A method for producing dimethyl sebacate by electrooxidation of monomethyl adipate and coupling hydrogen production

Abstract

The present invention discloses a method for producing dimethyl sebacate by electrooxidation of monomethyl adipate. In a diaphragm electrolyzer, while the electrochemical conversion of monomethyl adipate to dimethyl sebacate is achieved at the anode, the efficient production of high-purity hydrogen at the cathode is achieved through the design of high-performance cathode catalysts and electrodes. The method adopts an active cathode with a low hydrogen evolution overpotential and a dimensionally stable anode with high catalytic activity, and utilizes a constant current electrolysis strategy to improve the selective electrocatalytic oxidation performance of monomethyl adipate and achieve efficient electrocatalytic conversion of monomethyl adipate to dimethyl sebacate. At the same time, the cathode hydrogen evolution overpotential and the cell voltage are greatly reduced. Compared with traditional electrosynthesis processes, the current efficiency is greatly improved, the energy consumption is reduced, and the method has good industrialization prospects.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by coupling electrochemical synthesis of organic matter with electrolysis of water, and in particular to a method for producing dimethyl sebacate by electrooxidation of monomethyl adipate with coupling hydrogen production. Background Art

[0002] Dimethyl sebacate is an important chemical substance with the molecular formula C 12 H 22 O4 can be used as a plasticizer, softener, and solvent for cellulose resins, vinyl resins, and synthetic rubber. It is widely used as a primary raw material for the production of light stabilizers such as UV-770, UV-750, and UV-123, and can also be used as an intermediate in organic synthesis. Traditionally, dimethyl sebacate is produced by the esterification of sebacic acid, which is primarily obtained by the pyrolysis of castor oil. Patent publication CN101318892A describes a method for preparing sebacic acid from castor oil compounds: castor oil is saponified to produce ricinoleic acid, which is then cracked under strong alkaline conditions. The resulting cracked liquid undergoes a series of operations, including acidification and purification, to produce sebacic acid. Sebacic acid is then esterified with methanol to produce dimethyl sebacate. This traditional production method has low yields, uses toxic and hazardous reagents, and consumes high energy in the pyrolysis process, hindering carbon emissions reduction.

[0003] As a green energy source, hydrogen boasts the advantages of being clean, renewable, and having a high calorific value. It is hailed as the "ultimate energy source" for resolving the global environmental and energy crises of the 21st century and holds significant strategic significance for the sustainable development of the global economy. Using renewable energy sources (such as solar and wind energy) to directly split water into H₂ and O₂ through electrocatalytic technology is considered one of the most promising green hydrogen production pathways. However, the electrolysis of water to produce hydrogen still faces numerous challenges. Conventional water electrolysis processes require a complex four-electron oxygen production process at the anode, resulting in a high oxygen evolution overpotential, significantly increasing energy consumption. Furthermore, the generated O₂ has a low added value and is generally unusable. Furthermore, the simultaneous generation of H₂ and O₂ within the same electrolyzer presents significant safety risks. In summary, existing water electrolysis hydrogen production technologies suffer from high energy consumption, low added value oxygen production, and safety concerns.

[0004] In summary, the traditional castor oil pyrolysis method for synthesizing dimethyl sebacate and the electrolysis of water for hydrogen production still face various challenges. The electrochemical preparation technology of fine chemicals is an effective method to solve the problems of high energy consumption, heavy pollution, and low product quality in traditional synthesis processes. The "Kolbe reaction" can realize the electrooxidative coupling of carboxylic acids or carboxylic acid esters to produce diesters. In recent years, this classic process has been used to synthesize benzathine penicillin, construct chiral bisphosphine ligands and dimers of silyl acetic acid, etc., realizing the greenness of the synthesis process. Coupling the anodic process of this process with the cathodic electrolysis of water for hydrogen production is an excellent strategy to solve the problems faced by the traditional castor oil pyrolysis method for synthesizing dimethyl sebacate and the electrolysis of water for hydrogen production. Summary of the Invention

[0005] In view of the above problems, the present invention provides a method for producing dimethyl sebacate by electrooxidation of monomethyl adipate,

[0006] The technical solutions adopted are as follows:

