CN114702381A - Method for extracting lactic acid from heavy-phase lactic acid - Google Patents

Method for extracting lactic acid from heavy-phase lactic acid Download PDF

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CN114702381A
CN114702381A CN202210632027.7A CN202210632027A CN114702381A CN 114702381 A CN114702381 A CN 114702381A CN 202210632027 A CN202210632027 A CN 202210632027A CN 114702381 A CN114702381 A CN 114702381A
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lactic acid
exchange resin
heavy
anion exchange
resin column
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CN114702381B (en
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张天惕
唐海静
杨�嘉
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Oushangyuan Intelligent Equipment Co ltd
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Aoshangyuan Tianjin Co ltd
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    • C07C51/00Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/09Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid esters or lactones
    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00Preparation of carboxylic acids or their salts, halides or anhydrides
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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00Preparation of carboxylic acids or their salts, halides or anhydrides
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Abstract

The invention discloses a method for extracting lactic acid from heavy-phase lactic acid, which comprises the following steps: (1) diluting the heavy phase lactic acid to 20-35% by mass of lactic acid; (2) acidolysis of the heavy phase lactic acid solution; (3) carrying out lactate adsorption on the heavy phase lactic acid solution subjected to acidolysis by adopting a weak-base anion exchange resin column; (4) washing the weak-base anion exchange resin column with water; (5) carrying out acid elution on the washed weak-base anion exchange resin column by using a hydrochloric acid solution, and collecting eluent; (6) passing the eluate through a strongly basic anion exchange resin column; (8) the solution passing through the strong-base anion exchange resin column is sent to a cation exchange resin column and a granular carbon decolorizing column to obtain pure lactic acid solution. The invention adopts an ion exchange mode to purify the heavy phase lactic acid to obtain the refined lactic acid, the purity is more than 99.2 percent, the yield of the lactic acid is improved, and the environmental protection dilemma caused by accumulation of the heavy phase lactic acid is solved.

Description

Method for extracting lactic acid from heavy-phase lactic acid
Technical Field
The invention relates to a lactic acid separation and purification technology, in particular to a method for extracting lactic acid from heavy-phase lactic acid.
Background
Lactic acid is a hydroxy acid and is widely applied in the fields of food, brewing, medicine, livestock raising and the like. The existing lactic acid preparation method generally adopts microbial fermentation to obtain fermentation liquor, and the refined lactic acid is finally produced by the steps of filtering, concentrating, evaporating or ion exchanging the lactic acid fermentation liquor and the like. However, in the preparation process of refined lactic acid, heavy-phase lactic acid is generated, the mass of lactic acid in the heavy-phase lactic acid generally accounts for 60-70%, if molecular distillation is adopted, a heavy-phase lactic acid solution with the mass concentration percentage of 65-85% can be obtained (as described in chinese patent CN 113248365A), the heavy-phase lactic acid also contains a large amount of impurities such as sugar, pigment, protein and the like, is dark in color and is also called as black lactic acid or red lactic acid, because the impurities are too many, although the content of lactic acid is not low, the lactic acid cannot be effectively utilized, most of the lactic acid can be treated only according to waste materials, huge environmental protection pressure is brought to lactic acid production enterprises, and the waste of resources is also caused.
Therefore, lactic acid manufacturers are looking for the possibility of further extracting lactic acid from the heavy phase lactic acid. In the prior art, the method for extracting lactic acid by adopting heavy-phase lactic acid comprises the following steps: the method comprises the steps of extracting most of lactic acid in heavy-phase lactic acid into an organic phase by adopting an organic extraction phase, wherein the organic extraction phase is extracted by using a special organic extraction phase, for example, Chinese patents CN102643191A, CN102659563A and CN102701950A, namely, the lactic acid is selectively transferred into the organic extraction phase to form a loaded organic phase, and then the loaded organic phase is subjected to back extraction by using an alkali solution to obtain a lactate aqueous solution, wherein the organic extraction phase consists of an extracting agent, a solvent and a phase regulator, the extracting agent is an amide compound or a mixture of the amide compounds, the solvent is liquid paraffin, and the phase regulator is an alcohol compound or a mixture of the alcohol compounds. The method needs to add a step of extracting lactic acid from an organic phase, and the used organic reagent needs to be subjected to post-treatment after extraction is finished, so that the pollution to the environment can be reduced.
