Method for producing ethyl acetate by using acetic acid in fermentation wastewater

Abstract

The invention relates to a method for producing ethyl acetate by using acetic acid in fermentation wastewater, which comprises the following steps: carrying out on-line acetic acid concentration monitoring on clostridium ethanolicum fermentation wastewater to obtain acetic acid-containing wastewater; dissolving a polymer in the buffer solution to obtain a polymer solution; the polymer solution and the CALB solution are sequentially subjected to stirring, microsphere forming and cross-linking curing, and immobilized CALB is obtained; putting the immobilized CALB, the acetic acid-containing wastewater, ethanol and an organic extraction agent into a reaction tank, and carrying out esterification reaction and real-time extraction to obtain a reaction mixture; pumping an organic extraction phase containing ethyl acetate in the upper layer of the reaction mixture into a rectifying tower for distillation separation to obtain ethyl acetate, and returning the organic extraction agent to the reaction tank for recycling; introducing the lower layer of the reaction mixture into a standing tank for phase separation to obtain a separated phase; pumping an organic extraction phase containing ethyl acetate at the upper layer of the separation phase into a reaction tank for recycling, and feeding a water phase at the lower layer of the separation phase into sewage treatment. Finally, resource utilization of the fermentation wastewater is realized.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ethyl acetate preparation, and particularly relates to a method for producing ethyl acetate by using acetic acid in fermentation wastewater. BACKGROUND

[0002] Clostridium autoethanogenum is a key strain for producing ethanol by using one-carbon gas. During the fermentation process of Clostridium autoethanogenum, acetic acid is an important precursor for ethanol synthesis, and the concentration balance of acetic acid directly affects the fermentation efficiency of Clostridium autoethanogenum. If the concentration of acetic acid is too high, the phenomenon of “acid collapse” will be caused, resulting in abnormal fermentation or even premature termination. If the concentration of acetic acid is too low, it is difficult to provide sufficient precursors for ethanol synthesis, which is not conducive to the efficient production of ethanol. Moreover, after the fermentation is completed, the remaining acetic acid is directly discharged with wastewater, which not only causes waste of valuable carbon sources, but also increases the burden of wastewater treatment.

[0003] As a key industrial solvent and food flavor raw material, the traditional industrial production of ethyl acetate mainly relies on two routes: one is the acid catalytic esterification method of ethanol and acetic acid, which has high process energy consumption, uses corrosive reagents and is prone to produce by-products; the other is the ethylene addition method, which needs to be carried out at high temperature and high pressure and the cost of the catalyst is high. Both of these two methods have environmental pollution or product safety risks. Compared with the above two methods, the biological enzyme catalysis method is carried out at a moderate temperature and near neutral pH, and almost no other by-products are produced during the reaction process, and the purity of ethyl acetate can reach more than 98%; and no toxic reagents such as strong acid and strong base are used, which completely eliminates waste acid discharge and environmental pollution from the source; and through the immobilization technology, the enzyme can be recycled and utilized, thereby reducing the cost; finally, there is no chemical residue in ethyl acetate, which completely meets the highest safety standards of the food and pharmaceutical industries.

[0004] Therefore, it is urgent to combine the biological enzyme catalysis method with the resource utilization of acetic acid in fermentation wastewater to provide an ideal path for realizing clean production and high-value application. SUMMARY

[0005] The application provides a method for producing ethyl acetate by using acetic acid in fermentation wastewater, so as to solve the technical problem of how to solve the resource utilization of acetic acid in Clostridium autoethanogenum fermentation wastewater.

[0006] The application provides a method for producing ethyl acetate by using acetic acid in fermentation wastewater, which comprises the following steps: Online acetic acid concentration monitoring is performed on Clostridium autoethanogenum fermentation wastewater to obtain acetic acid-containing wastewater; The polymer is dissolved in a buffer solution to obtain a polymer solution; The polymer solution and a CALB solution are sequentially stirred, microspheres are formed, and cross-linking solidification is performed to obtain immobilized CALB; The immobilized CALB, the acetic acid-containing wastewater, ethanol and organic extractant are placed in a reaction tank to perform esterification and real-time extraction, so as to obtain a reaction mixture; The organic extraction phase containing ethyl acetate in the upper layer of the reaction mixture is pumped into a rectifying column to perform distillation separation, so as to obtain ethyl acetate, and the extracted organic extractant is returned to the reaction tank for recycling. The lower layer of the reaction mixture is introduced into a standing tank to perform phase separation, so as to obtain a separation phase; The organic extraction phase containing ethyl acetate in the upper layer of the separation phase is pumped into the reaction tank for reuse, and the water phase in the lower layer of the separation phase is introduced into sewage treatment.

