A method for separating and extracting lactic acid, a lactic acid product, and a method for producing the same

Abstract

The present application relates to the field of biological fermentation monomer extraction and purification, and discloses a method for separating and extracting lactic acid, a lactic acid product and a preparation method thereof, the method comprising: performing extraction treatment on a first solution by using an extraction system to obtain an aqueous solution and an organic solution, wherein the extraction treatment causes at least part of lactic acid in the first solution to be extracted into the organic solution; wherein the first solution comprises lactic acid fermentation liquor and / or lactic acid fermentation treatment liquor; the extraction system comprises a complexing extractant and a diluent, and the complexing extractant is an organic amine compound. The method provided by the present application can effectively reduce the pigment content in the organic phase while maintaining a high lactic acid extraction efficiency, and improve the efficiency of stripping lactic acid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of biological fermentation monomer extraction and purification, in particular to a method for separating and extracting lactic acid, a lactic acid product and a preparation method thereof. BACKGROUND

[0002] Lactic acid is a raw material for producing biodegradable polylactic acid materials. With the increasing demand for biodegradable polymers, lactic acid is currently produced by biological methods in the industry. The production process is as follows: starch, glucose, biomass, etc. are used as raw materials, and molds or lactic acid bacteria are inoculated to generate a fermentation broth containing lactic acid or lactic acid salt through fermentation. Then, lactic acid is obtained by separation. The lactic acid fermentation broth is a very complex system. In addition to lactic acid, it also contains a large amount of bacteria, proteins, residual sugars, pigments, inorganic salts, by-product organic acids and other metabolites. In particular, in the lactic acid biological manufacturing using biological waste (such as straw) as raw material, the composition of the raw material is complex, including five-carbon sugars, six-carbon sugars and various polysaccharides, etc. The content of pigments and inorganic salts is much higher than that of fermentation broth using single starch as raw material, which makes the extraction and purification of lactic acid in this field very difficult. In actual production, the extraction cost of lactic acid accounts for 50% to 60% of the total production cost. The choice of extraction method not only directly affects the quality and yield of the product, but also is the technical bottleneck and difficulty of lactic acid industrialization.

[0003] Currently, the main methods for separating and extracting lactic acid from fermentation broth include calcium salt crystallization method, esterification and hydrolysis method, extraction method, molecular distillation method, membrane separation method, adsorption method and in-situ separation technology coupled with fermentation. At present, the extraction of lactic acid mostly adopts complex extraction method. The extraction efficiency (single stage) of amine extractant is higher than that of phosphorus oxygen extractant, but it also leads to the easy entry of pigments into the extraction phase, resulting in increased separation cost. SUMMARY

[0004] The purpose of the present application is to solve the problems of low back-extraction recovery rate of lactic acid and high pigment extraction rate in the existing extraction system. A method for separating and extracting lactic acid, a lactic acid product and a preparation method thereof are provided. The method can maintain high lactic acid extraction efficiency while reducing the content of pigments in the organic phase and improving the efficiency of back-extracting lactic acid.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a lactic acid product, the chemical purity of which is 98wt% or more, further 98.5wt% or more, and / or the content of reducing sugar in the lactic acid product is 200ppm or less.

[0006] The second aspect of the present application provides a method for separating and extracting lactic acid, which comprises: using an extraction system to extract a first solution to obtain an aqueous solution and an organic solution, the extraction treatment causing at least a part of the lactic acid in the first solution to be extracted into the organic solution;

[0007] The first solution comprises lactic acid fermentation liquor and / or lactic acid fermentation treatment liquor; the extraction system comprises a complexing extractant and a diluent, and the complexing extractant is an organic amine compound.

[0008] The third aspect of the present application provides a method for preparing a lactic acid product, which comprises: obtaining a lactic acid solution by the method of the second aspect of the present application, and then directly purifying the lactic acid solution to obtain the lactic acid product, or first acidifying the lactic acid solution and then purifying the lactic acid solution to obtain the lactic acid product.