Another treatment method of the heavy-phase lactic acid is to dilute distillation residues (heavy-phase lactic acid) formed by molecular distillation with acid water obtained by falling film evaporation until the mass fraction of lactic acid is 15-30%, decolor the lactic acid by a particle carbon column, enter the falling film evaporation, and perform cyclic molecular distillation, so as to improve the yield of the lactic acid, for example, the chinese patent CN 103724183A. If the heavy-phase lactic acid returns to a reduction system, the production load of the original system can be increased, and the quality of the finished product lactic acid is reduced.
The existing heavy-phase lactic acid extraction method can not obtain lactic acid with higher purity under the conditions of lower economic cost and environmental protection cost.
Disclosure of Invention
The invention discloses a method for extracting lactic acid from heavy-phase lactic acid, which adopts an ion exchange technology to reduce the investment cost of enterprises. By the method, more lactic acid in the heavy phase lactic acid is extracted, so that the yield of the lactic acid is improved, and the accumulation of waste materials is reduced.
The technical scheme of the invention is as follows: a method for extracting lactic acid from heavy phase lactic acid comprises the following steps:
(1) diluting the heavy phase lactic acid to 20-35% by mass of lactic acid; the heavy phase lactic acid is one-time molecular distillation residual liquid, or two or more-time molecular distillation residual liquid, or membrane filtration concentrated liquid, and a mixture of two or three of the three; the chroma of the primary molecular distillation residual liquid is lower than that of the secondary or more molecular distillation residual liquid; the chroma of the heavy phase lactic acid formed by two or more molecular distillations can reach 9000-10000 APHA;
(2) carrying out acidolysis on the diluted heavy-phase lactic acid solution;
(3) carrying out lactate adsorption on the heavy-phase lactic acid solution subjected to acidolysis by using a weak-base anion exchange resin column;
(4) washing the weak-base anion exchange resin column adsorbed with lactate with water; removing impurities in the remaining column by water washing;
(5) carrying out acid elution on the washed weak-base anion exchange resin column by using a hydrochloric acid solution, and collecting eluent;
(6) passing the eluate through strongly basic anion exchange resin column to remove Cl-、SO4 2-And oxalate radicals;
(7) the solution passing through the strong-base anion exchange resin column is sent to a cation exchange resin column and a granular carbon decolorizing column to obtain pure lactic acid solution.
Preferably, the heavy phase lactic acid solution is decolorized before being sent to a weak base anion exchange resin column;
preferably, powdered activated carbon with the mass of 1 per mill to 5 per mill of the heavy phase lactic acid solution is added for stirring and decoloring.
Preferably, the decolored heavy phase lactic acid solution is obtained by stirring powdered activated carbon, decoloring and then filtering with a plate frame.
Preferably, the heavy phase lactic acid is diluted with pure water.
Preferably, the amount of the sulfuric acid solution added during acidolysis is 1-5 per mill of the mass of the heavy phase lactic acid solution feed, and the concentration of the sulfuric acid solution is 98%.
Preferably, the heavy phase lactic acid solution is loaded onto the weak base anion exchange resin column for adsorption at a flow rate of 3-5 m/h.
Preferably, when the weak base anion exchange resin column is used for adsorbing the lactic acid solution, the pH value of the liquid flowing out of the weak base anion exchange resin column is detected, the pH value is reduced to 3 +/-0.2, and the feeding is stopped. Whether the weak base anion exchange resin column is adsorbed and saturated or not is determined through pH detection, so that the loss of lactic acid is reduced, and the treatment difficulty of waste liquid is reduced.
Preferably, the liquid obtained by washing the weak base anion exchange resin column with water is recycled for the next ion exchange of lactate adsorption, the content of lactic acid in the liquid is detected, and after the content of lactic acid is 0, the liquid is not recycled.
Preferably, the weak base anion exchange resin column is washed with water, the color of the liquid is observed, and the washing with water is stopped after visual inspection for the absence of the pigment.
Preferably, when hydrochloric acid solution is used for acid elution of the washed weak base anion exchange resin column, the pH value of the eluent is detected, the eluent is collected when the pH value is reduced to 3 +/-0.2, whether chloride ions appear in the eluent is detected, and the elution is stopped when the chloride ions appear.
Preferably, the weakly basic anion exchange resin column after water washing is eluted by using a hydrochloric acid solution with the mass concentration of 10% -15%.