[0007] Optionally, the concentration of the polymer is 2% to 4%.

[0008] Optionally, the polymer includes at least one of sodium alginate, polylactic acid-glycolic acid copolymer and chitosan.

[0009] Optionally, the pH value of the buffer solution is 6.0 to 8.0.

[0010] Optionally, the stirring time is 10 min to 20 min.

[0011] Optionally, the crosslinking agent for crosslinking and solidification includes at least one of calcium chloride and glutaraldehyde.

[0012] Optionally, the crosslinking and solidification time is 1 h to 2 h.

[0013] Optionally, the extraction is performed by at least one of mechanical stirring and air-lift stirring.

[0014] Optionally, the organic extractant is dodecane; and the solubility of ethyl acetate in the dodecane is 120 g / L to 150 g / L.

[0015] Optionally, when the concentration of ethyl acetate in the dodecane is 30 g / L to 90 g / L, the feeding of the ethanol and the acetic acid-containing wastewater is suspended, the organic extractant containing ethyl acetate is pumped into a rectifying column to extract ethyl acetate, and the extracted organic extractant is returned to the reaction tank for recycling.

[0016] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages: The embodiment of the present application provides a method for producing ethyl acetate by using acetic acid in fermentation wastewater, first, CALB (Candida antarctica lipase B) is immobilized by using a polymer, a stable porous structure is formed through stirring, microsphere molding and crosslinking solidification, the catalytic activity of the enzyme is retained, and reuse of the enzyme is realized, so that the cost of the catalytic process is reduced; secondly, the immobilized CALB, acetic acid-containing wastewater, ethanol and an organic extractant are mixed in a reaction tank, esterification reaction is performed on the acetic acid in the wastewater to convert the acetic acid into ethyl acetate, the high solubility of the extractant to ethyl acetate is used to remove the product in real time, the reaction balance is broken, the inhibition of the product on the enzyme activity is avoided, and the conversion efficiency of the acetic acid is improved; further, resource closed loop is realized through the cooperative operation of phase separation and rectification, the organic extraction phase in the reaction mixture is purified through distillation to obtain high-value ethyl acetate product, the extractant is recycled and used in the reaction system, and after the lower aqueous phase is separated and recovered by standing, the remaining wastewater enters a sewage treatment link.

[0017] To sum up, the scheme converts the waste acetic acid in fermentation wastewater into ethyl acetate with economic value, realizes resource utilization of the acetic acid, reduces the pollution load of the wastewater through product separation and wastewater treatment, and solves the environmental risk and resource waste problems of Clostridium autoethanogenum fermentation wastewater. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the application.

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0020] Figure 1 A flow chart of a method for producing ethyl acetate by using acetic acid in fermentation wastewater is provided for the embodiment of the present application. Figure 2 A route map of a method for producing ethyl acetate by using acetic acid in fermentation wastewater is provided for the embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0022] The range descriptions described herein, such as numerical range, ratio range and the like, include all possible sub-ranges and single values within the range, for example, the range description of "1 to 6" or "1~6" covers all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single values (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "include", "contain" and the like used herein mean "include but not limited to"; the relationship terms "first", "second" and the like are only used to distinguish different entities or operations, and do not imply actual sequence or relationship. "And / or" means that multiple situations can exist independently or simultaneously. "At least one", "multiple", "at least one" and the like refer to any combination of the corresponding objects, including single or multiple combinations of objects. The proportional relationship involved herein, such as mass ratio, molar ratio and the like, should be understood as the corresponding relationship between the front and the rear in the proportional form according to the description order. The raw materials, reagents, instruments and equipment used herein can be purchased or prepared by existing methods.

