Synthesis method and application of ionic liquid-based extraction adsorption resin

Abstract

The application discloses a synthesis method of an extraction adsorption resin based on an ionic liquid and application thereof, and belongs to the technical field of bio-chemical industry. The synthesis method comprises the following steps: mixing an imidazole-based ionic liquid and an anion exchange resin, adding a dispersing agent, and performing an impregnation synthesis reaction to prepare an extraction adsorption resin in which the imidazole-based ionic liquid is immobilized in the anion exchange resin. The ionic liquid is combined with the anion exchange resin as an extractant by a solvent impregnation method to prepare the immobilized resin, and lactic acid is extracted and adsorbed from a solution for separation. The application integrates the extraction and adsorption two separation units by using the ionic exchange resin to immobilize the extractant, so that the extraction and adsorption capacity of the resin for lactic acid can be significantly improved. Meanwhile, the obtained extraction adsorption resin can be recycled, the separation cost is reduced, and the separation efficiency of the resin is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of bio-chemical industry, and relates to a separation technology of microbial fermentation products, in particular to a synthesis method of an extraction adsorption resin based on an ionic liquid and application thereof in separation of lactic acid. BACKGROUND

[0002] Lactic acid is one of the most representative bio-based chemicals, which exists in large quantities in nature and is widely used in food, cosmetics, pharmaceuticals, textiles and other industries. In recent years, with the production of new biodegradable plastics-poly lactic acid as a monomer, the market size of lactic acid has been expanding.

[0003] Lactic acid is mainly produced by microbial fermentation pathway using carbohydrates as substrate. This method eliminates a series of environmental pollution, high cost and other problems caused by the use of non-renewable raw materials (such as nitriles, toxic hydrogen cyanide, etc.) in chemical synthesis route, and has obvious cost and operation advantages. At present, more than 90% of lactic acid in the world is produced by biological fermentation. Bio-based lactic acid production still faces many problems, among which downstream processing (separation, purification, recovery) as a key production link, due to the existence of a large amount of solid waste, complicated steps, low yield, high cost and other outstanding problems, accounts for 50% or even more of the production cost, and becomes an important factor restricting the large-scale application of lactic acid. Therefore, improving or innovating the separation method of bio-based lactic acid is crucial to further reduce the industrial production cost and expand the global production scale of lactic acid.

[0004] Bio-based lactic acid separation and purification is often composed of multiple unit operations. Common unit operations include precipitation method, extraction method, resin adsorption method, membrane separation method, electrodialysis method, molecular distillation method, etc. Among them, the resin adsorption method has the advantages of high selectivity and simple operation. Ion exchange resin as a common adsorption material has the characteristics of high specific surface area and high mechanical strength, and its polar functional groups can form hydrogen bonds with the hydroxyl and carboxyl groups in the lactic acid molecule, thereby having high lactic acid adsorption performance and becoming a common lactic acid separation adsorbent. Although the resin adsorption separation has the advantages of high selectivity, the low adsorption capacity is still the most important factor restricting its large-scale application. Patent CN101880225A discloses a method for extracting lactic acid from corn starch wastewater fermentation broth using ion exchange resin. The method uses 315 type anion exchange resin for adsorption separation of the pretreated lactic acid fermentation broth, and the adsorption effect of 315 resin on lactic acid is 274.9mg / g, and the lactic acid extraction rate is 78%-80%. The method has low resin adsorption capacity, large resin consumption and cannot be reused, and the process is relatively complex. Patent CN114181071A discloses a method for refining and purifying lactic acid fermentation broth. The fermentation broth pretreatment step includes heating sterilization, flocculation filtration, concentration acidolysis filtration and activated carbon decolorization. The subsequent separation process adopts alternating separation of anion and cation exchange resins, and needs to be concentrated after elution. The overall process is relatively complex and has high energy consumption. In the study of lactic acid adsorption separation, improving the adsorption capacity of resin on lactic acid has become one of the key problems to be solved.

