CN113416969B - Electrochemical synthesis method of dimethyl sebacate - Google Patents
Electrochemical synthesis method of dimethyl sebacate Download PDFInfo
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Abstract
The invention discloses an electrochemical synthesis method of dimethyl sebacate, which comprises the following steps: 1) mixing adipic acid and ester compounds thereof, an organic solvent and electrolyte, placing the mixture into an electrolytic cell, introducing carbon dioxide gas into the electrolytic cell to enable the system pressure to reach 0.5-4Mpa (gauge pressure), then heating the electrolytic cell to 60-80 ℃, and starting an electrolytic reaction; 2) adding a mixture of halogen acid and peroxide into the electrolytic reaction system in the step 1), and obtaining the dimethyl sebacate after the electrolytic reaction is finished. The method can obviously reduce the generation of the by-product methyl pentenoate and improve the selectivity of the dimethyl sebacate.
Description
Technical Field
The invention belongs to the field of organic electrochemical synthesis, and relates to an electrochemical synthesis method of dimethyl sebacate.
Background
Sebacic acid is an important raw material for the synthesis of polymer materials and organic synthesis. Publication CN101318892A describes a process for the preparation of sebacic acid from castor oil based compounds, sebacic acid being prepared by alkaline cleavage of ricinoleic acid under high pressure and high temperature; however, the method has high energy consumption and large price fluctuation of the raw material castor oil. In order to prepare sebacic acid inexpensively, researchers are actively searching for new raw materials and synthetic methods.
Wherein, the adipic acid is used as a raw material to synthesize adipate compounds through esterification, the sebacic ester compounds are synthesized through Brown-Walker electrolytic decarboxylation coupling, and then the sebacic acid is obtained through hydrolysis. For example, the following technical scheme is disclosed in the document 'preparation of sebacic acid from adipic acid. Liaoning chemical industry, 1981(03): 66-67':
esterification of adipic acid to monomethyl adipate:
HOOC(CH2)4COOH+CH3OH→CH3OOC(CH2)4COOH+H2O
decarboxylation coupling of monomethyl adipate to dimethyl sebacate:
2CH3OOC(CH2)4COOH→CH3OOC(CH2)8COOCH3+H2+2CO2
hydrolysis of dimethyl sebacate to sebacic acid:
CH3OOC(CH2)8COOCH3+2H2O→HOOC(CH2)8COOH+2CH3OH
however, the applicant finds that the dimethyl sebacate prepared by the existing electrochemical method can produce a large amount of byproducts, such as methyl pentenoate, and the byproduct methyl pentenoate of 0.15 ton of methyl pentenoate can be produced per ton of dimethyl sebacate, so that the reaction selectivity and the current efficiency of the electrochemical method are very low, and no effective means is available for solving the problem at present.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the electrochemical synthesis method of the dimethyl sebacate, which can obviously reduce the generation of a byproduct methyl pentenoate and improve the selectivity of the dimethyl sebacate.
In order to achieve the technical effects, the invention adopts the following technical scheme:
an electrochemical synthesis method of dimethyl sebacate comprises the following steps:
1) mixing adipic acid and ester compounds thereof, an organic solvent and electrolyte, placing the mixture into an electrolytic cell, introducing carbon dioxide gas into the electrolytic cell to enable the system pressure to reach 0.5-4Mpa (gauge pressure), then heating the electrolytic cell to 60-80 ℃, and starting an electrolytic reaction;
2) adding a mixture of halogen acid and peroxide into the electrolytic reaction system in the step 1), and obtaining the dimethyl sebacate after the electrolytic reaction is finished.
In step 1), the adipic acid and the ester compound thereof are adipic acid and methyl ester compounds thereof, preferably any one or a combination of at least two of monomethyl adipate, dimethyl adipate and adipic acid;
in the step 1) of the invention, the organic solvent adopted by the electrolytic system is selected conventionally in the field, no special requirement exists, and all organic solvents which can effectively dissolve adipic acid and ester compound raw materials thereof and do not have any adverse effect on the electrolytic system can be selected as the organic solvent of the system; preferably, the organic solvent is any one or a combination of at least two of benzene, nitrile and alcohol solvents, more preferably any one or a combination of at least two of benzene, acetonitrile, methanol, ethanol and propanol;
preferably, the mass ratio of the adipic acid and the ester compound thereof to the organic solvent is 0.5:1-2:1, preferably 1:1-1.2: 1.
