A method for treating an electrochemical synthesis sebacic acid dimethyl ester reaction solution

Abstract

The application discloses a device and method for treating dimethyl sebacate electrolysis reaction products. Some by-products exist in the product of the dimethyl sebacate electrolysis reaction product after water is added to remove the solvent, the method is to add an extractant and an auxiliary agent to the reaction product and to mix and disperse through a pipeline built-in component, through the treatment, dimethyl adipate and methyl hexahydroxyhexanoate are transferred to an organic phase, and the inorganic phase is treated to meet the reuse requirements. The effect of the application is that by introducing the extractant and the auxiliary agent, the reaction product is treated by using the high-efficiency dispersion mixing structure, the process is simple, and the energy consumption is low. By using the method, the product yield can be improved, the process is simplified, the system inventory is reduced, and the method can be applied to industrial application.

Description

Technical Field

[0001] This invention relates to the field of chemical separation, specifically to a method for processing reaction solutions used in the electrochemical synthesis of dimethyl sebacate. Background Technology

[0002] Dimethyl sebacate is an organic synthesis intermediate that can be used as a plasticizer, softener, and solvent in the synthesis of rubber from ethylene resins. It can also be used to produce light stabilizers through transesterification, and its market demand is strong. Dimethyl sebacate can be synthesized into sebamediamine through dehydration and hydrogenation, and then hydrolyzed to obtain sebamic acid. Compared with the castor oil method for producing sebamic acid, it has a more stable price, produces less waste, and has a clear competitive advantage.

[0003] Dimethyl sebacate is produced via a Brown-Walker electrolytic decarboxylation coupling reaction of monomethyl adipic acid in an electrolytic cell. The reaction solution obtained from the electrolysis reaction is hydrated and desolventized, resulting in two phases: an organic phase and an inorganic phase. The organic phase mainly consists of dimethyl sebacate; the inorganic phase mainly consists of aqueous solutions of organic salts, methyl hexanoate, and dimethyl adipic acid. After phase separation, the inorganic phase undergoes post-treatment and is then returned to the reaction system for recycling. During the reaction, byproducts such as dimethyl adipic acid and methyl hexanoate mainly enter the inorganic phase and are returned to the reaction system with it. With continuous reaction recycling, reaction byproducts accumulate in the system, leading to a decrease in reaction current efficiency, reduced selectivity, and shortened electrode life.

[0004] To address these issues, the conventional approach is to discharge large quantities of the circulating fluid containing byproducts externally to prevent their accumulation within the system. This undoubtedly increases the volume of waste liquid and does not fundamentally solve the problems. Therefore, a simple and effective treatment method is needed to separate the byproducts and is easily industrially feasible. Summary of the Invention

[0005] To address the problems existing in the above process, this invention provides a method for processing the reaction solution of electrochemically synthesized dimethyl sebacate. By using an extractant and employing the mixing and dispersion of multi-segment pipeline built-in components, combined with the optimization of process materials, the extraction process is completed within the flow pipeline. Subsequently, through liquid-liquid phase separation, the reaction by-products and recycled materials can be separated. This method can avoid the discharge of circulating materials, optimize investment and operating costs, and improve the competitiveness of the equipment.

[0006] To achieve the above technical effects, the present invention adopts the following technical solution:

[0007] A method for processing the reaction solution in the electrochemical synthesis of dimethyl sebacate includes the following steps:

[0008] (1) The reaction solution is collected from the electrolytic reactor of the electrochemical synthesis of dimethyl sebacate and the solvent is replaced with water. (2) The reaction solution obtained in step (1) is mixed with the extractant.

[0009] (3) Optionally, the mixture of the reaction solution and the extractant is mixed again with the extractant.

[0010] (4) Add an auxiliary agent to the last mixture after multiple mixing of the extractant and the reaction solution. The mixture containing the auxiliary agent enters the phase separation tank to separate the inorganic phase and the organic phase. The inorganic phase is post-treated to obtain the product for recycling and electrochemical reaction.

[0011] Preferably, step (3) can be repeated multiple times.

