behavior of 1,3-PDO, butyric acid and acetic acid separated by TOA / OCT extraction, where A is the partition coefficient and ratio, B is the extraction recovery rate and C is the selectivity coefficient.

[0036] Figure 7 The partitioning behavior of 1,3-PDO, butyric acid and acetic acid during TOA / OCT multi-stage extraction, where A is the partition coefficient of each substance in each extraction stage, B is the single-stage extraction recovery of each substance in each extraction stage, C is the single-stage selection coefficient of each substance in each extraction stage, and D is the total extraction recovery of each substance in each extraction stage.

[0037] Figure 8 The effect of TOA / OCT cyclic extraction on the partition behavior of 1,3-PDO, butyric acid and acetic acid, where A is the partition coefficient of each substance in each stage of cyclic extraction, B is the single-stage extraction recovery rate of each substance in each stage of cyclic extraction, C is the selection coefficient of each substance in each stage of cyclic extraction, and D is the extraction efficiency of butyric acid and acetic acid in each stage of extraction. Detailed Implementation

[0038] The specific embodiments of the present invention are described in detail below with reference to the technical solution, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, the experimental methods used are all conventional methods, and the reagents or instruments used can be commercially available conventional products.

[0039] All raw materials and preparation methods in this embodiment: (1) 1,3-PDO fermentation simulation broth: Prepare an aqueous solution according to the composition of 1,3-PDO and organic acids in the fermentation broth, wherein the concentrations of 1,3-PDO, butyric acid and acetic acid are 85 g / L, 15 g / L and 8 g / L, respectively.

[0040] (2) 1,3-PDO fermentation broth: The 1,3-PDO fermentation broth was obtained by batch fermentation of *Clostridium butyricum*. Fermentation conditions: inoculum size 10% (v / v), nitrogen purging 1 h before inoculation, fermentation temperature 37℃, fermentation stirring speed 250 rpm, and pH adjustment using 5 mol / L sodium hydroxide solution to maintain neutrality during fermentation. The initial glycerol concentration was 80 g / L, with two pulse feedings. When the glycerol concentration decreased to below 15 g / L, the concentration was increased to 80 g / L. Fermentation was terminated when glycerol was no longer consumed. The *Clostridium butyricum* used was a commercially available *Clostridium butyricum* strain commonly used in the field for the fermentation production of 1,3-PDO.

[0041] (3) 1,3-PDO fermentation membrane liquid: Centrifuge the 1,3-PDO fermentation liquid at 7000 rpm for 30 min, and pass the supernatant through a hollow fiber membrane.

[0042] (4) 1,3-PDO concentrate: The 1,3-PDO concentrate used is obtained by dehydration of 1,3-PDO fermentation simulation broth, wherein the concentration of 1,3-PDO is 85~425 g / L, the concentration of butyric acid is 15~75 g / L, and the concentration of acetic acid is 8~40 g / L.

[0043] The concentrations of 1,3-PDO, glycerol, butyric acid and acetic acid were determined by high performance liquid chromatography (HPLC). The detection conditions were: Aminex HPX-87H column, differential detector at a wavelength of 410 nm, injection volume of 20 μL, mobile phase of 5 mmol / L sulfuric acid, flow rate of 0.6 mL / min, and detection time of 27 min.

[0044] Octanol in the aqueous phase was detected by gas chromatography-mass spectrometry (GC-MS): TG-5 column, 30 m; carrier gas: nitrogen; injection volume: 1 μL; injection port temperature: 280℃; detector: mass spectrometer.

[0045] Trioctylamine in the aqueous phase was detected by liquid chromatography-mass spectrometry (LC-MS): Hypersil GOLD C18 column, 150 mm × 2.1 mm; mobile phase: 0.1% formic acid aqueous solution + acetonitrile; flow rate: 0.2 mL / min; injection volume: 5 μL; column temperature: 35℃; detection time: 15 min.

[0046] After extraction and phase separation, the concentrations of 1,3-PDO, butyric acid, and acetic acid in the upper and lower phases were measured respectively, and the partition coefficient (K), phase ratio (P), extraction selectivity (S), extraction recovery (Y), and back-extraction recovery (T) were calculated.