[0007] A method for producing dimethyl sebacate by electrooxidation of monomethyl adipate, coupled with hydrogen production, adopts a diaphragm electrolyzer, uses a dimensionally stable electrode with high catalytic activity as the anode, and an electrode with low hydrogen evolution overpotential as the cathode; the anolyte comprises 1.0-40.0 wt.% of monomethyl adipate, 47.0-97.5 wt.% of lower alcohols, 0.5-3.0 wt.% of water, and 1.0-10.0 wt.% of a supporting electrolyte; and the catholyte comprises 60.0-98.5 wt.% of lower alcohols, 0.5-30.0 wt.% of water, and 1.0-10.0 wt.% of a supporting electrolyte.

[0008] The lower alcohol is a combination of one or more of methanol, ethanol, and propanol; the supporting electrolyte is a combination of one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, triethylamine, and ionic liquid;

[0009] Through constant current electrolysis, monoadipate is electro-oxidatively coupled to generate dimethyl sebacate at the anode of the electrolytic cell, and high-purity hydrogen is obtained at the cathode.

[0010] Anodic reaction:

[0011]

[0012] Cathode reaction:

[0013]

[0014] Optionally, the diaphragm electrolyzer described in the above technical solution is an H-type diaphragm electrolyzer or a plate-and-frame flow diaphragm electrolyzer, and the diaphragm used is any one of a cation exchange membrane, an anion exchange membrane, and a proton exchange membrane. Preferably, the diaphragm electrolyzer is a plate-and-frame flow diaphragm electrolyzer using a cation exchange membrane.

[0015] The highly catalytically active, dimensionally stable anode described in the above technical solution can be one or more titanium-based precious metal oxide-coated titanium electrodes, any one of titanium-based tin-antimony oxide-coated electrodes, titanium-based lead dioxide electrodes, modified graphite, and modified carbon felt. Preferably, one or more titanium-based precious metal oxide-coated titanium electrodes are used as the anode.

[0016] The active cathode with low hydrogen evolution overpotential described in the above technical solution has a hydrogen evolution overpotential lower than 200 mV, and is preferably a supported catalytic cathode, comprising a substrate and a supported catalytic material; the cathode substrate is any one of carbon paper, carbon cloth, nickel sheet, copper sheet, titanium sheet, silver sheet, nickel foam, copper foam, iron foam, silver foam, titanium foam, stainless steel mesh, and FTO conductive glass; the cathode catalytic material is any one or more of Pt, Pd, Au, and Ag precious metals, alloys, or carbon complexes, Fe compounds, Co compounds, Ni compounds, Mo compounds, W compounds, and Bi compounds.

[0017] Preferably, the cathode substrate is one of foamed nickel, foamed copper, foamed silver, foamed titanium, and stainless steel mesh.

[0018] Preferably, the cathode catalytic material is prepared by one of electrodeposition, pyrolysis and hydrothermal synthesis.

[0019] Preferably, the lower alcohol is methanol, and the same lower alcohol is selected in the anode chamber and the cathode chamber.

[0020] Preferably, the supporting electrolyte is one of potassium hydroxide, sodium hydroxide, sodium methoxide, and potassium methoxide, and the same supporting electrolyte is selected in the anode chamber and the cathode chamber.

[0021] Preferably, the content of monomethyl adipate in the anolyte is 15.0-25.0 wt.%, the content of water is 1.0-2.0 wt.%, and the concentration of the supporting electrolyte is 3.0-5.0 wt.%.

[0022] Preferably, the water content in the cathode liquid is 10.0-20.0 wt.%, and the concentration of the supporting electrolyte is 3.0-5.0 wt.%.

[0023] Optionally, the electrolysis process described in the above technical solution is carried out in a constant current mode, and the current density is controlled to be 0.8~5.0A / dm 2 Preferably, the current density is 1.0~2.5 A / dm 2.

[0024] Optionally, the electrolysis temperature described in the above technical solution is 50~60℃.

[0025] The high-purity hydrogen produced by the cathode described in the above technical solution is connected to the hydrogen separation device from the cathode chamber of the electrolyzer through a hydrogen liquid pipe. The device separates the hydrogen produced by the cathode into gas and liquid. The separated liquid enters the electrolysis cycle, and the gas is compressed and stored after drying.

