TWI432580B - Process for the purification of organic acids - Google Patents

Description

Organic acid purification method

The present invention relates to a method for recovering and purifying organic acids having high heat stability, and more particularly to a method for recovering and purifying lactic acid having high heat stability from a fermentation broth containing lactic acid using a membrane technique.

Since organic acids such as lactic acid, citric acid, ascorbic acid, gluconic acid or fumaric acid are widely used in food, pharmaceutical, detergent or biodegradable plastics industries, the demand for organic acids is increasing year by year. The fermentation process allows the production of organic acids to reach an industrial scale. The organic acid produced by the fermentation process is substantially in the form of a salt depending on the pH requirements of the bacterial strain used. The recovery of organic acids from fermentation broths is a challenge for separation experts.

Conventional methods for recovering and purifying organic acids from fermentation broth generally comprise one or several precipitation stages. For example, in a known method of producing lactic acid, the fermentation broth is usually heated to about 70 ° C to kill the bacteria and then acidified to pH 1.8 with sulfuric acid. The precipitated salt was removed by filtration, and then any colorant in the product liquid was removed using activated carbon treatment, and then the clear liquid was ion-exchanged and concentrated to 80%. The odor and taste can be further improved by oxidation treatment (for example with hydrogen peroxide). The lactic acid obtained at this stage is usually only a consumable quality, not suitable for the pharmaceutical grade, and several additional purification steps are required to achieve the pharmaceutical grade. The biggest drawback of the traditional method is that there is a large amount of lactic acid lost.

In order to make the downstream treatment more environmentally friendly, alternative downstream treatment technologies have been studied. For example, it has been proposed to use electrodialysis membrane technology to recover and purify lactic acid. However, known electrodialysis membranes require high quality feeds, and require high currents due to rapid organic acid transport and relatively high operating costs due to the use of bipolar membranes in this process.

Another known organic acid purification technique is reactive liquid-to-liquid extraction in which an organic acid is extracted into an organic phase using a suitable carrier, followed by back extraction of the organic acid to an aqueous phase. US Patent No. 6,472,559 to Baniel et al. discloses the use of lactic acid phase transfer extraction from an aqueous phase to a water-insoluble amine organic phase in a high pressure carbon dioxide environment. After removal of the carbon dioxide environment, the lactic acid is back extracted into an aqueous phase. The disadvantage of this technique is the large amount of organic solvent used. In addition, it is often necessary to carry out further purification steps to remove impurities.

Liquid membrane separation is another technique used to purify organic acids. There are several liquid membranes made of different materials, such as liquid emulsion membranes, hollow fiber supported liquid membranes, and plate supported liquid membranes. The liquid film is subjected to liquid-liquid isolation of the source stream by an organic phase containing an active carrier to separate the organic acid, the organic acid is extracted into an organic phase, and then the organic phase is separated by a stripping solution to back-extract the organic acid. water box. The separation mechanism of the supported liquid membrane (SLM) is different from that of other membranes. Known membrane systems separate components by size, while supported liquid membranes extract the desired components by chemical means that assist in the delivery mechanism. The combination of the supported liquid membranes is essentially a liquid-liquid extraction. An important advantage of a supported liquid membrane over liquid-liquid extraction is that it requires very little organic solvent. However, the supported liquid membrane employed in practical industrial applications is limited by the stability (lifetime) of the supported liquid membrane because the solvent and/or carrier is lost to the aqueous phase. The water that is transported through the membrane plays an important role in disturbing the membrane. Therefore, there is a need for an improved method of using a supported liquid membrane to enhance the purification of organic acids.

According to a first aspect of the invention, a method for recovering and purifying an organic acid from a fermentation broth comprising a salt form of an organic acid comprises ultrafiltration or microfiltration of the fermentation broth to form a first permeate, the first permeate The liquid is concentrated to form a concentrated liquid, and the concentrated liquid is introduced into a supported liquid membrane to extract lactic acid to form a separated stream containing the extract, the extract is subjected to activated carbon treatment to remove the color, and the extract is subjected to cation exchange resin treatment for demineralization. And subjecting the extract to anion exchange resin treatment to remove anionic impurities to form a degraded organic acid, filtering the diluted organic acid to remove impurities exceeding a predetermined threshold value, and concentrating the diluted organic acid to a desired concentration .

From the above disclosure and the following more detailed description of the various preferred embodiments, the present invention clearly provides significant improvements in organic acid purification techniques for those skilled in the art. Of particular importance in this regard is the ability of the present invention to provide a method of making a thermally stable organic acid. Other features and advantages of the different preferred embodiments will be apparent from the following detailed description.

