Fatty acid ethyl ester transesterification method

Abstract

The invention discloses a fatty acid ethyl ester transesterification method. The method comprises the following steps: S1, feeding glycerol and fatty acid ethyl ester into a batching kettle to be mixed with enzyme; s2, introducing nitrogen through a high-pressure nitrogen feeding end, carrying out transesterification reaction to generate triglyceride type fish oil, and simultaneously generating gas ethanol and redundant nitrogen as byproducts; s3, purging the kettle bottom through a first nitrogen nozzle arranged at the bottom of the batching kettle to loosen the enzyme at the kettle bottom; s4, ethanol and nitrogen are pumped into a condenser through a vacuum pipeline and a vacuum pump, the ethanol is condensed into a liquid state and then guided into an ethanol tank to be collected, and uncondensed nitrogen is conveyed into a nitrogen tank to be recycled; s5, filtering the enzyme by using a first filter plate at the bottom of the batching kettle, and outputting a product through a first discharge pipe; the nitrogen tank serves as the feeding end of circulating nitrogen to supply nitrogen to the nozzle. By optimizing a raw material feeding path, arranging a multi-stage filter plate structure and adopting the design of vacuum negative pressure alcohol extraction, nitrogen recycling and the like, the yield and the product purity of triglyceride are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of fatty acid ethyl ester transesterification and discloses a fatty acid ethyl ester transesterification method. Background Art

[0002] With the growing demand for functional lipid nutritional supplements, fish oil products rich in polyunsaturated fatty acids such as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) have gained widespread application in health supplements, food additives, and pharmaceuticals. Fish oil products currently on the market are broadly divided into two categories: triglyceride (TG) and ethyl ester (EE). Triglyceride-based fish oils offer advantages in nutrient absorption, safety, and consumer acceptance due to their higher bioavailability and closer proximity to their naturally occurring form. However, due to purification and economic considerations, ethyl esters are often produced in large quantities as intermediates. Therefore, the efficient conversion of EE-based fish oil to TG-based fish oil has become a key technological path for the current industry development.

[0003] Traditional ethyl ester transesterification processes primarily involve strong acid or base catalysis. However, these reactions are demanding, requiring high temperatures and pressures. These reactions are prone to side reactions, which not only affect the purity of the target product but also introduce hazardous residues, posing safety risks. Furthermore, catalysts are difficult to separate and cannot be reused, increasing the pressure on wastewater treatment and failing to meet the requirements of green production. In recent years, enzymatic transesterification has become a mainstream approach. Using lipase as a biocatalyst, it can convert EE to TG under relatively mild conditions (e.g., around 60°C). Enzymatic transesterification offers advantages such as high specificity, high reaction efficiency, and minimal byproducts. However, due to issues such as high enzyme costs and long catalytic cycles, its industrial application remains limited by reaction efficiency and system design.

[0004] In addition, the transesterification process also involves several key technical points, such as the precise proportion of glycerol, ethyl ester, and enzyme, the effective removal of the by-product ethanol, the separation and recovery of the catalyst, and the high-purity output of the product. Existing reaction methods are mostly step-by-step processes, which are not only complex and energy-intensive, but also not conducive to achieving continuous production. Therefore, there is an urgent need for a fatty acid ethyl ester transesterification method with optimized structure, convenient operation, high degree of automation, and suitable for industrial application, in order to improve the conversion rate and purity of TG fish oil, while achieving the recycling of key resources such as catalysts and ethanol, and meeting the requirements of green and efficient production. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for transesterification of fatty acid ethyl ester, which achieves efficient conversion of fatty acid ethyl ester to triglyceride by optimizing the system structure and process flow.

