A separation method and separation system for separating phosphoric acid in the process of separating and purifying carboxylic acid by liquid-liquid extraction

Abstract

The present application discloses a separation system and a separation system for separating phosphoric acid in the process of separating and purifying carboxylic acid by liquid-liquid extraction, and relates to a method for purifying carboxylic acid in carboxylic acid fermentation broth, comprising an extraction solvent, a detergent, a carboxylic acid and a stripping agent, wherein the extraction solvent comprises an extractant and a diluent, and the carboxylic acid serves as a hydrogen bond donor; the extractant serves as a hydrogen bond acceptor, and the functional groups present in the diluent interact with the carboxylic acid to form a hydrophobic separation system. Therefore, the present application provides a separation method and a separation system for separating phosphoric acid in the process of separating and purifying carboxylic acid by liquid-liquid extraction, which has a simple process, low energy consumption and high recovery rate.

Description

Technical Field

[0001] The present application relates to a method for purifying carboxylic acid in carboxylic acid fermentation broth, and in particular to a process route and a separation system for separating phosphoric acid in the process of separating and purifying carboxylic acid by a liquid-liquid extraction method. Background Art

[0002] Phosphorus is one of the essential nutrients for plant growth and development. It is not only an important component of biological macromolecules such as nucleic acids, proteins and lipids, but also participates in a variety of metabolic processes, such as nucleotide synthesis, photosynthesis, energy transfer and signal transduction. In the soil, the mass fraction of total phosphorus is generally between 0.2 and 1.1 g kg-1, and its forms are mainly divided into inorganic phosphorus and organic phosphorus. Among them, inorganic phosphate ions (PO4 3- or HPO4 2- , its content generally accounts for about 0.1% of the total phosphorus in the soil, which is difficult to meet the needs of crop growth. When the concentration of effective phosphorus in the culture medium is low, various metabolic activities in the crop body are significantly affected, resulting in symptoms of phosphorus deficiency such as slow growth and weak plants, which ultimately lead to crop yield reduction. Therefore, in order to increase crop yields, increase the content of soluble sugars and phospholipids in plants, enhance the cold resistance of crops, strengthen photosynthesis and the synthesis and transport of carbohydrates, and enhance the adaptability of crops to acid-base changes, people use phosphorus fertilizers in saline-alkali land and soil.

[0003] Most of the carboxylic acids produced by fermentation are obtained by purifying crops (corn, dried potatoes, etc.) after microbial transformation. In addition to the main product carboxylic acid, the fermentation products of the deep fermentation process also contain residual sugars that have not been used up by fermentation, bacteria, proteins, pigments, colloids, inorganic salts, organic acids produced by fermentation, and various impurities brought in by the raw materials, including N, P, K and other nutrients contained in the crops themselves or added during the fermentation process. To obtain citric acid products that meet quality standards from such a complex mixed system, a series of physical and chemical methods must be used for treatment, which is the post-extraction process.

[0004] By analyzing various carboxylic acid fermentation broths, it was found that the impurities that affect the purity of carboxylic acids mainly include organic miscellaneous acids produced during the fermentation of carboxylic acids, residual fermentation sugars, proteins, pigments, etc. Since the impurity carboxylic acids and inorganic acids have similar physicochemical properties to the target carboxylic acids, it is difficult to effectively separate the impurity carboxylic acids from the target carboxylic acids, which affects the purity of the carboxylic acid products.

[0005] Phosphoric acid is a ternary medium-strong acid that ionizes in three steps. It is not easy to volatilize, not easy to decompose, and has certain oxidizing properties. It has the general properties of an acid. Therefore, in the process of extracting carboxylic acids, phosphoric acid is often mixed in and difficult to separate. Most of the current separation processes use anion exchange resins to remove anions such as phosphate, which is not only not conducive to the recovery of useful resources that can be reused, but also requires large equipment investment and high operating costs. The purified carboxylic acid solution still has a large amount of phosphoric acid in the mother liquor during the concentration process, which reduces the quality of the carboxylic acid product and increases the production cost of the company's products.

