A method for separating and extracting lactic acid, a lactic acid product and a method for preparing the same, and a method for preparing calcium lactate particles

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, and a preparation method of calcium lactate particles, which comprises the following steps: (1) performing first extraction treatment on a first solution by using a first extraction system to obtain a first aqueous solution and a first organic solution; (2) performing second extraction treatment on the first aqueous solution by using a second extraction system to obtain a second aqueous solution and a second organic solution; the first solution comprises lactic acid fermentation liquor and / or lactic acid fermentation treatment liquor; the second extraction system comprises a second extractant, and the second extractant is an oxygen-containing compound. According to the present application, lactic acid is efficiently extracted from lactic acid fermentation liquor through an extraction process, the extraction method can be continuously operated, and has the advantages of high selectivity, low cost, high yield and the like.

Description

TECHNICAL FIELD

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

[0002] Lactic acid is a raw material for producing biodegradable polylactic acid. With the increasing demand for biodegradable polymers, lactic acid is currently produced by biological methods in 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, and other metabolic products such as by-product organic acids. In particular, in the production of lactic acid from biological waste, the composition of the raw material is complex, including five-carbon sugars, six-carbon sugars, and various polysaccharides. The content of pigments and inorganic salts is much higher than that of fermentation broth using single starch as raw material, making 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, esterification and hydrolysis, extraction, molecular distillation, membrane separation, adsorption, and in-situ separation technology coupled with fermentation. In the lactic acid extraction process, lactic acid is first extracted from the fermentation broth by an extractant, and then recovered into another solvent by back extraction. Zhu Hualai et al. (Research Progress of Lactic Acid Extraction Technology, Contemporary Chemical Industry, 2020, v. 49; No. 297(10): 245-251) comprehensively summarized the progress of lactic acid extraction. Whether using phosphorus oxygen, amines, alcohols, etc. is aimed at the extraction of lactic acid molecules. The lactic acid fermentation broth is usually adjusted to pH with calcium salt, and the obtained lactic acid exists in the form of calcium lactate. After acid hydrolysis with sulfuric acid, lactic acid is extracted. Xiulian Ren et al. (AASRI Procedia 3 (2012) 341-350) used D2EHPA to extract Ca 2+ , which caused the water phase H + to increase, i.e. the water phase obtained lactic acid (calcium ions were not completely extracted). However, there is currently no systematic literature reporting on how to use extraction methods to directly separate lactic acid from lactic acid fermentation broth. SUMMARY

[0004] The object of the present application is to develop a new method for separating and extracting lactic acid. In order to achieve the above object, the present application provides, in a first aspect, a lactic acid product, the chemical purity of which is 98 wt% or more, further 98.5 wt% or more, and / or the total content of residual extractant and diluent in the lactic acid product is 100 ppm or less.

[0005] The present application provides, in a second aspect, a method for separating and extracting lactic acid, the method comprising:

[0006] (1) performing a first extraction treatment on a first solution using a first extraction system to obtain a first aqueous solution and a first organic solution, the first extraction treatment causing at least a portion of metal ions in the first solution to be extracted into the first organic solution;

[0007] (2) performing a second extraction treatment on the first aqueous solution using a second extraction system to obtain a second aqueous solution and a second organic solution, the second extraction treatment causing at least a portion of lactic acid in the first aqueous solution to be extracted into the second organic solution;

[0008] wherein the first solution comprises lactic acid fermentation broth and / or lactic acid fermentation treatment broth;

[0009] the second extraction system comprises a second extractant, the second extractant being an oxygen-containing compound.

[0010] Preferably, the method further comprises step (3): performing a stripping treatment on the second organic solution using a stripping agent to obtain a lactic acid aqueous solution or a lactic acid salt aqueous solution.

[0011] The present application provides, in a third aspect, a method for preparing a lactic acid product, the method comprising: obtaining a lactic acid aqueous solution or a lactic acid salt aqueous solution using the method of the second aspect of the present application, and then purifying the lactic acid aqueous solution to obtain a lactic acid product; or first performing acidolysis on the lactic acid salt aqueous solution to obtain a lactic acid aqueous solution, and then purifying the lactic acid aqueous solution to obtain a lactic acid product;

[0012] Further, the method for purification comprises: subjecting the lactic acid aqueous solution to first-step concentration, activated carbon decolorization, further concentration and dehydration, and molecular distillation to obtain a lactic acid product, wherein the first-step concentration causes the concentration of lactic acid to be 15-40 wt%; or

[0013] subjecting the lactic acid aqueous solution to concentration, activated carbon decolorization, resin purification, nanofiltration membrane purification, concentration and dehydration to obtain a lactic acid product; or

[0014] subjecting the lactic acid aqueous solution to concentration, dehydration, and multi-stage molecular distillation to obtain a lactic acid product, wherein the number of stages of the molecular distillation is 2 or more.