[0009] The fourth aspect of the present application provides a lactic acid product obtained by the method for preparing a lactic acid product according to the third aspect of the present application, wherein the chemical purity of the lactic acid product is 98 wt% or more, further 98.5 wt% or more, and more further 99 wt% or more; and / or

[0010] The content of residual metal ions in the lactic acid product is 100 ppm or less, further 50 ppm or less, and more further 10 ppm or less; and / or

[0011] The content of residual reducing sugar in the lactic acid product is 200 ppm or less, further 100 ppm or less, and more further 30 ppm or less; and / or

[0012] The total content of residual extractant and diluent in the lactic acid product is 100 ppm or less, further 50 ppm or less, and more further 10 ppm or less.

[0013] By the above technical solution, the present application efficiently extracts lactic acid from lactic acid fermentation liquor and / or lactic acid fermentation treatment liquor by an extraction process, thereby reducing the difficulty of subsequent purification; at the same time, the extraction process can be operated continuously, and has the advantages of large processing capacity, strong selectivity, low cost, high yield, recyclable extractant, etc. In addition, the extracted lactic acid is dissociated and recovered by a stripping process, so that the entire lactic acid system is separated from metal ions, and a relatively pure lactic acid aqueous solution is obtained, and then a high-purity and high-yield lactic acid product is obtained by a purification process. In addition, the method provided by the present application solves the problems of low lactic acid stripping recovery rate and high pigment extraction rate of conventional extractants, maintains a high lactic acid extraction rate, improves the stripping efficiency, reduces the proportion of pigments entering the oil phase, reduces the separation and extraction cost, and optimizes the quality and stripping efficiency of lactic acid in the subsequent process. DETAILED DESCRIPTION

[0014] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not considered critical for the purposes of the application. The ranges disclosed herein are understood to include all values and subranges therebetween, unless otherwise indicated. For ranges of values, the endpoints are included as well as the individual points within the ranges.

[0015] As previously described, the first aspect of the present application provides a lactic acid product, wherein the chemical purity of the lactic acid product is 98 wt% or more, further 98.5 wt% or more, and / or the content of reducing sugar in the lactic acid product is 200 ppm or less.

[0016] In some embodiments of the present application, the chemical purity of the lactic acid product is 99 wt% or more.

[0017] In some embodiments of the present application, the content of reducing sugar in the lactic acid product is 100 ppm or less, further 30 ppm or less.

[0018] In some embodiments of the present application, the content of residual metal ions in the lactic acid product is 100 ppm or less, further 50 ppm or less, and further 10 ppm or less. The metal ions include, but are not limited to, one or more of calcium ions, magnesium ions and iron ions.

[0019] In some embodiments of the present application, the total content of residual extractant and diluent in the lactic acid product is 100 ppm or less, further 50 ppm or less, and further 10 ppm or less.

[0020] In some embodiments of the present application, the extractant is selected from one or more of primary amine compounds, secondary amine compounds, tertiary amine trialkyl compounds and quaternary ammonium salt compounds; wherein the primary amine compounds have a general formula of RR'CHNH2, R+R'=C 16 -C 22 ; the secondary amine compounds have a general formula of (R2CH)2NH, R=C6-C8; the tertiary amine trialkyl compounds have a general formula of R3N, R is C m H 2m+1 , m is 8, 9 or 10; and the quaternary ammonium salt compounds have a general formula of R3N + CH3Cl - , R=C8H 17 -C 10 H 21 .

[0021] In some embodiments of the present application, the diluent comprises one or more of an ether compound, an ester compound, a linear, branched or cyclic alcohol compound, a phosphine oxide compound, a halogenated alkane, an aromatic compound and an alkane, and further, the diluent comprises a phosphine oxide compound and at least one selected from an ether compound, an ester compound, a linear, branched or cyclic alcohol compound, a halogenated alkane, an aromatic compound and an alkane.

[0022] The second aspect of the present application provides a method for separating and extracting lactic acid, which comprises: subjecting a first solution to extraction treatment using an extraction system to obtain an aqueous solution and an organic solution, the extraction treatment causing at least part of the lactic acid in the first solution to be extracted into the organic solution.

[0023] In the method, the first solution comprises a lactic acid fermentation broth and / or a lactic acid fermentation treatment broth; the extraction system comprises a complexing extractant and a diluent, and the complexing extractant is an organic amine compound.

[0024] In some embodiments of the present application, the carbon source in the fermentation medium used in the first solution is derived from a hydrolysate of agricultural and forestry waste, which includes but is not limited to at least one of straw (corn straw, wheat straw, rice straw, rape straw, barley straw, oat straw, sorghum straw, etc.), rice husk, softwood, hardwood, tree branches and livestock manure.