[0023] Figure 1 A flow chart of a method for producing ethyl acetate from acetic acid in fermentation wastewater provided by the embodiments of the present application.

[0024] See Figure 1 The embodiments of the present application provide a method for producing ethyl acetate from acetic acid in fermentation wastewater, comprising: S1, on-line acetic acid concentration monitoring of Clostridium autoethanogenum fermentation wastewater is performed to obtain acetic acid-containing wastewater; S2, a polymer is dissolved in a buffer solution to obtain a polymer solution; S3, the polymer solution and a CALB solution are sequentially stirred, microsphere forming and cross-linking solidification are performed to obtain immobilized CALB; S4, the immobilized CALB, the acetic acid-containing wastewater, ethanol and an organic extractant are placed in a reaction tank to perform esterification reaction and real-time extraction, and a reaction mixture is obtained; S5, the upper acetic acid ethyl ester-containing organic extraction phase of the reaction mixture is pumped into a rectifying column for distillation separation to obtain ethyl acetate, and the extracted organic extractant is returned to the reaction tank for recycling; S6, introducing the lower layer of the reaction mixture into a standing tank for phase separation to obtain a separated phase; S7, pumping the upper layer of the separated phase containing ethyl acetate organic extraction phase into a reaction tank for reuse, and introducing the lower layer of the separated phase into sewage treatment.

[0025] In the above technical solution, first, the immobilization of CALB by the polymer forms a porous microsphere carrier, which realizes the reuse of the enzyme while retaining the enzyme activity; then, during the esterification reaction in the reaction tank, the high solubility of the organic extractant for ethyl acetate is used to remove the product in real time, which not only breaks the reaction equilibrium to improve the conversion rate, but also avoids the inhibition of the enzyme activity by the product; the key separation stage is realized by the difference in physical properties, the reaction mixture is subjected to the first phase separation in the standing tank by means of the density difference between the organic phase and the aqueous phase, the upper layer of the organic phase enriched with the product is subjected to distillation to purify ethyl acetate by means of the boiling point difference and recycle the extractant; and the lower layer (mainly aqueous phase mixed with a small amount of organic phase) is subjected to secondary separation to further recover the residual organic phase, finally realizing a triple closed loop: the reuse of the immobilized enzyme reduces the catalytic cost, the recycling of the extractant reduces the raw material consumption, and the maximum recovery of the product before wastewater treatment solves the problems of resource waste and environmental pollution of acetic acid in fermentation wastewater.

[0026] In some embodiments, the concentration of the polymer is 2% to 4%.

[0027] The concentration of the polymer is between 2% and 4%, which can make the polymer form a microsphere with a suitable porous structure, which can physically trap CALB molecules to prevent enzyme loss, and also allow acetic acid and ethanol to freely diffuse with ethyl acetate, thereby maintaining the catalytic activity and reusability of the enzyme. For example, the concentration of the polymer can be 2%, 3%, 4%, etc.

[0028] In some embodiments, the polymer includes at least one of sodium alginate, polylactic acid-glycolic acid copolymer, and chitosan.

[0029] Sodium alginate has low cost and good biocompatibility, which is suitable for conventional scenarios; polylactic acid-glycolic acid copolymer is biodegradable, which is suitable for long-term reuse requirements; chitosan has strong stability and high mechanical strength, which can improve the durability of the microsphere. All of them can optimize the performance of the immobilized CALB according to the application scenario.

[0030] In some embodiments, the pH value of the buffer solution is 6.0 to 8.0.

[0031] The pH value of the buffer solution is between 6.0 and 8.0, which can prevent the enzyme protein from denaturation and inactivation caused by too high or too low pH value, and ensure the effective retention of enzyme activity during the immobilization process. For example, the pH value of the buffer solution can be 6.0, 7.0, 8.0, etc.

[0032] In some embodiments, the stirring time is between 10 min and 20 min.

[0033] The stirring time is between 10 min and 20 min, which can fully mix the polymer solution and the CALB solution, ensure the uniform distribution of the enzyme in the polymer microspheres, avoid local high or low enzyme concentration, and avoid the damage to the enzyme activity caused by the shear force generated by long-time stirring. For example, the stirring time can be 10 min, 15 min, 20 min, etc.