In step 1) of the present invention, the electrolyte is any one or a combination of at least two of potassium methoxide, sodium methoxide, potassium hydroxide, sodium hydroxide, and triethylamine, preferably potassium methoxide and/or potassium hydroxide;
preferably, the electrolyte is added in an amount of 15 to 30% by mole, such as 15%, 20%, 22%, 25%, 28%, 30%, preferably 22 to 28% by mole, based on the molar amount of adipic acid and ester compounds thereof.
In the step 1) of the invention, carbon dioxide gas is introduced into the electrolytic cell, and the pressure of the system is controlled to reach 0.5-4MPa (gauge pressure) by the adding amount of the carbon dioxide gas, and the initial pressure of the system is not too high because a small amount of hydrogen and carbon dioxide are generated in the electrolytic process, preferably 1-2 mPa.
In step 1) of the present invention, the electrolytic cell comprises an anode and a cathode;
preferably, the anode is a platinum electrode, a platinum titanium electrode or a DSA electrode, preferably a Ti-based PbO electrode2、IrO2、RuO2Any one of the above;
preferably, the cathode is any one of a nickel electrode, a silver electrode or a titanium silver-plated electrode.
In step 1) of the present invention, the electrolysis reaction is carried out at an electrolysis temperature of 60 to 80 ℃, for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, preferably 65 to 75 ℃; the electrolysis time is 5-20h, such as 5h, 10h, 15h, 20h, preferably 10-15 h;
the electrolytic reaction, the electrolytic potential interval of the electrolytic cell is 2-3V, such as 2.0V, 2.2V, 2.4V, 2.5V, 2.7V, 2.9V, 3V, preferably 2.5-2.8V; the electrolytic current density interval is 1200-2000A/m2E.g. 1200A/m2、1300A/m2、1400A/m2、1500A/m2、1600A/m2、1700A/m2、1800A/m2、1900A/m2、2000A/m2Preferably 1600-1800A/m2。
In step 2) of the present invention, the mixture of the halogen acid and the peroxide has a molar ratio of the peroxide to the halogen acid of 0.3:1 to 2:1, preferably 0.5:1 to 1:1, the halogen acid is calculated by the hydrogen halide; the halogen acid is an aqueous solution with the concentration of 25-37 wt%, preferably 33-37 wt%;
preferably, the hydrohalic acid is hydrochloric acid and/or hydrobromic acid;
preferably, the peroxide is any one or a combination of at least two of hydrogen peroxide, sodium peroxide, potassium peroxide, di-tert-butyl peroxide, peracetic acid and cumyl peroxide, preferably hydrogen peroxide and/or di-tert-butyl peroxide;
preferably, the mixture of hydrohalic acid and peroxide is added in an amount of 3-7%, such as 3%, 4%, 5%, 6%, 7%, preferably 4-6% of the molar amount of adipic acid and its ester compound in step 1), based on the molar amount of hydrogen halide;
preferably, the mixture of the halogen acid and the peroxide is continuously fed, preferably dropwise, for 4.5 to 19.5 hours, preferably 9.5 to 14.5 hours; the dropwise adding and feeding time is contained in the electrolysis reaction time;
preferably, the mixture of the halogen acid and the peroxide is added to the electrolysis reaction system in the step 1) during the electrolysis reaction, and preferably, the mixture of the halogen acid and the peroxide is added to the system after 30min from the beginning of the electrolysis reaction, more preferably within 30-60min from the beginning of the electrolysis reaction.
In step 2), after the electrolysis reaction is finished, post-treatment processes such as desolventizing, dehydrogenation and heavy component removal are also included, which are conventional operations in the field, for example, in some examples, it is preferable that the reaction solution obtained from the electrolysis reaction sequentially passes through a desolventizing tower, a dehydrogenation tower and a heavy component removal tower, so as to obtain a pure product of dimethyl sebacate.