[0006] The technical solutions provided by the present invention are as follows: on the one hand: A method for transesterification of fatty acid ethyl esters comprises the following steps: S1: Glycerol and fatty acid ethyl ester are fed into the batching kettle through the glycerol feed end and the ethyl ester feed end respectively and mixed with the enzyme; S2: High-pressure nitrogen is introduced into the batching kettle through the high-pressure nitrogen feed port to form an inert protective atmosphere, and the materials in the kettle are stirred to perform a transesterification reaction to produce triglyceride-type fish oil, while producing ethanol gas and excess nitrogen as by-products; S3: blowing nitrogen gas from a plurality of first nitrogen nozzles provided at the bottom of the batching kettle to the bottom of the kettle to loosen the enzyme at the bottom of the kettle; S4: The ethanol and nitrogen generated during the reaction are drawn into a condenser through a vacuum pipe and a vacuum pump located at the top of the batching kettle. The ethanol in the condenser is condensed into liquid and then introduced into an ethanol tank for collection. The uncondensed nitrogen is transported to a nitrogen tank for recovery. S5: The enzyme is filtered using the first filter plate at the bottom of the batching kettle, and the product is discharged through the first discharge pipe and purged with nitrogen from the second nitrogen nozzle to assist in discharge; The nitrogen tank serves as a feed end of circulating nitrogen and is connected to the first nitrogen nozzle and the second nitrogen nozzle to supply nitrogen thereto.

[0007] In some embodiments, the outlet of the high-pressure nitrogen feed end is connected to a nitrogen tank to ensure the amount of nitrogen in the nitrogen tank.

[0008] In some embodiments, a plurality of vertically arranged second filter plates are provided in the batching kettle to filter the enzyme, and the filtered product is transported to the discharge end through the second discharge pipe.

[0009] In some embodiments, the materials from the first discharge pipe and the second discharge pipe are combined and transported to the discharge end. When the inlet of the discharge end is closed, the materials squeezed out of the first discharge pipe and the second discharge pipe are returned to the batching kettle through the return line.

[0010] In some embodiments, the batching kettle is heated by a water bath heating device, and the batching kettle is temperature-controlled and heated by the heating tank, the heating wall, and the circulating water path therebetween.

[0011] In some embodiments, the first nitrogen jet is purged toward the bottom of the batching kettle.

[0012] In some embodiments, the enzyme is fed through the enzyme feed port at the top of the batching tank.

[0013] In some embodiments, the material after the first discharge pipe and the second discharge pipe are combined is transported by the discharge pipe to the fish oil temporary storage tank for temporary storage.

[0014] In some embodiments, a low-pressure nitrogen inlet is provided at the top of the fish oil temporary storage tank, and the air pressure in the temporary storage tank is maintained stable through the low-pressure nitrogen feed end to prevent oxidation.

[0015] In some embodiments, a fish oil discharge pipe is provided at the bottom of the fish oil temporary storage tank to discharge the finished fish oil to the fish oil discharge port, and the fish oil is discharged from the fish oil discharge pipe with the assistance of a high-pressure nitrogen feed end.

[0016] On the other hand, the fatty acid ethyl ester transesterification method of the present application is further illustrated by the system structure: A fatty acid ethyl ester transesterification system, comprising: At least one batching kettle for mixing glycerol, ethyl ester and enzyme to produce triglyceride fish oil; Feed end, used to transport raw materials to the batching kettle, including glycerol feed end, ethyl ester feed end and high-pressure nitrogen feed end; At least one set of discharge ends connected to the bottom of the batching kettle for transporting and storing finished fish oil; A first filter plate is provided at the bottom of the batching kettle for filtering the enzyme in the batching kettle. The discharge port of the first filter plate is connected to the discharge end through a first discharge pipe. A plurality of first nitrogen nozzles are provided at the bottom of the batching kettle, and a second nitrogen nozzle is provided at the discharge port of the first filter plate. A vacuum pipe is provided on the top of the batching kettle, which transports the ethanol generated by the reaction in the batching kettle and excess nitrogen to the condenser through a vacuum pump. The condensed liquid ethanol enters the ethanol tank for subsequent reuse, and the excess nitrogen is transported to the nitrogen tank. The nitrogen tank serves as the feed end of the circulating nitrogen and is connected to the first nitrogen nozzle and the second nitrogen nozzle to supply nitrogen thereto.

[0017] Furthermore, the high-pressure nitrogen feed end is connected to a nitrogen tank.