[0006] The precipitation method is widely used in the fermentation production of carboxylic acids due to its advantages such as easy availability of raw materials, simple technology, mature process and stable product properties. At present, the calcium salt precipitation method is still the most commonly used method for industrial carboxylic acid separation, but it has obvious shortcomings, such as the large amount of sulfuric acid and calcium salt added as chemical reagents, which cannot be reused, high production costs, poor quality of by-product calcium sulfate, no commercial value, and serious environmental pollution. In addition, the neutralization and acidification process of this method is not selective, and the purity of the obtained product is not high, which is difficult to meet the purity requirements as a fine chemical, and needs to be further refined and purified by other methods.

[0007] Extraction is a commonly used separation method with the advantages of simple operation, large processing volume, low energy consumption, and suitability for continuous and automated operation. Currently, the methods with relatively high extraction efficiency for carboxylic acids are mainly complex extraction and aqueous two-phase extraction.

[0008] The present application adopts a liquid-liquid extraction method to separate carboxylic acid and phosphoric acid in a carboxylic acid raw material, and utilizes the physical and chemical characteristics of carboxylic acid and phosphoric acid to separate and extract carboxylic acid and remove acidic impurities such as phosphoric acid during the liquid-liquid extraction process. At present, there is no reported separation process for the separation of phosphoric acid from carboxylic acid. The method proposed in the present application for purifying carboxylic acid by liquid-liquid extraction and separating it from phosphoric acid is selective and innovative. It saves equipment investment and operating costs, and the product quality is good and the purity is high. More importantly, it can avoid the severe three waste pollution caused by the neutralization and acidification processes in the current traditional process, and is a green, low-carbon, clean and efficient separation technology. Summary of the invention

[0009] The purpose of the present application is to provide a separation method and separation system for separating phosphoric acid in the process of separating and purifying carboxylic acids by liquid-liquid extraction, thereby reducing energy consumption, improving recovery rate, and making the process simpler.

[0010] The present application provides a separation system for separating phosphoric acid in the process of separating and purifying carboxylic acid by a liquid-liquid extraction method, comprising an extraction solvent, a detergent, a carboxylic acid and a stripping agent, wherein the extraction solvent comprises an extractant and a diluent, and the carboxylic acid serves as a hydrogen bond donor; the extractant serves as a hydrogen bond acceptor, and the functional groups present in the diluent interact with the carboxylic acid to form a hydrophobic separation system.

[0011] Preferably, the extractant includes one or more of primary amine, secondary amine and tertiary amine, and the diluent includes one or more of alkane compounds, ketone compounds and thioether compounds.

[0012] Preferably, when the carboxylic acid is citric acid, the detergent is a sodium citrate solution; when the carboxylic acid is lactic acid, the detergent is a mixed solution of sodium lactate solution and lactic acid solution; when the carboxylic acid is succinic acid, the detergent is one or more of a succinic acid solution or a sodium succinate solution.

[0013] Preferably, the carboxylic acid is one or more of lactic acid, citric acid, succinic acid, malic acid, aconitic acid, and itaconic acid, and the stripping agent is water.

[0014] The present application provides a separation system for separating phosphoric acid in the process of separating and purifying carboxylic acid using the above-mentioned liquid-liquid extraction method, and the separation method comprises the following steps:

[0015] S1 extraction, mixing an extraction solvent with a carboxylic acid raw material for extraction, so that the carboxylic acid and phosphoric acid enter the organic phase to obtain a loaded organic phase;

[0016] S2 washing, selecting a detergent according to the carboxylic acid to wash the above-mentioned loaded organic phase under specific conditions, the phosphoric acid is washed off, and a purified loaded organic phase is obtained;

[0017] S3 stripping, stripping the purified loaded organic phase with a stripping agent to obtain a stripping solution and a lean organic phase;

[0018] S4 regeneration, regenerating the lean organic phase to obtain a blank extractant that is recycled to the extraction section for reuse.

[0019] Preferably, in step S1, the mixing temperature of the extraction solvent and the carboxylic acid is 30-70° C., the mixing stirring speed is 50-1000 rpm, and the stirring time is 2-10 min.