[0026] Beneficial effects of the present invention:

[0027] 1. The present invention utilizes an active cathode with a low hydrogen evolution overpotential and a dimensionally stable anode with high catalytic activity, utilizing constant current electrolysis to improve the selective electrocatalytic oxidation performance of monomethyl adipate, achieving efficient electrocatalytic conversion of monomethyl adipate to dimethyl sebacate. Simultaneously, the cathode hydrogen evolution overpotential is significantly reduced, thereby lowering the cell voltage.

[0028] 2. The present invention couples the anodic oxidation of monomethyl adipate with the cathodic electrolysis of water to produce hydrogen, thereby addressing a series of challenges faced in the traditional production of dimethyl sebacate, such as unstable raw material supply, poor atom economy, severe pollution, and high energy consumption. It also addresses the high energy consumption, low added value of oxygen production, and potential safety hazards associated with traditional water electrolysis to produce hydrogen. In short, the effective coupling of the cathodic and anodic reactions improves the atom economy of the overall reaction, reduces energy consumption, and increases overall economic benefits, making it highly commercializable. DETAILED DESCRIPTION

[0029] The present invention provides a method for the electrooxidation of monomethyl adipate to dimethyl sebacate coupled with hydrogen production. To clarify the objectives, technical solutions, and effects of the present invention, the following examples further illustrate the present invention in detail. It should be understood that the present invention is not limited to the examples listed and encompasses any other known modifications within the scope of the claims.

[0030] In the present invention, the term noble metal refers specifically to Ru, Rh, Ir and Pt.

[0031] In the embodiment, a plate-and-frame flow diaphragm electrolyzer is used, and a commercial dimensionally stable electrode with high catalytic activity is selected as the anode.

[0032] In the examples, a series of active electrodes with low hydrogen evolution overpotentials are used as cathodes, comprising a substrate and a supported catalytic material. The cathode substrate is any one of carbon paper, carbon cloth, nickel sheet, copper sheet, titanium sheet, silver sheet, nickel foam, copper foam, iron foam, silver foam, titanium foam, stainless steel mesh, and FTO conductive glass. The cathode catalytic material is selected from any one or more of Pt, Pd, Au, and Ag noble metals, their alloys, or carbon-complexes, and compounds of Fe, Co, Ni, Mo, W, and Bi.

[0033] In the examples, gas chromatography was used to determine the selectivity of dimethyl sebacate, and the chromatographic analysis conditions were as follows: instrument model: Shimadzu GC2010; chromatographic column: DB-5 (30 m × 0.32 mm × 0.25 μm); column temperature: programmed temperature (50 ° C. for 4 min, then increased to 100 ° C. at a heating rate of 5 ° C. / min, then increased to 300 ° C. at a heating rate of 25 ° C. / min, and maintained for 5 min); injection port temperature: 280 ° C.; FID temperature: 300 ° C.; carrier gas (N2) flow rate: 1 mL / min; split injection, split ratio of 25:1; injection volume: 1 μL.

[0034] In the examples, the Faraday efficiency of hydrogen production is calculated by measuring the volume of hydrogen produced and the amount of electricity passing through the cathode, and this parameter is used to illustrate the performance of hydrogen production by cathode water electrolysis.

[0035] Example 1

[0036] A plate-and-frame flow diaphragm electrolyzer was used, with a RuO2 / IrO2-coated titanium electrode as the anode and a NiMo / Ni electrode as the cathode. 500 g of a mixed solution of 15.0 wt.% monomethyl adipate, 1.0 wt.% water, 5.0 wt.% potassium hydroxide, and 79.0 wt.% methanol was used as the anolyte, and 500 g of a mixed solution of 10.0 wt.% water, 5.0 wt.% potassium hydroxide, and 85.0 wt.% methanol was used as the catholyte. Constant current electrolysis was performed at 40°C with a current density of 1 A / dm 2 In this embodiment, the selectivity of dimethyl sebacate synthesized at the anode is 80.2%, and the coulombic efficiency of hydrogen production at the cathode is 98.2%.