[0005] Ionic liquid is a salt composed of anions and cations in a liquid state at room temperature or near room temperature, known as green solvent. It has the characteristics of extremely low vapor pressure, structure design, good thermal stability, etc., and is widely used in lignocellulose pretreatment, drug synthesis, CO2 capture, industrial catalysis, extraction separation and other fields. In recent years, as a replacement for organic solvent extraction, it has begun to be applied in the separation of bio-based chemicals. SUMMARY

[0006] In view of the deficiencies in the prior art, the purpose of the present application is to provide a new technology for extracting and adsorbing lactic acid based on a new green solvent-ionic liquid, that is, to immobilize ionic liquid as an extractant into ion exchange resin by solvent impregnation method. In the solvent impregnation process, the ionic liquid is uniformly dispersed into the dispersant under the action of strong shaking, and then enters the internal pore of the resin under the action of heating and is immobilized. After washing off the residual dispersant, a new type of extraction and adsorption resin is obtained.

[0007] The purpose of the present application is achieved by the following technical solutions.

[0008] In a first aspect of the present application, a method for synthesizing lactic acid extraction and adsorption resin based on ionic liquid is provided, comprising the following steps:

[0009] The imidazolium-based ionic liquid and the anion exchange resin are mixed and a dispersant is added to perform an impregnation synthesis reaction to prepare an extraction adsorption resin in which the imidazolium-based ionic liquid is immobilized in the anion exchange resin.

[0010] Further, in the above technical solution, the extractant is one or two imidazolium-based ionic liquids with the number of alkyl carbon atoms in the side chain greater than 2. Preferably, the imidazolium-based ionic liquid includes 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6), 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim]PF6), and 1-octyl-3-methylimidazolium hexafluorophosphate ([Omim]PF6).

[0011] Further, in the above technical solution, the anion exchange resin is a resin for biochemical separation, preferably, the anion exchange resin is a weakly basic anion exchange resin capable of ion exchange with lactate ions, more preferably, the anion exchange resin includes resin 335, D301, D314, D315, D318, and D918.

[0012] Further, in the above technical solution, the mass ratio of the imidazolium-based ionic liquid to the anion exchange resin is 1:1-1:10.

[0013] Further, in the above technical solution, the dispersant is a liquid solvent capable of dissolving the imidazolium-based ionic liquid, preferably, the dispersant is an alcohol solvent, and the alcohol solvent is preferably methanol, ethanol, and butanol.

[0014] Further, in the above technical solution, the mass ratio of the dispersant to the imidazolium-based ionic liquid is 1:1-1:20.

[0015] Further, in the above technical solution, the impregnation synthesis reaction conditions are as follows: the rotation speed is 150-200 r / min, the impregnation time is 12-14 h, preferably 14 h, and the impregnation temperature is 40-60℃, preferably 60℃.

[0016] Further, in the above technical solution, after the impregnation synthesis reaction is completed, the impregnation system is allowed to stand, filtered, and cooled to room temperature to obtain the extraction adsorption resin.

[0017] In a second aspect of the present application, an extraction adsorption resin prepared by the above synthesis method is provided.

[0018] In a third aspect of the present application, the application provides a use of the extraction adsorption resin prepared by the above synthesis method in lactic acid separation. Specifically, a lactic acid-containing solution is separated by the extraction adsorption resin to obtain lactic acid. The lactic acid-containing solution can be a lactic acid-containing fermentation broth in a process for producing lactic acid by microbial fermentation, or an aqueous solution containing appropriate amount of lactic acid and other components.

[0019] Further, in the above technical solution, the lactic acid-containing solution is adsorbed into the extraction adsorption resin by a static adsorption method or a dynamic adsorption method, and after the adsorption is completed, one or two of water, ethanol, hydrochloric acid, sodium hydroxide and sodium chloride solutions are used for elution. In the adsorption process and the elution process, the temperature is maintained at 15-65℃.