[0020] Preferably, in step S2, the volume ratio of the loaded organic phase to the detergent is 10:1-20:1, and the phosphoric acid is washed in water by the detergent by heating at 30-70°C;

[0021] Preferably, in step S3, the volume ratio of the purified loaded organic phase to the stripping agent is 1:1-10:1, and the purified carboxylic acid is transferred from the organic phase to the aqueous phase by heating at 50-90°C, and finally the stripped carboxylic acid solution is evaporated and concentrated to obtain a high-purity carboxylic acid product.

[0022] Preferably, in step S1, pH <pKa。

[0023] Preferably, in step S4, the process of regenerating the organic phase after stripping is: alkali washing and water washing to remove the residual acid in the organic phase.

[0024] Therefore, the present application adopts the above-mentioned liquid-liquid extraction method to separate phosphoric acid in the process of separating and purifying carboxylic acid, which has the following beneficial effects:

[0025] 1. In the present application, the solvent extraction method is fully utilized to purify and separate the carboxylic acid, and the extractant can be fully recycled, which simplifies the process of separating and purifying the carboxylic acid;

[0026] 2. The solvent extraction method can purify carboxylic acid, which can reduce the material consumption and wastewater volume of the traditional process in terms of process principle, and completely eliminates the generation of solid waste and waste gas;

[0027] 3. It can effectively reduce the phosphate content in carboxylic acid products, and improve the purity and quality of carboxylic acid products on the basis of meeting the national standards for carboxylic acids;

[0028] 4. It can effectively reduce the amount of mother liquor in the process of concentrating carboxylic acid, and at the same time reduce the content of phosphate in the mother liquor, avoiding the vicious cycle of phosphate accumulation during multiple crystallization of the mother liquor;

[0029] 5. During the phosphoric acid washing process, the eluted phosphate can be recycled and used as a phosphate fertilizer resource cycle.

[0030] The present invention adopts the method for separating phosphoric acid in the process of purifying carboxylic acid by the solvent extraction method, and has the advantages of simple process, low energy consumption, high recovery rate, green environmental protection, less pollution, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Flowchart of this application.

[0032] Figure 2 In this application, taking citric acid as an example, the product purity and washing effect change trend chart with detergent. DETAILED DESCRIPTION

[0033] The present application provides a separation system for separating phosphoric acid in the process of separating and purifying carboxylic acids by liquid-liquid extraction, including an extraction solvent, a detergent, a carboxylic acid and a stripping agent, wherein the carboxylic acid serves as a hydrogen bond donor; the extractant serves as a hydrogen bond acceptor, and the functional groups present in the diluent interact with the carboxylic acid to form a new hydrophobic solvent separation and purification system having a linear, planar or multi-dimensional network structure. The separation system used for the extraction and separation of carboxylic acids is different due to the different characteristics of the carboxylic acids; and thus the detergents and washing methods used to separate phosphoric acid impurities in the purification process are also different. The extractant, detergent and washing method are determined according to the specific carboxylic acid situation. The extraction solvent includes an extractant and a diluent, and the extractant includes primary amines, secondary amines and tertiary amines, and the diluent includes one or more of alkane compounds, ketone compounds and thioether compounds. When the carboxylic acid is citric acid, the detergent is one or more of sodium citrate solution or citric acid solution; when the carboxylic acid is lactic acid, the detergent is one or more of sodium lactate solution or lactic acid solution; when the carboxylic acid is succinic acid, the detergent is one or more of succinic acid solution or sodium succinate solution; the carboxylic acid is one or more of lactic acid, citric acid, succinic acid, malic acid, aconitic acid, itaconic acid, and the stripping agent is water.

[0034] As the extraction solvent is hydrophobic, the carboxylic acid is transferred from the aqueous phase to the organic phase, thereby achieving separation from sugars, pigments, proteins and inorganic ions. At the same time, as the extractant is selective, it can only form a new solvent system with proton carboxylic acids of a certain structure, thereby achieving separation of a certain carboxylic acid from other impurity carboxylic acids and inorganic acids. High-purity carboxylic acids are obtained through this method.