Preferably, the flow rate of the hydrochloric acid solution is between 0.5 and 0.8 m/h.
Preferably, the flow rate of the lactic acid solution entering the cation exchange resin column and the granular carbon decolorization column is 2-3m for cultivation/h.
Preferably, the weak base anion exchange resin column is flushed with water to push out the excess hydrochloric acid, washed to pH5.0, and regenerated with 2-3 times the resin volume of 10% -30% ammonia water to recover the resin for reuse in the adsorption process.
The invention adopts an ion exchange mode to purify the heavy phase lactic acid to obtain the refined lactic acid, the purity is more than 99.2 percent, and the investment cost is lower than that of the existing extraction method, so that the investment cost of an enterprise is lower, the treatment amount of organic pollutants is reduced, and the method is more environment-friendly and energy-saving. Meanwhile, the yield of the lactic acid is improved, and the environmental protection dilemma caused by accumulation of the heavy phase lactic acid is solved.
Drawings
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a schematic representation of the heavy phase lactic acid starting material of example 4;
FIG. 3 is a real drawing of the heavy phase lactic acid solution of example 4 fed to a column of a weakly basic anion exchange resin;
FIG. 4 is a schematic representation of the lactic acid solution of example 4 entering a strongly basic anion exchange resin column;
FIG. 5 is a picture of the effluent of the lactic acid solution of example 4 after decolorization by a granular carbon decolorizing column.
Detailed Description
In order to more clearly illustrate the technical solution of the present invention, the present invention will be described below by way of examples. It is apparent that the embodiments in the following description do not limit the present invention.
A method for extracting lactic acid from heavy phase lactic acid, as shown in fig. 1, comprising the steps of:
(1) diluting: diluting the heavy-phase lactic acid into a heavy-phase lactic acid solution with the mass percent of 20-35% of lactic acid by pure water;
(2) acid hydrolysis: pumping the diluted heavy-phase lactic acid solution into a reaction kettle by using a centrifugal pump for acidolysis (the amount of added sulfuric acid is 1-5 per mill of the feeding mass of the heavy-phase lactic acid solution, the concentration of the sulfuric acid is 98%), stirring and heating to 120 ℃ after the acid addition is finished, keeping the temperature for two hours, cooling to 80 ℃, and adding acid to decompose the polymerized lactic acid;
(3) and (3) decoloring: adding powdered activated carbon with the mass of 1 per mill-5 per mill of the heavy-phase lactic acid solution, stirring and decoloring for 30 minutes;
(4) and (3) filtering: filtering out the powdered activated carbon by using a plate frame to obtain a decolorized solution;
(5) adsorption: sending the decolorized solution into a weak base anion exchange resin column at a flow rate of 3-5 m/h for adsorption, starting to flow out, wherein the pH of the liquid flowing out of the weak base anion exchange resin column is higher, and stopping feeding when the pH is gradually reduced to 3 +/-0.2 so as to avoid lactic acid loss, wherein the weak base anion exchange resin column for adsorption can adopt a multi-column series connection mode;
(6) washing with water: after adsorption is finished, feeding water into the weak-base anion exchange resin column for washing, beginning to contain lactic acid in water, recovering, discharging after no lactic acid exists, and stopping washing until no pigment exists during visual inspection;
(7) acid elution: and after the water washing is finished, introducing a hydrochloric acid solution with the mass concentration of 10% -15% into the weak-base anion exchange resin column for elution, wherein the acid washing and elution flow rate is 0.5-0.8 m/h, the pH of an effluent liquid is gradually reduced during elution, and when the pH is reduced to 3 +/-0.2, the eluate is collected, wherein the pH: 1-1.5 times, continuously sampling and detecting chloride ions in the effluent, gradually reducing the flow rate of elution, stopping elution once the chloride ions are found in the effluent, and introducing hydrochloric acid solution for acid elution by adopting a multi-column series connection mode;
the alkalescent anion exchange resin column is flushed with water to push out redundant hydrochloric acid, washed to pH5.0 or so, and regenerated by ammonia water with the mass concentration of 10% -30% 2-3 times of the volume of the resin, so that the resin is recovered and can be reused in the adsorption process;
(8) removal of Cl-、SO4 2-And oxalate radicals: subjecting the lactic acid solution obtained by acid elution to strong base anion exchange resin column at 2-3 m/h, subjecting Cl to strong base anion exchange resin column under acidic condition-、SO4 2-The absorption of the heteropolyacid ions such as oxalate radical is strong, but the lactate is hardly absorbed, even if the lactate is absorbed by a small amount, the lactate is also absorbed by the Cl contained in the subsequent lactic acid liquid-、SO4 2-By substitution with oxalate ions, Cl can be removed-、SO4 2-And miscellaneous acid ions such as oxalate radicals;
(9) cation removal and decoloration: removing impurities such as cations, proteins and pigments from the lactic acid solution passing through the strongly basic anion exchange resin column at a flow rate of 2-3 m/h through a cation exchange resin column and a granular carbon decolorizing column, removing cations such as calcium ions from the lactic acid solution passing through the cation exchange resin column, and decolorizing the filtrate through the granular carbon decolorizing column to obtain a pure lactic acid solution;
the quality index of the lactic acid solution obtained after the steps can reach: the mass concentration is 15-25%, the purity is more than or equal to 99.2%, the chroma is less than 100APHA, the iron ion is less than 2ppm, the sulfate radical is less than 5ppm, and the chloride ion is less than 2 ppm. The index of the final product after passing through the evaporator can reach the mass concentration of more than or equal to 80 percent.