[0020] Further, in the above technical solution, the concentration of lactic acid in the lactic acid-containing solution is 30-400g / L.

[0021] Beneficial effects:

[0022] The present application provides a novel extraction adsorption resin based on ionic liquid and a synthesis method thereof, in which the ionic liquid is used as an extractant and is immobilized into an anion ion exchange resin by a solvent impregnation method. When the extraction adsorption resin synthesized by the method of the present application is used to separate lactic acid, in addition to the ion exchange adsorption of the resin itself, the ionic liquid in the resin acts as an extractant, so that the impregnated resin has the ability of adsorption and extraction at the same time, thereby improving the separation effect of the resin on lactic acid.

[0023] The extraction adsorption resin of the present application has the advantages of both adsorption and extraction methods, and after the immobilization of the extractant, the adsorption effect of the resin on lactic acid is greatly improved, and the separation efficiency of the resin is improved. Meanwhile, the resin synthesized by the method of the present application can be reused, thereby reducing the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present application and are incorporated in and constitute a part of this application, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application. In the drawings:

[0025] Figure 1 Fig. 4 shows the comparison results of the adsorption capacity of different weakly basic anion exchange resins on lactic acid.

[0026] Figure 2 Fig. 5 shows the effects of pH and initial lactic acid concentration on the static adsorption separation of lactic acid by IL-335 resin, wherein (a) shows the effect of pH on the separation of lactic acid by IL-335 resin, and (b) shows the effect of initial lactic acid concentration on the separation of lactic acid by IL-335 resin.

[0027] Figure 3This represents the breakthrough curve of IL-335 resin and the fitting results of the dynamic adsorption model.

[0028] Figure 4 The results of IL-335 resin cyclic chromatography separation of lactic acid are shown, where (a) is 6 rounds of cyclic shake-flask adsorption and (b) is 6 rounds of cyclic column chromatography. The solid line in the figure represents lactic acid adsorption and the dashed line represents lactic acid desorption. Detailed Implementation

[0029] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the materials and reagents used can be purchased from biological or chemical companies.

[0030] In this invention, lactic acid concentration is detected by high-performance liquid chromatography (HPLC). Detection conditions: HPX-87H chromatographic column ( The column temperature was 55℃, the mobile phase was 5mM sulfuric acid, the flow rate was 0.6mL / min, the injection volume was 20μL, the column temperature was 55℃, and the detection time was 18min. Sample preparation method: The sample was diluted and filtered through a 0.22μm filter membrane before injection and detection.

[0031] The formula for calculating resin adsorption capacity is as follows:

[0032]

[0033] In the formula, q e The equilibrium adsorption capacity (mg / g), C0 and C e The initial and equilibrium lactic acid concentrations are represented by (g / L), V represents the volume of the lactic acid solution (mL), and m represents the resin mass (g).

[0034] The Thomas penetration curve model can be represented as:

[0035]

[0036] In the formula, C0 and C t q represents the initial and time t lactate concentrations (g / L). e K represents the equilibrium adsorption capacity (mg / g). T denoted by Thomas rate constant (mL / (min·mg)), v represents volumetric flow rate (mL / min), m represents the mass of resin packed in the chromatography column (g), and t represents adsorption time (min).

[0037] The Yoon-Nelson penetration curve model can be represented as:

[0038]

[0039] where K Y represents the Yoon-Nelson rate constant (min -1 ) and τ represents the time required for 50% adsorbate uptake (min).