[0035] The diluent, carboxylic acid and extractant form a complex (pKa,amine>pKa,acid) in a certain ratio through ion pairing and hydrogen bonding, thereby extracting the carboxylic acid into the organic phase. The mechanism of the complexation reaction is mainly the ion association salt formation mechanism and the hydrogen bond association solvation mechanism. Only molecular carboxylic acids can be extracted, and the complexation extraction process usually requires controlling pH. <p Ka。

[0036] The present application provides a separation system for separating phosphoric acid in the process of separating and purifying carboxylic acid using the above-mentioned liquid-liquid extraction method, and the separation method comprises the following steps:

[0037] Extraction: Extraction is performed by mixing an extraction solvent with a carboxylic acid raw material solution, the mixing temperature is 30-70°C, the mixing stirring speed is 50-1000 rpm, and the stirring time is 2-10 min; at this time, carboxylic acid and phosphoric acid enter the organic phase through the molecular recognition technology between the organic phase and the target molecule, and a loaded organic phase is obtained; during the extraction process, pH <p Ka。

[0038] Washing: A specific detergent is selected to wash the above-mentioned loaded organic phase under specific conditions, and phosphoric acid is selectively washed off to obtain a purified loaded organic phase; the type and concentration of the detergent are determined according to the pKa of the target carboxylic acid, and the volume ratio of the loaded organic phase to the detergent is 10:1-20:1. By heating at 30-70°C, the phosphoric acid in the organic solvent is washed into the washing water through the detergent;

[0039] Stripping: Stripping the purified loaded organic phase with a stripping agent under specific stripping conditions to obtain a stripping solution and a lean organic phase; the volume ratio of the purified loaded organic phase to the stripping agent is 1:1-10:1, and the purified carboxylic acid is transferred from the organic phase to the aqueous phase by heating at 50-90°C, and finally the stripped carboxylic acid solution is evaporated and concentrated to obtain a high-purity carboxylic acid product.

[0040] Regeneration: The lean organic phase is regenerated using a regeneration agent. After alkali washing and water washing, the residual acid in the organic phase is removed to obtain a blank extractant which is recycled to the extraction section for reuse.

[0041] Example 1

[0042] A method for separating phosphoric acid during the purification of carboxylic acid by solvent extraction comprises the following steps:

[0043] (1) firstly, 20% tri-n-octylamine and 2-octanone are mixed to prepare an extraction solvent, and then the extraction solvent is mixed with about 16% citric acid fermentation broth, wherein the phosphate content is 2 g / L, at a ratio of 2:1 at a temperature of 35° C. for 2 minutes for extraction to obtain an organic phase loaded with citric acid and phosphate impurities; the citric acid first extraction rate is 50%, after 7-stage countercurrent extraction, the citric acid concentration in the citric acid raffinate is detected to be 0.5 g / L, and the citric acid 7-stage countercurrent extraction rate is 99.6%;

[0044] (2) using 14% sodium citrate solution as a detergent, mixing the loaded organic phase with the 14% sodium citrate solution at a ratio of 10:1, mixing at 35° C. for 2 min, and washing the phosphate in the loaded organic phase;

[0045] (3) Mixing the washed loaded organic phase with pure water in a ratio of 2:1 at 70°C for 2 minutes, and allowing to stand for stratification. The primary stripping rate of citric acid is 70%, the 10-stage countercurrent stripping rate is 99%, the stripping solution concentration is 14%, and the phosphate content in the stripping solution is less than 50 ppm;

[0046] (4) The organic phase after stripping is washed with alkali and water to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0047] Example 2

[0048] A method for separating phosphoric acid during the purification of carboxylic acid by solvent extraction comprises the following steps:

[0049] (1) 50% N,N-dimethyldodecylamine and 2-octanone are mixed to prepare an extraction solvent, and the mixture is mixed with about 20% lactic acid fermentation broth, wherein the phosphate content is 1.6 g / L, and the mixture is extracted at a ratio of 2.5:1 at a temperature of 40° C. for 2 minutes to obtain an organic phase loaded with lactic acid and phosphate impurities; the primary extraction rate of lactic acid is 38%, and after 10-stage countercurrent extraction, the lactic acid concentration in the lactic acid raffinate is detected to be 0.9 g / L, and the 10-stage countercurrent extraction rate of lactic acid is 99.0%;