[0015] The fourth aspect of the present application provides a lactic acid product obtained by the preparation method of 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

[0016] the optical purity of the lactic acid product is >99%; and / or

[0017] 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

[0018] the color number of the lactic acid product is <50; and / or

[0019] the total content of residual extractant and diluent in the lactic acid product is 100 ppm or less, further 50 ppm or less, further 10 ppm or less, and more further 5 ppm or less.

[0020] The fifth aspect of the present application provides a preparation method of calcium lactate particles, which comprises: adding water to the second organic solution obtained by the method of the second aspect of the present application, neutralizing the obtained second organic solution with a calcium source, separating to obtain a calcium lactate solution, and then sequentially concentrating and spray drying the calcium lactate solution to obtain calcium lactate particles, which can be used as a food additive raw material.

[0021] Through the above technical solution, the present application efficiently extracts lactic acid from lactic acid fermentation liquid and / or lactic acid fermentation treatment liquid through an extraction process, reducing the difficulty of subsequent purification. At the same time, the extraction method can be continuously operated, 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 through a stripping process, so that the entire lactic acid system is separated from metal ions, obtaining a relatively pure lactic acid aqueous solution, and then a high-purity, high-yield lactic acid product is obtained through a purification process; or the second organic solution is neutralized by a calcium source, separated, concentrated and spray dried to obtain calcium lactate particles, which can be used as a food additive raw material. DETAILED DESCRIPTION

[0022] The endpoints of the ranges and any values disclosed herein are not to be construed as limiting. The disclosure should be understood to encompass all values falling within the range, including the range limits (and sub-ranges) established by the endpoints. Ranges can be expressed as from about one particular value to about another; however, when such a range is broader than or includes within its scope the values stated, the disclosure is understood to encompass individual values stated, as well as the range limits (and sub-ranges) established by the range endpoints.

[0023] As mentioned above, the first aspect of the present application provides a lactic acid product, wherein the chemical purity of the lactic acid product is 98wt% or more, further 98.5wt% or more, and / or the total content of residual extractant and diluent in the lactic acid product is 100ppm or less.

[0024] In some embodiments of the present application, the chemical purity of the lactic acid product is 99wt% or more.

[0025] In some embodiments of the present application, the total content of residual extractant and diluent in the lactic acid product is 50ppm or less, further 10ppm or less, and more further 5ppm or less.

[0026] In some embodiments of the present application, the content of residual metal ion in the lactic acid product is 100ppm or less, further 50ppm or less, and more further 10ppm or less. The metal ion includes, but is not limited to, one or more of calcium ion, magnesium ion and iron ion, and is preferably calcium ion.

[0027] In some embodiments of the present application, the color number of the lactic acid product is <50.

[0028] In some embodiments of the present application, the extractant includes an acidic phosphorus oxygen type extractant and one or more of an alcohol compound, a ketone compound, an ether compound and an ester compound; wherein the acidic phosphorus oxygen type extractant has a general formula of XYP(O)OH, and X and Y are each independently a linear or branched alkyl group with a carbon number of 2-10.

[0029] In some embodiments of the present application, the diluent includes one or more of an ether compound, an ester compound, a linear, branched or cyclic alcohol compound, an alkane, a halogenated alkane and an aromatic compound.

[0030] The second aspect of the present application provides a method for separating and extracting lactic acid, which comprises:

[0031] (1) performing a first extraction treatment on a first solution using a first extraction system to obtain a first aqueous solution and a first organic solution, wherein the first extraction treatment causes at least a part of metal ions in the first solution to be extracted into the first organic solution;

[0032] (2) performing a second extraction treatment on the first aqueous solution using a second extraction system to obtain a second aqueous solution and a second organic solution, wherein the second extraction treatment causes at least a part of lactic acid in the first aqueous solution to be extracted into the second organic solution;

[0033] In some embodiments of the present application, the first solution includes lactic acid fermentation liquid and / or lactic acid fermentation treatment liquid.

[0034] The second extraction system comprises a second extractant, which is an oxygen-containing compound.

[0035] The source of the first solution is not particularly limited in the present application, and preferably, the first solution is obtained by fermenting lactic acid from agricultural and forestry waste or by other methods. The other methods are not particularly limited in the present application, for example, commercially available glucose, starch, etc. can be directly obtained, and lactic acid is fermented from the obtained glucose, starch, etc. as raw materials. The method for fermenting lactic acid is not particularly limited in the present application, and a conventional fermentation method in the art can be used.

[0036] The source of the agricultural and forestry waste is not particularly limited in the present application, and for example, one or more of the following can be included but is not limited to: straw (corn straw, wheat straw, straw, rape stem, barley straw, oat straw, sorghum straw, etc.), rice husk, softwood, hardwood, branches, livestock manure, etc.

[0037] In some embodiments of the present application, preferably, the first solution contains lactic acid, metal ions, pigments, proteins, sugars and water. In the present application, the lactic acid fermentation treatment solution is obtained by centrifuging and filtering the lactic acid fermentation liquid to remove impurities such as bacterial bodies; or the lactic acid fermentation liquid is adjusted to a pH of 6-10.5, and then centrifuged and filtered to remove impurities such as bacterial bodies. The centrifugation and filtration method is not particularly limited in the present application, and a conventional separation method in the art can be used. The lactic acid fermentation liquid or lactic acid fermentation treatment liquid in the present application can also be concentrated before lactic acid extraction, and the skilled person in the art can choose as needed according to the actual situation.