It is understood that the drawings are not necessarily to scale, The organic acid purification methods disclosed herein include, for example, specific design features of the specific dimensions of the devices used at different stages, some of which will be determined by the particular intended application and use environment. Some of the features of the illustrated embodiments are magnified or modified relative to others to provide a clear understanding. In particular, thin features such as can be thickened for clarity of illustration. All references to direction and position, unless otherwise indicated, refer to the orientation shown on the drawings.

For those skilled in the art (ie, those with knowledge or experience in this field), the organic acid purification methods disclosed herein are clearly applicable to a variety of uses and design changes. The following detailed discussion of various alternative features and examples will illustrate the general principles of the invention with respect to the purification of lactic acid. After reading this document, it will be apparent to those skilled in the art that other embodiments are suitable for other applications.

The invention discloses a method for recovering and purifying an organic acid (particularly lactic acid) from a fermentation broth. The process described herein is capable of accepting a lactic acid fermentation broth having any concentration greater than 1% lactate, particularly a lactic acid fermentation broth having a concentration of 8% or higher. Referring to the drawings, Figure 1 shows a schematic diagram of a process in which fermentation broth 1 is first fed into unit 3 via line 2. The fermentation broth may comprise an organic acid such as lactic acid, and may be in the form of a salt of an organic acid such as lactate. The device 3 is preferably, for example, a membrane of the microfiltration membrane 6 or the ultrafiltration membrane 3, or both. The ultrafiltration membrane has a filter pore size of 0.1 to 0.01 micrometers, and the ultrafiltration membrane may have several structural forms such as a hollow fiber, a tubular, a flat plate or a spiral wound unit. In one form, a hollow fiber membrane is used which provides an excellent surface area to volume ratio. The ultrafiltration membrane of the present invention can be made of a polymeric, ceramic or metallic material. The ultrafiltration membrane acts as a barrier to the suspension of suspended solids, biomass, and bacteria. The filtration method to be combined with the ultrafiltration membrane may be a cross flow method or an end point method. In cross-flow filtration, the operating stream is parallel to the membrane, and in the endpoint filtration, the operating stream flows vertically with the membrane. Compared to the endpoint filtration method, only a portion of the fermentation broth penetrates the membrane in the cross-flow filtration. The fermentation broth flowing parallel to the membrane has sufficient velocity to flush the retained particles away from the surface. This continuous sweeping action minimizes the accumulation of particles on the surface of the film, thereby extending the operational life of the film. In this cross-flow process, the ultrafiltration membrane is capable of recovering about 30 to 99% of the desired organic acid recovery from the fermentation broth, particularly 60 to 95% of the desired organic acid recovery.

To recover a higher organic acid from the fermentation broth, the concentrate from unit 3 enters microfiltration membrane unit 6 via line 5, and residual particulates and/or precipitates in the concentrate are removed from the microfiltration membrane. The microfiltration membrane has pores of 0.1 to 1 micron size. The apparatus 6 is capable of recovering about 50 to 90% of the organic acid from the fermentation broth, which increases the total recovery of the organic acid of the fermentation broth (both ultrafiltration and microfiltration) to about 90 to 99%. Further recovery of lactic acid can be achieved by microfiltration (MF) lactic acid fermentation broth with water addition. This method is called percolation. The combination of microfiltration and diafiltration is used to increase the recovery of lactic acid. The microfiltration membrane can be of several structural forms, such as hollow fiber, tubular, flat or spiral wound units, and comprises polymeric, ceramic or metallic materials. In another embodiment, the microfiltration-diafiltration combination can be used directly to purify the fermentation broth to achieve more than 99% lactic acid recovery without ultrafiltration of the fermentation broth. The first step obtained is the first permeate.

Figure 2 shows the next step of the process where the recovery/extraction rate can be enhanced by concentrating the lactic acid from the first permeate to form a concentrate. The first permeate is concentrated to a concentrate using an evaporator 9, especially in the concentrate having an organic acid content of 20 to 60%, and more particularly a content of 30 to 55%. The distillate obtained after the evaporation treatment generally contains less than 0.5% of the lactate. The distillate is almost water with some volatile organic carbons (VOCs) and traces of lactic acid, which can be easily clarified via line 10 through an activated carbon column (device 11 as shown in Figure 2) to produce primary quality water. 67. Alternatively, the distillate can be reused in the fermentation broth.