[0047] The formulas for calculating the partition coefficient (K), ratio (P), extraction selectivity (S), extraction recovery (Y), and back-extraction recovery (T) are as follows:

[0048]

[0049]

[0050]

[0051]

[0052] in i Represents 1,3-PDO, butyric acid, or acetic acid. c t and c b The concentration (g / L) of the target analyte in the upper and lower phases after equilibrium. V t and V b The volume of the upper and lower phases after equilibration (mL). Final recoveries of 1,3-PDO, butyric acid, and acetic acid (Y). f The calculation formula for ) is as follows:

[0053]

[0054]

[0055] in I , Ⅱ and Ⅲ These represent the number of stages in a multi-stage extraction process. c 1,3-PDO,0 , c BA,0 , c HAc,0 The initial concentrations of 1,3-propanediol, butyric acid, and acetic acid in the fermentation broth are given. V 0 represents the volume of fermentation broth added in the first extraction step.

[0056] In the DES recycling process, the extraction efficiency (η) of DES for 1,3-PDO, butyric acid, and acetic acid is calculated using the following formula:

[0057] in n This represents the number of iterations in the loop process.

[0058] Example 1: Separation of 1,3-PDO, butyric acid, and acetic acid by trioctylamine / long-chain fatty alcohols (1) Synthesis of DES: Trioctylamine (TOA) was mixed with n-octanol, n-nonanol, n-decanol, undecylol, dodecanol, tridecanol, tetradecanol and octadecylol in a molar ratio of 1:1 and reacted at 150 rpm for 3 h at 60 °C to form a homogeneous, transparent and stable mixed system, and DES was prepared.

[0059] (2) Extraction: The prepared DES was mixed with the 1,3-PDO fermentation simulation broth at a volume ratio of 1:1, vortexed for 10 min, and allowed to stand at room temperature for phase separation. The upper phase was an organic phase rich in butyric acid and acetic acid, and the lower phase was an aqueous phase rich in 1,3-propanediol. The partitioning behavior of 1,3-PDO, butyric acid, and acetic acid in different eutectic solvent extraction systems is as follows: Figure 1 As shown, the DES system formed by TOA / long-chain fatty alcohols achieved extraction recoveries of 94%–98% for butyric acid and 50%–72% for acetic acid, with only a small amount of 1,3-PDO (0.8%–1.6%) being extracted into the DES phase. In the DES system composed of TOA and long-chain alcohols, the selectivities for butyric acid and acetic acid relative to 1,3-PDO were 300–4076 and 20–215, respectively. This demonstrates that the TOA / long-chain fatty alcohol system can effectively achieve selective separation of 1,3-PDO and organic acids.

[0060] Example 2: TOMAC / Long-chain fatty acid separation of 1,3-PDO, butyric acid and acetic acid (1) Synthesis of DES: Methyltrioctylammonium chloride (TOMAC) was mixed with nonanoic acid, decanoic acid, lauric acid, myristic acid and stearic acid in a molar ratio of 1:1 and reacted at 150 rpm for 3 h at 60 °C to form a homogeneous, transparent and stable mixed system, and DES was prepared.

[0061] (2) Extraction: The prepared DES was mixed with the 1,3-PDO fermentation simulation broth at a volume ratio of 1:1, vortexed for 10 min, and allowed to stand at room temperature for phase separation. The partitioning behavior of 1,3-PDO, butyric acid, and acetic acid in different eutectic solvent extraction systems is as follows: Figure 2 As shown, the DES system formed by TOMAC / long-chain fatty acids showed an extraction recovery rate of 93%–95% for butyric acid and 67%–72% for acetic acid, with approximately 16%–23% of 1,3-PDO being extracted into the DES phase. In the TOMAC / long-chain fatty acid system, the selectivity of butyric acid and acetic acid relative to 1,3-PDO was 62–83 and 8–12, respectively, which was lower than that of the TOA / long-chain fatty alcohol system.

[0062] Example 3 Effect of different trioctylamine / n-octanol (TOA / OCT) ratios on the partition behavior of 1,3-PDO, butyric acid and acetic acid (1) TOA / n-octanol DES synthesis: Trioctylamine and n-octanol were mixed in a molar ratio of 1:0.25 to 1:4 and reacted at 150 rpm for 3 h at 60 °C to form a homogeneous, transparent and stable mixed system. TOA / OCT systems with different molar ratios were prepared.