[0038] The concentration of metal ions in the first solution is selected in a wide range in the present application, and preferably, the concentration of metal ions in the first solution is below 5wt%, further below 4wt%, and more further below 3wt%.

[0039] The concentration of lactic acid in the first solution is selected in a wide range in the present application, and preferably, the concentration of lactic acid in the first solution is below 50wt%, further below 30wt%, and more further below 5wt%.

[0040] In some embodiments of the present application, preferably, the pH value of the first solution is below 10.5, further 4-9, and more further 4.5-7; for example, 4.5, 5.2, 5.6, 6.0, 7.0, 8.0, etc.

[0041] The metal ions are selected in a wide range in the present application, and preferably, the metal ions include but are not limited to one or more of calcium ions, magnesium ions and iron ions.

[0042] In some embodiments of the present application, preferably, in step (1), the volume ratio of the first extraction system to the first solution is (0.1-15):1, further (0.2-10):1, and more further (0.25-8):1.

[0043] In some embodiments of the present application, preferably, the first extraction system comprises a first complexing extractant and optionally a first diluent; wherein the molar ratio of the first complexing extractant to the metal ion in the first solution is (0.1-50):1, further (0.5-50):1, further (1-30):1, and more further (2-20):1; for example, 0.3:1, 0.6:1, 0.9:1, 1.5:1, 3:1, 5:1, 6:1, 9:1, 10:1, 12:1, 15:1, 18:1, 25:1, etc.

[0044] In view of the viscosity and the layering effect of the first complexing extractant, the present application improves the physicochemical properties of the first extraction system by adding the first diluent, so as to better improve the extraction effect. The present application does not have a particular limitation on the ratio between the first complexing extractant and the first diluent, as long as the metal can be extracted, and the person skilled in the art can select as needed according to the actual situation.

[0045] In some embodiments of the present application, preferably, the first complexing extractant is an acidic phosphorus oxygen type extractant, and the general formula of the acidic phosphorus oxygen type extractant is XYP(O)OH; wherein X and Y are each independently a linear or branched structure alkoxy or alkyl with a carbon atom number of 2-10; more preferably, a linear or branched structure alkoxy or alkyl with a carbon atom number of 5-10. The acidic phosphorus oxygen type extractant of the present application includes but is not limited to 2-ethylhexyl phosphoric acid mono 2-ethylhexyl ester (P507), methyl phosphoric acid dimethyl heptyl ester (P350), di(2-ethylhexyl) phosphoric acid (P204), etc.

[0046] 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, alkanes, halogenated alkanes and aromatic compounds; further selected from at least one of ether compounds with a carbon atom number of 4-10, ester compounds with a carbon atom number of 2-10, linear, branched or cyclic alcohol compounds containing at least four carbon atoms, linear or cyclic alkanes compounds containing five carbon atoms and mixtures thereof, halogenated alkanes with a carbon atom number of 1-3 and aromatic compounds.

[0047] In a specific embodiment of the present application, the ether compounds with a carbon atom number of 4-10 include but are not limited to isopropyl ether, ethyl ether, n-butyl ether, etc.

[0048] In one embodiment of the present application, the ester compound having 2-10 carbon atoms is ethyl acetate and / or butyl acetate.

[0049] In one embodiment of the present application, the linear, branched or cyclic alcohol compound having at least four carbon atoms is at least one selected from the group consisting of n-octanol, iso-octanol, heptanol, cyclohexanol, iso-butanol and decanol.

[0050] In one embodiment of the present application, the linear or cyclic alkane compound having five carbon atoms and mixtures thereof include, but are not limited to, one, two or more of kerosene, n-pentane, n-hexane, cyclohexane, n-dodecane, n-tridecane.

[0051] In one embodiment of the present application, the halogenated alkane having 1-3 carbon atoms can be chloroalkane and / or bromoalkane, and can also be mono-halogenated alkane, di-halogenated alkane, tri-halogenated alkane, tetra-halogenated alkane, for example, including but not limited to carbon tetrachloride, chloroform, dichloromethane, 1,2-dichloroethane, etc.

[0052] In one embodiment of the present application, the aromatic compound includes, but is not limited to, benzene, toluene, ethylbenzene, chlorobenzene, xylene, etc.

[0053] According to one preferred embodiment of the present application, the first diluent is at least one selected from the group consisting of dichloromethane, carbon tetrachloride, xylene, ethyl acetate, butyl acetate, isopropyl ether, n-octanol, iso-octanol, heptanol, cyclohexanol, iso-butanol and decanol.

[0054] In some embodiments of the present application, preferably, in step (1), the absolute value of the difference ΔpH between the pH value of the first aqueous solution and the pH value of the first solution is >0.5, further >1, and more further >2; for example, greater than or equal to 0.5, 1, 1.5, 2, 3, etc. The higher the absolute value of ΔpH, the more metal ions are extracted, and the less lactic acid is extracted.