[0012] Preferably, the reaction solution collected from the electrolytic reactor for the electrochemical synthesis of dimethyl sebacate is prepared using monomethyl adipic acid as a raw material, a salt of monomethyl adipic acid as a conductive medium, and methanol as a solvent. Under specific current and voltage, and through electrode action, a decarboxylation coupling reaction occurs to generate the main product, dimethyl sebacate, and simultaneously produce byproducts such as dimethyl adipic acid and methyl hexahydroxyhexanoate. The electrolytic reactor reactants are homogeneous. The collected electrolytic reactor reactants are first subjected to solvent replacement, replacing the organic solvent with water. After adding water to the electrolytically collected reactants and removing the solvent, the reactants to be processed are obtained. The reactants are divided into two phases: the organic phase mainly consists of the reaction product and reaction byproducts, and the inorganic phase mainly consists of the water-soluble organic salt of monomethyl adipic acid and the water-soluble reaction byproducts.

[0013] The solvent replacement method involves first adding water to the reaction solution in the electrolytic cell, and then removing the solvent.

[0014] Preferably, the reaction solution after solvent replacement in step (1) comprises: 42-60 wt% dimethyl sebacate, 3-7 wt% dimethyl adipate, 2.5-5.5 wt% methyl hexahydroxyhexanoate, 5-14.2 wt% water, 0.7-3.0 wt% dimethyl tetradecanoate, and 12.5-28.3 wt% organic salts.

[0015] Preferably, the mixture of extractant and reaction solution is mixed and dispersed through a pipe containing a built-in spiral component to achieve thorough mixing of reaction products and extractant.

[0016] Preferably, the pipe with built-in helical component has multiple sections, and the pipe contains built-in helical component to achieve full mixing and dispersion of materials and extractant in the pipe, and the by-products are transferred to the organic phase, thereby achieving the removal of by-products in the reaction system.

[0017] In this invention, the extractant is one or more of hydrocarbons, esters or ketones, preferably one or more of toluene, methyl isobutyl ketone, n-octane, n-pentane, n-hexane, decane, and butyl acetate.

[0018] Preferably, the total mass of the extractant added is 0.1 to 0.8 of the mass of the reaction solution obtained in step (1); more preferably, it is 0.4 to 0.6; the extractant is added in multiple equal portions.

[0019] Preferably, the additive is a lipophilic substance, wherein the substance is one or more of the following: propylene glycol fatty acid ester, diethylene glycol fatty acid ester, polyoxyethylene alkylphenol, sorbitan lauryl ester, triethanolamine oleate, glyceryl fatty acid ester, and polyoxyethylene monostearate, preferably one or more of propylene glycol fatty acid ester, diethylene glycol fatty acid ester, and sorbitan lauryl ester. Through the action of the additive, the residence time of the aqueous and oil phases can be shortened, reducing the volume of the phase separation tank. The mass ratio of the additive to the reaction solution obtained in step (2) is (0.02–0.05):1.

[0020] Preferably, the extractant is added in 1-10 portions, more preferably 2-5 portions, and after each addition, it is mixed through a pipe with a built-in rotating component. The pipe with the built-in rotating component is divided into multiple sections, each section having 1-3 spiral blades.

[0021] The thickness of the built-in helical component is 0.5-2.5mm, the width is 0.4-0.8D, and the pitch is 1-2D. Where D is the inner diameter of the pipe.

[0022] The operating pressure of the extraction process is 0.5-1.0 MPaG, preferably 0.6-0.7 MPaG; the operating temperature is 50-120℃, preferably 70-90℃. The system includes pipelines and a phase separation tank. The residence time in the phase separation tank is 10-60 min, more preferably 10-30 min.

[0023] Preferably, the phase separator is provided with an oil phase outlet at the top and an aqueous phase outlet at the bottom; the oil phase at the top of the phase separator is separated by a subsequent separation system to finally obtain dimethyl sebacate product, and the aqueous phase at the bottom of the phase separator is treated by a treatment system and then returned to the electrolysis system for recycling.

[0024] In summary, the positive effects of the present invention are as follows:

[0025] 1) This invention achieves the main entry of reaction byproducts such as dimethyl adipate and methyl hexahydroxyhexanoate into the organic phase through the redistribution of the extractant, avoiding the disadvantages of decreased reaction current efficiency, precipitation on the electrode surface, shortened electrode life, and decreased current efficiency caused by recycling. Furthermore, it avoids material loss and increased waste liquid caused by the inability to separate reaction byproducts and their direct discharge.

[0026] 2) This invention uses a component with a spiral structure inside the pipeline to fully mix and disperse the reaction products and the extractant, thereby transferring the reaction byproducts into the organic phase. This avoids the increased investment required by using extraction equipment and improves economic efficiency.