[0018] In some embodiments, a plurality of vertically arranged second filter plates are provided in the batching kettle, and the discharge ports of the second filter plates are connected to the discharge end through second discharge pipes.

[0019] Furthermore, the first discharge pipe and the second discharge pipe are connected to the discharge end after merging, and a return pipe is provided in front of the inlet of the discharge end, and the return pipe is connected to the batching kettle. When the inlet of the discharge end is closed, the material squeezed out by the first discharge pipe and the second discharge pipe is returned to the batching kettle.

[0020] Furthermore, a water bath heating device is provided on one side of the batching kettle, and the water bath heating device includes a heating wall provided on the wall of the batching kettle, a heating tank, and a circulating water path connecting the heating wall and the heating tank.

[0021] Furthermore, the gas outlets of the plurality of first nitrogen nozzles are arranged toward the bottom of the batching kettle.

[0022] Furthermore, an enzyme feeding end is provided on the top of the batching kettle.

[0023] Furthermore, the discharge end includes a fish oil temporary storage tank, and the first discharge pipe and the second discharge pipe are connected to the fish oil temporary storage tank after merging.

[0024] Furthermore, a low-pressure nitrogen inlet is provided on the top of the fish oil temporary storage tank and is connected to the low-pressure nitrogen feed end.

[0025] Furthermore, a fish oil discharge pipe is provided at the bottom of the fish oil temporary storage tank, the fish oil discharge pipe is connected to the fish oil discharge port, and the high-pressure nitrogen feed end is connected to the fish oil discharge pipe.

[0026] In summary, the beneficial effects of the present invention are as follows: (1) The present method achieves precise control over the entire transesterification reaction process through the coordinated configuration of multiple filter plates inside and outside the batching kettle, a vacuum extraction and condensation recovery device, a water bath heating system, and a nitrogen protection and propulsion structure. The enzyme is precisely added through the top feed port and maintains high activity in the temperature-controlled water bath environment. The bottom nitrogen nozzle and the side wall heating layer ensure reaction uniformity. The enzyme is efficiently retained by the first filter plate, the second filter plate, and other structures to prevent it from entering the finished product, thereby improving the purity of the target product.

[0027] (2) In the present invention, the by-product ethanol is extracted in real time through a vacuum pipeline and liquefied through a condenser and recovered to an ethanol tank, thereby avoiding inhibition of reaction equilibrium and recycling resources at the same time; the excess nitrogen in the batching kettle is recovered to a nitrogen tank through a vacuum device and then supplied to the nozzle for use. At the same time, the high-pressure nitrogen feed end is connected to the nitrogen tank, and when the recovered nitrogen is insufficient, the nitrogen at the nozzle can be supplemented to achieve recycling and reduce operating costs.

[0028] (3) The method of the present invention has a high overall integration level. The design achieves effective separation and reuse of enzymes, closed-loop recovery of by-products, and continuous output of products. The discharge system is equipped with a return line and a temporary fish oil storage tank, which is suitable for continuous production mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Flow chart of the method of the present invention.

[0030] Figure 2 Schematic diagram of the system structure of the present invention; Figure 3 It is a schematic structural diagram of the batching kettle of the present invention.

[0031] The reference numerals are as follows: 1. Ingredient kettle; 2. Glycerol feed port; 3. Ethyl ester feed port; 4. High-pressure nitrogen feed port; 5. First filter plate; 6. First discharge pipe; 7. First nitrogen nozzle; 8. Second nitrogen nozzle; 9. Vacuum pipe; 10. Vacuum pump; 11. Condenser; 12. Ethanol tank; 13. Nitrogen tank; 14. Second filter plate; 15. Second discharge pipe; 16. Return pipe; 17. Heating wall; 18 Heating tank; 19. Enzyme feed port; 20. Fish oil temporary storage tank; 21. Low-pressure nitrogen feed port; 22. Fish oil discharge pipe; 23. Fish oil discharge port. DETAILED DESCRIPTION

[0032] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0033] Example 1 like Figure 1-3 As shown, the system of this method primarily comprises at least one batching kettle 1. This vertical structure can withstand negative pressure and a certain temperature. The main body of the batching kettle is made of 316L stainless steel to ensure good corrosion resistance and food-grade performance. High-pressure nitrogen is used to stir the interior of the batching kettle 1 to ensure thorough mixing of the raw materials, improving reaction uniformity and transesterification efficiency.