[0055] In some embodiments of the present application, preferably, the pH value of the first solution is greater than the pH value of the first aqueous solution.

[0056] In some embodiments of the present application, preferably, the first extraction process has an extraction rate of metal ions of 30% or more, further 50% or more, further 85% or more, and more further 90% or more. In the present application, the extraction rate of metal ions refers to the percentage of metal ions entering the first organic solution relative to the metal ions in the first solution.

[0057] The temperature of the first extraction treatment is not particularly limited in the present application, and preferably, the temperature of the first 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℃, etc.

[0058] In some embodiments of the present application, preferably, the extraction stages of the first extraction treatment are 1-30 stages, more preferably 1-20 stages, and further preferably 1-10 stages, and the first extraction can be carried out by using multi-stage countercurrent or multi-stage crossflow extraction. The present application can carry out a concentration step between any two extraction stages.

[0059] The present application does not have a particular limitation on the way of contacting the first extraction system with the first solution to carry out the first extraction treatment, and the conventional way in the art can be used, for example, when the first extraction system only contains the first complexing extractant, the first complexing extractant is mixed with the first solution to realize the contact of the first solution with the first complexing extractant, thereby carrying out the extraction; when the first extraction system contains the first complexing extractant and the first diluent at the same time, the first complexing extractant is mixed with the first diluent first, and then mixed with the first solution to realize the contact of the first solution with the first complexing extractant and the first diluent, thereby carrying out the extraction.

[0060] In the present application, by using the first extraction system to carry out complexing extraction on the metal ions in the first solution, the metal ions are transferred from the aqueous phase to the organic phase, thereby separating the metal ions from lactic acid in the fermentation broth, so that at least most of the lactic acid is retained in the first aqueous solution, which plays a role in separating and purifying lactic acid and improves the process efficiency.

[0061] In some embodiments of the present application, preferably, in step (2), the volume ratio of the second extraction system to the first aqueous solution is (0.1-50):1, further (0.2-40):1, further (0.2-20):1, and more further (0.5-10):1.

[0062] In some embodiments of the present application, preferably, the second extraction system further comprises a second diluent. The present application does not have a particular limitation on the ratio between the second extractant and the second diluent, and the person skilled in the art can select as needed according to the actual situation, and preferably, the mass ratio of the second extractant to the second diluent is 1:(0-20), further 1:(0.1-15), and more further 1:(0.2-10).

[0063] In some embodiments of the present application, preferably, in step (2), the oxygen-containing compound is at least one selected from the group consisting of alcohol compounds, ketone compounds, ether compounds and ester compounds.

[0064] In a specific embodiment of the present application, the alcohol compounds include C4-C 18 straight-chain alcohols, isomeric alcohols, unsaturated alcohols and cyclic alcohols, such as, but not limited to, n-butanol, isobutyl alcohol, n-octanol, oleyl alcohol, cyclohexanol, heptyl alcohol, etc.

[0065] In a specific embodiment of the present application, the ketone compounds include C5-C8 ketone compounds, such as, but not limited to, pentanone, etc.

[0066] In a specific embodiment of the present application, the ether compounds include C2-C6 ether compounds, such as, but not limited to, diethyl ether, isopropyl ether, cyclic ether, etc.

[0067] In a specific embodiment of the present application, the ester compounds include C4-C 36 ester compounds, such as, but not limited to, ethyl acetate, butyl acetate, castor oil, etc.

[0068] In some embodiments of the present application, preferably, the second diluent is at least one selected from the group consisting of alkanes, halogenated alkanes and aromatic compounds, and further at least one selected from the group consisting of straight-chain or cyclic alkanes containing five carbon atoms and mixtures thereof, halogenated alkanes having 1-3 carbon atoms and aromatic compounds. In the present application, the second diluent can be the same as or different from the aforementioned first diluent, which can be selected by those skilled in the art according to actual conditions. The further preferred substances of the second diluent are as described above, which will not be repeated here.

[0069] In some embodiments of the present application, preferably, in step (2), the extraction stages of the second extraction treatment are 1-24 stages, preferably 1-15 stages.

[0070] In some embodiments of the present application, preferably, the temperature of the second extraction treatment is below 50°C, preferably 10-30°C.

[0071] In the present application, by using the second extraction system to extract lactic acid in the first aqueous solution, the lactic acid is transferred from the aqueous phase to the organic phase, so as to separate the lactic acid from the residual metal ions in the fermentation broth, etc., so that at least most of the lactic acid is extracted into the organic phase, which plays a role in separating and purifying lactic acid and improves the process efficiency.