[0034] In some embodiments, the cross-linking agent for cross-linking and solidification includes at least one of calcium chloride and glutaraldehyde.

[0035] Calcium chloride is a common cross-linking agent for polysaccharide polymers such as sodium alginate, which binds to the carboxyl groups in the polymer to form a stable gel structure. Glutaraldehyde cross-links the amino groups in the enzyme protein or polymer, enhancing the mechanical strength and structural stability of the microspheres. The use of both or either of them can prevent the immobilized CALB from being damaged during the reaction due to factors such as stirring and pH changes, thereby ensuring the retention of enzyme molecules and preventing enzyme loss.

[0036] In some embodiments, the cross-linking and solidification time is between 1 h and 2 h.

[0037] The cross-linking and solidification time is between 1 h and 2 h, which ensures that the cross-linking reaction proceeds fully. If the cross-linking and solidification time is too short, the structure of the polymer microspheres is not fully stable and is prone to damage in subsequent reactions. If the cross-linking and solidification time is too long, the microspheres may be over-cross-linked, the pores may be blocked, and the diffusion of acetic acid and ethanol and ethyl acetate may be hindered, reducing the enzyme catalytic efficiency. For example, the cross-linking and solidification time can be 1 h, 2 h, etc.

[0038] In some embodiments, the extraction is performed by at least one of mechanical stirring and gas-lift stirring.

[0039] The core role of stirring is to enhance the contact area between the aqueous phase (containing acetic acid, ethanol, and immobilized enzyme) and the organic phase (extractant). Mechanical stirring pushes the two phases to mix by rotating the blades, which is suitable for conventional reaction systems. Gas-lift stirring forms a circulating flow by introducing gas, which is more gentle and reduces the shear damage to the immobilized enzyme, making it suitable for scenarios with high requirements for enzyme activity protection. Both can improve the efficiency of the transfer of ethyl acetate from the aqueous phase to the organic phase and reduce the inhibition of ethyl acetate on the enzyme.

[0040] In some embodiments, the organic extractant is dodecane; and the solubility of ethyl acetate in the dodecane is between 120 g / L and 150 g / L.

[0041] Dodecane is an inert organic solvent, which does not react with acetic acid, ethanol and ethyl acetate, has a density less than water, and can form a stable upper organic phase, which is convenient for subsequent phase separation; the solubility of ethyl acetate in dodecane is 120 g / L-150 g / L, which can effectively dissolve the ethyl acetate generated in the esterification reaction, promote the transfer of the product from the aqueous phase to the organic phase, reduce the concentration of ethyl acetate in the aqueous phase, thereby relieving the inhibition of ethyl acetate on CALB and improving the conversion rate of acetic acid. At the same time, the high boiling point of dodecane is quite different from that of ethyl acetate, which is convenient for subsequent rectification separation, and the extractant can also be recycled. For example, the solubility of ethyl acetate in dodecane can be 120 g / L, 130 g / L, 140 g / L, 150 g / L, etc.

[0042] In some embodiments, when the concentration of ethyl acetate in the dodecane is 30 g / L-90 g / L, the feeding of the ethanol and the acetic acid-containing wastewater is suspended, and the organic extractant containing ethyl acetate is pumped into the rectification tower to extract ethyl acetate, and the extracted organic extractant is returned to the reaction tank for recycling.

[0043] When the concentration of ethyl acetate in the dodecane is 30 g / L-90 g / L, the feeding of ethanol and acetic acid-containing wastewater is suspended to terminate the esterification reaction, prevent the addition of new acetic acid and ethanol from causing the product concentration to exceed the appropriate range, and at the same time avoid the interference of heat, stirring and other factors in the reaction process on the stability of subsequent distillation; then the organic extractant containing ethyl acetate is pumped into the rectification tower to extract ethyl acetate, and the ethyl acetate is separated in time to prevent excessive accumulation of ethyl acetate and reverse diffusion into the aqueous phase, inhibit the catalytic activity of the immobilized CALB, and maintain the high activity state of the enzyme; the extracted organic extractant is returned to the reaction tank for recycling, realizing the reuse of the extractant, greatly reducing the procurement cost, and at the same time avoiding the pollution of the waste extractant to the environment.