[0050] (2) washing the loaded organic phase with a mixed solution of 10% sodium lactate and 16% lactic acid in a ratio of 12:1 at 40° C. for 2 min to wash the phosphate in the loaded organic phase;

[0051] (3) Mixing the washed loaded organic phase with pure water at a ratio of 2.5:1 at 60°C for 2 min, and allowing to stand for stratification. The first stripping rate was 79%, the 9-stage countercurrent stripping rate was 99%, the stripping solution concentration was 15%, and the phosphate content in the stripping solution was <30 ppm;

[0052] (4) The organic phase after stripping is washed with alkali and water to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0053] Example 3

[0054] A method for separating phosphoric acid during the purification of carboxylic acid by solvent extraction comprises the following steps:

[0055] (1) Using 60% N,N-dimethyloctadecylamine and white oil to prepare an extraction solvent, and diluting the mother liquor with about 20% citric acid, wherein the phosphate content is 10 g / L, the mixture is mixed at a ratio of 4:1 at a temperature of 55° C. for 2 minutes for extraction to obtain an organic phase loaded with citric acid and phosphoric acid impurities; the citric acid extraction rate is 60% in one time, and after 6-stage countercurrent extraction, the citric acid concentration in the raffinate of the citric acid diluted mother liquor is detected to be 1 g / L, and the 6-stage countercurrent extraction rate of citric acid is 99.8%;

[0056] (2) using 15% sodium citrate solution, mixing with the loaded organic phase at a ratio of 10:1, at a temperature of 55° C. for 2 min to wash the loaded organic phase, thereby washing away the phosphate in the loaded organic phase;

[0057] (3) Mixing the washed loaded organic phase with pure water at a ratio of 4:1 at 70°C for 2 minutes, and standing to separate into layers. The first stripping rate is 50%, the 10-stage countercurrent stripping rate is 97%, the stripping solution concentration is 20%, and the phosphate content in the stripping solution is less than 100 ppm;

[0058] (4) The organic phase after stripping is subjected to two-stage alkaline washing and one-stage water washing to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0059] Example 4

[0060] A process route and separation system for separating phosphoric acid in the process of purifying carboxylic acid by liquid-liquid extraction method, comprising the following steps:

[0061] (1) 36% trilaurylamine and dibutyl sulfide are mixed to prepare an extraction solvent, and about 16% citric acid fermentation broth, wherein the phosphate content is 1.14 g / L, is mixed at a ratio of 2.5:1 at a temperature of 45° C. for 2 minutes for extraction to obtain an organic phase loaded with citric acid and phosphate impurities; the citric acid primary extraction rate is 50%, and after 7-stage countercurrent extraction, the citric acid concentration in the citric acid raffinate is detected to be 0.5 g / L, and the citric acid 7-stage countercurrent extraction rate is 99.6%;

[0062] (2) using 14% sodium citrate solution, with a ratio of 10:1, and mixing at 45° C. for 2 min to wash the loaded organic phase, thereby washing away the phosphate in the loaded organic phase;

[0063] (3) Mixing the washed loaded organic phase with pure water in a ratio of 3:1 at 80° C. for 2 min, and allowing to stand for stratification. The first stripping rate is 50%, the 19-stage countercurrent stripping rate is 99%, the stripping solution concentration is 14%, and the phosphate content in the stripping solution is less than 50 ppm;

[0064] (4) The organic phase after stripping is subjected to two-stage alkaline washing and one-stage water washing to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0065] Example 5

[0066] A process route and separation system for separating phosphoric acid in the process of purifying carboxylic acid by liquid-liquid extraction method, comprising the following steps:

[0067] (1) A mixture of 50% trioctylamine and dibutyl sulfide is used to prepare an extraction solvent, and about 8% succinic acid fermentation broth, wherein the phosphate content is 0.3 g / L, is mixed at a ratio of 2.2:1 at a temperature of 50° C. for 2 minutes for extraction to obtain an organic phase loaded with succinic acid and phosphate impurities; the first extraction rate of succinic acid is 52%, and after 8-stage countercurrent extraction, the free succinic acid concentration in the succinic acid raffinate is detected to be 0.7 g / L, and the countercurrent extraction rate of succinic acid is 99.6%;