Where the initial pH of the fermentation broth is higher than its enzyme activating factor (pKa) (e.g., lactic acid pKa = 3.86), the concentrate requires an additional acidification step. The acidifying agent 14 (shown in Figure 2) suitable for use in the present invention is a mineral acid such as hydrochloric acid or sulfuric acid. Because sulfuric acid does not carry too much smoke and moisture, the use of sulfuric acid does not cause excessive reduction in lactate concentration. The purpose of acidification is to convert the organic acid salt in the fermentation broth into an organic acid. In general, pH is a controlling factor for adjustment. The fermentation broth typically has a pH of from 5 to 6.5 and should be adjusted to a lower pKa than the organic acid, particularly from 1.5 to 3.8, more preferably from 2 to 3.6. If the fermentation broth has reached a low pH, no further acidification is required to produce an acidified liquid. The amount of acidifying agent 14 required depends on the initial pH of the fermentation broth. When the fermentation broth is cooled in the tank 13, the inorganic salt 19 may precipitate from the solution, and the inorganic salt 19 formed depends on the alkali and acidifying agent 14 used to control the pH of the fermentation during the fermentation. For example, if ammonium hydroxide is used to control the fermentation pH and acidified using sulfuric acid, the inorganic salt 19 formed will be ammonium sulfate. Another reason why sulfuric acid is a preferred acidifying agent is that sulfates are generally easier to precipitate than other acidifying agents. The reaction formula 1 shows an example of a reaction which occurs when sulfuric acid is introduced into a solution containing lactate.

Reaction formula 1: Hydrochloric acid is converted into lactic acid by sulfuric acid

2 LacNH ₄ +H ₂ SO ₄ →2 LacH+(NH ₄ ) ₂ SO ₄

The acidification process of the acidic liquid by the addition of an acid is exothermic, so it generates heat and causes an increase in the temperature of the solution. After the solution is cooled to about 50 ° C (preferably 25 ° C), the salt precipitates. In the above examples, ammonium sulfate will begin to precipitate. When the solution was cooled to room temperature (25 ° C), a large amount of sulfate precipitated crystals. In fermentation, the lactate may be calcium lactate, sodium lactate or ammonium lactate. During acidification using sulfuric acid, the corresponding sulfate will be produced. If any salts are formed during this process, they can be filtered out using, for example, a centrifuge. In general, if (i) the initial fermentation broth has a pH of 5 or higher (in sodium lactate or ammonium lactate); (ii) sulfuric acid as an acidifying agent; and (iii) during the step of concentrating the first permeate, The concentration of the fermentation broth has increased to more than 20% and there will be considerable salt formation. The salt can be effectively separated from the fermentation broth by means of a device 17, which can be a filter press or any other solid-liquid separator. The remaining steps of the method are preferably carried out in close proximity to environmental conditions.

The (filtered, acidified and) concentrated liquid can be filtered as described above. Concentrates generally contain low levels of suspended solids. The concentrate may be a clear liquid or a dark viscous liquid containing more than 20% (particularly 20 to 65% lactic acid concentration) of lactic acid, depending on the concentration of lactic acid to be recovered. This concentrate is transferred to the tank 21 shown in Figures 2-4. When the filtered acidified fermentation broth 20 is fed into the apparatus 23, lactic acid recovery will be performed as shown in FIG. The means 23 for extracting lactic acid from the acidified concentrate is referred to as a supported liquid membrane (SLM).

The supported liquid film 23 contains an organic layer composed of a suitable component, which is impregnated on another film (base film), such as a membrane of the ultrafiltration (UF) or microfiltration (MF) type. A microfiltration membrane is used in one form because of its high density of pore regions. The base film used in the supported liquid film has hydrophobic properties and may comprise a hydrophobic polymer such as polypropylene (PP), polyethylene difluoride (PVDF), and polyethylene (PE), or, for example, polyfluorene (PSF), An amphoteric polymer of polyether oxime (PES) and polyethylene sulfite (PVS). Hydrophobic polymers are generally suitable base film materials; polypropylene polymers are used in the most preferred form because of their high hydrophobicity, relatively low cost, excellent mechanical properties and excellent chemical stability.

The supported liquid film 23 has an organic layer immersed in the base film, which stabilizes the base film by the pinning of the pores (here, micropores) of the film during the harsh operation. The organic layer comprises four components: a carrier, a co-extractant, a diluent and a stabilizer. The carrier comprises a water-insoluble amine, especially a first, second, third aliphatic or aromatic amine, preferably an amine comprising at least one alkyl chain having from C _{4 to} C ₂₄ . In a more preferred form, the third carrier is an aliphatic amine alkyl chain of C ₈ -C _12.

The co-extractant assists a liquid of the carrier in the organic acid extraction process, and the co-extractant may comprise an aliphatic alcohol having a small amount of water solubility, particularly an alcohol having a C ₂ -C ₂₉ carbon chain, more particularly An alcohol containing a C ₆ -C ₁₀ carbon chain. The functionality of the alcohol can be at the end of the carbon chain (n-alcohol) or in the branch. The co-extractant may comprise, for example, a C ₈ -C ₁₀ normal chain alcohol or a C ₆ -C ₉ branched alcohol.