[0063] (2) Extraction: The prepared TOA / OCT was mixed with the 1,3-PDO fermentation simulation broth at a volume ratio of 1:1, vortexed for 10 min, and allowed to stand at room temperature for phase separation. The effects of different TOA / OCT ratios on the partition behavior of 1,3-PDO, butyric acid, and acetic acid are as follows: Figure 3 As shown, when the molar ratio of trioctylamine to n-octanol in the DES system was 1:2, the extraction recoveries of butyric acid and acetic acid were the highest, at 97.1% and 78.6%, respectively, with only 1.8% of 1,3-PDO being extracted into the DES phase; no characteristic peaks of trioctylamine and n-octanol were detected in the 1,3-PDO-rich raffinate phase (the residual amount was below the detection limit).

[0064] Example 4 Effect of vortexing time on the partition behavior of 1,3-PDO, butyric acid and acetic acid separated by TOA / OCT extraction The prepared TOA / OCT system (molar ratio 1:2) was mixed with the 1,3-PDO fermentation simulation broth at a volume ratio of 1:1, vortexed for 0.5–10 min, and allowed to stand at room temperature for phase separation. The effects of different vortexing times on the partitioning behavior of 1,3-PDO, butyric acid, and acetic acid are as follows: Figure 4 As shown, the emulsification phenomenon became more pronounced with increasing vortex time. When the vortex time was 0.5 min, the extraction recoveries of butyric acid and acetic acid were 98.9% and 84.7%, respectively, with only 0.5% of 1,3-PDO being extracted into the DES phase.

[0065] Example 5: Effect of extraction temperature on the partition behavior of 1,3-PDO, butyric acid and acetic acid separated by TOA / OCT extraction The prepared TOA / OCT system (molar ratio 1:2) was mixed with the 1,3-PDO fermentation simulation broth at a volume ratio of 1:1, vortexed for 0.5 min, and allowed to stand at 20–60 °C for phase separation. Extraction temperature had no significant effect on the partitioning behavior of 1,3-PDO and organic acids. When the extraction temperature was 30 °C, the extraction recoveries of butyric acid and acetic acid were 98.6% and 82.5%, respectively, with only 0.6% of 1,3-PDO being extracted into the DES phase.

[0066] Example 6 Effects of 1,3-PDO, butyric acid and acetic acid concentrations on TOA / OCT extraction and separation The prepared TOA / OCT system (molar ratio 1:2) was mixed with 1,3-PDO fermentation simulant or concentrated broth (concentration factor 2-5 times) at a volume ratio of 1:1, vortexed for 0.5 min, and allowed to stand at room temperature for phase separation. The distribution behavior was as follows: Figure 5 As shown in the figure, compared to the increase with increasing concentration factor, the partition coefficient of butyric acid showed a trend of first increasing and then decreasing with increasing concentration factor, reaching a maximum of 272 at a concentration factor of 2. The concentration factor had no significant effect on the extraction recovery rate of butyric acid and acetic acid, but with increasing concentration factor, i.e., increasing 1,3-PDO concentration, the extraction recovery rate of 1,3-PDO showed a trend of first increasing and then decreasing. When the concentration factor was 4, the concentration of 1,3-PDO in the raffinate phase was 340 g / L, and approximately 8.4% of 1,3-PDO was extracted into the DES phase.

[0067] Example 7 Effect of pH on the partition behavior of 1,3-PDO, butyric acid and acetic acid separated by TOA / OCT extraction A certain amount of sodium hydroxide was added to the 1,3-PDO fermentation simulation broth to adjust the pH to 2.7–7.0. The prepared TOA / OCT system (molar ratio 1:2) was mixed with the simulation broths at different pH values ​​at a volume ratio of 1:1, vortexed for 0.5 min, and allowed to stand at room temperature for phase separation. The distribution behavior was as follows: Figure 6 As shown, the partition coefficients and extraction recoveries of organic acids both decreased with increasing pH. At pH 5.0, the partition coefficients of butyric acid and acetic acid decreased to 1.7 and 0.1, respectively, and the extraction recoveries of butyric acid decreased from 98.6% to 62.4%, and those of acetic acid decreased from 82.5% to 12.0%. Organic acids in an undissociated state are more readily extracted into the DES phase. pH changes had no significant effect on the partition behavior of 1,3-PDO.