[0034] Regarding raw material feeding, the system is equipped with multiple independent feed ports, specifically: glycerol feed port 2, ethyl ester feed port 3, and high-pressure nitrogen feed port 4. Glycerol feed port 2 and ethyl ester feed port 3 are each connected to a raw material storage tank, and metering pumps deliver a fixed amount of raw materials to batching kettle 1. High-pressure nitrogen feed port 4 delivers high-pressure nitrogen for system gas protection, material mixing, and pressure feeding. Upon entering batching kettle 1, nitrogen creates an inert atmosphere, preventing volatile components like ethyl ester from reacting with air or oxidizing. It also acts as a pusher and compressor during material mixing and discharge.

[0035] A first filter plate 5 is provided at the bottom of the batching kettle 1. The filter plate adopts a stainless steel porous mesh structure and is used to filter the residual enzyme after the reaction to prevent it from entering the finished fish oil and affecting the quality. The discharge port of the first filter plate 5 is connected to the discharge end through a first discharge pipe 6. In order to prevent the filter plate from being blocked and to improve the filtration efficiency, a second nitrogen nozzle 8 is also provided at the discharge port of the first filter plate 5. By continuously spraying nitrogen, nitrogen can be sprayed during discharge to promote the flow of materials in the discharge pipe, prevent material retention, and promote the material to pass through the filter plate smoothly and enter the discharge pipe. A number of first nitrogen nozzles 7 are also evenly arranged at the bottom of the batching kettle 1. The gas outlet direction of these nozzles is toward the bottom of the batching kettle 1. They can play a stirring auxiliary role during the reaction process to loosen the enzymes deposited on the filter plate, improve the fluidity of the bottom material, effectively avoid dead corner material accumulation and promote the filtration process, ensure the uniformity of the reaction, and at the same time assist in pressurizing the bottom material during the discharge process.

[0036] To separate and recycle the ethanol byproduct generated by the reaction, a vacuum line 9 is installed at the top of the batching kettle 1. This line is connected to a vacuum pump 10. In this embodiment, the vacuum pump 10 is a screw vacuum pump. During the reaction, a moderate negative pressure environment is created inside the batching kettle 1, which facilitates the volatilization of the ethanol and accelerates the conversion rate of the reaction equilibrium. The extracted ethanol gas and excess nitrogen enter the condenser 11 through the vacuum line 9 for condensation. In this embodiment, the condenser is a cold trap. The coolant temperature in the condenser 11 can be controlled between -10°C and 5°C, effectively cooling the ethanol gas to a liquid state. The condensed ethanol liquid is stored in the ethanol tank 12 and can be used for the next batch of production, thus achieving resource recycling. The remaining uncondensed nitrogen is discharged through the gas separation port and transported to the nitrogen tank 13 for storage. It can then be supplied to the first nitrogen nozzle 7 and the second nitrogen nozzle 8, forming a closed-loop gas supply system and reducing nitrogen consumption. At the same time, the high-pressure nitrogen feed end 4 is connected to the nitrogen tank 13, so that when the recovered nitrogen is insufficient, the nitrogen at the nozzle can be supplemented to achieve recycling and reduce operating costs.

[0037] Example 2 This embodiment is formed on the basis of embodiment 1, by further optimizing the discharging method of the batching kettle, thereby improving the discharging rate. Specifically: In order to enhance the filtering capacity of the system, several vertically arranged second filter plates 14 can be added inside the batching kettle 1. The second filter plates 14 are distributed in the bottom space of the batching kettle and are arranged along the sinking path of the reactants to increase the filtration area of ​​the enzyme and improve the filtration efficiency. The discharge port of the second filter plate 14 is connected to the discharge end through the second discharge pipe 15, forming a two-stage filtration structure with the first filter plate 5 to ensure the discharge rate.