A diluent is added to the organic layer to dilute the concentration of the carrier to increase the viscosity of the carrier to aid in the extraction rate. In general, any organic liquid that is compatible with the base film but not water compatible can be used. Suitable diluents include hydrocarbons, ketones, ethers or esters. Suitable hydrocarbons may include, for example, kerosene, methyl isobutyl ketone, monoisobutyl ketone, and butyl acetate. After reading this document, it will be apparent to those skilled in the art that other suitable diluents are available.

The stabilizer helps to stabilize the organic component (ie, the extractant, co-extractant, and diluent in the base film). The service life of a supported liquid membrane depends on the rate of loss of the organic component in its environment, ie, the aqueous phase. In conventional supported liquid membranes, losses occur within a few hours. The stabilizers described herein are a nonionic surfactant having very low water solubility and low water surface tension, depending on the highly desirable characteristics. The stabilizer acts as a barrier between the organic phase and the aqueous phase in the organic component, thereby reducing the mixing of the two phases.

Stabilizers suitable for use in the present invention have three main groups which are: hydrocarbyl, sulfhydryl and fluorocarbon based stabilizers. The nonionic surfactant is a fluorocarbon based group. Nonionic surfactants are in the form of surfactants without an ionic head group. The hydrophilic group of the fluorocarbon-based surfactant is a group of nonionic carboxylates and therefore has very little water solubility. The tail group of the fluorocarbon-based surfactant is hydrophobic and lipophilic. This ensures that the stabilizer will remain primarily in the solvent-water interface. The boundary created by the fluorocarbon-based surfactant will limit the mixing of the water within the membrane with the organic solution, thereby reducing the moisture transport through the membrane, thus extending the stability of the supported liquid membrane. The nonionic nature of the surfactant also serves as an additional barrier to the ionic species, thus improving the selectivity of the membrane for organic acids. In contrast, surfactants are less obstructive to organic acids in the acid form, while organic acids such as sulfuric acid and hydrochloric acid are completely ionized in aqueous media and are thus restricted from entering the liquid film phase (because moisture transport is limited) ), which results in better selectivity between organic and inorganic acids. In a typical experimental setup with a liquid film composition of 0.01% stabilizer, the selectivity of the organic acid relative to the mineral acid can be as high as several thousand times.

Likewise, the limitation of water-liquid membrane interaction also reduces the transport of glucose across the membrane. The stability of the supported liquid film of the present invention comprising suitable selection of the above extractant, co-extractant and diluent is over 180 days. In general, from 0.001 to 10% stabilizer can be added, and a high amount of stabilizer makes the film more stable but has a low extraction rate. The optimum stabilizer concentration is from 0.005 to 0.020 ppm. The fluorocarbon-based nonionic surfactant has the general structure of R _f CH ₂ CH ₂ O(CH ₂ CH ₂ O) _x H, where x is a number from 0-25, and R _f is The fluorocarbon group F(CF ₂ CF ₂ ) _y , _y in the formula is 1 to 20.

The carrier, co-extractant, diluent and stabilizer are mixed into a homogeneous phase prior to being impregnated into the pores of the base film. The base film is formed into a hollow fiber structure. The device 23 allows a stream to flow along the lumen of the fiber while another stream flows along the sheath side of the fiber. A more preferred configuration is to cause the source solution to flow along the sheath side and a receiving solution (also known as a stripping solution) to flow along the lumen. The two solutions are recirculated along their respective sides: the source solution enters device 23 along line 22 (as shown in Figure 3) and carries the solution back to tank 21 along line 24; the receiving solution is transported along line 26 into device 23 The solution is brought back to the support tank 25 along line 27. The pH of the source phase is maintained below the pKa by the acid 28 through the dose line 29, for example 1.5 to 3.6 for the lactic acid solution. Acid 28 is generally the same as acidifier 14. The receiving solution may be just water or a chemical containing, for example, hydrochloric acid or sodium carbonate. The best receiving solution is pure water as this will reduce the effect of polishing at a later stage. The extraction method comprises:

(I) Protonation of organic acids and carriers

[R ₃ N] _org +[LacH] _aq [R ₃ NH ⁺ Lac ^- ] _org

During protonation, the organic acid binds to the amine

(II) Lactic acid is transferred to the receiving solution side through the organic layer.

The lactate amine complex is transported from the source solution side through the organic layer to the receiving solution side. The transport mechanism is the diffusion of the complex or the jump of the lactate molecule:

[R ₃ NH ⁺ Lac ^- ] _org +[R ₃ N'] [R ₃ N'H ⁺ Lac ^- ] _org +[R ₃ N]

N' in the equation is close to the receiving end and at the receiving end;

(III) Deprotonation of amines

The lactic acid (or generally organic acid) is transferred from the source solution to the receiving solution.