[0072] The present application does not have special limitation on the extraction method, and the extraction of lactic acid can be performed after the extraction of calcium using a second extraction system; alternatively, the extraction of the metal ions and lactic acid can be performed alternately using the first extraction system and the second extraction system, so as to separate the metal ions and lactic acid, respectively. Specifically, the first solution is subjected to first extraction using the first extraction system to obtain a first aqueous solution and a first organic solution; the first aqueous solution is subjected to second extraction using the second extraction system to obtain a second aqueous solution and a second organic solution; the second aqueous solution is subjected to third extraction using the first extraction system, and so on, until the metal ions and lactic acid meet the required separation requirements. The skilled in the art can select as required according to the actual situation, and preferably, the extraction of lactic acid is performed after the extraction of calcium using the second extraction system.

[0073] The present application does not have special limitation on the extraction equipment used for the first extraction and the second extraction, and the 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.

[0074] According to a preferred embodiment of the present application, the method further comprises step (3): stripping the second organic solution using a stripping agent to obtain an aqueous lactic acid solution or an aqueous lactic acid salt solution.

[0075] In some embodiments of the present application, preferably, in step (3), the volume ratio of the stripping agent to the second organic solution is (0.1-100): 1, further (0.2-50): 1, and more further (0.2-30): 1.

[0076] In some embodiments of the present application, preferably, the stripping agent is water or an alkaline solution. The present application has a wide selection range of the alkaline solution, such as, but not limited to, ammonia water, sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide solution, calcium oxide solution and combinations thereof.

[0077] In the present application, when water is used for stripping the second organic solution, hot water at 50-120℃ is preferably used for stripping. Meanwhile, when water is used for stripping, one-stage extraction or extraction of two or more stages is preferred, and a concentration step can be performed between any two stages of stripping.

[0078] In the present application, when the second organic solution is back-extracted with an alkali solution, the present application does not have a particular limitation on the adding method of the alkali solution, which can be one-time input, batch input, or inputting multiple alkali solutions respectively, or mixing the components and then adding once. The present application also does not have a particular limitation on the concentration of the alkali solution, which can be 0.01-8 mol / L, further 0.05-5 mol / L, further 0.1-5 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2.5 mol / L, 3 mol / L, 4 mol / L, etc.

[0079] According to a preferred embodiment of the present application, the molar concentration ratio of the alkali equivalent in the alkali solution to lactic acid in the second organic solution is (0.95-1.2):1, further (0.98-1.1):1.

[0080] In some embodiments of the present application, preferably, the extraction stage number of the back-extraction is 1-24, more preferably 1-15. The back-extraction of the present application can be carried out in a multi-stage countercurrent manner.

[0081] In some embodiments of the present application, preferably, the temperature of the back-extraction is 10-120℃, further 20-100℃, and more further 20-95℃.

[0082] In a specific embodiment, the temperature of the back-extraction process can be 10-120℃, further 50-120℃, and more further 80-100℃, for example, 60℃, 70℃, 90℃, etc.

[0083] In another specific embodiment, the temperature of the back-extraction process can be 10-100℃, further 20-40℃, for example, 25℃, 30℃, 35℃, etc.

[0084] In the present application, the lactic acid in the organic phase is transferred to the aqueous phase by contacting the back-extraction agent with the second organic solution, and by controlling the back-extraction process conditions, as few as possible metal ions are extracted into the aqueous phase, and as many as possible lactic acid is extracted into the aqueous phase.

[0085] The present application provides a method for preparing a lactic acid product, which comprises: obtaining a lactic acid aqueous solution or a lactic acid salt aqueous solution by the method as described above, then purifying the lactic acid aqueous solution to obtain a lactic acid product, or first acidifying the lactic acid salt aqueous solution to obtain a lactic acid aqueous solution, and then purifying the lactic acid aqueous solution to obtain a lactic acid product.

[0086] The present application does not have a particular limitation on the purification method, and the existing purification method in the art can be used.

[0087] In one specific embodiment of the present application, the purification method comprises: concentrating a lactic acid aqueous solution in a first step to obtain a lactic acid concentration of 15-40 wt%, decolorizing the lactic acid aqueous solution with activated carbon, further concentrating and dehydrating the lactic acid aqueous solution, and distilling the lactic acid aqueous solution to obtain a lactic acid product.

[0088] In another specific embodiment of the present application, the purification method comprises: concentrating a lactic acid aqueous solution, decolorizing the lactic acid aqueous solution with activated carbon, purifying the lactic acid aqueous solution with a resin, purifying the lactic acid aqueous solution with a nanofiltration membrane, concentrating and dehydrating the lactic acid aqueous solution to obtain a lactic acid product.

[0089] In another specific embodiment of the present application, the purification method comprises: concentrating a lactic acid aqueous solution, dehydrating the lactic acid aqueous solution, and distilling the lactic acid aqueous solution in multiple stages to obtain a lactic acid product, wherein the number of distillation stages is 2 or more.

[0090] The fourth aspect of the present application provides a lactic acid product obtained by the preparation method as described above, wherein the performance of the lactic acid product is as described above.

[0091] The fifth aspect of the present application provides a preparation method of calcium lactate particles, which comprises: adding water to the second organic solution obtained by the method as described above, neutralizing the second organic solution with a calcium source, separating to obtain a calcium lactate solution, and then sequentially concentrating and spray drying the calcium lactate solution to obtain calcium lactate particles, which can be used as a food additive raw material.