[0027] 3) By adding an auxiliary agent during the extraction process, this invention achieves rapid mixing and dispersion of reactants and extractants without changing the extraction effect, shortens the separation time of the two phases, avoids the entrainment of organic phase in the aqueous phase, shortens the residence time of phase separation, reduces equipment volume and material inventory, lowers equipment investment, and improves process safety. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process flow of the reaction solution treatment system for the electrochemical synthesis of dimethyl sebacate according to the present invention.

[0029] Where 1 is the electrochemical reaction liquid, 2 is the organic phase, 3 is the inorganic phase, 4 is the extractant, 5 is the auxiliary agent, D1 is the phase separation tank, L is the pipe with built-in spiral components, L1 is the first section of the pipe, L2 is the second section of the pipe, and L3 is the third section of the pipe. Detailed Implementation

[0030] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0031] Chromatographic analysis conditions:

[0032] Instrument Model: Shimadzu GC2010

[0033] Column: DB-5 (30m × 0.53mm × 1.5um)

[0034] Column temperature: programmed temperature rise (50℃ for 2 min, rise at a rate of 15℃ / min to 200℃, then rise at a rate of 25℃ / min to 300℃ and hold for 3 min)

[0035] Heater temperature: 305℃

[0036] H2 flow rate: 40 mL / min

[0037] Air flow rate: 400 mL / min

[0038] Purging gas flow rate: 25 mL / min

[0039] Septum purge flow rate: 3 mL / min

[0040] Split injection, split ratio 50:1

[0041] Split flow rate: 120 mL / min

[0042] Absorption column conditions:

[0043] Diameter: 2.5cm

[0044] Height: 60cm

[0045] The reaction solution from the electrolytic reactor used in the electrochemical synthesis of dimethyl sebacate is a reaction solution in which monomethyl adipic acid ester is used as raw material, a salt of monomethyl adipic acid ester is used as conductive medium, methanol is used as solvent, and a decarboxylation coupling reaction occurs under certain current and voltage and under the action of electrodes to generate dimethyl sebacate. Then, water is added to replace the organic solvent.

[0046] The reaction solution after solvent replacement mainly consists of: dimethyl sebacate 58wt%, dimethyl adipate 7.5wt%, methyl hexahydroxyhexanoate 3.6wt%, water 7.5wt%, dimethyl tetradecanoate 3.0wt%, and the remaining organic salts 20.4wt%.

[0047] Unless otherwise specified, all other products are ordinary products purchased from the market.

[0048] like Figure 1 As shown, the untreated reactants are first mixed with the extractant and enter a pipeline containing built-in components. The internal components of the pipeline achieve mixing and dispersion of the two materials. After mixing and dispersion, the materials are mixed with the extractant again and enter a second pipeline containing built-in components. The materials are mixed and dispersed with the extractant a second time. After the second mixing, the materials are mixed with the extractant and additives again and enter a third pipeline containing built-in spiral components. The materials are mixed and dispersed a third time in the pipeline. After three mixing and dispersion, the materials enter a phase separation tank. In the phase separation tank, the light and heavy phases are separated by gravity settling. The light phase is taken out from the top of the settling tank and enters the subsequent separation system for further separation. The heavy phase is taken out from the bottom of the tank and returned to the electrolysis system for recycling after subsequent processing.

[0049] Each section of the pipeline has two built-in spiral internal components with opposite spiral directions. The internal components are 3m long. Through the two built-in components, the material is fully mixed and dispersed with the extractant by the spiral centrifugal force inside the pipeline.

[0050] The selected extractant is methyl isobutyl ketone, and the mass ratio of the total extractant to the reaction solution is controlled at 0.1 to 0.8. By adjusting the extractant ratio, the distribution of by-products between the two phases is controlled.

[0051] The ratio of the amount of additive added to the mass of the reaction solution is (0.02~0.05):1. By utilizing the lipophilic properties of the additive, the separation of the two phases is accelerated, thereby shortening the material residence time, reducing system inventory, and improving the safety of the device.

