Method for refining long-chain dicarboxylic acid in fermentation liquor by using aqueous phase
Technical Field
The invention belongs to the technical field of biochemical engineering, and particularly relates to a method for refining long-chain dicarboxylic acid in fermentation liquor by using a water phase.
Background
The long-chain dicarboxylic acid refers to aliphatic dicarboxylic acid (DCn or DCA for short) containing more than 10 carbon atoms in a carbon chain, and the aliphatic dicarboxylic acid comprises saturated and unsaturated dicarboxylic acid, is a fine chemical product with important and wide industrial application, and is an important raw material for synthesizing high-grade perfume, high-performance nylon engineering plastics, high-grade nylon hot melt adhesives, high-temperature dielectrics, high-grade paints and coatings, high-grade lubricating oil, cold-resistant plasticizers, resins, medicines, pesticides and the like in the chemical industry.
The long-chain dicarboxylic acid is prepared by taking alkane as a substrate and adopting a microbial transformation mode, and the fermentation liquor has complex components and mainly comprises thalli, proteins, macromolecular pigments, inorganic salts and other intermediate metabolites besides the dicarboxylic acid. The long-chain dicarboxylic acid is extracted from the fermentation broth, and generally subjected to unit operations such as demulsification, acid precipitation, filtration and the like, so that the process flow is complex, and the separation cost of the long-chain dicarboxylic acid accounts for a large proportion of the production cost.
At present, the separation and refining process of long-chain dicarboxylic acid mainly comprises a solvent method and a water phase method. The solvent method has the advantages of high cost due to the fact that a large amount of organic solvents are used, considerable solvent loss is caused by evaporation in the process, and the solvents are needed to be treated and recycled. The enterprises mainly producing long-chain dicarboxylic acid in China mostly use an acetic acid solvent refining process, but because of the strong corrosiveness of acetic acid, the process equipment investment and the solvent recycling treatment section have higher energy consumption, the process flow is complex, and the solvent hazard is larger.
The aqueous phase method for separating and refining dicarboxylic acid is carried out in a medium using water as a solvent. The method generally comprises the following treatment means: and (3) carrying out microfiltration and ultrafiltration on the dicarboxylic acid fermentation liquor, decolorizing and removing impurities by using active carbon, activated clay and the like, adding inorganic acid to precipitate dicarboxylic acid, and filtering, washing and drying to obtain a dicarboxylic acid product. The existing technology for refining and purifying dicarboxylic acid by an aqueous phase method has poor removal capability of water-soluble protein/protein pigment remained in fermentation liquor, and the heating operation in the latter half of the process can promote the oxidative denaturation of pigment/protein, and can be adsorbed in dicarboxylic acid crystallization crystals along with temperature drop, so that the quality of a final product is reduced. The aqueous refining and purifying technology has simple and safe process, less investment and no pollution, but needs to further improve the refining process to obtain high-quality long-chain dicarboxylic acid products.
Patent CN102911036a discloses a process for obtaining high purity dicarboxylic acids comprising: i, heating and inactivating the fermentation stopping liquid; II, acidifying to crystallize and separate out the dicarboxylic acid, and filtering to obtain a dicarboxylic acid filter cake; III, mixing the dicarboxylic acid filter cake with an ether solvent to dissolve dicarboxylic acid, and separating an organic phase from a water phase, wherein the ether solvent is diethyl ether, propyl ether, butyl ether, amyl ether or hexyl ether; IV, adding an adsorbent into the organic phase obtained in the step III, and filtering to remove solids; and V, cooling the organic phase obtained in the step IV until the dicarboxylic acid is crystallized and separated out, filtering to obtain a dicarboxylic acid crystal filter cake, and drying the dicarboxylic acid crystal filter cake to obtain a dicarboxylic acid product with the dicarboxylic acid purity of more than 98.5% by weight. The method is a solvent recrystallization method, the solvent consumption in the refining process is large, the solvent volatilization/evaporation amount is considerable, and the corresponding recovery mode occupies a certain cost in industrial scale-up. The product refined by the method contains solvent taste because the solvent is entrapped in the crystallization process, and no effective cleaning means is found at present.