[0025] In some embodiments of the present application, the carbon source in the fermentation medium used in the first solution comprises a six-carbon sugar, which includes but is not limited to at least one of glucose, fructose, galactose and mannose.

[0026] In some embodiments of the present application, the carbon source in the fermentation medium used in the first solution further comprises a five-carbon sugar, which includes at least one of xylose, arabinose, ribose and deoxyribose.

[0027] In some embodiments of the present application, the first solution can comprise a lactic acid fermentation broth, a lactic acid fermentation treatment broth or a mixture of the two. In the present application, the lactic acid fermentation treatment broth is obtained by centrifuging and filtering the lactic acid fermentation broth to remove impurities such as bacterial cells, or by adjusting the pH of the lactic acid fermentation broth to 6-10.5, and then centrifuging and filtering to remove impurities such as bacterial cells. The present application does not particularly limit the centrifuging and filtering method, and any conventional separation method can be used. The lactic acid fermentation treatment broth can also be concentrated before lactic acid extraction, and the skilled person can choose as needed according to the actual situation.

[0028] In some embodiments of the present application, the first solution contains lactic acid, metal ions, pigments, proteins, sugars and water.

[0029] The present application has a wide range of selection for the concentration of metal ions in the first solution. Preferably, the concentration of metal ions in the first solution is below 5wt%, further below 4wt%, and more further below 3wt%.

[0030] The present application has a wide range of selection for the concentration of lactic acid in the first solution. Preferably, the concentration of lactic acid in the first solution is below 50wt%, further below 30wt%, and more further below 15wt%.

[0031] In some embodiments of the present application, the pH value of the first solution is below 10, further between 1 and 5, and more further between 1 and 4; for example, 1.0, 1.5, 2.1, 2.6, 3.0, 3.5, 4.0, etc.

[0032] The present application has a wide range of selection for the metal ions. Preferably, the metal ions include, but are not limited to, one or more of calcium ions, magnesium ions, and iron ions.

[0033] In some embodiments of the present application, the molar ratio of the complexing extractant to lactic acid in the first solution is between (0.5-40) : 1, further between (1-40) : 1, further between (1.5-40) : 1, further between (3-40) : 1, further between (3-20) : 1, and further between (5-20) : 1.

[0034] In some embodiments of the present application, preferably, the organic amine compound is selected from at least one of primary amine compounds, secondary amine compounds, tertiary amine trialkyl compounds, and quaternary ammonium salt compounds.

[0035] In a specific embodiment of the present application, the primary amine compound has a general formula of RR'CHNH2, where R+R'=C 16 -C 22 In the present application, R and R' respectively represent a hydrocarbon group or an alkyl group with a certain number of carbon atoms, and R+R'=C 16 -C 22 represents the sum of the number of carbon atoms contained in R and R' is between 16 and 22. The primary amine compound of the present application includes, for example, but is not limited to, secondary carbon primary amine (N1923), etc.

[0036] In a specific embodiment of the present application, the secondary amine compound has a general formula of (R2CH)2NH, where R=C6-C8. In the present application, R=C6-C8 represents a hydrocarbon group or an alkyl group with a number of carbon atoms between 6 and 8. The secondary amine compound of the present application includes, for example, but is not limited to, N7201 secondary amine (with a structural formula of (R2CH)2NH, R=C 7-9 , etc.).

[0037] In one embodiment of the present application, the tertiary amine trialkyl compound has a general formula of R3N, wherein R is C m H 2m+1 , m is 8, 9 or 10. The tertiary amine trialkyl compound of the present application includes, but is not limited to, trioctylamine (TOA), tri(octyl-decyl)amine (commonly known as 7301 extractant, N235), and the like.

[0038] In one embodiment of the present application, the quaternary ammonium salt compound has a general formula of R3N + CH3Cl - , wherein R = C8H 17 -C 10 H 21 .

[0039] In some embodiments of the present application, preferably, the diluent includes a first diluent and a second diluent, and the mass ratio of the complexing extractant to the first diluent is 1:(0.1-20), further 1:(0.5-15), further 1:(1-10), such as 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:20, and the like. In the present application, the volume ratio of the extraction system to the first solution is (0.4-50):1, further (0.5-40):1, further (0.8-20):1, and further (1-10):1.