[0038] The first and second discharge pipes 6 and 15 converge at their junction to form the main discharge line, which ultimately leads to the discharge port. To enhance system operational flexibility, a return line 16 is provided at the discharge port entrance, connecting to the interior of the batching kettle 1. When the discharge port entrance is closed, the material discharged from the first and second discharge pipes 6 and 15 in the batching kettle 1 automatically flows back into the batching kettle 1 through the return line 16, ensuring sufficient reaction of the material.

[0039] Regarding temperature control, a water bath heating device is installed on one side of the batching kettle 1. This device comprises a heating wall 17, a heating tank 18, and a circulating water circuit connecting the two. In this embodiment, the circulating water is derived from condensate from other equipment or tap water, which is heated and heat-exchanged before being discharged into a drain. The heating tank 18 has a stainless steel inner structure. An electric heater heats the medium (such as water or thermal oil). A circulating pump drives the water through the circulating water circuit and into the interior of the heating wall 17. The heating wall 17 is in close contact with the outer wall of the batching kettle 1, and heats the reaction system within the kettle through heat conduction, ensuring that the reaction temperature remains within a preset range (e.g., 45-60°C). This satisfies the thermal environment required for the enzymatic transesterification reaction and improves the reaction rate.

[0040] To ensure precise enzyme dosing, an enzyme feed port 19 is located on top of the batching kettle 1. This port is connected to an automatic metering device, allowing lipase to be quantitatively added according to process requirements. This design avoids the potential contamination and inaccurate dosing caused by manual dosing, improving overall controllability and automation.

[0041] The discharge end is provided with a fish oil temporary storage tank 20, which adopts a closed insulation structure for storing triglyceride fish oil that has completed the transesterification reaction and has been filtered through the filter plate. A low-pressure nitrogen inlet is provided on the top of the fish oil temporary storage tank 20, which is connected to the low-pressure nitrogen feed end 21 to form an inert gas protective layer in the tank body to prevent the finished fish oil from being oxidized by air during storage, thereby maintaining its stability and nutritional activity. A fish oil discharge pipe 22 is provided at the bottom of the fish oil temporary storage tank 20, which eventually leads to the fish oil discharge port 23 to achieve the final discharge and transportation of the finished product. At the same time, to prevent the fish oil from flowing slowly due to viscosity during transportation, the fish oil discharge pipe 22 is also connected to the high-pressure nitrogen feed end 4, utilizing nitrogen pressure to assist the fish oil transportation, making the discharge smoother and more efficient. It should be noted that each pipeline of the present application is provided with at least one control valve, and the transportation of the liquid relies on a centrifugal pump to achieve control of the gas circuit or liquid circuit.

[0042] In summary, the fatty acid ethyl ester transesterification method provided by the present invention not only significantly improves the yield and product purity of triglycerides, but also improves the automation and environmental protection level of the production process through comprehensive designs such as optimizing the raw material feeding path, setting a multi-stage filter plate structure, adopting vacuum negative pressure alcohol extraction, nitrogen recovery and reuse, water bath temperature control heating, and nitrogen-assisted discharging, but also is suitable for the industrial transesterification production of various fatty acid ethyl ester systems such as fish oil and vegetable oil, and has broad promotion prospects.

[0043] It should be noted that any implementations not shown or described in the drawings or the main text of the specification are known to those skilled in the art and are not described in detail. In addition, the above definitions of the various elements and methods are not limited to the various specific structures, shapes, or methods mentioned in the embodiments.

[0044] It should also be noted that while examples of parameters including specific values ​​may be provided herein, these parameters do not need to be exactly equal to the corresponding values, but rather may approximate the corresponding values ​​within acceptable error tolerances or design constraints. Directional terms mentioned in the embodiments, such as "upper," "lower," "front," "back," "left," "right," "inner," and "outer," are merely references to the directions in the accompanying drawings and are not intended to limit the scope of protection of this application.