The ratio of the amount of the source solution to the amount of the receiving solution is preferably from 1:1 to 8:1, and more preferably from 1:1 to 4:1. Part of the extraction time is determined by the ratio of source to receiver, organic acid concentration, and extraction device (ie, the supported liquid membrane). When the source phase organic concentration is more than 20% compared to the receiving phase concentration, the extraction process should be stopped because the extraction rate will be too slow. The receiving solution should be collected for further processing. A fresh receiving phase is circulated through the system to further extract lactic acid. After several extractions, the source solution contains less than 8% lactic acid, which would be unsuitable for extraction because the extraction rate would become too slow. In one embodiment, the source to receiver ratio is 2:1 and the source phase lactic acid concentration is initially 48%; the source solution lactate concentration is reduced to 7 to 10% after every 3 to 5 hours of 6 rounds of extraction. . The average lactic acid concentration in the receiving solution is 1 to 15%. A unique advantage of this device 23 is the high selectivity of the organic acid. Usually, the amount of glucose in the receiving solution is not significant, which is a raw material for lactic acid fermentation. Because lactic acid has been extracted into a clean solution, the color of the receiving phase is low relative to the source solution. Compared to the clarified fermentation liquid phase (after ultrafiltration/microfiltration), the color may be reduced by 50 to 500 times. The highly selective nature of the supported liquid membrane ensures that the receiving phase contains minimal ionic impurities and is virtually independent of the source phase ionic impurity concentration. In a preferred apparatus implementation comprising an initial source of 48% lactate, pH 3.2, 4.0-4.5% ammonium, 10-20% sulfate, the receiving solution should comprise 0.0001-0.05% ammonium and 0.0001-0.04% sulfuric acid. salt.

In order to increase the recovery rate, the concentrated solution is sent to another evaporator 31 through line 30 for further concentration. The evaporation capacity of the device 31 is about 5 to 8 times smaller than that of the device 9, and the discharge of the device 31 may include 15-60%. The lactic acid is generally about 30-50%. Since the ammonium sulfate contained in the solution is close to the saturation point, ammonium sulfate is precipitated during concentration, especially when the concentration exceeds 40%. The concentrate is filtered in the same manner as previously described, passed through line 33 into a cooling bath 34, and passed through line 35 to a filter press or any suitable solid-liquid separation device 36 to obtain a clean collection in tank 40. The concentrate and the ammonium sulfate crystals in 38 or any carbonized precipitate. In this filtration step, since the concentrate is already at a low pH, no further pre-acidification is necessary. The clarified concentrate in tank 40 is then subjected to lactic acid extraction using the same extraction method of apparatus 23 described above using a supported liquid membrane of apparatus 42. Before the fermentation broth solution is introduced into the apparatus 31 for further concentration, the formed solution can be disposed of or fed through the line 49 to the apparatus 50 for further ultrafiltration.

All of the received extract from the supported liquid membrane process (collected in tanks 25 and 44) is combined into a liquid stream containing some of the compounds that will color the extract. The combined stream is fed to an activated carbon column unit 54 (as shown in Figure 7) where the color of the solution is attenuated by introducing activated carbon into the extract. Activated carbon is combined with the colored compounds and removed from the extract.

As shown in Figure 7, the decolorized extract from the apparatus 54 can be introduced into the apparatus 69 through line 68 for concentration. In general, the apparatus 69 can be any apparatus capable of concentrating the organic acid from the fermentation broth solution, particularly concentrating the feed solution from as low as 0.05% to a concentration of up to 50%, preferably in a preferred embodiment. In the example, the concentration is concentrated from a feed concentration of 1-8% to an output concentration of up to 8-10%. In the preferred embodiment, device 69 is a polymeric membrane that, in its mode of operation, only allows water in the extract to flow through the membrane. The water tolerance of device 69 can be pressure driven, vacuum driven, and/or thermally driven. In the preferred embodiment, a reverse osmosis (RO) membrane (a pressure driven membrane) is used in apparatus 69, and the use of apparatus 69 can concentrate the extract to a higher concentration with lower energy costs than conventional evaporation apparatus. Preconcentration of device 69 effectively reduces the volume that the device needs to handle in subsequent steps. The water removed by the device 69 can be introduced into the devices 25 and 44 as the source of the fermentation broth or other desired location. Alternatively, the concentration step can be carried out prior to the decolorization step.