The electrochemical synthesis method of the dimethyl sebacate of the invention is characterized in that a mixed solution of hydrohalic acid (hydrochloric acid or hydrobromic acid) and peroxide is dripped in the electrolytic process, so that the byproduct methyl pentenoate can be subjected to anti-Markov addition to generate 1-halogen (chlorine/bromine) methyl valerate, and then CO is added2In the environment, the raw material is converted into monomethyl adipate through cathode electro-carboxylation, and the dimethyl sebacate is generated through continuous reaction. Can obviously reduce the generation of a by-product of methyl pentenoate and improve the reaction selectivity and the current efficiency.
Detailed Description
The present invention is further illustrated by the following examples, which should be construed as limiting the scope of the invention.
The raw material information is as follows:
monomethyl adipate, Syngnathus chemical Co., Ltd, product specification > 98%;
dimethyl adipate, Syngnathus chemical Co., Ltd, product specification > 99%;
adipic acid, Beijing Bailingwei science and technology Limited, product specification > 98%;
potassium methoxide, Shanghai Michelin Biochemical technology Limited, product specification > 95%;
sodium methoxide, Beijing Bailingwei science and technology Limited, product specification > 95%;
potassium hydroxide, Beijing Bailingwei science and technology Limited, product specification > 85%;
sodium hydroxide, Beijing Bailingwei science and technology Limited, product specification > 85%;
a platinum titanium electrode, Siam Tai gold, Inc., with a plating thickness of 1 μm;
ti radical IrO2An anode, Jiangsu Yianteng special electrode Co., Ltd., an iridium titanium mesh 50 x 100;
ti-based PbO2Anode, Jiangsu Yianteng special electrode Co., Ltd., lead-titanium mesh 50X 100;
ti-based RuO2Anode, Jiangsu Yianteng Special electrode Co., Ltd., ruthenium titanium mesh 50X 100.
Other raw materials or reagents are commercially available unless otherwise specified.
The detection method used in the examples is described below:
the conversion rate and selectivity are determined by using gas chromatography area correction normalized analysis, and the chromatographic analysis conditions are as follows:
the instrument model is as follows: shimadzu GC 2010; a chromatographic column: DB-5 (30X 0.32X 0.25); column temperature: temperature programming (keeping the temperature at 50 ℃ for 4min, then increasing the temperature to 100 ℃ at the temperature increasing rate of 5 ℃/min, then increasing the temperature to 300 ℃ at the temperature increasing rate of 25 ℃/min, and keeping the temperature for 5 min); sample inlet temperature: 230 ℃; FID temperature: 300 ℃; n is a radical of2Flow rate: 1 mL/min; h2Flow rate: 40 mL/min; shock insulatorPurging (N)2) Flow rate: 3 mL/min; carrier gas (N)2) Flow rate: 1 mL/min; split-flow sample introduction, split-flow ratio: 50; sample introduction amount: 0.1. mu.L.
Example 1
An electrochemical synthesis method of dimethyl sebacate comprises the following steps:
1) 80g (0.5mol) of monomethyl adipate, 160g of benzene and 5.25g (0.075mol) of potassium methoxide are uniformly mixed and transferred into an electrolytic cell, wherein the mass ratio of the raw material monomethyl adipate to an organic solvent benzene is 0.5:1, and the addition amount of electrolyte potassium methoxide accounts for 15 percent of the molar amount of the raw material monomethyl adipate according to the molar amount. The anode of the electrolytic cell adopts a platinum-titanium electrode, and the cathode adopts a nickel cathode. By using CO2After the air in the electrolytic cell is replaced by the air for 5 times, CO is filled into the electrolytic cell2Heating the electrolytic cell to 60 ℃ to 0.5MPa, and starting electrolytic reaction, wherein the current density of the electrolytic cell is 1200A/m2And an electrolytic potential of 2V.