[0044] The present application will be further described below in conjunction with specific examples. The experimental methods in the following examples are generally determined according to the national standards / industry standards / the contents disclosed herein; if there is no corresponding national standard / industry standard / the contents disclosed herein, the general international standards, conventional conditions or the conditions recommended by the manufacturer are used.

[0045] Example 1 The Clostridium autoethanogenum fermentation wastewater is subjected to online acetic acid concentration monitoring to obtain acetic acid-containing wastewater; a polymer with a concentration of 2% is dissolved in a buffer solution with a pH value of 6 to obtain a polymer solution; then the polymer solution and the CALB solution are subjected to stirring for 10 minutes, microsphere forming and cross-linking solidification for 1 hour in sequence to obtain immobilized CALB; the immobilized CALB, the acetic acid-containing wastewater, ethanol and dodecane are placed in a reaction tank to perform esterification and real-time extraction, and a reaction mixture is obtained; when the concentration of ethyl acetate in the dodecane is 30 g / L, the feeding of ethanol and the acetic acid-containing wastewater is suspended, the upper organic extraction phase containing ethyl acetate in the reaction mixture is pumped into a rectifying column for distillation separation to obtain ethyl acetate, and the extracted dodecane is returned to the reaction tank for recycling; finally, the lower layer of the reaction mixture is introduced into a standing tank for phase separation, the upper organic extraction phase containing ethyl acetate is pumped into the reaction tank for reuse, and the lower aqueous phase is introduced into sewage treatment.

[0046] Example 2 The Clostridium autoethanogenum fermentation wastewater is subjected to online acetic acid concentration monitoring to obtain acetic acid-containing wastewater; a polymer with a concentration of 2% is dissolved in a buffer solution with a pH value of 6.5 to obtain a polymer solution; then the polymer solution and the CALB solution are subjected to stirring for 10 minutes, microsphere forming and cross-linking solidification for 1 hour in sequence to obtain immobilized CALB; the immobilized CALB, the acetic acid-containing wastewater, ethanol and dodecane are placed in a reaction tank to perform esterification and real-time extraction, and a reaction mixture is obtained; when the concentration of ethyl acetate in the dodecane is 50 g / L, the feeding of ethanol and the acetic acid-containing wastewater is suspended, the upper organic extraction phase containing ethyl acetate in the reaction mixture is pumped into a rectifying column for distillation separation to obtain ethyl acetate, and the extracted dodecane is returned to the reaction tank for recycling; finally, the lower layer of the reaction mixture is introduced into a standing tank for phase separation, the upper organic extraction phase containing ethyl acetate is pumped into the reaction tank for reuse, and the lower aqueous phase is introduced into sewage treatment.

[0047] Example 3 The Clostridium autoethanogenum fermentation wastewater is subjected to online acetic acid concentration monitoring to obtain acetic acid-containing wastewater; a polymer with a concentration of 3% is dissolved in a buffer solution with a pH value of 7 to obtain a polymer solution; then the polymer solution and the CALB solution are subjected to stirring for 15 minutes, microsphere forming and cross-linking solidification for 1.5 hours in sequence to obtain immobilized CALB; the immobilized CALB, the acetic acid-containing wastewater, ethanol and dodecane are placed in a reaction tank to perform esterification and real-time extraction, and a reaction mixture is obtained; when the concentration of ethyl acetate in the dodecane is 70 g / L, the feeding of ethanol and the acetic acid-containing wastewater is suspended, the upper organic extraction phase containing ethyl acetate in the reaction mixture is pumped into a rectifying column for distillation separation to obtain ethyl acetate, and the extracted dodecane is returned to the reaction tank for recycling; finally, the lower layer of the reaction mixture is introduced into a standing tank for phase separation, the upper organic extraction phase containing ethyl acetate is pumped into the reaction tank for reuse, and the lower aqueous phase is introduced into sewage treatment.