[0037] In this embodiment, the NiMo / Ni cathode is prepared by the following method:

[0038] The NiMo / Ni cathode was prepared by electrodeposition. The working electrode was nickel foam, the reference electrode was Ag / AgCl, and the counter electrode was platinum. First, a mixed solution of nickel nitrate and sodium molybdate with a molar ratio of 1:1 was prepared as the electrolyte. Then, the treated nickel foam was subjected to cyclic voltammetry scanning in the range of -1.2~0.2 V at a rate of 5 mV / s, and the number of cycles was set to 24. After cleaning, the NiMo / Ni cathode was obtained.

[0039] Example 2

[0040] A plate-and-frame flow diaphragm electrolyzer was used, with a graphite electrode as the anode and a NiMo / Ni electrode as the cathode. 500 g of a mixed solution of 15.0 wt.% monomethyl adipate, 1.0 wt.% water, 5.0 wt.% potassium hydroxide, and 79.0 wt.% methanol was used as the anolyte, and 500 g of a mixed solution of 10.0 wt.% water, 5.0 wt.% potassium hydroxide, and 85.0 wt.% methanol was used as the catholyte. Constant current electrolysis was performed at 40 °C with a current density of 1 A / dm 2 , the electrolysis time was 4 h. In this embodiment, the selectivity of dimethyl sebacate synthesized at the anode was 68.9%, and the coulombic efficiency of hydrogen at the cathode was 96.9%.

[0041] In this embodiment, the method for preparing the NiMo / Ni cathode is the same as that in Example 1.

[0042] Example 3

[0043] A plate-and-frame flow diaphragm electrolyzer was used, with a RuO2 / IrO2-coated titanium electrode as the anode, a NiMo / Ni electrode as the cathode, 500 g of a mixed solution of 20.0 wt.% monomethyl adipate, 1.0 wt.% water, 5.0 wt.% potassium hydroxide, and 74.0 wt.% methanol as the anolyte, and 500 g of a mixed solution of 20.0 wt.% water, 5.0 wt.% potassium hydroxide, and 75.0 wt.% methanol as the catholyte. Constant current electrolysis was performed at 40°C with a current density of 1 A / dm 2 , the electrolysis time was 4 h. In this embodiment, the selectivity of dimethyl sebacate synthesized at the anode was 82.2%, and the coulombic efficiency of hydrogen at the cathode was 98.9%.

[0044] In this embodiment, the method for preparing the NiMo / Ni cathode is the same as that in Example 1.

[0045] Example 4

[0046] A plate-and-frame flow diaphragm electrolyzer was used, with a RuO2 / IrO2-coated titanium electrode as the anode and a Pt / NiCoOH / Ni electrode as the cathode. 500 g of a mixed solution of 20.0 wt.% monomethyl adipate, 1.0 wt.% water, 5.0 wt.% potassium hydroxide, and 74.0 wt.% methanol was used as the anolyte, and 500 g of a mixed solution of 20.0 wt.% water, 5.0 wt.% potassium hydroxide, and 75.0 wt.% methanol was used as the catholyte. Electrolysis was carried out at 40°C with a constant current density of 1 A / dm 2 , the electrolysis time is 4 h. In this embodiment, the selectivity of dimethyl sebacate synthesized at the anode is 81.6%, and the coulombic efficiency of hydrogen at the cathode is 99.0%.

[0047] In this embodiment, the Pt / NiCoOH / Ni cathode was prepared by the following method:

[0048] First, a 50 mL mixed electrolyte solution of cobalt nitrate, nickel nitrate, and chloroplatinic acid at appropriate concentrations was prepared. A three-electrode system was then constructed using clean nickel foam as the cathode, an Ag / AgCl electrode as the reference electrode, and a platinum sheet as the anode. The nickel cobalt / platinum hydroxide catalytic material was deposited on the nickel foam substrate via constant voltage deposition at a voltage of -1.0 V for 500 s.