[0052] Example 1

[0053] according to Figure 1 As shown in the process diagram, the extractant is added to the system in three stages, with the same amount added in each stage. The electrochemical reaction solution, after being treated with water to remove methanol, is first mixed with the extractant methyl isobutyl ketone. Then, it enters the first stage pipe L1, where the material is mixed and dispersed by the spiral force of the mixing internal components. The material exiting the first stage pipe L1 is mixed again with fresh methyl isobutyl ketone and enters the second stage pipe, where the material is mixed and dispersed again. The material exiting the second stage pipe is then mixed again with methyl isobutyl ketone and diethylene glycol fatty acid esters and enters the third stage pipe L3. After being mixed again in the pipe, the material exiting the third stage pipe L3 enters the phase separation tank. The organic phase is collected from the top of the phase separation tank and returned to the subsequent separation system for separation, while the inorganic phase is collected from the bottom of the tank, processed, and returned to the reaction system. The reaction solution feed rate was 20 kg / h, with the total extractant to reaction solution mass ratio being 0.4:1. The extractant was added in stages and evenly. The diethylene glycol fatty acid ester added was added in a mass ratio of 0.03:1 to the reaction solution. The operating pressure was 0.5 MPaG, the operating temperature was 90℃, and the phase separation residence time was 30 min. The proportion of reaction byproducts in the organic phase to the total amount of byproducts was determined by chromatography, and the results are shown in Table 1.

[0054] Example 2

[0055] according to Figure 1 The process shown has an extractant to electrochemical reaction solution mass ratio of 0.5:1, and the auxiliary agent is sorbitol lauryl ester. The remaining operating load and operating conditions are the same as in Example 1. The results are shown in Table 1 below.

[0056] Example 3

[0057] according to Figure 1 The process shown has an extractant to electrochemical reaction solution mass ratio of 0.6:1, propylene glycol fatty acid ester as the auxiliary agent, and other operating loads and conditions consistent with Example 1. The results are shown in Table 1.

[0058] Example 4

[0059] like Figure 1 The process shown has a mass ratio of diethylene glycol fatty acid ester to reaction solution of 0.05:1. The residence time in the phase separation tank is controlled at 15 minutes. The remaining operating load and operating conditions are the same as in Example 2. The results are shown in Table 1.

[0060] Example 5

[0061] like Figure 1The process shown is as follows: the extractant and auxiliary agent are added once in the first stage, and the remaining operating conditions are the same as in Example 4. The results are shown in Table 1.

[0062] Example 6

[0063] like Figure 1 The process shown uses polyoxyethylene alkylphenol as the auxiliary agent at a mass ratio of 0.05:1 to the reaction solution, toluene as the extractant, and the remaining operating conditions are the same as in Example 1. The results are shown in Table 1.

[0064] Example 7

[0065] like Figure 1 The process shown uses triethanolamine oleate as the auxiliary agent at a mass ratio of 0.05:1 to the reaction solution, and n-hexane as the extractant. The remaining operating conditions are the same as in Example 1. The results are shown in Table 1.

[0066] Example 8

[0067] like Figure 1 The process shown uses glycerol fatty acid ester as the auxiliary agent at a mass ratio of 0.05:1 to the reaction solution, decane as the extractant, and the remaining operating conditions are the same as in Example 1. The results are shown in Table 1.

[0068] Example 9

[0069] like Figure 1 The process shown has a mass ratio of polyoxyethylene monostearate to reaction solution of 0.05:1, and the extractant is butyl acetate. The other operating conditions are the same as in Example 1. The results are shown in Table 1.

[0070] Comparative Example 1

[0071] The raw material processing method of Example 1 was followed, except that no auxiliary agents were added during the reactant processing. Other operating procedures and conditions were the same as in Example 1, and the results are shown in Table 1.

[0072] The proportion of dimethyl adipate is the ratio of the mass content of the organic phase after phase separation to the mass content of the reaction solution before extraction; the proportion of methyl hexahydroxyhexanoate is the ratio of the mass content of the organic phase after phase separation to the mass content of the reaction solution before extraction.

[0073]

[0074]

[0075] The above experimental data show that, through the use of extractants and auxiliaries and the special process and material mixing reaction product processing device and method of the present invention, the process requires less equipment, occupies less space, has low energy consumption, reduces investment, and improves overall competitiveness.

[0076] The addition of additives reduces the phase separation time of the two phases without affecting the extraction effect, thereby reducing the system inventory and improving the system safety.