[0040] Example 1 Adsorption of lactic acid by different ion exchange resins

[0041] 5.0 g of different types of weakly basic anion exchange resins were each mixed with 100 mL of an aqueous lactic acid solution (containing 200 g / L lactic acid) in a conical flask and allowed to stand for adsorption at 25°C for 6 h to ensure that adsorption equilibrium was reached. The lactic acid concentration in the supernatant was determined by high performance liquid chromatography, and the equilibrium adsorption capacity of the different resins for lactic acid was calculated. The results are shown in Table 1. Figure 1

[0042] Figure 1 The results shown in Table 1 indicate that the weakly basic anion exchange resins 335, D301, D314, D315, D318 and D918 all showed good adsorption effects for lactic acid, with adsorption capacities greater than 100 mg / g. Figure 1 In Table 1, the 335 resin showed the best adsorption effect, with an adsorption capacity for lactic acid of 319 mg / g. In subsequent experiments, the 335 resin was selected as the carrier for the preparation of novel extractive adsorption resins.

[0043] Example 2 Extraction of lactic acid by different ionic liquids

[0044] The extraction effects of three ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF6), 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim]PF6) and 1-octyl-3-methylimidazolium hexafluorophosphate ([Omim]PF6), as extractants for lactic acid were investigated, with an initial lactic acid concentration of 200 g / L. Each extractant and the aqueous lactic acid solution were added to a test tube with a stopper in a ratio of 1:1 (v / v) and mixed thoroughly in a shaker, and then allowed to stand for 8 h. The lactic acid content in the upper and lower phases was then analysed by high performance liquid chromatography. The recoveries of [Bmim]PF6, [Hmim]PF6 and [Omim]PF6 for lactic acid were 10.16%, 5.46% and 0.33%, respectively. [Bmim]PF6 had the highest recovery for lactic acid, at 10.16%. [Bmim]PF6 was then selected as the extractant for the preparation of extractive adsorption resins using the solvent impregnation method.

[0045] Example 3 Preparation of extractive adsorption resins with different ratios of impregnating agent

[0046] ​Five kinds of extraction adsorption resins were prepared as follows: 20 g of [Bmim]PF6 ionic liquid and 100 g of dispersant (ethanol) were mixed in a conical flask. After the ionic liquid was completely dissolved, 20 g, 40 g, 60 g, 80 g, and 100 g of 335 resin were added, respectively. The mixture was heated and shaken in a 50°C constant-temperature shaking table at a shaking speed of 200 rpm for 12 h. After standing, the mixture was filtered. The impregnated resin was cooled to room temperature to obtain the extraction adsorption resin.

[0047] 5.0 g of each of the extraction adsorption resins prepared under different impregnation conditions was mixed with 100 mL of lactic acid aqueous solution (containing 200 g / L of lactic acid). After adsorption equilibrium, the lactic acid concentration in the supernatant was analyzed, and the lactic acid adsorption capacity of each extraction adsorption resin was calculated. The results showed that the lactic acid adsorption capacities of the five kinds of extraction adsorption resins were between 328 mg / g and 411 mg / g, all showing good adsorption capacity. When the impregnation agent (ionic liquid) to 335 resin ratio was 1:4 (w / w), i.e., the amount of resin added was 80 g, the lactic acid adsorption capacity of the extraction adsorption resin was the largest, reaching 411 mg / g.

[0048] Example 4 Preparation of extraction adsorption resins under different impregnation times

[0049] Five kinds of extraction adsorption resins were prepared as follows: 20 g of [Bmim]PF6 ionic liquid and 100 g of dispersant (ethanol) were mixed in a conical flask. After the ionic liquid was completely dissolved, 80 g of 335 resin was added. The mixture was heated and shaken in a 50°C constant-temperature shaking table at a shaking speed of 200 rpm for 10 h, 12 h, 14 h, 16 h, and 18 h, respectively. After standing, the mixture was filtered. The impregnated resin was cooled to room temperature to obtain the extraction adsorption resin.

[0050] 5.0 g of each of the extraction adsorption resins prepared under different impregnation times was mixed with 100 mL of lactic acid simulation solution (containing 200 g / L of lactic acid). After adsorption equilibrium, the lactic acid concentration in the supernatant was analyzed, and the lactic acid adsorption capacity of each resin was calculated. The results showed that the lactic acid adsorption capacities of the five kinds of extraction adsorption resins were between 340 mg / g and 419 mg / g, all showing good adsorption capacity. The lactic acid adsorption capacity of the extraction adsorption resin after impregnation for 14 h was the largest, reaching 419 mg / g.