[0048] Example 4 The online acetic acid concentration monitoring was performed on the Clostridium autoethanogenum fermentation wastewater to obtain acetic acid-containing wastewater; the polymer with a concentration of 3% was dissolved in a buffer solution with a pH value of 7.5 to obtain a polymer solution; then the polymer solution and the CALB solution were sequentially stirred for 20 min, microsphere forming and cross-linking solidification for 2 h to obtain immobilized CALB; the immobilized CALB, the acetic acid-containing wastewater, ethanol and dodecane were placed in a reaction tank to perform esterification and real-time extraction to obtain a reaction mixture; when the concentration of ethyl acetate in dodecane was 80 g / L, the feeding of ethanol and acetic acid-containing wastewater was suspended, the organic extraction phase containing ethyl acetate in the upper layer of the reaction mixture was pumped into a rectifying column for distillation separation to obtain ethyl acetate, and the extracted dodecane was returned to the reaction tank for recycling; finally, the lower layer of the reaction mixture was introduced into a standing tank for phase separation, the organic extraction phase containing ethyl acetate in the upper layer was pumped into the reaction tank for reuse, and the lower layer of the aqueous phase was introduced into sewage treatment.

[0049] Example 5 The online acetic acid concentration monitoring was performed on the Clostridium autoethanogenum fermentation wastewater to obtain acetic acid-containing wastewater; the polymer with a concentration of 4% was dissolved in a buffer solution with a pH value of 8 to obtain a polymer solution; then the polymer solution and the CALB solution were sequentially stirred for 20 min, microsphere forming and cross-linking solidification for 2 h to obtain immobilized CALB; the immobilized CALB, the acetic acid-containing wastewater, ethanol and dodecane were placed in a reaction tank to perform esterification and real-time extraction to obtain a reaction mixture; when the concentration of ethyl acetate in dodecane was 90 g / L, the feeding of ethanol and acetic acid-containing wastewater was suspended, the organic extraction phase containing ethyl acetate in the upper layer of the reaction mixture was pumped into a rectifying column for distillation separation to obtain ethyl acetate, and the extracted dodecane was returned to the reaction tank for recycling; finally, the lower layer of the reaction mixture was introduced into a standing tank for phase separation, the organic extraction phase containing ethyl acetate in the upper layer was pumped into the reaction tank for reuse, and the lower layer of the aqueous phase was introduced into sewage treatment.

[0050] Comparative Example 1 The Clostridium autoethanogenum fermentation wastewater is subjected to online acetic acid concentration monitoring to obtain acetic acid-containing wastewater; the polymer with a concentration of 2% is dissolved in a buffer solution with a pH value of 5 to obtain a polymer solution; then the polymer solution and the CALB solution are subjected to 10 minutes of stirring, microsphere forming and 1 hour of cross-linking and solidification in sequence to obtain the immobilized CALB; the immobilized CALB, the acetic acid-containing wastewater, ethanol and dodecane are placed in a reaction tank to perform esterification and real-time extraction to obtain a reaction mixture; when the concentration of ethyl acetate in the dodecane is 20 g / L, the feeding of ethanol and the acetic acid-containing wastewater is suspended, the upper organic extraction phase containing ethyl acetate of the reaction mixture is pumped into a rectifying column for distillation separation to obtain ethyl acetate, and the extracted dodecane is returned to the reaction tank for recycling; finally, the lower layer of the reaction mixture is introduced into a standing tank for phase separation, wherein the upper organic extraction phase containing ethyl acetate is pumped into the reaction tank for reuse, and the lower aqueous phase is introduced into sewage treatment.

[0051] Comparative Example 2 The Clostridium autoethanogenum fermentation wastewater is subjected to online acetic acid concentration monitoring to obtain acetic acid-containing wastewater; the polymer with a concentration of 2% is dissolved in a buffer solution with a pH value of 5 to obtain a polymer solution; then the polymer solution and the CALB solution are subjected to 10 minutes of stirring, microsphere forming and 1 hour of cross-linking and solidification in sequence to obtain the immobilized CALB; the immobilized CALB, the acetic acid-containing wastewater, ethanol and dodecane are placed in a reaction tank to perform esterification and real-time extraction to obtain a reaction mixture; when the concentration of ethyl acetate in the dodecane is 20 g / L, the feeding of ethanol and the acetic acid-containing wastewater is suspended, the upper organic extraction phase containing ethyl acetate of the reaction mixture is pumped into a rectifying column for distillation separation to obtain ethyl acetate, and the extracted dodecane is returned to the reaction tank for recycling; finally, the lower layer of the reaction mixture is introduced into a standing tank for phase separation, wherein the upper organic extraction phase containing ethyl acetate is pumped into the reaction tank for reuse, and the lower aqueous phase is introduced into sewage treatment.