[0049] Example 5

[0050] A plate-and-frame flow diaphragm electrolyzer was used, with a RuO2 / IrO2-coated titanium electrode as the anode and a Ni2P / Ni electrode as the cathode. 500 g of a mixed solution of 20.0 wt.% monomethyl adipate, 1.0 wt.% water, 5.0 wt.% potassium hydroxide, and 74.0 wt.% methanol was used as the anolyte, and 500 g of a mixed solution of 20.0 wt.% water, 5.0 wt.% potassium hydroxide, and 75.0 wt.% methanol was used as the catholyte. Constant current electrolysis was performed at 40°C with a current density of 1 A / dm 2 , the electrolysis time is 4 h. In this embodiment, the selectivity of dimethyl sebacate synthesized at the anode is 83.3%, and the coulombic efficiency of hydrogen at the cathode is 99.2%.

[0051] In this embodiment, the Ni2P / Ni cathode is prepared by the following method:

[0052] 50 mL of 0.2 mol L -1A nickel nitrate aqueous solution is vigorously stirred, and 500 mg of CO(NH2)2 and 120 mg of NH4F are added to the solution. The solution is then transferred to a Teflon-lined stainless steel autoclave, and a piece of nickel foam is immersed in the reaction solution. The autoclave is heated at 120°C for 16 hours to obtain a nickel foam loaded with Ni(OH)2. This foam is then washed and dried. This foam and NaH2PO2 are then placed in a tube furnace and heated at 300°C under an argon atmosphere for 1 hour. After cooling, Ni2P / Ni is obtained.

[0053] Example 6

[0054] A plate-and-frame flow diaphragm electrolyzer was used, with a RuO2 / IrO2-coated titanium electrode as the anode, a (NiCo)P / Ni electrode as the cathode, 500 g of a mixed solution of 20.0 wt.% monomethyl adipate, 1.0 wt.% water, 5.0 wt.% potassium hydroxide, and 74.0 wt.% methanol as the anolyte, and 500 g of a mixed solution of 20.0 wt.% water, 5.0 wt.% potassium hydroxide, and 75.0 wt.% methanol as the catholyte. Galvanostatic electrolysis was performed at 40 °C with a current density of 1 A / dm 2 In this embodiment, the selectivity of dimethyl sebacate synthesized at the anode is 82.9%, and the coulombic efficiency of hydrogen at the cathode is 99.5%.

[0055] In this embodiment, the (NiCo)P / Ni cathode is prepared by the following method:

[0056] Dissolve nickel nitrate and cobalt nitrate in water at a molar ratio of 1:1 and stir vigorously to ensure that the total ion concentration is 0.2 mol / L -1 To the above solution, 500 mg of CO(NH2)2 and 120 mg of NH4F were added. The solution was then transferred to a Teflon-lined stainless steel autoclave, and a piece of nickel foam was immersed in the reaction solution. The autoclave was heated at 120°C for 16 hours to obtain a nickel foam loaded with Ni(OH)2 and Co(OH)2. The foam was then washed and dried. This foam and NaH2PO2 were then placed in a tube furnace and heated at 300°C under an argon atmosphere for 1 hour. After cooling, NiCoP / Ni was obtained.

[0057] In summary, the present invention provides a method for the coupled hydrogen production from the electrooxidation of monomethyl adipate to dimethyl sebacate. This method not only addresses the challenges faced by thermochemical processes for the production of dimethyl sebacate, such as unstable raw material supply, poor atom economy, severe pollution, and high energy consumption, but also addresses the high energy consumption, low added value of oxygen production, and potential safety hazards associated with conventional hydrogen production by water electrolysis. The effective coupling of cationic and anodic reactions improves the current efficiency of the entire reaction, reduces energy consumption, and enhances the overall economic benefits of the reaction, thus possessing excellent industrial value.

[0058] It should be understood that the foregoing description is intended to be illustrative and not limiting. Numerous embodiments and applications beyond the examples provided will be readily apparent to those skilled in the art upon reading the foregoing description. Therefore, the scope of protection of this patent should be determined not by reference to the foregoing description, but rather by reference to the full scope of the preceding claims.