Whether or not further concentration is performed from device 69, the extract can then be introduced into a series of columns for polishing to improve quality. The series of desalination columns may comprise, for example, i) a cation exchange column (demineralization) for removing cationic impurities; ii) an anion exchange column for removing anionic impurities; iii) a desalinated decolorizing resin or activated carbon column for decolorization . Although in a preferred embodiment, the cation exchange column is preferably between the anion exchange columns, and the decolorizing or activated carbon column can be placed before, after or between the cation exchange column and the anion exchange column, the three columns can be optionally Operate in sequence.

The pre-concentrate from unit 69 and the decolorized fermentation broth from unit 54 are introduced into cation exchange column unit 56 via line 70 or line 55 to individually remove any traces of cationic impurities. In general, any strong cation exchange resin can be used in unit 56, and a macroporous type of cation exchange resin is an option. In addition to removing cationic impurities, the cation exchange column 56 further removes some or all of the color of the fermentation broth. The demineralized lactic acid solution is then further treated by anion exchange unit 58 through line 57. All anion impurities are removed in the anion exchange unit 58. A weak anion exchange resin is required in device 58, and in one embodiment a macroporous type of resin is used.

The step of removing the color can be repeated if necessary. In addition, the concentration step can be repeated after cation exchange, anion exchange, and color removal. For example, although the extract from the anion exchange unit 58 is generally colorless, after any anion exchange in the process, the low level of color continues to exist and the effluent from the anion exchange column can be further permeable, for example, by desalination. A device 60 of resin or activated carbon is used for decolorization. Depending on the initial concentration, the product extract typically contains 7-12% lactic acid. If the concentration of the solution product is required to be less than 10%, it is advantageous to pass the solution through another concentration device 62. Device 62 can be similar to any particular device of device 69. In a preferred embodiment, another RO membrane can be used in device 62, which is capable of concentrating the solution to 11-15% lactic acid. Depending on the initial concentration and the concentration of the product, the water 63 removed by the device 62 may comprise from 0.1 to 6% lactic acid. The product extract contains 11-15% organic acid which is then purified by means of apparatus 72. Device 72 is a molecular weight cut-off separation device that removes large molecular weight impurities that may have passed above a predetermined threshold of all previous processes. Device 72 is preferably a nanofiltration membrane having a cutoff molecular weight (MWCO) of from 100 to 300 Daltons, more preferably having a MWCO of from 100 to 150 Daltons to purify the lactic acid. Device 72 allows lactic acid to pass through the membrane while retaining most of the impurities having a molecular weight above its MWCO, which improves the color value of the lactic acid solution when further concentrated to a higher concentration of more than 75%.

The permeate from unit 72 can then be further concentrated using a product evaporator (i.e., apparatus 75 as shown in Figure 8). The concentration factor of device 75 can be 20-40 times, typically 25-35 times. Concentrate 76 from device 75 can be directed to the product packaging. Concentrate 74 from device 72 can be vaporized through device 9 or 31 or returned to device 54 to increase the recovery of lactic acid, as shown in FIG. The desalted organic acid can be treated with an oxidizing agent such as hydrogen peroxide to produce a thermally stable organic acid, that is, an acid that is resistant to decolorization at high temperatures.

Figure 9 shows that the available equipment 11 treats the distillates from units 14, 28 and 75 to remove volatile organic carbons (VOCs) and traces of lactic acid to produce primary quality water 67. The amount of water 67 is generally sufficient to supplement 70-90% of the overall process requirements including equipment flushing. Alternatively, the distillate from units 14 and 28 can be used directly to prepare the fermentation broth, while the distillate from unit 75 can be used as a receiving solution for the supported liquid membrane.

The invention is further illustrated by the following examples, but these examples should not be construed as limiting the scope of the invention in any way.

Example 1 - Ultrafiltration

The 253 liter fermentation broth was circulated in an ultrafiltration membrane system having a feed pressure of 2 bar, which is a polyether fluorene-based hollow fiber membrane having an effective area of 3.5 m ² . The feed solution is fed into and flows within the chamber of the fiber. The discharge pressure is controlled at a pressure of 1.6 bar and the transmembrane pressure is 1.8 bar. The initial permeate flow rate was 1.9 liters/min and dropped to 0.5 liters/min after 86% recovery over 3 hours. The average liquidity is 19.5 LMH. The suspended solids in the original fermentation broth and in the first permeate were 3.88 g/liter and 0.005 g/liter, respectively, and the concentrate of the liquid had a suspended solid of 49.78 g/liter.

Example 2 - Microfiltration

A 16 liter ultrafiltration (UF) concentrate (i.e., a microfiltration (MF) feed) is circulated through a stainless steel microfiltration membrane having a titanium dioxide coating. The membrane had a pore size of 0.1 micron and the microfiltration feed had 49.78 grams per liter of suspended solids which was operated at a 3 bar transmembrane pressure with an average throughput of 80 LMH.