Example 1
A method for extracting lactic acid from heavy phase lactic acid is shown in figure 1, and comprises the following steps:
(1) diluting: and diluting the heavy-phase lactic acid with pure water to obtain a heavy-phase lactic acid solution with the mass percent of lactic acid being 20%.
(2) Acid hydrolysis: pumping the diluted heavy-phase lactic acid solution into a reaction kettle by a centrifugal pump for acidolysis (the amount of added sulfuric acid is 1 per mill of the feeding mass of the heavy-phase lactic acid solution, the concentration of the sulfuric acid is 98%), stirring and heating to 120 ℃ after the acid addition is finished, keeping the temperature for two hours, and cooling to 80 ℃. The addition of acid can decompose the polymerized lactic acid.
(3) And (3) decoloring: adding powdered activated carbon with the mass of 1 per mill of the heavy-phase lactic acid solution, stirring and decoloring for 30 minutes.
(4) And (3) filtering: filtering the powdered activated carbon by using a plate frame to obtain a decolorized solution.
(5) Adsorption: and after adsorption, sending the decolorized solution into a weak-base anion exchange resin column at the flow rate of 5 m/h for adsorption, wherein the pH of the liquid which starts to flow out of the weak-base anion exchange resin column is higher, and feeding is stopped when the pH is gradually reduced to 3 so as to avoid lactic acid loss, and the weak-base anion exchange resin column for adsorption can adopt a multi-column series connection mode.
(6) Washing with water: and after adsorption is finished, feeding water into the weak-base anion exchange resin column for washing, beginning to recover lactic acid in water, discharging the lactic acid after no lactic acid is produced, and stopping washing until no pigment is produced by visual inspection.
(7) Acid elution: and after the water washing is finished, introducing a hydrochloric acid solution with the mass concentration of 10% into the weak-base anion exchange resin column for elution, wherein the pickling and stripping flow speed is 0.8 m/h, the pH of the effluent is gradually reduced during elution, and the effluent is collected when the pH is reduced to 3. pH: 1-1.5 times of the total amount of the components are high fraction of lactic acid, then continuously sampling and detecting chloride ions in effluent, and gradually reducing the flow rate of elution. As soon as the effluent found chloride ions, the elution was stopped. The acid elution can be carried out by introducing hydrochloric acid solution in a multi-column series connection mode. The lactic acid solution obtained by acid elution has most of the impurities removed.
And (3) ejecting redundant hydrochloric acid out of the weak base anion exchange resin column by using water, washing the column to the pH value of about 5.0, and regenerating by using ammonia water with the mass concentration of 10% and the volume of 2-3 times of the resin so that the resin can be recovered and reused in the adsorption process.
(8) Removal of Cl-、SO4 2-And oxalate radicals: subjecting the lactic acid solution obtained by acid elution to strong basic anion exchange resin column at 3 m/h, subjecting Cl to strong basic anion exchange resin column under acidic condition-、SO4 2-The absorption of the heteropolyacid ions such as oxalate radical is strong, but the lactate is hardly absorbed, even if the lactate is absorbed by a small amount, the lactate is also absorbed by the Cl contained in the subsequent lactic acid liquid-、SO4 2-And substitution of oxalate radical by plasmaThus, Cl can be removed-、SO4 2-And a heteropolyacid ion such as an oxalate group.