2) 1.48g of 37 wt% (0.015 mol as HCl) hydrochloric acid was mixed with 0.153g (0.0045mol) of hydrogen peroxide, wherein the amount of hydrochloric acid was 3% by mole of the monomethyl adipate as the electrolysis raw material, based on the mole of hydrogen halide, and the molar ratio of the amount of peroxide added to hydrochloric acid (HCl) was 0.3: 1.
Starting the reaction after the temperature in the electrolytic cell reaches 60 ℃, beginning to dropwise add the mixed solution of the hydrochloric acid and the peroxide within 30min after the electrolytic reaction in the step 1) begins, wherein the dropwise add time is 19.5h, and the reaction is finished after the electrolytic reaction is 20 h. After the reaction is finished, the materials sequentially pass through a desolventizing tower, a light component removing tower and a heavy component removing tower, and then dimethyl sebacate is obtained by collection.
In the embodiment, the conversion rate of the raw material of the adipic acid monomethyl ester is 89.0 percent, the selectivity of the synthesized dimethyl sebacate is 85.2 percent, the selectivity of the by-product methyl pentenoate is 0.03 percent, and the selectivity of the gamma-valerolactone is 0.01 percent; the current efficiency was 74.6%.
Example 2
1) 87g (0.5mol) of dimethyl adipate, 145g of pyridine and 5.4g (0.01mol) of sodium methoxide are uniformly mixed and transferred into an electrolytic cell, wherein the mass ratio of the raw material dimethyl adipate to the organic solvent pyridine is 0.6:1, and the addition amount of the electrolytic sodium methoxide is calculated according to the molar quantityIs 20 percent of the molar weight of the raw material dimethyl adipate. The anode of the electrolytic cell adopts Ti-based IrO2The anode and the cathode adopt a nickel cathode. By using CO2After the air in the electrolytic cell is replaced by the air for 5 times, CO is filled into the electrolytic cell2Heating the electrolytic cell to 65 ℃ to 0.8MPa, and starting electrolytic reaction, wherein the current density of the electrolytic cell is 1400A/m2And the electrolytic potential is 2.2V.
2) 2.56g of 25 wt% (0.018 mol as HCl) hydrochloric acid was mixed with 0.683g (0.0087mol) of sodium peroxide, the amount of hydrochloric acid used was 3.5 mol, based on the molar amount of hydrogen halide, of monomethyl adipate as the electrolysis raw material, and the molar ratio of the amount of peroxide added to hydrochloric acid (HCl) was 0.5: 1.
Starting the reaction after the temperature in the electrolytic cell reaches 65 ℃, beginning to dropwise add the mixed solution of the hydrochloric acid and the peroxide after 60min from the beginning of the electrolytic reaction in the step 1), wherein the dropwise add time is 17h, and the reaction is finished after 18h of the electrolytic reaction. After the reaction is finished, the materials sequentially pass through a desolventizing tower, a light component removing tower and a heavy component removing tower, and then dimethyl sebacate is obtained by collection.
In the embodiment, the conversion rate of the dimethyl adipate serving as a raw material is 85.6%, the selectivity of the synthesized dimethyl sebacate is 84.3%, the selectivity of the by-product methyl pentenoate is 0.05%, and the selectivity of gamma-valerolactone is 0.02%; the current efficiency was 75.3%.
Example 3
1) 73g (0.5mol) of adipic acid, 91.25g of acetonitrile and 6.16g (0.01mol) of potassium hydroxide are uniformly mixed and transferred into an electrolytic cell, wherein the mass ratio of the adipic acid as a raw material to the acetonitrile as an organic solvent is 0.8:1, and the addition amount of electrolyte potassium hydroxide is 22 percent of the molar amount of the adipic acid as a raw material. The anode of the electrolytic bath adopts Ti-based PbO2The anode and the cathode adopt a nickel cathode. By using CO2After the air in the electrolytic cell is replaced by the air for 5 times, CO is filled into the electrolytic cell2Heating the electrolytic cell to 70 ℃ to 1.0MPa, and starting electrolytic reaction, wherein the current density of the electrolytic cell is 1500A/m2And the electrolytic potential is 2.4V.