[0052] Effect data: The effect data of Examples 1 to 5 and Comparative Examples 1 to 2 are shown in Table 1.

[0053] Experimental method of effect data: The laboratory small test device is used to simulate the industrial scale reaction system.

[0054] 1. Calculation of ethyl acetate yield:

[0055] Table 1

[0056] From the above effect data table, the differences between different examples and comparative examples can be directly compared. The following conclusions can be drawn: From Examples 1-5 and Comparative Examples 1-2, it can be seen that the key parameters of the CALB immobilization process include the buffer pH, polymer concentration, stirring time, cross-linking curing time, and the ethyl acetate concentration in the extractant entering the rectification process, which are the core factors affecting the yield. The buffer pH directly affects the catalytic activity of CALB, and the polymer concentration, stirring time, and cross-linking curing time affect the enzyme activity by affecting the structure of the immobilized enzyme and prolonging the number of repeated uses, thereby providing a guarantee for high conversion of the esterification reaction; and the ethyl acetate concentration in the extractant before rectification has a significant effect on the yield, and the examples control this concentration to ensure efficient transfer of ethyl acetate and avoid product inhibition. The examples significantly improve the yield by optimizing these factors, which is much better than the comparative examples that are not optimized.

[0057] The above description is merely that of a specific implementation of the application, and persons skilled in the art can understand or implement the application. Various modifications to these examples will be apparent to those skilled in the art, and the general principles defined in this application can be implemented in other examples without departing from the spirit or scope of the application. Therefore, the application will not be limited to these examples shown in the application, but will conform to the widest scope consistent with the principles and novel features sought by the application.

Claims

1. A method for producing ethyl acetate from acetic acid in fermentation wastewater, characterized in that, The method includes: Online monitoring of acetic acid concentration was performed on Clostridium ethanol fermentation wastewater to obtain acetic acid-containing wastewater. The polymer was dissolved in a buffer solution to obtain a polymer solution; The polymer solution and CALB solution were stirred, microspheres were formed, and cross-linked and cured sequentially to obtain immobilized CALB. The immobilized CALB, the acetic acid-containing wastewater, ethanol, and organic extractant were placed in a reaction vessel to carry out esterification and real-time extraction to obtain a reaction mixture. The organic extract phase containing ethyl acetate in the upper layer of the reaction mixture is pumped into a distillation column for distillation and separation to obtain ethyl acetate. The extracted organic extractant is then returned to the reaction tank for recycling. The lower layer of the reaction mixture is introduced into a settling tank for phase separation to obtain the separated phase; The upper organic extract phase containing ethyl acetate in the separated phase is pumped into a reaction tank for reuse, and the lower aqueous phase of the separated phase is sent to wastewater treatment.

2. The method according to claim 1, characterized in that, The concentration of the polymer is 2% to 4%.

3. The method according to claim 1, characterized in that, The polymer includes at least one of sodium alginate, polylactic acid-glycolic acid copolymer, and chitosan.

4. The method according to claim 1, characterized in that, The pH value of the buffer solution is 6.0~8.

0.

5. The method according to claim 1, characterized in that, The stirring time is 10 min to 20 min.

6. The method according to claim 1, characterized in that, The cross-linking agent for cross-linking curing includes at least one of calcium chloride and glutaraldehyde.

7. The method according to claim 1, characterized in that, The cross-linking and curing time is 1h to 2h.

8. The method according to claim 1, characterized in that, The extraction is performed by at least one of mechanical stirring and airlift stirring.

9. The method according to claim 1, characterized in that, The organic extractant is dodecane; the solubility of ethyl acetate in dodecane is 120 g / L to 150 g / L.

10. The method according to claim 9, characterized in that, When the concentration of ethyl acetate in the dodecane is 30 g / L to 90 g / L, the feeding of ethanol and acetic acid-containing wastewater is suspended, and the organic extractant containing ethyl acetate is pumped into a distillation column to extract ethyl acetate. The extracted organic extractant is then returned to the reaction tank for recycling.

Images