(9) Cation removal and decoloration: and (2) carrying out 3 m/h flow velocity on the lactic acid solution subjected to the strong-base anion exchange resin column to remove impurities such as cations, proteins and pigments through a cation exchange resin column and a granular carbon decolorizing column, carrying out cation removal on the lactic acid solution through the cation exchange resin column, such as calcium ions, and decolorizing the effluent through the granular carbon decolorizing column to obtain a pure lactic acid solution.
The quality index of the lactic acid solution obtained after the steps are finished can reach 15-25 percent, the purity is more than or equal to 99.2 percent, and the index of the final product after passing through an evaporator can reach more than or equal to 80 percent.
Example 2
A method for extracting lactic acid from heavy phase lactic acid comprises the following steps:
(1) diluting: the heavy phase lactic acid is diluted to 30 percent by mass of lactic acid solution by pure water.
(2) Acid hydrolysis: pumping the diluted heavy-phase lactic acid solution into a reaction kettle by a centrifugal pump for acidolysis (the amount of added sulfuric acid is 3 per mill of the feeding mass of the heavy-phase lactic acid solution, the concentration of the sulfuric acid is 98%), stirring and heating to 120 ℃ after the acid addition is finished, keeping the temperature for two hours, and cooling to 80 ℃. The addition of acid can decompose the polymerized lactic acid.
(3) And (3) decoloring: adding powdered activated carbon with the weight of 4 per mill of the weight of the heavy phase lactic acid solution, stirring and decoloring for 30 minutes.
(4) And (3) filtering: filtering out the powdered activated carbon by using a plate frame to obtain a decolorized solution.
(5) Adsorption: sending the decolorized solution into a weak base anion exchange resin column at the flow speed of 3 m/h for adsorption, wherein the pH of the liquid which begins to flow out of the weak base anion exchange resin column is higher, and stopping feeding when the pH is gradually reduced to 3.2 so as to avoid the loss of lactic acid. The weakly basic anion exchange resin column for adsorption can adopt a multi-column series connection mode.
(6) Washing with water: and after adsorption is finished, feeding water into the weak-base anion exchange resin column for washing, beginning to recover lactic acid in water, discharging the lactic acid after no lactic acid is produced, and stopping washing until no pigment is produced by visual inspection.
(7) Acid elution: and after the water washing is finished, introducing a hydrochloric acid solution with the mass concentration of 13% into the weak-base anion exchange resin column for elution, wherein the acid washing and elution flow rate is 0.5 m/h, the pH of the effluent liquid is gradually reduced during elution, and the eluate is collected when the pH is reduced to 3.2. pH: 1-1.5 times of the total amount of the components are high fraction of lactic acid, then continuously sampling and detecting chloride ions in effluent, and gradually reducing the flow rate of elution. Elution was stopped as soon as chloride was found in the effluent. The acid elution can be carried out by introducing hydrochloric acid solution in a multi-column series connection mode. The lactic acid solution obtained by acid elution has most of the impurities removed.
And (3) ejecting redundant hydrochloric acid out of the weak base anion exchange resin column by using water, washing the column to the pH value of about 5.0, and regenerating by using ammonia water with the mass concentration of 20% and the volume of 2-3 times of the resin so that the resin can be recovered and reused in the adsorption process.
(8) Removal of Cl-、SO4 2-And oxalate radicals: subjecting the lactic acid solution to 2 m/h chromatography with strongly basic anion exchange resin to induce Cl precipitation under acidic condition-、SO4 2-The absorption of the heteropolyacid ions such as oxalate radical is strong, but the lactate is hardly absorbed, even if the lactate is absorbed by a small amount, the lactate is also absorbed by the Cl contained in the subsequent lactic acid liquid-、SO4 2-By substitution with oxalate ions, Cl can be removed-、SO4 2-And a heteropolyacid ion such as an oxalate group.
(9) Cation removal and decoloration: and (2) carrying out 2 m/h flow rate on the lactic acid solution subjected to the strong-base anion exchange resin column to remove impurities such as cations, proteins and pigments through a cation exchange resin column and a granular carbon decolorizing column, carrying out cation removal on the lactic acid solution through the cation exchange resin column, such as calcium ions, and decolorizing the effluent through the granular carbon decolorizing column to obtain a pure lactic acid solution.