Claims

1. A method for processing the reaction solution of dimethyl sebacate in the electrochemical synthesis, characterized in that, Includes the following steps: Step (1): The reaction solution is collected from the electrolytic cell reactor for the electrochemical synthesis of dimethyl sebacate and solvent replacement is performed to replace the solvent in the reaction solution with water; Step (2): Mix the reaction solution obtained in step (1) with the extractant; Step (3): Optionally, the mixture of the reaction solution and the extractant is mixed again with the extractant; Step (4): Add an auxiliary agent to the last mixture after multiple mixing of the extractant and the reaction solution. The mixture containing the auxiliary agent enters the phase separation tank to separate the inorganic phase and the organic phase. The inorganic phase is post-treated to obtain the product for recycling and electrochemical reaction. The solvent replacement method involves first adding water to the electrolytic cell reaction solution, and then removing the solvent. The reaction solution after solvent replacement in step (1) includes 5-14.2 wt% water. The auxiliary agent is a lipophilic substance, which is one or more of the following: propylene glycol fatty acid ester, diethylene glycol fatty acid ester, polyoxyethylene alkylphenol, sorbitan lauryl ester, triethanolamine oleate, glyceryl fatty acid ester, and polyoxyethylene monostearate. The reaction solution from the electrolytic reactor used for the electrochemical synthesis of dimethyl sebacate is a reaction solution in which monomethyl adipic acid ester is used as raw material, a salt of monomethyl adipic acid ester is used as a conductive medium, and methanol is used as a solvent. Under the action of electrodes, a decarboxylation coupling reaction occurs to generate dimethyl sebacate.

2. The processing method according to claim 1, characterized in that, Step (3) can be repeated multiple times.

3. The processing method according to claim 1, characterized in that, The reaction solution after solvent replacement in step (1) includes: 42-60 wt% dimethyl sebacate, 3-7 wt% dimethyl adipate, 2.5-5.5 wt% methyl hexahydroxyhexanoate, 5-14.2 wt% water, 0.7-3.0 wt% dimethyl tetradecanoate, and 12.5-28.3 wt% organic salts.

4. The processing method according to claim 1, characterized in that, The mixture of extractant and reaction solution is mixed and dispersed through a pipe containing a built-in spiral component.

5. The processing method according to claim 1, characterized in that, The pipe with the built-in helical component has multiple sections, and the pipe contains the built-in helical component.

6. The processing method according to claim 1, characterized in that, The extractant is one or more of hydrocarbons, esters, or ketones.

7. The processing method according to claim 6, characterized in that, The extractant is one or more of toluene, methyl isobutyl ketone, n-octane, n-pentane, n-hexane, decane, and butyl acetate.

8. The processing method according to claim 1, characterized in that, The total mass of the extractant added is 0.1 to 0.8 of the mass of the reaction solution obtained in step (1).

9. The processing method according to claim 8, characterized in that, The total mass of the extractant added is 0.4 to 0.6 of the mass of the reaction solution obtained in step (1).

10. The processing method according to claim 8, characterized in that, The extractant was added in multiple equal portions.

11. The processing method according to claim 1, characterized in that, The adjuvant is one or more of propylene glycol fatty acid ester, diethylene glycol fatty acid ester, and sorbitol lauryl ester.

12. The processing method according to claim 1, characterized in that, The mass ratio of the amount of the additive to the reaction solution obtained in step (2) is (0.02~0.05):

1.

13. The processing method according to claim 1, characterized in that, The extractant is added in 1-10 portions, and after each addition, it is mixed through a pipe with a built-in rotating component. The pipe with the built-in rotating component is divided into multiple sections, each with 1-3 spiral blades.

14. The processing method according to claim 13, characterized in that, The extractant is added in 2-5 portions.

15. The processing method according to claim 13, characterized in that, The thickness of the built-in helical component is 0.5-2.5mm, the width is 0.4-0.8D, and the pitch is 1-2D, where D is the inner diameter of the pipe.

16. The processing method according to claim 1, characterized in that, The operating pressure of the extraction process is 0.5-1.0 MPaG; the operating temperature is 50~120℃.

17. The processing method according to claim 16, characterized in that, The operating pressure of the extraction process is 0.6-0.7 MPaG; the operating temperature is 70-90℃.

18. The processing method according to claim 1, characterized in that, The residence time in the phase separation tank is 10~60 min.

19. The processing method according to claim 18, characterized in that, The residence time in the phase separation tank is 10-30 minutes.

20. The processing method according to claim 1, characterized in that, The phase separation tank has an oil phase outlet at the top and an aqueous phase outlet at the bottom. The oil phase at the top of the phase separation tank is sent to the subsequent separation system for separation, and finally dimethyl sebacate is obtained. The aqueous phase at the bottom of the phase separation tank is treated by the treatment system and then returned to the electrolysis system for recycling.

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