[0040] In some embodiments of the present application, preferably, the first diluent is selected from at least one of ether compounds, ester compounds, linear, branched or cyclic alcohol compounds, phosphine oxide compounds, halogenated alkanes, aromatic compounds and alkanes, further preferably phosphine oxide compounds having a general formula of XYP(O)OH; wherein X and Y are each independently linear or branched alkyl having 2-10 carbon atoms; preferably linear or branched alkyl having 5-10 carbon atoms; further, the phosphine oxide compound is selected from at least one of mono-2-ethylhexyl 2-ethylhexyl phosphonate (P507), dimethylheptyl phosphonate (P350) and di(2-ethylhexyl) phosphoric acid (P204). Other compounds of the first diluent of the present application are further preferably within the scope as described below, which will not be repeated here.

[0041] In some embodiments of the present application, preferably, the second diluent is selected from at least one of an ether compound having 4-10 carbon atoms, an ester compound having 2-10 carbon atoms, a linear, branched or cyclic alcohol compound having at least four carbon atoms, a linear or cyclic alkane compound having five carbon atoms, and a mixture thereof, a halogenated alkane having 1-3 carbon atoms, and an aromatic compound.

[0042] In a specific embodiment of the present application, the ether compound having 4-10 carbon atoms includes, but is not limited to, isopropyl ether, diethyl ether, n-butyl ether, and the like.

[0043] In a specific embodiment of the present application, the ester compound having 2-10 carbon atoms is ethyl acetate and / or butyl acetate.

[0044] In a specific embodiment of the present application, the linear, branched or cyclic alcohol compound having at least four carbon atoms is selected from at least one of n-octanol, isooctanol, n-heptanol, cyclohexanol, isobutyl alcohol, and decanol.

[0045] In a specific embodiment of the present application, the linear or cyclic alkane compound having five carbon atoms and the mixture thereof includes, but is not limited to, one, two or more of kerosene, n-pentane, n-hexane, cyclohexane, n-dodecane, and n-tridecane.

[0046] In a specific embodiment of the present application, the halogenated alkane having 1-3 carbon atoms can be a chlorinated alkane and / or a brominated alkane, and can also be a monohalogenated alkane, a dihalogenated alkane, a trihalogenated alkane, a tetrahalogenated alkane, such as, but not limited to, carbon tetrachloride, chloroform, dichloromethane, 1,2-dichloroethane, and the like.

[0047] In a specific embodiment of the present application, the aromatic compound includes, but is not limited to, benzene, toluene, ethylbenzene, chlorobenzene, xylene, and the like.

[0048] In some embodiments of the present application, preferably, the absolute value of the difference ΔpH between the pH value of the aqueous solution and the pH value of the first solution is 0-5, further 0-3, and more further 0.4-2; for example, equal to 0.5, 1, 1.2, 1.4, 1.8, and the like. The higher the absolute value of ΔpH, the more lactic acid is extracted.

[0049] In some embodiments of the present application, preferably, the pH value of the first solution is less than or equal to the pH value of the aqueous solution.

[0050] The temperature of the extraction treatment is not particularly limited in the present application, and preferably, the temperature of the extraction treatment is 10-95℃, further 20-60℃, and more further 20-40℃, such as 10℃, 22℃, 25℃, 28℃, 30℃, 32℃, 35℃, 38℃, 50℃, 60℃, 70℃, 80℃, 90℃, and the like.

[0051] In some embodiments of the present application, preferably, the total extraction stage number of the extraction treatment is 1-24 stages, preferably 1-15 stages, and the extraction is performed by using a multi-stage countercurrent or multi-stage crossflow extraction mode. The present application can perform a concentration step between any two stages of the extraction treatment.

[0052] The present application does not have a particular limitation on the mode of contacting the extraction system with the first solution for the extraction treatment, and a conventional mode in the art can be used. When the extraction system contains both a complexing extractant and a diluent, the complexing extractant is mixed with the diluent first, and then mixed with the first solution to realize the contact of the first solution with the complexing extractant and the diluent, thereby performing the extraction of lactic acid.