Example 3
A method for extracting lactic acid from heavy phase lactic acid is shown in figure 1, and comprises the following steps:
(1) diluting: the heavy phase lactic acid is diluted to a lactic acid solution with the mass percent of 35% by pure water.
(2) Acid hydrolysis: pumping the diluted heavy-phase lactic acid solution into a reaction kettle by using a centrifugal pump for acidolysis (the amount of added sulfuric acid is 4 per mill of the feeding mass of the heavy-phase lactic acid solution, the concentration of the sulfuric acid is 98%), stirring and heating to 120 ℃, keeping the temperature for two hours after the acid addition is finished, and cooling to 80 ℃. The addition of acid can decompose the polymerized lactic acid.
(3) And (3) decoloring: adding powdered activated carbon with the mass of 5 per mill of the weight of the heavy phase lactic acid solution, stirring and decoloring for 30 minutes.
(4) And (3) filtering: filtering out the powdered activated carbon by using a plate frame to obtain a decolored solution, wherein the decolored solution is shown in figure 3, and the color of the decolored solution is darker although the decolored solution is decolored by the activated carbon.
(5) Adsorption: sending the decolorized solution into a weak base anion exchange resin column at the flow speed of 4 m/h for adsorption, wherein the pH of the liquid which begins to flow out of the weak base anion exchange resin column is higher, and stopping feeding when the pH is gradually reduced to 2.8 so as to avoid the loss of lactic acid. The weakly basic anion exchange resin column for adsorption can adopt a multi-column series connection mode.
(6) Washing with water: and after adsorption is finished, feeding water into the weak-base anion exchange resin column for washing, beginning to recover lactic acid in water, discharging the lactic acid after no lactic acid is produced, and stopping washing until no pigment is produced by visual inspection.
(7) Acid elution: and after the water washing is finished, introducing a hydrochloric acid solution with the mass concentration of 12% into the weak-base anion exchange resin column for elution, wherein the acid washing and elution flow rate is 0.6 m/h, the pH of the effluent liquid is gradually reduced during elution, and the eluate is collected when the pH is reduced to 2.8. pH: 1-1.5 times of the total amount of the components are high fraction of lactic acid, then continuously sampling and detecting chloride ions in effluent, and gradually reducing the flow rate of elution. Elution was stopped as soon as chloride was found in the effluent. The acid elution can be carried out by introducing hydrochloric acid solution in a multi-column series connection mode. The lactic acid solution obtained by acid elution has most of the impurities removed.
And (3) ejecting redundant hydrochloric acid out of the weak base anion exchange resin column by using water, washing the column to the pH value of about 5.0, and regenerating the column by using ammonia water with the mass concentration of 30% and the volume of 2-3 times of that of the resin so that the resin can be recovered and reused in the adsorption process.
(8) Removal of Cl-、SO4 2-And oxalate radicals: subjecting the lactic acid solution obtained by acid elution to strong base anion exchange resin column at 2.5 m/h, subjecting Cl to strong base anion exchange resin column under acidic condition-、SO4 2-The absorption of the heteropolyacid ions such as oxalate radical is strong, but the lactate is hardly absorbed, even if the lactate is absorbed by a small amount, the lactate is also absorbed by the Cl contained in the subsequent lactic acid liquid-、SO4 2-By substitution with oxalate ions, Cl can be removed-、SO4 2-And a heteropolyacid ion such as an oxalate group.
(9) Cation removal and decoloration: and (2) carrying out 2.5 m/h flow rate on the lactic acid solution subjected to the strong-base anion exchange resin column to remove impurities such as cations, proteins and pigments through a cation exchange resin column and a granular carbon decolorizing column, carrying out cation removal on the lactic acid solution through the cation exchange resin column, such as calcium ions, and decolorizing the effluent through the granular carbon decolorizing column to obtain a pure lactic acid solution.
The quality index of the lactic acid solution obtained after the steps are finished can reach 15-25 percent, the purity is more than or equal to 99.2 percent, and the index of the final product after passing through an evaporator can reach more than or equal to 80 percent.