[0068] (2) using a mixed solution of 3% succinic acid solution and 2% sodium succinate solution at a ratio of 10:1 and a temperature of 50° C. for 2 min to wash the loaded organic phase, thereby washing the phosphate in the loaded organic phase;

[0069] (3) Mixing the washed loaded organic phase with pure water in a ratio of 3:1 at 80°C for 2 minutes, and allowing to stand for stratification. The first stripping rate was 55%, the 16-stage countercurrent stripping rate was 99%, the stripping solution concentration was 6%, and the phosphate content in the stripping solution was <50 ppm;

[0070] (4) The organic phase after stripping is subjected to two-stage alkaline washing and one-stage water washing to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0071] The separation system to be protected in the present application is an extraction solvent corresponding to a specific carboxylic acid, and the extraction solvent includes an extractant and a diluent. The extractant includes primary amines, secondary amines, and tertiary amines, and the diluent includes one or more of alkane compounds, ketone compounds, and thioether compounds.

[0072] Comparative Example 1

[0073] (1) firstly, 20% of n-hexanol and 2-octanone are mixed to prepare an extraction solvent, and then the extraction solvent and about 16% of citric acid fermentation broth, wherein the phosphate content is 2 g / L, are mixed at a ratio of 2:1 at a temperature of 35° C. for 2 minutes for extraction to obtain an organic phase loaded with citric acid and phosphate impurities; the citric acid first extraction rate is 10%, after 25-stage countercurrent extraction, the citric acid concentration in the citric acid raffinate is detected to be 3 g / L, and the 25-stage countercurrent extraction rate of citric acid is 98%;

[0074] (2) using 14% sodium citrate solution as a detergent, mixing the loaded organic phase with the 14% sodium citrate solution at a ratio of 10:1, mixing at 35° C. for 2 min, and washing the phosphate in the loaded organic phase;

[0075] (3) Mixing the washed loaded organic phase with pure water at a ratio of 2:1 at 70°C for 2 minutes, and allowing to stand for stratification. The primary stripping rate of citric acid is 50%, the 20-stage countercurrent stripping rate is 97%, the stripping solution concentration is 12%, the purity is 98%, and the phosphate content in the stripping solution is less than 50 ppm;

[0076] (4) The organic phase after stripping is washed with alkali and water to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0077] Comparative Example 2

[0078] (1) firstly, 20% tri-n-octylamine and n-butyl ether are mixed to prepare an extraction solvent, and then the extraction solvent and about 16% citric acid fermentation broth, wherein the phosphate content is 2 g / L, are mixed at a ratio of 2:1 at a temperature of 35° C. for 2 minutes for extraction to obtain an organic phase loaded with citric acid and phosphate impurities; the citric acid first extraction rate is 30%, after 15-stage countercurrent extraction, the citric acid concentration in the citric acid raffinate is detected to be 2 g / L, and the citric acid 15-stage countercurrent extraction rate is 99%;

[0079] (2) using 14% sodium citrate solution as a detergent, mixing the loaded organic phase with the 14% sodium citrate solution at a ratio of 10:1, mixing at 35° C. for 2 min, and washing the phosphate in the loaded organic phase;

[0080] (3) Mixing the washed loaded organic phase with pure water at a ratio of 2:1 at 70°C for 2 minutes, and allowing to stand for stratification. The primary stripping rate of citric acid is 40%, the 18-stage countercurrent stripping rate is 98%, the stripping solution concentration is 13%, the purity is 98%, and the phosphate content in the stripping solution is less than 50 ppm;

[0081] (4) The organic phase after stripping is washed with alkali and water to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0082] Comparative Example 3

[0083] (1) firstly, 20% tri-n-octylamine and 2-octanone are mixed to prepare an extraction solvent, and then the extraction solvent is mixed with about 16% citric acid fermentation broth, wherein the phosphate content is 2 g / L, at a ratio of 2:1 at a temperature of 35° C. for 2 minutes for extraction to obtain an organic phase loaded with citric acid and phosphate impurities; the citric acid first extraction rate is 50%, after 7-stage countercurrent extraction, the citric acid concentration in the citric acid raffinate is detected to be 0.5 g / L, and the citric acid 7-stage countercurrent extraction rate is 99.6%;