CN108947809a discloses a method for extracting and refining long-chain dicarboxylic acid from fermentation broth, comprising (1) pretreatment of fermentation broth: adding an alkaline pH regulator into the fermentation broth to control the pH of the system in an alkaline range, and heating to promote dissolution of the intracellular long-chain dicarboxylic acid; (2) collecting fermentation clear liquid: filtering to obtain fermentation clear liquid after the treatment of the step (1), and taking a water phase clear liquid layer after standing and layering; (3) extracting and refining long-chain dicarboxylic acid: controlling the temperature of the clear liquid of the water phase to be 70-85 ℃, adding an organic solvent according to a proportion, heating to 80-90 ℃, then adding an acidic pH regulator to control the pH of the system to be in an acidic range, heating to 90-100 ℃, standing and layering to separate the water phase after long-chain dicarboxylic acid in the system is completely dissolved, and filtering and drying the organic phase to obtain a long-chain dicarboxylic acid refined product. According to the method, a state of mixing a water phase and an organic phase is formed in a system through the addition of an organic solvent, and then the long-chain dicarboxylic acid is directly transferred into the organic phase from the water phase by utilizing the pH change and temperature control of the system, so that the extraction process is completed in one reactor, the refining of the long-chain dicarboxylic acid can be realized by only one process unit, the refining process of the long-chain dicarboxylic acid from the liquid phase to the solid phase and from the solid crude acid to the organic extraction phase in the traditional process is simplified, the crude acid extraction process in the traditional process is reduced, the loss in the extraction process is reduced, and the operation steps and the yield are reduced. However, the dicarboxylic acid is finally extracted in the organic phase, the amount of organic solvent is relatively large, and a part of the dicarboxylic acid is lost with evaporation.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for refining long-chain dicarboxylic acid in fermentation liquor by using a water phase. Compared with the prior art, the invention is based on the aqueous phase method, and obtains the polymer grade product with high purity and low total nitrogen corresponding to the solvent method on the premise of low cost, low loss, environmental protection, safety, simple flow and the like.
The method for refining long-chain dicarboxylic acid in fermentation liquor in aqueous phase comprises the following steps:
(1) Pretreating long-chain dicarboxylic acid fermentation liquor to remove thalli and partial pigment;
(2) Adding alkali to regulate pH to not less than 8 and reacting for certain time;
(3) Adding a small amount of ether solvent, fully back mixing at 80-95 ℃, and standing for layering;
(4) Cutting out the lower water phase, acidifying at 80-95 deg.c, cooling, filtering, washing filter cake and stoving to obtain the product.
The long-chain dicarboxylic acid fermentation broth in the step (1) is fermentation broth obtained by fermenting microorganisms with alkane and the like to prepare long-chain dicarboxylic acid, wherein the long-chain dicarboxylic acid has a molecular formula of C n H 2n-2 O 4 Wherein n is 10 to 18.
The pretreatment of the fermentation broth in the step (1) adopts a method for removing thalli and pigment conventionally used in the field, for example, a method such as heating, filtering, decoloring and the like can be adopted, and specifically, the following steps can be adopted: heating the long-chain dicarboxylic acid fermentation liquor to 70-80 ℃, carrying out microfiltration, ultrafiltration and the like, and then carrying out active carbon decolorization and filtration to remove thalli and partial pigment.
And (3) adding alkali in the step (2) to adjust the pH value to be not less than 8, preferably 9-11. The alkali can be at least one of potassium hydroxide, sodium hydroxide and the like, and for equipment and field operation, alkali liquor with a certain concentration is preferably used, and the mass concentration of the alkali liquor is 30-40%.
And (3) adding alkali to adjust the pH value in the step (2), and reacting for 10-60 min.
The ether solvent in the step (3) may be at least one of diethyl ether, propyl ether, butyl ether, pentyl ether, hexyl ether, heptyl ether, etc., preferably at least one of butyl ether, pentyl ether, hexyl ether, etc.
The added volume of the ether solvent is 2-5% of the volume of the fermentation liquor.
And (3) adding an ether solvent, then carrying out back mixing at 80-95 ℃ for at least 45min, and standing for layering. The standing delamination does not need to preserve heat, and the standing time is 60-90 min.
The acid used for the acidification in the step (4) is any one or more of inorganic acids, such as at least one of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid and the like, and sulfuric acid is preferred. The pH value of acidification is 2-4, the acidification temperature is 80-95 ℃, and the acidification time is 1.5-2.5 h.
Cooling to not higher than 40 ℃ in the step (4), and filtering; the filtration adopts a conventional filtration form such as plate-and-frame filtration.
The washing liquid in the step (4) is desalted water, and the washing is stopped when the pH of the filtrate is above 5.5, preferably 5.5-6.5. The drying temperature is 95-100 ℃, the drying time is 1.5-2 h, and the drying can be performed by adopting a conventional method, such as hot air type drying.