[0092] The calcium source used in the present application has a wide selection range, for example, but not limited to, calcium oxide, calcium carbonate, calcium hydroxide, etc.

[0093] The present application will be described in detail below by way of examples. In the following examples, various raw materials used are available from commercial channels unless otherwise specified; the physical property parameters of the raw materials or the performance parameters of the products are determined by conventional methods in the art.

[0094] Preparation of the first solution

[0095] The first solution is prepared according to the method disclosed in CN112941117A, specifically comprising:

[0096] The pretreated solid granular corn stalk with 30(w / w)% solid content was put into a fermentor as raw material, 5mg protein / g stalk(dry basis) cellulase was added, and pre-saccharification was carried out at 48℃, 200rpm for 6.5h; after the pre-saccharification, Pediococcus acidilactici seed liquid was inoculated into the fermentor at an inoculation amount of 5%(v / v), and nutrient salts(10g / L peptone, 10g / L yeast extract, 2g / L diammonium hydrogen citrate and 0.25g / L manganese sulfate monohydrate) were added, 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, and the fermentation was carried out at 42℃, 200rpm for 96h, then the fermentation liquor was separated from the corn stalk residue by filtration to obtain a first solution for standby, the concentration of lactic acid in the first solution was 9wt%, and the concentration of calcium ions was 2wt%.

[0097] Extraction of lactic acid

[0098] Example 1

[0099] (1) The first solution was subjected to first extraction treatment at a temperature of 24℃ using a first extraction system(including P204 and n-octanol), the extraction stage was 8 stages, and a first aqueous solution(pH value was 2.4) and a first organic solution were obtained, wherein the volume ratio of the first extraction system to the first solution was 1.3:1, and the molar ratio of P204 to calcium ions in the first solution was 4:1; the first extraction treatment caused calcium ions in the first solution to be extracted into the first organic solution, so that the extraction rate of calcium ions was 97.5%;

[0100] (2) The first aqueous solution was subjected to second extraction treatment at a temperature of 25℃ using a second extraction system(isopropyl ether), the extraction stage was 8 stages, and a second aqueous solution and a second organic solution were obtained, wherein the volume ratio of the second extraction system to the first aqueous solution was 1:1, and the second extraction treatment caused lactic acid in the first aqueous solution to be extracted into the second organic solution, so that the extraction rate of lactic acid was 95.6%;

[0101] (3) The second organic solution was subjected to back extraction at 30℃ using a back extraction agent(caustic soda solution), the extraction stage was 1 stage, and a lactic acid salt aqueous solution was obtained, wherein the volume ratio of the back extraction agent to the second organic solution was 1:1, and the back extraction caused the back extraction rate of lactic acid to be 97.8%, and the performance of the obtained product is listed in Table 1.

[0102] The remaining examples were carried out using the same process as Example 1, and the specific process conditions and the performance of the obtained products are listed in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] Preparation of lactic acid product

[0107] Examples 6 and 7

[0108] The aqueous lactic acid salt solution obtained in Example 1 was first subjected to acid hydrolysis with sulfuric acid to obtain an aqueous lactic acid solution, and then subjected to concentration, activated carbon decolorization, resin purification, nanofiltration membrane purification, concentration and dehydration in sequence to obtain a lactic acid product.

[0109] The aqueous lactic acid solution obtained in Example 2 was subjected to concentration, activated carbon decolorization, resin purification, nanofiltration membrane purification, concentration and dehydration in sequence to obtain a lactic acid product.

[0110] It was determined that the chemical purity, optical purity, color number, content of residual metal ions and total content of residual extractant and diluent of the obtained lactic acid product were listed in Table 2.

[0111] Table 2

[0112]

[0113] Preparation of calcium lactate particles

[0114] Example 8

[0115] An appropriate amount of water was added to the second organic solution obtained in step (2) of Example 1, and the obtained second organic solution was neutralized with calcium carbonate to obtain calcium lactate. The oil phase was separated, and the water phase was a calcium lactate solution. Then, the calcium lactate solution was subjected to concentration and spray drying in sequence to obtain calcium lactate particles, which can be used as a food additive raw material.

[0116] The preferred embodiments of the present application are described in detail above, 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. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for separating and extracting lactic acid, characterized by, The method comprises: (1) a first extraction system is used to treat a first solution by first extraction to obtain a first aqueous solution and a first organic solution, the first extraction treatment makes at least part of metal ions in the first solution be extracted into the first organic solution; (2) a second extraction system is used to treat the first aqueous solution by second extraction to obtain a second aqueous solution and a second organic solution, the second extraction treatment makes at least part of lactic acid in the first aqueous solution be extracted into the second organic solution; Wherein, the first solution comprises lactic acid fermentation liquid and / or lactic acid fermentation treatment liquid; The first extraction system comprises a first complexing extractant and a first diluent, the first complexing extractant is an acidic phosphorus oxygen type extractant, the general formula of the acidic phosphorus oxygen type extractant is XYP(O)OH, X and Y are each independently linear or branched structure alkoxy, alkyl with carbon atom number of 2-10; the first diluent is selected from at least one of ether compounds, ester compounds, linear, branched or cyclic alcohol compounds, alkanes, halogenated alkanes and aromatic compounds; The second extraction system comprises a second extractant and a second diluent, the second extractant is an oxygen-containing compound, the oxygen-containing compound is selected from at least one of n-butanol, isobutyl alcohol, n-octanol, oleyl alcohol and cyclohexanol, the second diluent is selected from one, two or more of n-pentane, n-hexane, cyclohexane, n-dodecane, n-tridecane.