2) 4.91g of 33 wt% (0.02 mol based on HBr) hydrobromic acid was mixed with 1.76g (0.016mol) of potassium peroxide, wherein the amount of hydrobromic acid used was 4.0 mol based on the molar amount of hydrogen halide based on the molar amount of adipic acid as the starting material for electrolysis, and the molar ratio of the amount of peroxide added to the amount of hydrobromic acid (HBr) was 0.8: 1.
Starting the reaction after the temperature in the electrolytic cell reaches 70 ℃, beginning to dropwise add the mixed solution of the hydrochloric acid and the peroxide within 30min after the electrolytic reaction in the step 1) begins, wherein the dropwise add time is 14.5h, and the reaction is finished after the electrolytic reaction is 15 h. After the reaction is finished, the materials sequentially pass through a desolventizing tower, a light component removing tower and a heavy component removing tower, and then dimethyl sebacate is obtained by collection.
In the embodiment, the conversion rate of the raw material adipic acid is 86.9%, the selectivity of the synthesized dimethyl sebacate is 86.6%, the selectivity of the by-product methyl pentenoate is 0.02%, and the selectivity of gamma-valerolactone is 0.01%; the current efficiency was 77.6%.
Example 4
1) 80g (0.5mol) of monomethyl adipate, 80g of methanol and 5.0g (0.125mol) of sodium hydroxide are uniformly mixed and transferred into an electrolytic cell, wherein the mass ratio of the raw material monomethyl adipate to an organic solvent benzene is 1:1, and the addition amount of electrolyte potassium methoxide accounts for 25 percent of the molar amount of the raw material monomethyl adipate. The anode of the electrolytic cell adopts Ti-based RuO2The anode and the cathode adopt silver cathodes. By using CO2After the air in the electrolytic cell is replaced by the air for 5 times, CO is filled into the electrolytic cell2Heating the electrolytic cell to 75 ℃ to 1.5MPa, and starting electrolytic reaction, wherein the current density of the electrolytic cell is 1600A/m2And the electrolytic potential is 2.5V.
2) 6.15g of 33 wt% (0.025mol based on HBr) of hydrobromic acid was mixed with 3.65g (0.025mol) of di-tert-butyl peroxide, wherein the amount of hydrobromic acid used was 5.0 mol based on the molar amount of hydrogen halide based on the molar amount of adipic acid as the starting material for electrolysis, and the molar ratio of the amount of peroxide added to the amount of hydrobromic acid (HBr) was 1: 1.
Starting the reaction after the temperature in the electrolytic cell reaches 75 ℃, beginning to dropwise add the mixed solution of the hydrochloric acid and the peroxide within 30min after the electrolytic reaction in the step 1), wherein the dropwise add time is 11.5h, and the reaction is finished after the electrolytic reaction is 12 h. After the reaction is finished, the materials sequentially pass through a desolventizing tower, a light component removing tower and a heavy component removing tower, and then dimethyl sebacate is obtained by collection.
In the embodiment, the conversion rate of the raw material of the adipic acid monomethyl ester is 91.0%, the selectivity of the synthesized dimethyl sebacate is 84.9%, the selectivity of the by-product methyl pentenoate is 0.04%, and the selectivity of the gamma-valerolactone is 0.01%; the current efficiency was 76.2%.
Example 5
1) 80g (0.5mol) of monomethyl adipate, 66.7g of ethanol and 14.1g (0.14mol) of triethylamine are uniformly mixed and transferred to an electrolytic cell, wherein the mass ratio of the raw material monomethyl adipate to an organic solvent benzene is 1.2:1, and the addition amount of the electrolyte triethylamine is 28% of the molar amount of the raw material monomethyl adipate according to the molar amount. The anode of the electrolytic cell adopts a platinum anode, and the cathode adopts a titanium silver-plated cathode. By using CO2After the air in the electrolytic cell is replaced by the air for 5 times, CO is filled into the electrolytic cell2Heating the electrolytic cell to 80 ℃ to 2MPa, and starting electrolytic reaction, wherein the current density of the electrolytic cell is 1700A/m2And the electrolytic potential is 2.7V.