[0053] The present application does not have a particular limitation on the extraction equipment used for the extraction treatment, and a conventional extraction equipment in the art can be used, such as but not limited to centrifugal extraction, mixing and clarification tank, vibrating sieve plate tower, rotating disc tower, packed tower, supergravity rotating bed, and the like.

[0054] In some embodiments of the present application, preferably, the method further comprises: using a stripping agent to strip the organic solution to obtain a lactic acid solution; and the stripping agent comprises an aqueous phase system, and the concentration of the basic substance in the aqueous phase system is 0-8 mol / L.

[0055] In some embodiments of the present application, preferably, the volume ratio of the stripping agent to the organic solution is (0.1-100) : 1, further (0.2-50) : 1, and more further (0.2-30) : 1.

[0056] The present application has a wide selection range of the basic substance, such as but not limited to ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide, and combinations thereof.

[0057] In the present application, when the aqueous phase system is used to strip the organic solution, preferably, the aqueous phase system at 10-120℃ is used to strip, and low temperature can further reduce the energy consumption. At the same time, when the aqueous phase system is used to strip, preferably, the stripping is performed by using one-stage extraction or more than two-stage extraction, and a concentration step can be performed between any two stages of the stripping.

[0058] In the present application, when the organic solution is back-extracted by using an aqueous phase system containing more than 0 mol / L of alkaline substances, the present application does not have a special limitation on the adding method of the aqueous phase system, which can be one-time input, can be batch input, can be input respectively by using an aqueous phase system containing multiple alkaline substances, or can be mixed by using an aqueous phase system containing different alkaline substances and then added at one time. The present application does not have a special limitation on the concentration of alkaline substances in the aqueous phase system, which can be 0.01-8 mol / L, further can be 0.05-5 mol / L, further can be 0.1-5 mol / L, and specifically can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2.5 mol / L, 3 mol / L, 4 mol / L, etc.

[0059] According to a preferred embodiment of the present application, the molar concentration ratio of alkaline equivalents in the aqueous phase system to lactic acid in the organic solution is (0.95-1.2):1, further is (0.98-1.1):1.

[0060] In some embodiments of the present application, preferably, the extraction stage number of the back-extraction is 1-24, more preferably is 1-15. The back-extraction of the present application can be carried out by using a multi-stage countercurrent method.

[0061] In some embodiments of the present application, preferably, the temperature of the back-extraction is 10-120℃, further is 20-100℃, more further is 20-95℃, and again further preferably is 25-30℃. Compared with the prior art of back-extraction by using hot water at high temperature, the present application can effectively back-extract at normal temperature, further reducing the energy consumption.

[0062] The third aspect of the present application provides a preparation method of a lactic acid product, which comprises: obtaining a lactic acid solution by using the method as described above, and then directly purifying the lactic acid solution to obtain a lactic acid product, or first acidifying the lactic acid solution and then purifying to obtain a lactic acid product.

[0063] In a specific embodiment of the present application, the purification method comprises: concentrating the lactic acid solution in a first step, decolorizing by using activated carbon, further concentrating and dehydrating, and molecular distillation to obtain a lactic acid product, wherein the first step concentration makes the concentration of lactic acid to be 15-40 wt%.

[0064] In another specific embodiment of the present application, the purification method comprises: concentrating the lactic acid solution, decolorizing by using activated carbon, purifying by using a resin, purifying by using a nanofiltration membrane, concentrating and dehydrating to obtain a lactic acid product.

[0065] In another specific embodiment of the present application, the purification method comprises: concentrating, dehydrating and multi-stage molecular distillation of the lactic acid solution to obtain a lactic acid product, wherein the number of stages of the molecular distillation is 2 or more.

[0066] The fourth aspect of the present application provides a lactic acid product obtained by the preparation method as described above, and the performance of the lactic acid product is as described above.

[0067] The present application will be described in detail below by way of examples. In the following examples, various raw materials used are commercially available unless otherwise specified; the physical property parameters of the raw materials and the performance parameters of the products are determined by conventional methods in the art.