Further, the residual water phase and solvent phase are naturally cooled and then are conveyed to a storage tank for storage, and after a plurality of batches are accumulated, for example, 4-6 batches can be treated and recycled uniformly. The specific method comprises the following steps: heating the mixed solution to 85-90 ℃, standing for 30-60 min, cutting off a lower water phase, naturally cooling the remaining solvent phase after the water phase is treated in the step (4), and centrifuging at a low temperature of-15-5 ℃, wherein a high-speed centrifuge is usually selected, the centrifugal speed is not less than 9500rpm, and the centrifugal duration is not more than 10min, so as to ensure the separation effect. The components of the centrifugal clear liquid can be directly returned to a solvent storage tank for continuous use, and the residual liquid is treated by waste liquid and waste solid.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention adds alkali into the pretreated fermentation liquor, so that the pH of the fermentation liquor is higher than 8, and the temperature is raised, under the condition, partial water-soluble protein is promoted to be denatured, and the fermentation liquor is easy to dissolve in a small amount of ether solvent, so that pigment and impurities enter an organic phase, and then are separated from water phase in which the product is dissolved by cutting water, thereby realizing the efficient removal of the pigment and the impurities. The dicarboxylic acid salt is extracted in the water phase, and the crystallization environment is cleaner, so that the long-chain dicarboxylic acid with higher purity and meeting the requirements of polymer-grade products is easy to obtain.
(2) Compared with the traditional solvent recrystallization method, the method changes the traditional concept of solvent extraction of the target product, uses the solvent to directly extract impurities in the fermentation broth, omits the process of preparing the crude product by the fermentation broth, shortens the flow, and greatly reduces the solvent consumption and the process loss. The product is crystallized in the water phase, the solvent entrapped in the crystallization process is water, salt or inorganic acid aqueous solution, and the solvent can be removed by a simple washing method, such as pulping and leaching, so that the risks of entrapping organic solvent and impurities dissolved in the organic solvent are avoided, the polymerization grade product is obtained, and the technical problem that the high-quality long-chain dicarboxylic acid cannot be refined by the current water phase method is solved.
(3) The invention adopts the ether solvent as the impurity carrier, has good thermal stability and chemical stability, and has little dosage, no need of pressurizing operation in the reaction process and little solvent loss. And the solvent and the long-chain dicarboxylic acid do not have side reaction, and the product can be directly applied to downstream polymerization reaction. The solvent has short use flow, less single-pass loss, simple operation and small potential safety hazard.
Detailed Description
The method and effect of the long-chain dicarboxylic acid in the aqueous-phase refined fermentation broth of the present invention will be further described below with reference to examples. The embodiments and specific operation procedures are given on the premise of the technical scheme of the invention, but the protection scope of the invention is not limited to the following embodiments. In the invention, wt% is mass fraction and vt% is volume fraction.
The experimental methods in the following examples, unless otherwise specified, are all conventional in the art. The experimental materials used in the examples described below were purchased from biochemical reagent stores unless otherwise specified.
In the invention, the total acid content is measured and calculated by an acid-base titration method, the monoacid content is measured and calculated by a gas chromatography peak area normalization method, and the total nitrogen content is detected by a boat sample injection chemiluminescence method.
Example 1
(1) 2000mL of 160g/L C was taken 12 H 22 O 4 Pretreatment of fermentation liquor: heating the fermentation liquor to 75 ℃ for inactivation, then carrying out microfiltration and ultrafiltration membrane filtration, and then decolorizing and filtering by activated carbon.
(2) And (3) adding a NaOH solution with the mass concentration of 32% into the fermentation broth obtained in the step (1) until the pH value reaches 9.5, and stopping reacting for 30min.
(3) 100mL of n-amyl ether was added, the reaction was stopped after stirring at 91.5℃for 45min, and left to stand for 60min, and the lower aqueous phase was cut out.
(4) After the cut aqueous phase was collected, 95% sulfuric acid was slowly added and stirring was turned on, and the addition was stopped when the pH was lowered to 2.8, and the mixture was acidified at 85℃for 2 hours. Naturally cooling to 40 ℃, carrying out plate-frame filtration, then using desalted water to wash the filter cake, stopping washing when the pH value of the washing liquid is raised to 6.0, discharging the filter cake after purging, and conveying the filter cake into a hot air dryer for drying at 100 ℃ for 1.5h to obtain the product. The results are shown in Table 1.
Example 2
(1) 2000mL of C with 150g/L concentration is taken 10 H 18 O 4 Fermentation broth, pretreatment: heating the fermentation liquor to 70 ℃ for inactivation, then carrying out microfiltration and ultrafiltration membrane filtration, and then decolorizing and filtering by activated carbon to remove thalli and pigment.
(2) And (3) adding the fermentation liquor obtained in the step (1) into a NaOH solution with the mass concentration of 30% until the pH value reaches 8.1, and stopping reacting for 20min.