[0084] (2) using 14% citric acid solution as a detergent, mixing the loaded organic phase with 14% sodium citrate solution in a ratio of 10:1, mixing at 35° C. for 2 min, and washing the phosphate in the loaded organic phase;

[0085] (3) Mixing the washed loaded organic phase with pure water at a ratio of 2:1 at 70°C for 2 minutes, and allowing to stand for stratification. The primary stripping rate of citric acid is 70%, the 10-stage countercurrent stripping rate is 99%, the stripping solution concentration is 14%, the purity is 96%, and the phosphate content in the stripping solution is 800 ppm;

[0086] (4) The organic phase after stripping is washed with alkali and water to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0087] Comparative Example 4

[0088] (1) 50% of n-hexanol and 2-octanone are mixed to prepare an extraction solvent, and the mixture is mixed with about 20% of a lactic acid fermentation broth having a phosphate content of 1.6 g / L at a ratio of 2.5:1 at a temperature of 40° C. for 2 min for extraction to obtain an organic phase loaded with lactic acid and phosphate impurities; the primary extraction rate of lactic acid is 35%, and after 11-stage countercurrent extraction, the lactic acid concentration in the lactic acid raffinate is detected to be 1.5 g / L, and the 10-stage countercurrent extraction rate of lactic acid is 98%;

[0089] (2) washing the loaded organic phase with a mixed solution of 10% sodium lactate and 16% lactic acid in a ratio of 12:1 at 40° C. for 2 min to wash the phosphate in the loaded organic phase;

[0090] (3) Mixing the washed loaded organic phase with pure water at a ratio of 2.5:1 at 60°C for 2 min, and allowing to stand for stratification. The first stripping rate was 75%, the 12-stage countercurrent stripping rate was 98%, the stripping solution concentration was 14%, the stripping solution purity was 98.5%, and the phosphate content in the stripping solution was <30 ppm;

[0091] (4) The organic phase after stripping is washed with alkali and water to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0092] Comparative Example 5

[0093] (1) 50% N,N-dimethyldodecylamine and n-butyl ether are mixed to prepare an extraction solvent, and about 20% of a lactic acid fermentation broth, wherein the phosphate content is 1.6 g / L, is mixed at a ratio of 2.5:1 at a temperature of 40° C. for 2 minutes for extraction to obtain an organic phase loaded with lactic acid and phosphate impurities; the primary extraction rate of lactic acid is 34%, and after 10-stage countercurrent extraction, the lactic acid concentration in the lactic acid raffinate is detected to be 2 g / L, and the 10-stage countercurrent extraction rate of lactic acid is 97.5%;

[0094] (2) washing the loaded organic phase with a mixed solution of 10% sodium lactate and 16% lactic acid in a ratio of 12:1 at 40° C. for 2 min to wash the phosphate in the loaded organic phase;

[0095] (3) Mixing the washed loaded organic phase with pure water at a ratio of 2.5:1 at 60°C for 2 min, and allowing to stand for stratification. The first stripping rate was 77%, the 9th-stage countercurrent stripping rate was 98%, the stripping solution concentration was 14%, the stripping solution purity was 98.5%, and the phosphate content in the stripping solution was <30 ppm;

[0096] (4) The organic phase after stripping is washed with alkali and water to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0097] Comparative Example 6

[0098] (1) using 50% N, N-dimethyldodecylamine and 2-octanone to prepare an extraction solvent, and mixing with about 20% lactic acid fermentation broth, wherein the phosphate content is 1.6 g / L, at a ratio of 2.5:1 at a temperature of 40° C. for 2 minutes for extraction, to obtain an organic phase loaded with lactic acid and phosphate impurities; the first extraction rate of lactic acid is 35%, after 11-stage countercurrent extraction, the lactic acid concentration in the lactic acid raffinate is detected to be 1.5 g / L, and the 10-stage countercurrent extraction rate of lactic acid is 98%;