[0068] Preparation of the first solution

[0069] The first solution was prepared according to the method disclosed in CN11294117A, specifically comprising:

[0070] The pretreated solid granular form corn straw with a solid content of 30 (w / w) % was put into a fermentation tank as raw material, and 5 mg of cellulase per g of straw (dry basis) was added, and the pre-saccharification was carried out at 48℃ and 200 rpm for 6.5 h; after the pre-saccharification was completed, the Pediococcus acidilactici seed liquid was inoculated into the fermentation tank at an inoculation amount of 5% (v / v), and nutrient salts (10 g / L of peptone, 10 g / L of yeast extract, 2 g / L of diammonium hydrogen citrate and 0.25 g / L of manganese sulfate monohydrate) were added, and calcium carbonate was used as a neutralizing agent to adjust and maintain the pH value of the fermentation liquor to 5.4 during the fermentation process, and the fermentation was carried out at 42℃ and 200 rpm for 96 h, and then the fermentation liquor was separated from the corn straw residue by filtration, and the pH value of the fermentation liquor was adjusted to 2.01 with sulfuric acid to obtain the first solution for standby, wherein the concentration of lactic acid in the first solution was 9 wt%, and the concentration of calcium ions was 2 wt%.

[0071] Example 1

[0072] The first solution (the concentration of lactic acid was 9 wt%, the concentration of calcium ions was 2 wt%, and the pH value was 2.01) was taken in a separatory funnel, and tri-octylamine (TOA), P204 and C12 alkane were added, so that the molar ratio of tri-octylamine (TOA) to lactic acid in the first solution was 1:1, and the mass ratio of tri-octylamine (TOA) to P204 was 2.2:1, and the four-stage countercurrent extraction was carried out at 25℃ to obtain an aqueous solution (pH value was 2.8) and an organic solution, wherein the above extraction treatment caused the lactic acid in the first solution to be extracted into the organic solution, the extraction rate of lactic acid was 98.5%, and the colority ratio was 30%;

[0073] The organic solution is subjected to 4-stage countercurrent back-extraction in an aqueous phase system containing sodium hydroxide at 30°C, the volume ratio of the aqueous phase system containing sodium hydroxide to the organic solution is 1:1, and a lactic acid aqueous solution is obtained, the back-extraction rate of lactic acid is 90% through the back-extraction.

[0074] The remaining examples adopt the same process as that in Example 1, and the specific process parameters and obtained effects are listed in Table 1.

[0075]

[0076] It can be seen from Table 1 that the method provided by the application can effectively reduce the pigment content in the organic phase and improve the lactic acid back-extraction efficiency while maintaining a high lactic acid extraction efficiency.

[0077] Example 11

[0078] 10 mL of the first solution (the concentration of lactic acid is 9 wt%, the concentration of calcium ions is 2 wt%, and the pH value is 2.01) is taken in a separatory funnel, 10 mL of trioctylamine (TOA), P204 and C12 alkane are added, the molar ratio of trioctylamine (TOA) to lactic acid in the first solution is 1:1, and the mass ratio of trioctylamine (TOA) to P204 is 0.91:1, 4-stage countercurrent extraction is carried out at 25°C, and an aqueous solution (the pH value is 4.0) and an organic solution are obtained, the lactic acid in the first solution is extracted into the organic solution through the extraction treatment, the extraction rate of lactic acid is 99.5%, and the colority ratio is 69%.

[0079] The organic solution is subjected to 4-stage countercurrent back-extraction in an aqueous phase system containing sodium hydroxide at 30°C, the volume ratio of the aqueous phase system containing sodium hydroxide to the organic solution is 1:1, and a lactic acid aqueous solution is obtained, the back-extraction rate of lactic acid is 90% through the back-extraction.

[0080] Example 12

[0081] 10 mL of the first solution (the concentration of lactic acid is 9 wt%, the concentration of calcium ions is 2 wt%, and the pH value is 2.01) is taken in a separatory funnel, 10 mL of trioctylamine (TOA), P204 and C12 alkane are added, the molar ratio of trioctylamine (TOA) to lactic acid in the first solution is 1:1, and the mass ratio of trioctylamine (TOA) to P204 is 1.1:1, 4-stage countercurrent extraction is carried out at 25°C, and an aqueous solution (the pH value is 3.5) and an organic solution are obtained, the lactic acid in the first solution is extracted into the organic solution through the extraction treatment, the extraction rate of lactic acid is 99.4%, and the colority ratio is 58%.

[0082] The organic solution is subjected to 4-stage countercurrent stripping at 30°C using an aqueous phase system, the volume ratio of the aqueous phase system to the organic solution being 1:1, to obtain a lactic acid aqueous solution, the stripping rate of lactic acid being 97.5% by the above stripping.