[0045] The foregoing description shows and describes preferred embodiments of the present invention. As previously mentioned, it should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Instead, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the inventive concept described herein by the teachings above or by techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the present invention are intended to be within the scope of the appended claims.

Claims

1. A method for transesterification of fatty acid ethyl esters, characterized in that: The following steps are involved: S1: Glycerol and fatty acid ethyl ester are respectively fed into the batching kettle (1) through the glycerol feed end (2) and the ethyl ester feed end (3) and mixed with the enzyme; S2: High-pressure nitrogen is introduced into the batching kettle (1) through the high-pressure nitrogen feed end (4) to form an inert protective atmosphere, and the materials in the kettle are stirred to perform a transesterification reaction to generate triglyceride-type fish oil, while producing gaseous ethanol and excess nitrogen; S3: blowing the bottom of the batching kettle (1) through a plurality of first nitrogen nozzles (7) provided at the bottom of the batching kettle (1) to loosen the enzyme at the bottom of the kettle; S4: The ethanol and nitrogen generated during the reaction are drawn into a condenser (11) through a vacuum pipe (9) and a vacuum pump (10) provided at the top of the batching kettle (1), the ethanol in the condenser (11) is condensed into a liquid state and then introduced into an ethanol tank (12) for collection, and the uncondensed nitrogen is transported to a nitrogen tank (13) for recovery; S5: The enzyme is filtered using the first filter plate (5) at the bottom of the batching kettle (1), and the product is discharged through the first discharge pipe (6), while the nitrogen purge from the second nitrogen nozzle (8) assists in discharge; The nitrogen tank (13) serves as a feed end for circulating nitrogen and is connected to the first nitrogen nozzle (7) and the second nitrogen nozzle (8) to supply nitrogen thereto.

2. The fatty acid ethyl ester transesterification method according to claim 1, wherein The outlet end of the high-pressure nitrogen feed end (4) is connected to the nitrogen tank (13) to ensure the amount of nitrogen in the nitrogen tank (13).

3. The fatty acid ethyl ester transesterification method according to claim 1, wherein A plurality of vertically arranged second filter plates (14) are provided in the batching kettle (1) to filter the enzyme, and the filtered product is transported to the discharge end through the second discharge pipe (15).

4. The fatty acid ethyl ester transesterification method according to claim 3, wherein The materials from the first discharge pipe (6) and the second discharge pipe (15) are combined and transported to the discharge end. When the inlet of the discharge end is closed, the materials squeezed out from the first discharge pipe (6) and the second discharge pipe (15) are returned to the batching kettle (1) through the return pipe (16).

5. The fatty acid ethyl ester transesterification method according to claim 1, wherein The batching kettle (1) is heated by a water bath heating device, and the batching kettle (1) is temperature-controlled and heated by a heating tank (18), a heating wall (17), and a circulating water path therebetween.

6. The fatty acid ethyl ester transesterification method according to claim 1, wherein The first nitrogen nozzle (7) blows toward the bottom of the batching kettle (1).

7. The fatty acid ethyl ester transesterification method according to claim 1, wherein The enzyme is fed through the enzyme feed port (19) at the top of the batching kettle (1).

8. The fatty acid ethyl ester transesterification method according to claim 4, wherein The material that has been combined through the first discharge pipe (6) and the second discharge pipe (15) is transported by the discharge pipe to the fish oil temporary storage tank (20) for temporary storage.

9. The fatty acid ethyl ester transesterification method according to claim 8, wherein A low-pressure nitrogen inlet is provided at the top of the fish oil temporary storage tank (20), and the air pressure in the temporary storage tank is kept stable through the low-pressure nitrogen feed end (21) to prevent oxidation.

10. The method for transesterification of fatty acid ethyl ester according to claim 8, wherein A fish oil discharge pipe (22) is provided at the bottom of the fish oil temporary storage tank (20) to discharge the finished fish oil to the fish oil discharge port (23). At the same time, the fish oil is discharged from the fish oil discharge pipe (22) with the assistance of a high-pressure nitrogen feed end (4).

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