[0051] Example 5 Preparation of extraction adsorption resins under different temperatures

[0052] Five kinds of extraction adsorption resins were prepared as follows: 20 g of [Bmim]PF6ionic liquid and 100 g of dispersant (ethanol) were mixed in a conical flask. After the ionic liquid was completely dissolved, 80 g of 335 resin was added. The mixture was heated and shaken in a constant temperature shaker at 30°C, 40°C, 50°C, 60°C, and 70°C, respectively, at a shaking speed of 200 rpm for 14 h. After standing, the mixture was filtered, and the impregnated resin was cooled to room temperature to obtain the extraction adsorption resin.

[0053] 5.0 g of the extraction adsorption resin prepared at different temperatures was mixed with 100 mL of lactic acid simulation solution (200 g / L). After adsorption equilibrium, the lactic acid concentration in the supernatant was analyzed, and the lactic acid adsorption capacity of each resin was calculated. The results showed that the adsorption capacity of the five kinds of extraction adsorption resins for lactic acid was between 363 mg / g and 432 mg / g, all showing good adsorption capacity. The extraction adsorption resin prepared at 60°C had the largest adsorption capacity for lactic acid, which was 432 mg / g. The extraction adsorption resin prepared under this condition was named IL-335 resin and was used in the following examples.

[0054] Example 6 Lactic acid separation effect of IL-335 resin at different pH values of lactic acid aqueous solution

[0055] 5.0 g of IL-335 resin was mixed with 100 mL of lactic acid aqueous solution (containing 200 g / L of lactic acid) with pH values of 1.6, 2.0, 3.0, 4.0, 5.0, 6.0, and 7.0, respectively. After shaking and standing, the lactic acid concentration in the supernatant was analyzed, and the lactic acid adsorption capacity was calculated. The results are shown in Table a. Figure 2 As shown in Table a, the lactic acid separation effect of IL-335 resin decreased with the increase of the pH value of lactic acid solution, and the adsorption capacity ranged from 65 mg / g to 432 mg / g. The largest adsorption capacity was 432 mg / g at pH 1.6.

[0056] Example 7 Lactic acid separation effect of IL-335 resin at different initial concentrations of lactic acid aqueous solution

[0057] 5.0 g of IL-335 resin was mixed with 25 g / L, 50 g / L, 100 g / L, 150 g / L, and 200 g / L lactic acid aqueous solution (100 mL, pH = 1.6), respectively. After shaking and standing, the lactic acid concentration in the supernatant was analyzed, and the lactic acid adsorption capacity was calculated. The results are shown in Table b. Figure 2 As shown in Table b, the lactic acid separation effect of IL-335 resin increased with the increase of the initial lactic acid concentration, and the adsorption capacity of IL-335 resin was the highest at an initial lactic acid concentration of 200 g / L.

[0058] Figure 2As can be seen from b, the initial concentration of the lactic acid aqueous solution affects the adsorption capacity of lactic acid on the resin. When using the resin prepared by this invention to separate lactic acid, considering factors such as adsorption capacity and cost, it is better to use an initial concentration of lactic acid of 30 g / L to 200 g / L.

[0059] Example 8: Static adsorption of lactic acid by IL-335 resin

[0060] 5.0 g of IL-335 and 335 resin were mixed with 100 mL of lactic acid aqueous solution (200 g / L, pH = 1.6). After shaking and settling, the lactic acid concentration in the supernatant was analyzed, and the lactic acid adsorption capacity was calculated. The maximum adsorption efficiency of IL-335 resin was 432 mg / g, while the maximum adsorption efficiency of untreated 335 resin was 319 mg / g. In comparison, the extraction efficiency of IL-335 resin accounted for 26.16%, and the adsorption efficiency accounted for 73.84%, with the overall separation efficiency improving by 35.42% compared to before impregnation.