[0068] Example 8: Multistage extraction of 1,3-PDO and organic acids The prepared TOA / OCT system (molar ratio 1:2) was mixed with the 1,3-PDO fermentation simulation broth at a volume ratio of 1:1, vortexed for 0.5 min, and allowed to stand at room temperature for phase separation. The residual phase was then vortexed again with the TOA / OCT system under the same conditions for secondary and tertiary extraction. After each extraction and phase separation, samples were taken to determine the concentration of each substance in the lower phase, and the recovery rates of each extraction stage and the total extraction recovery (Y) were calculated. The results are shown below. Figure 7 As shown in the figure, under the above operating conditions, the total recoveries of butyric acid by secondary and tertiary extraction were 99.7% and 99.8%, respectively, and the total recoveries of acetic acid by secondary and tertiary extraction were 95.2% and 96.3%, respectively. After secondary and tertiary extraction, only 3.3% and 4.7% of 1,3-PDO were extracted to the DES phase, respectively. This demonstrates that secondary extraction can effectively achieve the selective separation of organic acids and 1,3-propanediol.

[0069] Example 9 Back-extraction of butyric acid and acetic acid The prepared TOA / OCT system (molar ratio 1:2) was mixed with the 1,3-PDO fermentation simulation broth at a volume ratio of 1:1, vortexed for 0.5 min, and allowed to stand at room temperature for phase separation. 50 g / L sodium hydroxide aqueous solution, 50 g / L sodium carbonate aqueous solution, and 50 g / L sodium bicarbonate aqueous solution were respectively mixed with the DES phase at a volume ratio of 1:1, vortexed for 0.5 min, and allowed to stand at room temperature for phase separation for organic acid back-extraction. Samples were taken during both extraction and back-extraction steps to determine the concentration of each substance in the lower phase, and the back-extraction recovery rate (T) was calculated. When using sodium hydroxide, sodium carbonate, and sodium bicarbonate solutions for back-extraction, the back-extraction recovery rates for butyric acid were 96.8%, 95.0%, and 84.0%, respectively, and the back-extraction recovery rates for acetic acid were 97.3%, 97.4%, and 97.9%, respectively. Subsequently, a 50 g / L sodium hydroxide aqueous solution was mixed with the DES phase at a volume ratio of 1:1 to 1:5, vortexed for 0.5 min, and allowed to stand at room temperature for phase separation. At a volume ratio of 1:1, the highest back-extraction recoveries of butyric acid and acetic acid were 96.8% and 97.5%, respectively.

[0070] Example 10: Recycling and Reuse of DES The prepared TOA / OCT system (molar ratio 1:2) was mixed with the 1,3-PDO fermentation simulation broth at a volume ratio of 1:1, vortexed for 0.5 min, and allowed to stand at room temperature for phase separation. As described in Example 9, a 50 g / L sodium hydroxide aqueous solution was mixed with the DES phase at a volume ratio of 1:1, vortexed for 0.5 min, and allowed to stand at room temperature for phase separation, followed by back-extraction of organic acids. The back-extracted DES was then subjected to cyclic extraction and back-extraction with fresh 1,3-PDO fermentation simulation broth for 5 cycles. During each cycle, samples were taken during the extraction and back-extraction steps to determine the concentration of each substance in the lower phase, and the extraction recovery rate (Y) and extraction efficiency (η) were calculated.

[0071] The results are as follows Figure 8 As shown, after five rounds of recycling, the extraction recoveries of butyric acid and acetic acid by the recovered DES still reached 94.3% and 82.3%, respectively, with only 2.5% of 1,3-PDO being extracted into the DES phase. Compared with the first round of extraction, the extraction efficiencies of the recovered DES for butyric acid and acetic acid still reached 99.2% and 96.6%, respectively.

[0072] Example 11 Extraction and separation of 1,3-PDO fermentation membrane liquid The 1,3-PDO fermentation broth was centrifuged and then filtered through a membrane to prepare the filtered solution. The pH was adjusted to 3.0. The concentrations of 1,3-PDO, butyric acid, and acetic acid in the filtered solution were measured to be 85.24 g / L, 15.23 g / L, and 8.29 g / L, respectively. The prepared TOA / OCT system (molar ratio 1:2) was mixed with the 1,3-PDO fermentation filtered solution at a volume ratio of 1:1, vortexed for 0.5 min, and allowed to stand at room temperature for phase separation. The extraction recoveries of butyric acid and acetic acid were 89.2% and 37.8%, respectively, with only 1.1% of 1,3-PDO being extracted into the DES phase.