[0099] (2) washing the loaded organic phase with a 16% lactic acid mixed solution at a ratio of 12:1 at 40° C. for 2 min to wash the phosphate in the loaded organic phase;

[0100] (3) Mixing the washed loaded organic phase with pure water at a ratio of 2.5:1 at 60°C for 2 minutes, and allowing to stand for stratification. The first stripping rate was 75%, the 12-stage countercurrent stripping rate was 98%, the stripping solution concentration was 13%, the stripping solution purity was 98.5%, and the phosphate content in the stripping solution was <200 ppm;

[0101] (4) The organic phase after stripping is washed with alkali and water to remove the acid residue in the organic phase, thereby obtaining a new organic phase which is recycled within the system.

[0102] Therefore, the present application provides a process route and separation system for removing phosphoric acid from carboxylic acid during liquid-liquid extraction separation and purification of carboxylic acid with simple process, low energy consumption and high recovery rate.

[0103] In the description of this specification, the description with reference to the terms "an experimental example", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the experimental example or example are included in at least one experimental example or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same experimental example or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more experimental examples or examples in a suitable manner.

[0104] Finally, it should be noted that the above experimental examples are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred experimental examples, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A separation system for separating phosphoric acid in the process of separating and purifying carboxylic acids by liquid-liquid extraction, characterized in that: It includes an extraction solvent, a detergent, a carboxylic acid and a stripping agent, wherein the extraction solvent includes an extractant and a diluent, and the carboxylic acid serves as a hydrogen bond donor; The extractant acts as a hydrogen bond acceptor and the functional groups present in the diluent all interact with the carboxylic acid to form a hydrophobic separation system; When the carboxylic acid is citric acid, the detergent is a sodium citrate solution; when the carboxylic acid is lactic acid, the detergent is a mixed solution of a sodium lactate solution and a lactic acid solution; when the carboxylic acid is succinic acid, the detergent is one or more of a succinic acid solution and a sodium succinate solution; The extractant includes one or more of primary amines, secondary amines, and tertiary amines, and the diluent includes one or more of alkane compounds, ketone compounds, and thioether compounds; The carboxylic acid is any one of lactic acid, citric acid and succinic acid, and the stripping agent is water.

2. A method for separating phosphoric acid in the process of separating and purifying carboxylic acid by liquid-liquid extraction, characterized in that: The separation system for separating phosphoric acid in the process of separating and purifying carboxylic acid by the liquid-liquid extraction method according to claim 1 comprises the following steps: S1 extraction, mixing an extraction solvent with a carboxylic acid raw material for extraction, so that the carboxylic acid and phosphoric acid enter the organic phase to obtain a loaded organic phase; S2 washing, selecting a detergent according to the carboxylic acid, the volume ratio of the loaded organic phase to the detergent is 10:1-20:1, and washing is performed by heating to 30-70°C, the phosphoric acid is washed off, and a purified loaded organic phase is obtained; S3 stripping, stripping the purified loaded organic phase with a stripping agent to obtain a stripping solution and a lean organic phase; S4 regeneration, regenerating the lean organic phase to obtain a blank extraction solvent that is recycled to the extraction section for reuse.

3. The method for separating phosphoric acid in a process of separating and purifying carboxylic acid by liquid-liquid extraction according to claim 2, characterized in that: In step S1, the mixing temperature of the extraction solvent and the carboxylic acid raw material is 30-70°C, the mixing stirring speed is 50-1000 rpm, and the stirring time is 2-10 min.

4. The method for separating phosphoric acid in a process of separating and purifying carboxylic acid by liquid-liquid extraction according to claim 2, characterized in that: In step S3, the volume ratio of the purified loaded organic phase to the stripping agent is 1:1-10:1, and the purified carboxylic acid is transferred from the organic phase to the aqueous phase by heating to 50-90°C. Finally, the stripped carboxylic acid solution is evaporated and concentrated to obtain a high-purity carboxylic acid product.

5. The method for separating phosphoric acid in a process of separating and purifying carboxylic acid by liquid-liquid extraction according to claim 2, characterized in that: In step S4, the process of regenerating the lean organic phase after stripping is: alkali washing and water washing to remove the residual acid in the organic phase.

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