Example 3 - The first permeate is concentrated from 11% to 48%

100 liters of the first permeate was concentrated from 11% to 48%. The amount of concentrated concentrate recovered was 22.9 liters, while 77.1 liters were collected as distillate.

Example 4 - Acidification and crystallization of ammonium sulfate

A 77.2 liter concentrated solution containing 48.6% lactate was acidified to pH 3.2 from pH 5.6 with 13.8 kg of sulfuric acid. After acidification and cooling of the solution to 25 ° C, 6.1 kg (wet weight) of ammonium sulfate crystals were precipitated. After filtering off the ammonium sulfate crystals, 82.2 liters of the acidified liquid was recovered. The lactate recovery reached 99.5%.

Example 5 - Extraction of Lactic Acid with a Supported Liquid Membrane

A concentrated lactic acid liquid having a concentration of 40-48% lactate was extracted with a hollow fiber supported liquid membrane (SLM) having a membrane area of 70 m ² . The organic layer impregnated in the film contains 0.001 to 10% of a carrier, 99.9 to 90.0% of a co-extractant, and a diluent. Use water as the receiving liquid. The amount of the receiving liquid used is half of the starting source solution for each extraction, and the extraction is continued for 3 to 5 hours. The same method was scaled up to an industrial size module with an effective membrane area of 300 m ² .

Example 6 - Decolorization with activated carbon

A total of 77.2 liters of extract from the supported liquid membrane procedure was treated with an activated carbon column having a length of 1 m, a column diameter of 1.5 inches, and a weight of 0.8 kg of carbon.

Example 7 - Demineralization with strong cation exchange resin

A total of 82.2 liters of the extracted lactic acid solution which had been treated with activated carbon was treated with a macroporous strong cation exchange resin column having a length of 1 m, a diameter of 1.5 inches and a weight of 0.7 kg of resin.

Example 8 - Removal of anionic impurities by weak anion exchange resin

A total of 84.29 liters of demineralized lactic acid solution was treated with a macroporous weak anion exchange resin having a length of 1 m, a diameter of 1.5 inches and a weight of 0.6 kg of resin.

Example 9 - Nanofiltration membrane

The extracted lactic acid solution obtained from unit 62 (RO membrane) was passed through two different treatment routes: i) directly concentrated to 88 ± 5% via unit 75; ii) treated with apparatus 72 (evaporator), followed by apparatus 75 (evaporation) The permeate from device 72 (NF membrane) is concentrated.

Example 10 - Product Concentration

The 88 liter diluted and purified desalted lactic acid solution was concentrated to a concentration of 88% lactic acid.

Effect of stabilizers in supported liquid membranes

The stability of the liquid film is highly correlated with the transport of water through the membrane, and higher water transport will result in low stability. In the experimental case, water is generally transferred from the receiving liquid to the source solution. A two-new liquid membrane module made of the same batch of polymer substrate fibers was used. The organic layer impregnated in the microporous fibers has the same composition except for a nonionic surfactant having 0.001 to 0.02%. The same L-lactic acid fermentation broth source was used in these experiments.

Effect of hydrogen peroxide

The extract obtained from unit 72 (NF membrane) was subjected to i) hydrogen peroxide treatment; ii) without hydrogen peroxide treatment, followed by concentration to 88 ± 3% wt/wt lactic acid concentrate.

Thermal stability test

The 88% concentrated desalted lactic acid solution (45 MT) obtained by one of the above methods was subjected to a heat stability test at 195 ± 5 ° C at different times. The color of the final solution was measured.

Various modifications, additions, and other alternative embodiments are apparent to those skilled in the art. The embodiments discussed are chosen and described in order to provide a description of the embodiments of the present invention All changes and modifications are still within the scope of the invention when the scope of the appended claims is interpreted in a fair, legal, and equitable manner.

1. . . Fermentation liquid

2. . . Pipeline

3. . . Device

5. . . Pipeline

6. . . Device

9. . . Evaporator

10. . . Pipeline

11. . . Device

13. . . groove

14. . . Acidifier

17. . . Device

19. . . Inorganic salt

twenty one. . . groove

twenty two. . . Pipeline

twenty three. . . Device

twenty four. . . Pipeline

25. . . groove

26. . . Pipeline

27. . . Pipeline

28. . . acid

29. . . Dose line

30. . . Pipeline

31. . . Device

33. . . Pipeline

34. . . Cooling tank

35. . . Pipeline

36. . . Filter press

40. . . groove

42. . . Device

44. . . groove

49. . . Pipeline

50. . . Device

54. . . Device

55. . . Pipeline

56. . . Device

57. . . Pipeline

58. . . Device

60. . . Device

62. . . Device

63. . . water

67. . . water

68. . . Pipeline

69. . . Device

70. . . Pipeline

72. . . Device

74. . . Concentrate

75. . . Device

76. . . Concentrate

1 shows a schematic diagram of a method of filtering a raw fermentation broth according to an embodiment.