[0061] Example 9: Separation of lactic acid by IL-335 resin chromatography

[0062] 50.0g of resin was loaded into a custom-made glass chromatography column using a wet loading method. In this process, a peristaltic pump continuously pumped 200 g / L of lactic acid aqueous solution into the column at a constant flow rate (2.0 mL / min). After complete adsorption, 3 BV of deionized water was pumped into the column to remove residual lactic acid. Then, 5 BV of NaOH solution was used for elution. The lower eluent was collected, the lactic acid concentration was analyzed, and the breakthrough curve was determined. The residual eluent was rinsed with deionized water, and the resin was regenerated before the next cycle of chromatography. A total of 6 cycles were performed.

[0063] The penetration curve was fitted using the Thomas model and the Yoon-Nelson model, and the results are as follows: Figure 3 As shown in Table 1, the penetration curves are in good agreement with both the Thomas and Yoon-Nelson models (R0). 2 >0.99) indicates that the chromatography process is stable.

[0064] Results of cyclic column chromatography as follows Figure 4 As shown in b, after six rounds of column chromatography, the IL-335 resin still maintained a high lactic acid separation efficiency, with the elution effect consistently exceeding 81%.

[0065] Table 1. Fitting parameters and correlation coefficients of the breakthrough curve models of the Thomas and Yoon-Nelson models.

[0066]

[0067] The results show that, due to the hydrophobicity and the extraction of lactic acid of the [Bmim]PF6 ionic liquid, the IL-335 resin has better lactic acid separation effect than the 335 resin, and the adsorption capacity of the resin after solvent impregnation is obviously improved. The cycle column chromatography shows that the IL-335 resin can be repeatedly used for many times, and has good economic value. The application combines extraction and adsorption technology, can be applied to the green and efficient separation of bio-based lactic acid, so as to expand the application in the separation and extraction of bio-based chemicals, wastewater treatment and the like, and provides a new idea for solving the bottleneck problem in the industrialized production of bio-based chemicals.

[0068] Some parts of the application are not described in detail, which are known in the art.

[0069] The above specific embodiments further illustrate the purposes, technical solutions and beneficial effects of the application. It should be understood by those skilled in the art that the application is not limited by the above embodiments, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. An application of an ionic liquid-based extraction and adsorption resin in the separation of lactic acid from a solution containing lactic acid, characterized in that, include: An imidazole-based ionic liquid and anion exchange resin are mixed and a dispersant is added, and an impregnation synthesis reaction is carried out to prepare an extraction and adsorption resin in which the imidazole-based ionic liquid is immobilized in the anion exchange resin. The imidazole-based ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate, and the anion exchange resin is resin 335. The concentration of lactic acid in the solution containing lactic acid is 30 g / L - 400 g / L; The lactic acid-containing solution is a lactic acid-containing fermentation broth from a process that produces lactic acid through microbial fermentation.

2. The application according to claim 1, characterized in that, The mass ratio of the imidazole-based ionic liquid to the anion exchange resin is 1:1 to 1:

10.

3. The application according to claim 1, characterized in that, The dispersant is an alcohol solvent, and the mass ratio of the dispersant to the imidazole ionic liquid is 1:1 to 1:

20.

4. The application according to claim 1, characterized in that, The impregnation synthesis reaction was carried out at a rotation speed of 150-200 r / min, an impregnation time of 12-14 h, and an impregnation temperature of 40-60 °C. o It is carried out under condition C.

5. The application according to claim 1, characterized in that, The lactic acid-containing solution is adsorbed into the extraction and adsorption resin by static or dynamic adsorption. After adsorption, it is eluted with one or two of the following solutions: water, ethanol, hydrochloric acid, sodium hydroxide, and sodium chloride.

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