Claims

1. A method for producing dimethyl sebacate by electrooxidation of monomethyl adipate, characterized in that: The method adopts a diaphragm electrolyzer, wherein the anolyte is composed of 1.0-40.0 wt.% of monomethyl adipate, 47.0-97.5 wt.% of lower alcohols, 0.5-3.0 wt.% of water and 1.0-10.0 wt.% of supporting electrolyte, and the catholyte is composed of 60.0-98.5 wt.% of lower alcohols, 0.5-30.0 wt.% of water and 1.0-10.0 wt.% of supporting electrolyte; The lower alcohol is a combination of one or more of methanol, ethanol, and propanol; the supporting electrolyte is a combination of one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, triethylamine, and ionic liquid; The anode is a dimensionally stable electrode with high catalytic activity, selected from any one of a titanium-based precious metal oxide-coated titanium electrode, a titanium-based tin antimony oxide-coated electrode, a titanium-based lead dioxide electrode, modified graphite, and modified carbon felt; the cathode is a low hydrogen evolution overpotential electrode, with a hydrogen evolution overpotential of less than 200 mV; Through constant current electrolysis, monoadipate is electro-oxidatively coupled to generate dimethyl sebacate at the anode of the electrolytic cell, and high-purity hydrogen is obtained at the cathode.

2. The method for preparing dimethyl sebacate by electrooxidation of monomethyl adipate according to claim 1, characterized in that: The diaphragm electrolyzer is an H-type diaphragm electrolyzer or a plate-and-frame flow-type diaphragm electrolyzer, and the diaphragm used in the diaphragm electrolyzer is any one of a cation exchange membrane, anion exchange membrane and proton exchange membrane.

3. The method for preparing dimethyl sebacate by electrooxidation of monomethyl adipate according to claim 1, characterized in that: The anode is a titanium electrode coated with a titanium-based precious metal oxide.

4. The method for preparing dimethyl sebacate by electrooxidation of monomethyl adipate according to claim 1, characterized in that: The active cathode with low hydrogen evolution overpotential is a supported catalytic cathode, comprising a substrate and a supported catalytic material; the cathode substrate is any one of carbon paper, carbon cloth, nickel sheet, copper sheet, titanium sheet, silver sheet, foam nickel, foam copper, foam iron, foam silver, foam titanium, stainless steel mesh, and FTO conductive glass; the cathode catalytic material is any one or more of Pt, Pd, Au, and Ag noble metals, alloys, or carbon-complexes, Fe compounds, Co compounds, Ni compounds, Mo compounds, W compounds, and Bi compounds.

5. The method for preparing dimethyl sebacate by electrooxidation of monomethyl adipate according to claim 1, characterized in that: The lower alcohol is methanol, and the same lower alcohol is selected in the anode chamber and the cathode chamber; the supporting electrolyte is one of potassium hydroxide, sodium hydroxide, sodium methoxide, and potassium methoxide, and the same supporting electrolyte is selected in the anode chamber and the cathode chamber.

6. The method for preparing dimethyl sebacate by electrooxidation of monomethyl adipate according to claim 1, characterized in that: The content of monomethyl adipate in the anolyte is 15.0-25.0 wt.%, the content of water is 1.0-2.0 wt.%, and the concentration of the supporting electrolyte is 3.0-5.0 wt.%.

7. The method for preparing dimethyl sebacate by electrooxidation of monomethyl adipate according to claim 1, characterized in that: The water content in the cathode liquid is 10.0~20.0 wt.%, and the concentration of the supporting electrolyte is 3.0~5.0 wt.%.

8. The method for preparing dimethyl sebacate by electrooxidation of monomethyl adipate according to claim 1, characterized in that: The electrolysis process is carried out in a constant current mode, and the current density is controlled at 0.8~5.0A / dm 2 .

9. The method for preparing dimethyl sebacate by electrooxidation of monomethyl adipate according to claim 1, characterized in that: The electrolysis temperature is 50-60°C.

10. The method for preparing dimethyl sebacate by electrooxidation of monomethyl adipate according to claim 1, characterized in that: The cathode chamber of the electrolytic cell is connected to a hydrogen separation device through a hydrogen liquid pipe. The device separates the hydrogen produced at the cathode into gas and liquid. The separated liquid enters the electrolysis cycle, and the gas is compressed and stored after drying.