[0083] Preparation of lactic acid product

[0084] Examples 13 and 14

[0085] The lactic acid aqueous solution obtained in Example 1 is first acidified with sulfuric acid to obtain a lactic acid aqueous solution, and then concentrated, decolorized with activated carbon, purified with resin, purified with nanofiltration membrane, concentrated and dehydrated to obtain a lactic acid product; the lactic acid aqueous solution obtained in Example 12 is directly concentrated, decolorized with activated carbon, purified with resin, purified with nanofiltration membrane, concentrated and dehydrated to obtain a lactic acid product.

[0086] It is determined that the chemical purity, the content of residual metal ions, the content of reducing sugar and the total content of residual extractant and diluent of the obtained lactic acid product are listed in Table 2.

[0087] Table 2

[0088]

[0089] The above describes the preferred embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as the disclosed content of the present application, and all fall within the protection scope of the present application.

Claims

1. A method for separating and extracting lactic acid, characterized by, The method comprises: performing extraction treatment on the first solution by using an extraction system to obtain an aqueous solution and an organic solution, the extraction treatment causing at least part of lactic acid in the first solution to be extracted into the organic solution; performing back extraction on the organic solution by using a back extraction agent to obtain a lactic acid solution; The first solution comprises lactic acid fermentation liquid and / or lactic acid fermentation treatment liquid; the extraction system comprises a complexing extractant and a diluent, the complexing extractant is an organic amine compound, the organic amine compound is selected from a tertiary amine trialkyl compound, the general formula of the tertiary amine trialkyl compound is R3N, wherein R is C m H 2m+1 , m is 8, 9 or 10; the stripping agent comprises an aqueous phase system; The diluent comprises a first diluent and a second diluent, the first diluent comprises a phosphorus oxygen compound, and a general formula of the phosphorus oxygen compound is XYP(O)OH; wherein X and Y are each independently linear or branched alkyl with a carbon atom number of 2-10; the second diluent is selected from n-dodecane and / or n-tridecane; A mass ratio of the complexing extractant to the first diluent is 1:(0.8-1.2).

2. The method of claim 1, wherein, The carbon source in the fermentation medium used by the first solution is derived from a hydrolysate of agricultural and forestry waste, and the agricultural and forestry waste comprises at least one of straw, rice husk, softwood, hardwood, branches and livestock manure; and / or, The carbon source in the fermentation medium used by the first solution comprises a six-carbon sugar, and the six-carbon sugar comprises at least one of glucose, fructose, galactose and mannose; and / or, The carbon source in the fermentation medium used by the first solution further comprises a five-carbon sugar, and the five-carbon sugar comprises at least one of xylose, arabinose, ribose and deoxyribose.

3. The method of claim 1, wherein, The first solution contains lactic acid, metal ions, pigments, proteins, sugars and water; The concentration of the metal ions in the first solution is below 5wt%; and / or, The concentration of the lactic acid in the first solution is below 50wt%; and / or, The pH value of the first solution is below 10; and / or, The metal ions are selected from at least one of calcium ions, magnesium ions and iron ions.

4. The method of claim 1, wherein, The molar ratio of the complexing extractant to the lactic acid in the first solution is (0.5-40):1; and / or, The concentration of the metal ions in the first solution is below 4wt%; and / or, The concentration of the lactic acid in the first solution is below 30wt%; and / or, The pH value of the first solution is 1-5.

5. The method of claim 4, wherein, The tertiary amine trialkyl compound comprises trioctylamine and / or tri(octyl-decyl)amine.

6. The method of claim 1, wherein, The concentration of the metal ions in the first solution is below 3wt%; and / or, The concentration of the lactic acid in the first solution is below 15wt%; and / or, The pH value of the first solution is 1-4; and / or, The molar ratio of the complexing extractant to the lactic acid in the first solution is (1-40):

1.

7. The method of claim 6, wherein, X and Y are each independently linear or branched alkyl with a carbon atom number of 5-10.

8. The method of claim 6, wherein, The phosphorus oxygen compound is selected from at least one of 2-ethylhexyl phosphoric acid mono 2-ethylhexyl ester, dimethylheptyl methylphosphonate and di(2-ethylhexyl) phosphoric acid.