Figure 2 shows a schematic of a major process fluid concentration stage.

Figure 3 shows a schematic of a primary supported liquid membrane stage.

Figure 4 shows a schematic of a support process fluid concentration stage.

Figure 5 shows a schematic of an auxiliary supported liquid film stage.

Figure 6 shows a schematic of an auxiliary ultrafiltration stage.

Figure 7 shows a schematic of a fade phase.

Figure 8 shows a schematic of the product evaporation stage with a micro-nanofiltration desalination stage.

Figure 9 shows a schematic of the water recovery stage.

Figure 10 shows a schematic of the flow design of a supported liquid membrane.

Figure 11 shows a schematic diagram of an extraction method of a supported liquid membrane.

Figure 12 shows a schematic of the recycling step of a higher recovery organic acid.

1. . . Fermentation liquid

2. . . Pipeline

3. . . Device

5. . . Pipeline

6. . . Device

9. . . Evaporator

Claims (21)

A method for recovering and purifying an organic acid from a fermentation broth comprising a salt form of an organic acid, the method comprising the steps of: a. performing one of ultrafiltration and microfiltration of the fermentation broth to form a first permeate b. concentrating the first permeate to form a concentrate; c. introducing the concentrate into a supported liquid membrane to extract an organic acid to form a separated stream comprising the extract; d. subjecting the extract to activated carbon treatment Removing the color, subjecting the extract to cation exchange resin treatment for demineralization, and subjecting the extract to anion exchange resin treatment to remove anionic impurities to form a degraded organic acid; e. using a nanofiltration membrane to fade the product The organic acid is filtered to remove impurities exceeding a predetermined threshold, wherein the predetermined threshold is 100-300 Daltons; f. concentrating the diluted organic acid to a desired concentration; wherein the organic acid is lactic acid; The supported liquid film comprises a base film and an organic layer impregnated on the pores of the base film; and wherein the organic layer comprises a carrier, a co-extractant, a diluent and a stabilizer. According to the method of claim 1, wherein the stabilizer is a A nonionic surfactant in the form of an ethoxylated fluorocarbon based. The method of claim 1, wherein the carrier comprises one of a first aliphatic, a second aliphatic, a third aliphatic, and an aromatic amine. The method of claim 1, wherein the co-extractant is an aliphatic alcohol. The method of claim 1, wherein the diluent comprises one of a hydrocarbon, a ketone, an ether, and an ester. The method of claim 3, wherein the amine has one or more branched, linear, and cyclic C ₄ -C ₂₄ side chains. The method of claim 4, wherein the aliphatic alcohol comprises one of a C ₂ -C ₂₉ chain and a branch. The method of claim 1, wherein the base film comprises one of polypropylene, polyethylene, polyethylene difluoride, polyether oxime, and polyfluorene. The method of claim 1, wherein the supported liquid film has a hollow fiber structure defining two sides, wherein one side is an organic phase and the other side is an aqueous phase. The method of claim 9, wherein the organic phase comprises two or more constituents. The method of claim 1, wherein the ultrafiltration membrane has a pore size in the range of 0.1 to 0.01 μm, and the microfiltration membrane has a pore size in the range of 0.04 to 1 μm. According to the method of claim 1, further comprising water or The step of feeding the water mixed with the solute into the supported liquid membrane of step (c). The method of claim 1, wherein the step of subjecting the extract to a cation exchange resin treatment is preceded by the step of subjecting the extract to an anion exchange resin treatment. The method of claim 1, further comprising the step of acidifying the concentrate to a pH of from 1 to 4.8 and separating the salt from the concentrate prior to introducing the concentrate into the supported liquid membrane. The method of claim 14, further comprising the step of separating the precipitate by filtration prior to introducing the concentrate into the supported liquid membrane. The method of claim 1, further comprising the step of treating the desalted organic acid with an oxidizing agent. The method of claim 1, further comprising the step of concentrating the extract after introducing the concentrate into the supported liquid membrane and before filtering the desalted organic acid to remove impurities exceeding a predetermined threshold . The method of claim 17, wherein the step of concentrating the extract is performed using a reverse osmosis membrane that only allows water of the extract to flow through the membrane. The method according to claim 17, further comprising the step of subjecting the extract to an anion exchange resin treatment and after filtering the desalted organic acid to remove impurities exceeding a predetermined threshold The step of concentrating the liquid. The method of claim 1, wherein the predetermined threshold of the step (e) is 100-150 Daltons. The method of claim 16, wherein the oxidizing agent is hydrogen peroxide.