2) 9.72g of 25 wt% (0.03 mol based on HBr) hydrobromic acid was mixed with 1.9g (0.025mol) of peracetic acid in which the amount of hydrobromic acid used was 6.0% by mol based on the hydrogen halide based on the molar amount of adipic acid as the starting material for electrolysis and the molar ratio of the peroxide addition to the hydrobromic acid (HBr) was 1.2: 1.
Starting the reaction after the temperature in the electrolytic cell reaches 80 ℃, beginning to dropwise add the mixed solution of the hydrochloric acid and the peroxide within 30min after the electrolytic reaction in the step 1) begins, wherein the dropwise add time is 9.5h, and the reaction is finished after the electrolytic reaction is 10 h. After the reaction is finished, the materials sequentially pass through a desolventizing tower, a light component removing tower and a heavy component removing tower, and then dimethyl sebacate is obtained by collection.
In the embodiment, the conversion rate of the raw material of the monomethyl adipate is 91.4%, the selectivity of the synthesized dimethyl sebacate is 86.2%, the selectivity of the by-product methyl pentenoate is 0.03%, and the selectivity of the gamma-valerolactone is 0.01%; the current efficiency was 75.1%.
Example 6
1) 80g (0.5mol) of monomethyl adipate, 53.3g of propanol and 15.1g (0.15mol) of triethylamine are uniformly mixed and transferred into an electrolytic cell, wherein the mass ratio of the raw material monomethyl adipate to an organic solvent acetone is 1.5:1, and the addition amount of electrolyte triethylamine is 30% of the molar amount of the raw material monomethyl adipate according to the molar amount. The anode of the electrolytic cell adopts a platinum-titanium anodeThe cathode adopts a titanium silver-plated cathode. By using CO2After the air in the electrolytic cell is replaced by the air for 5 times, CO is filled into the electrolytic cell2Heating the electrolytic cell to 70 ℃ to 3MPa, and starting electrolytic reaction, wherein the current density of the electrolytic cell is 1800A/m2And the electrolytic potential is 2.9V.
2) 7.97g of 33 wt% (0.033 mol based on HBr) hydrobromic acid was mixed with 3.3g (0.022mol) cumene hydroperoxide, wherein the amount of hydrobromic acid used was 6.5% by mol based on the hydrogen halide based on the molar amount of adipic acid as the electrolysis raw material, and the molar ratio of the peroxide addition to the hydrobromic acid (HBr) was 1.5: 1.
Starting the reaction after the temperature in the electrolytic cell reaches 70 ℃, beginning to dropwise add the mixed solution of the hydrochloric acid and the peroxide within 30min after the electrolytic reaction in the step 1) begins, wherein the dropwise add time is 7.5h, and the reaction is finished after the electrolytic reaction lasts 8 h. After the reaction is finished, the materials sequentially pass through a desolventizing tower, a light component removing tower and a heavy component removing tower, and then dimethyl sebacate is obtained by collection.
In the embodiment, the conversion rate of the raw material of the monomethyl adipate is 90.2%, the selectivity of the synthesized dimethyl sebacate is 84.1%, the selectivity of the by-product methyl pentenoate is 0.06%, and the selectivity of the gamma-valerolactone is 0.02%; the current efficiency was 76.3%.
Example 7
1) 80g (0.5mol) of monomethyl adipate, 40g of benzene and 5.0g (0.125mol) of sodium hydroxide are uniformly mixed and transferred into an electrolytic bath, wherein the mass ratio of the raw material monomethyl adipate to the organic solvent benzene is 2:1, and the addition amount of electrolyte sodium hydroxide is 25 percent of the molar amount of the raw material monomethyl adipate according to the molar amount. The anode of the electrolytic cell adopts a platinum-titanium anode, and the cathode adopts a titanium silver-plated cathode. By using CO2After the air in the electrolytic cell is replaced by the air for 5 times, CO is filled into the electrolytic cell2Heating the electrolytic cell to 70 ℃ to 4MPa, and starting electrolytic reaction, wherein the current density of the electrolytic cell is 2000A/m2And the electrolytic potential is 3.0V.