2. The method of claim 1, wherein, The first solution is obtained by fermenting lactic acid with agricultural and forestry waste as raw material or by other ways.

3. The method of claim 2, wherein, The agricultural and forestry waste is selected from at least one of straw, rice husk, softwood, hardwood, branches and livestock manure.

4. The method of claim 1, wherein, The first solution contains lactic acid, metal ions, pigments, proteins, sugars and water; Wherein, the concentration of metal ions in the first solution is below 5wt%; and / or, The concentration of lactic acid in the first solution is below 50wt%; and / or, The pH value of the first solution is below 10.5; and / or, The metal ions are selected from at least one of calcium ions, magnesium ions and iron ions.

5. The method of claim 4, wherein, The concentration of metal ions in the first solution is below 4wt%; and / or, The concentration of lactic acid in the first solution is below 30wt%; and / or, The pH value of the first solution is 4-9.

6. The method of claim 4, wherein, The concentration of metal ions in the first solution is below 3wt%; and / or, The concentration of lactic acid in the first solution is below 5wt%; and / or, The pH value of the first solution is 4.5-7.

7. The method of claim 4, wherein, In step (1), the volume ratio of the first extraction system to the first solution is (0.1-15):1; and / or, The molar ratio of the first complexing extractant to the metal ions in the first solution is (0.1-50):

1.

8. The method of claim 7, wherein, In step (1), the volume ratio of the first extraction system to the first solution is (0.2-10):1; and / or, The molar ratio of the first complexing extractant to the metal ions in the first solution is (0.5-50):

1.

9. The method of claim 7, wherein, In step (1), the volume ratio of the first extraction system to the first solution is (0.25-8):1; and / or, The molar ratio of the first complexing extractant to the metal ion in the first solution is (1-30):

1.

10. The method of claim 7, wherein, The molar ratio of the first complexing extractant to the metal ion in the first solution is (2-20):1; and / or, X and Y are each independently a linear or branched alkoxy group or an alkyl group having 5-10 carbon atoms; and / or, The first 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, a mixture thereof, a halogenated alkane having 1-3 carbon atoms and an aromatic compound.

11. The method of claim 10, wherein, The acidic phosphorus oxygen type extractant is selected from at least one of 2-ethylhexyl phosphoric acid mono 2-ethylhexyl ester, methyl phosphoric acid dimethyl heptyl ester and di(2-ethylhexyl)phosphoric acid; and / or, The ether compound having 4-10 carbon atoms is selected from at least one of isopropyl ether, ethyl ether and n-butyl ether; the ester compound having 2-10 carbon atoms is ethyl acetate and / or butyl acetate; the linear, branched or cyclic alcohol compound having at least four carbon atoms is selected from at least one of n-octanol, iso-octanol, heptanol, cyclohexanol, iso-butanol and decanol; the linear or cyclic alkane compound having five carbon atoms and the mixture thereof are selected from one, two or more of kerosene, n-pentane, n-hexane, cyclohexane, n-dodecane, n-tridecane; the halogenated alkane having 1-3 carbon atoms is chlorinated alkane and / or brominated alkane; and the aromatic compound is selected from at least one of benzene, toluene, ethylbenzene, chlorobenzene and xylene.

12. The method of claim 11, wherein, The halogenated alkane having 1-3 carbon atoms is at least one of carbon tetrachloride, chloroform, dichloromethane and 1,2-dichloroethane.

13. The method of any of claims 1-12, wherein, In step (1), the absolute value of the difference ΔpH between the pH value of the first aqueous solution and the pH value of the first solution is >0.5; and / or, The pH value of the first solution is greater than the pH value of the first aqueous solution; and / or, The first extraction treatment has an extraction rate of metal ions of 30% or more; and / or, The temperature of the first extraction treatment is 10-95°C; and / or, The first extraction treatment has an extraction series of 1-30 stages, and the first extraction adopts a multi-stage countercurrent or multi-stage crossflow extraction mode.

14. The method of claim 13, wherein, The absolute value of the difference ΔpH between the pH value of the first aqueous solution and the pH value of the first solution is >1; and / or, The first extraction treatment has an extraction rate of metal ions of 50% or more; and / or, The temperature of the first extraction treatment is 20-60°C; and / or, The first extraction treatment has an extraction series of 1-20 stages.