Example 4 a method for extracting lactic acid from heavy phase lactic acid, as shown in figure 1, comprises the following steps:
(1) diluting: the heavy phase lactic acid was diluted with pure water to a lactic acid solution of 25% by mass, and the heavy phase lactic acid material was very dark as shown in fig. 2.
(2) Acid hydrolysis: and (2) pumping the diluted heavy-phase lactic acid solution into a reaction kettle by using a centrifugal pump for acidolysis (the amount of added sulfuric acid is 5 per mill of the feeding mass of the heavy-phase lactic acid solution, the concentration of the sulfuric acid is 98%), stirring and heating to 120 ℃ after the acid addition is finished, keeping the temperature for two hours, cooling to 80 ℃, and adding acid to decompose the polymerized lactic acid.
(3) And (3) decoloring: adding powdered activated carbon with the weight of 3 per mill of the heavy-phase lactic acid solution, stirring and decoloring for 30 minutes.
(4) And (3) filtering: filtering out the powdered activated carbon by using a plate frame to obtain a decolored solution, wherein the decolored solution is shown in figure 3, and although the decolored solution is decolored by the activated carbon, the color is darker.
(5) Adsorption: sending the decolorized solution into a weak base anion exchange resin column at the flow speed of 4 m/h for adsorption, wherein the pH of the liquid flowing out of the weak base anion exchange resin column is higher, and stopping feeding when the pH is gradually reduced to 3.1 so as to avoid the loss of lactic acid. The weakly basic anion exchange resin column for adsorption can adopt a multi-column series connection mode.
(6) Washing with water: and after adsorption is finished, feeding water into the weak-base anion exchange resin column for washing, beginning to recover lactic acid in water, discharging the lactic acid after no lactic acid is produced, and stopping washing until no pigment is produced by visual inspection.
(7) Acid elution: and introducing a hydrochloric acid solution with the mass concentration of 15% into the weak-base anion exchange resin column for elution, wherein the pickling and stripping flow rate is 0.7 m/h, the pH of an effluent liquid is gradually reduced during elution, and when the pH is reduced to 3.1, an eluate is collected, wherein the pH is: 1-1.5 times of the total amount of the components are high fraction of lactic acid, then continuously sampling and detecting chloride ions in effluent, and gradually reducing the flow rate of elution. Once the effluent liquid finds chloride ions, the elution is stopped immediately, acid elution can be carried out by introducing hydrochloric acid solution in a multi-column series mode, most impurities are removed from the lactic acid solution obtained by acid elution, and the color of the lactic acid solution is light as shown in figure 4.
And (3) ejecting redundant hydrochloric acid out of the weak base anion exchange resin column by using water, washing the column to the pH value of about 5.0, and regenerating by using ammonia water with the mass concentration of 25% and the volume of 2-3 times of the resin so that the resin can be recovered and reused in the adsorption process.
(8) Removal of Cl-、SO4 2-And oxalate radicals: subjecting the lactic acid solution obtained by acid elution to strong base anion exchange resin column at 2.8 m/h, subjecting Cl to strong base anion exchange resin column under acidic condition-、SO4 2-The absorption of the heteropolyacid ions such as oxalate radical is strong, but the lactate is hardly absorbed, even if the lactate is absorbed by a small amount, the lactate is also absorbed by the Cl contained in the subsequent lactic acid liquid-、SO4 2-By substitution with oxalate ions, Cl can be removed-、SO4 2-And a heteropolyacid ion such as an oxalate group.
(9) Cation removal and decoloration: and (2) carrying out high-speed ethanol distillation on the lactic acid solution after passing through the strong-base anion exchange resin column at the flow rate of 2.8 m/h through a cation exchange resin column and a granular carbon decolorizing column to remove impurities such as cations, proteins and pigments, carrying out high-speed ethanol distillation on the lactic acid solution after passing through the cation exchange resin column to remove cations such as calcium ions, and decolorizing the filtrate through the granular carbon decolorizing column to obtain a pure lactic acid solution, wherein the pure lactic acid solution is shown in fig. 5.
The lactic acid solution obtained after the steps can reach the quality index, the mass concentration is 15-25%, the purity is more than or equal to 99.2%, and the index of the final product after passing through an evaporator can reach the mass concentration more than or equal to 80%.