2) 8.61g of 33 wt% (0.035 mol based on HBr) hydrobromic acid was mixed with 0.55g (0.016mol) of hydrogen peroxide, wherein the amount of hydrobromic acid used was 7.0 mol based on the molar amount of hydrogen halide based on the molar amount of adipic acid as the starting material for electrolysis, and the molar ratio of the amount of peroxide added to the amount of hydrobromic acid (HBr) was 2: 1.
Starting the reaction after the temperature in the electrolytic cell reaches 70 ℃, beginning to dropwise add the mixed solution of the hydrochloric acid and the peroxide within 30min after the electrolytic reaction in the step 1) begins, wherein the dropwise add time is 4.5h, and the reaction is finished after the electrolytic reaction is 5 h. After the reaction is finished, the materials sequentially pass through a desolventizing tower, a light component removing tower and a heavy component removing tower, and then dimethyl sebacate is obtained by collection.
In the embodiment, the conversion rate of the raw material of the monomethyl adipate is 93.1%, the selectivity of the synthesized dimethyl sebacate is 84.8%, the selectivity of the by-product methyl pentenoate is 0.05%, and the selectivity of the gamma-valerolactone is 0.02%; the current efficiency is 74.9%.
Comparative example 1
Dimethyl sebacate was prepared according to the method and process conditions in example 4, with the difference that: in the step 1), CO is not filled into the electrolytic cell2And does not use CO2The air in the electrolytic cell was replaced, and the other operations were the same as in example 4.
In the comparative example, the conversion rate of the raw material monomethyl adipate is 74.8%, the selectivity of the synthesized dimethyl sebacate is 77.5%, the selectivity of the by-product methyl pentenoate is 4.23%, and the selectivity of gamma-valerolactone is 2.15%; the current efficiency was 63.2%.
Comparative example 2
Dimethyl sebacate was prepared according to the method and process conditions in example 4, with the difference that: in step 2), only the aqueous hydrobromic acid solution was added dropwise into the electrolytic cell without adding the peroxide, and the other operations were the same as in example 4.
In the comparative example, the conversion rate of the raw material monomethyl adipate is 75.1%, the selectivity of the synthesized dimethyl sebacate is 75.6%, the selectivity of the by-product methyl pentenoate is 3.98%, and the selectivity of gamma-valerolactone is 2.28%; the current efficiency was 61.1%.
Comparative example 3
Dimethyl sebacate was prepared according to the method and process conditions in example 4, with the difference that: in step 2), only peroxide was added dropwise into the electrolytic cell, and the aqueous hydrobromic acid solution was not added, and the other operations were the same as in example 4.
In the comparative example, the conversion rate of the raw material monomethyl adipate is 73.2 percent, the selectivity of the synthesized dimethyl sebacate is 76.0 percent, the selectivity of the by-product methyl pentenoate is 4.16 percent, and the selectivity of gamma-valerolactone is 2.09 percent; the current efficiency was 59.9%.
Claims (24)
1. An electrochemical synthesis method of dimethyl sebacate is characterized by comprising the following steps:
1) mixing adipic acid and methyl ester compounds thereof, an organic solvent and electrolyte, placing the mixture in an electrolytic cell, introducing carbon dioxide gas into the electrolytic cell to enable the system pressure to reach 0.5-4Mpa, then heating the electrolytic cell to 60-80 ℃, starting an electrolytic reaction, wherein the electrolytic potential interval of the electrolytic cell is 2-3V, and the electrolytic current density interval is 1200-2000A/m2；
2) Adding a mixture of halogen acid and peroxide into the electrolytic reaction system in the step 1), and obtaining the dimethyl sebacate after the electrolytic reaction is finished.
2. The method as claimed in claim 1, wherein in step 1), the adipic acid and the methyl ester compound thereof are selected from any one of monomethyl adipate, dimethyl adipate and adipic acid or a combination of at least two of the adipic acid and the methyl ester compound thereof;
the organic solvent is any one or the combination of at least two of benzene, nitrile and alcohol solvents;
the mass ratio of the adipic acid and the methyl ester compound thereof to the organic solvent is 0.5:1-2: 1.