15. The method of claim 13, wherein, The absolute value of the difference ΔpH between the pH value of the first aqueous solution and the pH value of the first solution is >2; and / or, The first extraction treatment has an extraction rate of metal ions of 85% or more; and / or, The temperature of the first extraction treatment is 20-40°C; and / or, The first extraction treatment has an extraction series of 1-10 stages.

16. The method of claim 13, wherein, The first extraction treatment has an extraction rate of metal ions of 90% or more.

17. The method of any one of claims 1-12, wherein, In step (2), the volume ratio of the second extraction system to the first aqueous solution is (0.1-50):1; and / or, The mass ratio of the second extractant to the second diluent is 1:(0-20).

18. The method of claim 17, wherein, The volume ratio of the second extraction system to the first aqueous solution is (0.2-40):1; and / or, The mass ratio of the second extractant to the second diluent is 1:(0.1-15).

19. The method of claim 17, wherein, The volume ratio of the second extraction system to the first aqueous solution is (0.2-20):1; and / or, The mass ratio of the second extractant to the second diluent is 1:(0.2-10).

20. The method of claim 17, wherein, The volume ratio of the second extraction system to the first aqueous solution is (0.5-10):

1.

21. The method of any one of claims 1-12, wherein, In step (2), the extraction stage number of the second extraction treatment is 1-24 stages; and / or, The temperature of the second extraction treatment is below 50℃.

22. The method of any one of claims 1-12, wherein, In step (2), the extraction stage number of the second extraction treatment is 1-15 stages; and / or, The temperature of the second extraction treatment is 10-30℃; and / or, The method further comprises step (3): stripping the second organic solution with a stripping agent to obtain a lactic acid aqueous solution or a lactic acid salt aqueous solution.

23. The method of claim 22, wherein, In step (3), the volume ratio of the stripping agent to the second organic solution is (0.1-100):1; and / or, The stripping agent is water or an alkali solution, wherein the molar concentration ratio of alkali equivalent in the alkali solution to lactic acid in the second organic solution, calculated based on hydroxide, is (0.95-1.2):1; and / or, The extraction stage number of the stripping is 1-24 stages; and / or, The temperature of the stripping is 10-120℃.

24. The method of claim 23, wherein, The volume ratio of the stripping agent to the second organic solution is (0.2-50):1; and / or, The molar concentration ratio of alkali equivalent in the alkali solution to lactic acid in the second organic solution, calculated based on hydroxide, is (0.98-1.1):1; and / or, The temperature of the stripping is 20-100℃.

25. The method of claim 23, wherein, The volume ratio of the stripping agent to the second organic solution is (0.2-30):1; and / or, The extraction stage number of the stripping is 1-15 stages; and / or, The temperature of the stripping is 20-95℃.

26. A method of producing a lactic acid product, characterized by, The method comprises: obtaining a lactic acid aqueous solution or a lactic acid salt aqueous solution by the method of any one of claims 22-25, then purifying the lactic acid aqueous solution to obtain a lactic acid product, or first acidizing the lactic acid salt aqueous solution to obtain a lactic acid aqueous solution, and then purifying the lactic acid aqueous solution to obtain a lactic acid product.

27. The method of claim 26, wherein, The purification method comprises: subjecting the lactic acid aqueous solution to first-step concentration, activated carbon decolorization, concentration dehydration, and molecular distillation to obtain a lactic acid product, wherein the first-step concentration makes the concentration of lactic acid 15-40wt%; or, Subjecting the lactic acid aqueous solution to concentration, activated carbon decolorization, resin purification, nanofiltration membrane purification, and concentration dehydration to obtain a lactic acid product; or, Subjecting the lactic acid aqueous solution to concentration, dehydration, and multi-stage molecular distillation to obtain a lactic acid product, wherein the stage number of the molecular distillation is 2 stages or more.

28. The method of claim 26, wherein, The chemical purity of the lactic acid product is 98wt% or more; and / or, The optical purity of the lactic acid product is >99%; and / or, the content of residual metal ions in the lactic acid product is 100 ppm or less; and / or, the color number of the lactic acid product is < 50; and / or, the total content of residual extractant and diluent in the lactic acid product is 100 ppm or less.

29. The method of claim 26, 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 total content of residual extractant and diluent in the lactic acid product is 50 ppm or less.

30. The method of claim 26, 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 total content of residual extractant and diluent in the lactic acid product is 10 ppm or less.

31. The method of claim 26, wherein, the total content of residual extractant and diluent in the lactic acid product is 5 ppm or less.

32. A method of preparing calcium lactate particles, characterized by, the method comprises adding water to the second organic solution obtained by the method according to any one of claims 1-25, neutralizing the obtained second organic solution with a calcium source, separating a calcium lactate solution, and then sequentially concentrating and spray drying the calcium lactate solution to obtain calcium lactate particles.

33. The method of claim 32, wherein, the calcium lactate particles are used as a food additive raw material; and / or, the calcium source is at least one selected from the group consisting of calcium oxide, calcium carbonate, and calcium hydroxide. the calcium source is at least one selected from the group consisting of calcium oxide, calcium carbonate, and calcium hydroxide.

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