Comparative example 1
The heavy phase lactic acid is decolorized, which comprises the following steps:
(1) diluting: diluting the heavy-phase lactic acid subjected to primary molecular distillation with pure water to obtain a lactic acid solution with the mass percentage of 25%; (2) acid hydrolysis: pumping the diluted heavy-phase lactic acid solution into a reaction kettle by a centrifugal pump for acidolysis (the amount of the added sulfuric acid is preferably 5 per mill of the feeding mass of the heavy-phase lactic acid solution), stirring and heating to 120 ℃, keeping the temperature for two hours after the acid addition is finished, and cooling to 80 ℃. The polymerized lactic acid can be decomposed by adding acid;
(3) and (3) decoloring: adding powdered activated carbon with the weight of 3 per mill of the heavy-phase lactic acid solution, stirring and decoloring for 30 minutes;
(4) and (3) filtering: filtering out the powdered activated carbon by using a plate frame to obtain a decolorized lactic acid solution.
TABLE 1 comparison table of product index after heavy phase lactic acid purification
Figure 381832DEST_PATH_IMAGE001
As can be seen from the above table, the heavy phase lactic acid of comparative example 1 is not subjected to the subsequent ion exchange treatment, and each index is far higher than that of examples 1-4, and the requirement of refining lactic acid cannot be met.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made on the basis of the technical solutions of the present invention should be included in the scope of the present invention.

Claims (10)

1. A method for extracting lactic acid from heavy-phase lactic acid is characterized by comprising the following steps:
(1) diluting the heavy phase lactic acid to 20-35% by mass of lactic acid;
(2) carrying out acidolysis on the diluted heavy-phase lactic acid solution;
(3) carrying out lactate adsorption on the heavy phase lactic acid solution subjected to acidolysis by adopting a weak-base anion exchange resin column;
(4) washing the weak-base anion exchange resin column adsorbed with lactate with water;
(5) carrying out acid elution on the washed weak-base anion exchange resin column by using a hydrochloric acid solution, and collecting eluent;
(6) passing the eluate through strongly basic anion exchange resin column to remove Cl-、SO4 2-And oxalate radicals;
(7) sending the solution passing through the strong-base anion exchange resin column into a cation exchange resin column and a granular carbon decolorizing column to obtain pure lactic acid solution.
2. The method for extracting lactic acid from heavy-phase lactic acid according to claim 1, wherein the amount of the sulfuric acid solution added during acid hydrolysis is 1 to 5 per mill of the mass of the heavy-phase lactic acid solution feed, and the concentration of the sulfuric acid solution is 98%.
3. The method for extracting lactic acid from heavy-phase lactic acid according to claim 1, wherein the pH of the liquid flowing out of the column of weakly basic anion exchange resin is measured while adsorbing the lactic acid solution by the column of weakly basic anion exchange resin, and the feeding is stopped when the pH is lowered to 3 ± 0.2.
4. The method of claim 3, wherein the liquid is recovered from the column of weakly basic anion exchange resin, the content of lactic acid in the liquid is measured, and the liquid is not recovered after the content of lactic acid is 0.
5. The method for extracting lactic acid from heavy-phase lactic acid according to claim 3, wherein the weak-base anion exchange resin column is washed with water, the color of the liquid is observed, and the washing with water is stopped after visual inspection of the absence of the coloring matter.
6. The method for extracting lactic acid from heavy-phase lactic acid according to claim 1, wherein the pH of the eluate is measured when the weak base anion exchange resin column after water washing is eluted with hydrochloric acid solution, the eluate is collected when the pH drops to 3 ± 0.2, and the presence of chloride ions in the eluate is measured, and the elution is stopped when chloride ions are present.
7. The method for extracting lactic acid from heavy-phase lactic acid according to claim 1, wherein the heavy-phase lactic acid solution is decolorized before being fed to the weak base anion exchange resin column.
8. The method for extracting lactic acid from heavy-phase lactic acid according to claim 7, wherein the decolored solution of the heavy-phase lactic acid is obtained by stirring powdered activated carbon, decoloring and filtering with a plate frame.
9. The method for extracting lactic acid from heavy phase lactic acid according to claim 1, wherein the heavy phase lactic acid solution is loaded onto the weak base anion exchange resin column for adsorption at a flow rate of 3-5 m/h.
10. The method for extracting lactic acid from heavy-phase lactic acid according to claim 1, wherein the washed weak base anion exchange resin column is eluted with 10% -15% by mass hydrochloric acid solution.
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