(3) 100mL of n-amyl ether was added, the reaction was stopped after stirring at 85℃for 60min, and left to stand for 45min, and the lower aqueous phase was cut out.
(4) After the cut aqueous phase was collected, 95% sulfuric acid was slowly added and stirring was turned on, and the addition was stopped when the pH was lowered to 2.6, and the mixture was acidified at 90℃for 2 hours. Naturally cooling to 35 ℃, conveying to a plate-frame filter, then using desalted water to wash a filter cake, stopping washing when the pH value of the washing liquid is raised to 5.5, discharging the filter cake after purging, conveying to a hot air dryer for drying, wherein the drying temperature is 95 ℃, and the drying time is 2 hours, thus obtaining the product. The results are shown in Table 1.
Example 3
(1) 2000mL of C with the concentration of 140g/L is taken 16 H 30 O 4 Fermentation broth, pretreatment: heating the fermentation liquor to 80 ℃ for inactivation, then carrying out microfiltration and ultrafiltration membrane filtration, and then decolorizing and filtering by activated carbon.
(2) And (3) adding the fermentation liquor obtained in the step (1) into a NaOH solution with the mass concentration of 40% until the pH value reaches 11, and reacting for 10min.
(3) 100mL of n-amyl ether is added, the reaction is stopped after stirring at 93 ℃ for 30min, the reaction is kept stand for 75min, and the lower water phase is cut out and then is conveyed to an acidifier in a heat preservation way.
(4) After the cut aqueous phase was collected, 95% sulfuric acid was slowly added and stirring was started, and the addition was stopped when the pH was lowered to 3.0, and the mixture was acidified at 90℃for 1.5 hours. Naturally cooling to 30 ℃, conveying to a plate-frame filter, then using desalted water to wash a filter cake, stopping washing when the pH value of the washing liquid is raised to 6.5, discharging the filter cake after purging, conveying to a hot air dryer for drying, wherein the drying temperature is 100 ℃, and the drying time is 1.5h, thus obtaining the product. The results are shown in Table 1.
Example 4
The refining process and operating conditions were the same as in example 1, except that: and (2) replacing sodium hydroxide with potassium hydroxide with the mass concentration of 32%, and adjusting the pH to 9.5.
Example 5
The refining process and operating conditions were the same as in example 1, except that: and (3) adopting a mixed solvent of n-butyl ether and n-heptyl ether (volume ratio is 1:1) to replace n-amyl ether.
Example 6
The refining process and operating conditions were the same as in example 1, except that: and (3) adopting diethyl ether to replace n-amyl ether.
Example 7
The refining process and operating conditions were the same as in example 1, except that: and (3) adopting n-propyl ether to replace n-amyl ether.
Example 8
The refining process and operating conditions were the same as in example 1, except that: and (3) adopting n-butyl ether to replace n-amyl ether.
Example 9
The refining process and operating conditions were the same as in example 1, except that: and (3) adopting n-hexyl ether to replace n-amyl ether.
Example 10
The refining process and operating conditions were the same as in example 1, except that: and (3) adopting n-heptyl ether to replace n-amyl ether.
Example 11
The refining process and operating conditions were the same as in example 1, except that: and (4) acidifying, namely replacing sulfuric acid with nitric acid.
Example 12
The refining process and operating conditions were the same as in example 1, except that: and (4) acidizing by adopting hydrochloric acid to replace sulfuric acid.
Comparative example 1
The refining process and operating conditions were the same as in example 1, except that: and (3) regulating the pH value to 7.8 in the step (2).
Comparative example 2
The refining process and operating conditions were the same as in example 1, except that: the reaction temperature in the step (3) is 75 ℃.
Comparative example 3
The refining process and operating conditions were the same as in example 1, except that: and (3) adopting n-butanol to replace n-amyl ether.
Comparative example 4
The refining process and operating conditions were the same as in example 1, except that: and (3) adopting ethyl acetate to replace n-amyl ether.
The residual water phase and solvent phase in each example and comparative example are naturally cooled and then are conveyed to a storage tank for storage, 6 batches are accumulated, and the treatment and the recycling are carried out uniformly. The specific method comprises the following steps: heating the mixed solution to 85 ℃, standing for 45min, cutting off a lower water phase, naturally cooling the rest solvent phase after the water phase is treated in the step (4), and centrifuging at a low temperature of 0 ℃ usually at a high-speed centrifuge with a centrifugal speed of 12000rpm for 10min to ensure the separation effect.
Table 1 effects of the products of examples and comparative examples
As can be seen from Table 1, the total nitrogen content in the product obtained by the technical scheme of the present application is significantly reduced, while the total nitrogen content of comparative examples 1-4 lacking the technical features of the present application is relatively high.