9. The method according to any one of claims 1 to 8, characterized in that, The absolute value of a difference ΔpH between the pH value of the aqueous solution and the pH value of the first solution is 0-5; and / or, The pH value of the first solution is less than or equal to the pH value of the aqueous solution; and / or, The temperature of the extraction treatment is 10-95℃; and / or, The total extraction stage number of the extraction treatment is 1-24 stages, and the extraction treatment adopts multi-stage countercurrent or multi-stage crossflow extraction mode; and / or, The molar ratio of the complexing extractant to lactic acid in the first solution is (1.5-40):

1.

10. The method of claim 1, wherein, The concentration of the basic substance in the aqueous phase system is 0-8 mol / L; and / or, The molar ratio of the complexing extractant to lactic acid in the first solution is (3-40):1; and / or, The absolute value of the difference ΔpH between the pH value of the aqueous solution and the pH value of the first solution is 0-3.

11. The method of claim 1, wherein, The volume ratio of the stripping agent to the organic solution is (0.1-100):1; and / or, The extraction stage number of the stripping is 1-24 stages; and / or, The temperature of the stripping is 10-120℃; and / or, The molar ratio of the complexing extractant to lactic acid in the first solution is (3-20):1; and / or, The absolute value of the difference ΔpH between the pH value of the aqueous solution and the pH value of the first solution is 0.4-2.

12. The method of claim 1, wherein, The molar ratio of the complexing extractant to lactic acid in the first solution is (5-20):1; and / or, The temperature of the extraction treatment is 20-60℃; and / or, The total extraction stage number of the extraction treatment is 1-15 stages; The volume ratio of the stripping agent to the organic solution is (0.2-50):1; and / or, The extraction stage number of the stripping is 1-15 stages; and / or, The temperature of the stripping is 20-100℃.

13. The method of claim 1, wherein, The temperature of the extraction treatment is 20-40℃; and / or, The volume ratio of the stripping agent to the organic solution is (0.2-30):1; and / or, The temperature of the stripping is 20-95℃.

14. A method for the preparation of a lactic acid product, characterized by, The method comprises: obtaining a lactic acid solution by the method of any one of claims 1-13, and then directly purifying the lactic acid solution to obtain a lactic acid product, or first acidifying the lactic acid solution and then purifying to obtain a lactic acid product.

15. The method of claim 14, wherein, The purification method comprises: concentrating the lactic acid solution in the first step, decolorizing with activated carbon, further concentrating and dehydrating, and molecular distillation to obtain a lactic acid product, wherein the first step of concentration makes the concentration of lactic acid 15-40 wt%; or The lactic acid solution is concentrated, decolorized with activated carbon, purified by resin, purified by nanofiltration membrane, concentrated and dehydrated to obtain a lactic acid product; or The lactic acid solution is concentrated, dehydrated, and subjected to multi-stage molecular distillation to obtain a lactic acid product, wherein the number of stages of molecular distillation is 2 or more.

16. The method of claim 14, wherein, The chemical purity of the lactic acid product is 98 wt% or more; and / or, The content of residual metal ions in the lactic acid product is 100 ppm or less; and / or, The content of reducing sugar in the lactic acid product is 200 ppm or less; and / or, The total content of residual extractant and diluent in the lactic acid product is 100 ppm or less.

17. The method of claim 14, wherein, The chemical purity of the lactic acid product is 98.5 wt% or more; and / or, The content of residual metal ions in the lactic acid product is 50 ppm or less; and / or, The content of reducing sugar in the lactic acid product is 100 ppm or less; and / or, The total content of residual extractant and diluent in the lactic acid product is 50 ppm or less.

18. The method of claim 14, wherein, the chemical purity of the lactic acid product is 99 wt% or more; and / or, the content of residual metal ions in the lactic acid product is 10 ppm or less; and / or, the content of reducing sugars in the lactic acid product is 30 ppm or less; the total content of residual extractant and diluent in the lactic acid product is 10 ppm or less. the chemical purity of the lactic acid product is 99 wt% or more; and / or, the content of residual metal ions in the lactic acid product is 10 ppm or less; and / or, the content of reducing sugars in the lactic acid product is 30 ppm or less; the total content of residual extractant and diluent in the lactic acid product is 10 ppm or less.

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