3. The method according to claim 2, wherein the organic solvent is any one of benzene, acetonitrile, methanol, ethanol, propanol or a combination of at least two thereof.
4. The method according to claim 2, wherein the mass ratio of the adipic acid and the methyl ester compound thereof to the organic solvent is 1:1-1.2: 1.
5. The method according to claim 1, wherein in step 1), the electrolyte is any one of potassium methoxide, sodium methoxide, potassium hydroxide, sodium hydroxide and triethylamine, or a combination of at least two of the above substances;
the addition amount of the electrolyte is 15-30% of the molar amount of adipic acid and methyl ester compounds thereof;
and introducing carbon dioxide gas to ensure that the initial pressure of the system is 1-2 MPa.
6. The method of claim 5, wherein the electrolyte is potassium methoxide and/or potassium hydroxide.
7. The method according to claim 5, wherein the electrolyte is added in an amount of 22 to 28 mol% based on the molar amount of adipic acid and methyl ester-based compounds thereof.
8. The method of claim 1, wherein in step 1), the electrolytic cell comprises an anode and a cathode;
the anode is any one of a platinum electrode, a platinum titanium electrode or a DSA electrode;
the cathode is any one of a nickel electrode, a silver electrode or a titanium silver-plated electrode.
9. The method of claim 8, wherein the DSA electrode is Ti-based PbO2、IrO2、RuO2Any one of them.
10. The method as claimed in claim 1, wherein in the step 1), the electrolysis reaction is carried out at the electrolysis temperature of 60-80 ℃ for 5-20 h;
the electrolytic reaction has an electrolytic potential interval of 2.5-2.8V and an electrolytic current density interval of 1600-1800A/m2。
11. The method as claimed in claim 10, wherein the electrolysis reaction is carried out at 65-75 ℃ for 10-15 h.
12. The process of claim 1 wherein in step 2) the mixture of hydrohalic acid and peroxide is present in a molar ratio of peroxide to hydrohalic acid of from 0.3:1 to 2:1, based on the hydrogen halide present therein.
13. The process of claim 12, wherein the molar ratio of peroxide to halogen acid is from 0.5:1 to 1:1, the hydrohalic acid is calculated as the hydrogen halide therein.
14. The method of claim 1, wherein in step 2), the hydrohalic acid is an aqueous solution having a concentration of 25 to 37 wt.%.
15. The method of claim 14, wherein the hydrohalic acid is an aqueous solution having a concentration of 33-37% wt.
16. The method of claim 14, wherein the hydrohalic acid is hydrochloric acid and/or hydrobromic acid.
17. The method according to claim 1, wherein in the step 2), the peroxide is any one of hydrogen peroxide, sodium peroxide, potassium peroxide, di-tert-butyl peroxide, peracetic acid and cumyl peroxide or a combination of at least two of the above.
18. The method of claim 17, wherein the peroxide is hydrogen peroxide and/or di-t-butyl peroxide.
19. The method as claimed in claim 1, wherein in the step 2), the mixture of the hydrohalic acid and the peroxide is added in an amount of 3-7% of the molar amount of the adipic acid and the methyl ester compound thereof in the step 1) based on the molar amount of the hydrogen halide;
the mixture of the halogen acid and the peroxide adopts a continuous feeding mode, and the feeding time is 4.5-19.5 h; the dropwise addition time is included in the electrolysis reaction time.
20. The method as claimed in claim 19, wherein the mixture of hydrohalic acid and peroxide is added in an amount of 4-6% by mole based on the moles of hydrogen halide therein.
21. The method of claim 19, wherein the mixture of hydrohalic acid and peroxide is added dropwise over a period of 9.5 to 14.5 hours.
22. The method as claimed in claim 1, wherein, in the step 2), the mixture of the halogen acid and the peroxide is added to the electrolysis reaction system of the step 1) during the electrolysis reaction.
23. The method as claimed in claim 22, wherein the mixture of the halogen acid and the peroxide is added to the system 30min after the start of the electrolysis reaction.
24. The method as claimed in claim 23, wherein the mixture of the halogen acid and the peroxide is added to the system within 30 to 60min from the start of the electrolysis reaction.
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