[0073] Example 121,3-PDO fermentation broth extraction and separation The prepared TOA / OCT system (molar ratio 1:2) was mixed with 1,3-PDO fermentation broth (pH adjusted to 3.0) at a volume ratio of 1:1, vortexed for 0.5 min, and allowed to stand at room temperature for phase separation. The removal rates of cells and proteins were 99.5% and 89.7%, respectively, and the extraction recoveries of butyric acid and acetic acid were 87.4% and 36.3%, respectively. Only 1.6% of 1,3-PDO was extracted into the DES phase. No characteristic peaks of trioctylamine and n-octanol were detected in the 1,3-PDO-rich raffinate phase (residual amounts were below the detection limit).

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for separating 1,3-PDO, butyric acid, and acetic acid based on eutectic solvent extraction, characterized in that, Includes the following steps: S1: Preparation of eutectic solvent: Trioctylamine (TOA) and long-chain fatty alcohol are mixed in a molar ratio of 1:0.25 to 1:4 or methyltrioctylammonium chloride (TOMAC) is mixed with long-chain fatty acids in a molar ratio of 1:0.25 to 1:4, and stirred at 50 to 70°C to prepare eutectic solvent (DES). S2: First step extraction: The eutectic solvent obtained in step S1 is mixed with an aqueous solution containing 1,3-PDO at a volume ratio of 1:5 to 5:

1. The mixture is vortexed, stirred or shaken to separate the phases, resulting in an extract phase and a raffinate phase. The raffinate phase is an aqueous phase rich in 1,3-PDO. S3: Multi-stage extraction: Add the eutectic solvent described in step S1 to the raffinate phase obtained in step S2, vortex, stir or shake, separate the phases to obtain the extract phase and the raffinate phase, and perform multi-stage extraction. S4: Back-extraction and DES recovery: Add an alkaline aqueous solution to the extract phase obtained in steps S2 and S3 for back-extraction to recover butyric acid and acetic acid, while recovering the eutectic solvent of the upper phase. S5: Separation and purification of 1,3-PDO: The raffinate obtained in step S3 is separated and purified to obtain 1,3-PDO.

2. The method according to claim 1, characterized in that, The long-chain fatty alcohol mentioned in step S1 is one or a combination of two or more of n-octanol, n-nonanol, n-decanol, undecylol, dodecanol, tridecanol, tetradecanol or octadecylol, preferably n-octanol; the molar ratio of trioctylamine to the long-chain fatty alcohol is 1:0.25 to 1:3, preferably 1:2; the long-chain fatty acid is one or a combination of two or more of nonanoic acid, decanoic acid, lauric acid, myristic acid or stearic acid, and the molar ratio of methyltrioctylammonium chloride to the long-chain fatty acid is 1:0.25 to 1:

2.

3. The method according to claim 1, characterized in that, The 1,3-PDO aqueous solution mentioned in step S2 is an aqueous solution mainly containing 1,3-PDO, butyric acid and acetic acid, untreated 1,3-PDO fermentation broth, 1,3-PDO fermentation membrane liquid or 1,3-PDO fermentation concentrate; the concentration of 1,3-PDO is 85~425 g / L, the concentration of butyric acid is 15~75 g / L, and the concentration of acetic acid is 8~40 g / L.

4. The method according to claim 1, characterized in that, In step S2, before extraction, the pH of the aqueous solution containing 1,3-PDO is adjusted to 2.7-7.0, preferably pH 2.7-4.

0.

5. The method according to claim 1, characterized in that, In step S2, the vortexing, stirring, or oscillation time is 0.5~10 min, preferably 0.5~5 min; the extraction temperature is 20~60℃, preferably 20~40℃.

6. The method according to claim 1, characterized in that, The number of stages in the multi-stage extraction described in step S3 is 1 to 4, preferably 2, and the extraction steps of the multi-stage extraction are the same as those in step S2.

7. The method according to claim 1, characterized in that, The alkaline aqueous solution mentioned in step S4 is one of sodium hydroxide aqueous solution, sodium carbonate aqueous solution, or sodium bicarbonate aqueous solution, preferably sodium hydroxide aqueous solution.

8. The method according to claim 7, characterized in that, The concentration of the alkaline aqueous solution in step S4 is 10~100 g / L, preferably 40~60 g / L; the volume ratio of the alkaline aqueous solution to the extraction phase in step S4 is 1:1~1:5, preferably 1:

1.

9. The method according to claim 1, characterized in that, The separation and purification described in step S5 includes vacuum distillation.

10. A 1,3-PDO solution obtained by means of any one of claims 1-9, characterized in that, The residual amount of eutectic solvent in the 1,3-PDO solution was below the instrument detection limit.

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