Method for preparing dimethyl sebacate through electrooxidation of monomethyl adipate and coupling hydrogen production

Abstract

The invention discloses a method for preparing dimethyl sebacate through electrooxidation of monomethyl adipate and coupling hydrogen production. In a diaphragm electrolytic cell, the electrochemical conversion from the monomethyl adipate to the dimethyl sebacate is realized at an anode, and meanwhile, the efficient production of high-purity hydrogen at a cathode is realized through the design of a high-performance cathode catalyst and an electrode. According to the method, an active cathode with low hydrogen evolution overpotential and a dimensionally stable anode with high catalytic activity are adopted, and a constant-current electrolysis strategy is utilized, so that the selective electrocatalytic oxidation performance of the monomethyl adipate is improved, and efficient electrocatalytic conversion from the monomethyl adipate to the dimethyl sebacate is realized. And meanwhile, the cathode hydrogen evolution overpotential and the cell voltage are greatly reduced. And compared with a traditional electrosynthesis process, the current efficiency is greatly improved, the energy consumption is reduced, and the method has a good industrialization prospect.

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 coupling hydrogen production by electrooxidation of monomethyl adipate to dimethyl sebacate. 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 resin, vinyl resin and synthetic rubber. It is widely used as the main raw material for producing light stabilizers UV-770, UV-750, UV-123, etc. It can also be used as an intermediate for organic synthesis. Traditionally, dimethyl sebacate is prepared by the esterification reaction of sebacic acid, and sebacic acid is mainly obtained by the pyrolysis of castor oil. Public patent CN101318892A records a method for preparing sebacic acid from castor oil compounds: castor oil is saponified to obtain ricinoleic acid, and ricinoleic acid is cracked under strong alkaline conditions. The cracked liquid after the reaction is acidified, purified, and a series of operations can be performed to obtain sebacic acid. Sebacic acid and methanol are esterified to obtain dimethyl sebacate. The traditional production method has low yield, toxic and harmful reagents are used in the production process, and the pyrolysis process consumes a lot of energy, which is not conducive to reducing carbon emissions.

[0003] As a green energy, hydrogen energy has the advantages of being clean, renewable, and having high calorific value. It is known as the "ultimate energy" to solve the earth's environmental and energy crises in the 21st century, and has important strategic significance for the sustainable development of the entire world economy. Using renewable energy (such as solar energy and wind energy) to directly decompose water into H2 and O2 through electrocatalytic technology is considered to be one of the most promising green hydrogen production methods. However, in the process of hydrogen production by electrolysis of water, there are still many problems. In the conventional water electrolysis process, the anode oxygen production process needs to undergo a complex four-electron reaction process, and the oxygen evolution overpotential is high, which greatly increases the energy consumption of water electrolysis, and the added value of the generated O2 is not high, and it is usually not further utilized. In addition, the H2 and O2 produced simultaneously in the same electrolyzer by conventional water electrolysis have great safety hazards. In short, the existing water electrolysis hydrogen production technology has problems such as high energy consumption, low added value of oxygen production, and safety hazards.

[0004] In summary, the traditional castor oil pyrolysis method for synthesizing dimethyl sebacate and electrolysis of water for hydrogen production still faces 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 electro-oxidative 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 greening of the synthesis process. Coupling the anode process of this process with the cathode electrolysis of water for hydrogen production is a good strategy to solve the problems faced by the traditional castor oil pyrolysis method for synthesizing dimethyl sebacate and 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 electro-oxidation of monomethyl adipate, The technical solutions adopted are as follows: A method for preparing dimethyl sebacate by electro-oxidation of monomethyl adipate, wherein the method adopts a diaphragm electrolyzer, a dimensionally stable electrode with high catalytic activity is used as an anode, and an electrode with low hydrogen evolution overpotential is used as a cathode, wherein an 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 a supporting electrolyte, and a 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 a 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; Through constant current electrolysis, adipic acid monoester is electro-oxidatively coupled to generate dimethyl sebacate at the anode of the electrolytic cell, and high-purity hydrogen is obtained at the cathode.

[0006] Anode reaction: Cathode reaction: Optionally, the diaphragm electrolyzer described in the above technical solution is an H-type diaphragm electrolyzer or a plate-frame flow diaphragm electrolyzer, and the diaphragm used is any one of a cation exchange membrane, anion exchange membrane and proton exchange membrane. Preferably, the diaphragm electrolyzer is a plate-frame flow diaphragm electrolyzer, using a cation exchange membrane.

[0007] The highly catalytically active dimensionally stable anode described in the above technical solution is: 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.

[0008] 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, 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 precious metals, alloys or composites with carbon, Fe compounds, Co compounds, Ni compounds, Mo compounds, W compounds, and Bi compounds.

[0009] Preferably, the cathode substrate is one of foamed nickel, foamed copper, foamed silver, foamed titanium, and a stainless steel mesh.

[0010] Preferably, the cathode catalyst material is prepared by one of electrodeposition, pyrolysis and hydrothermal synthesis.

[0011] Preferably, the lower alcohol is methanol, and the same lower alcohol is selected in the anode chamber and the cathode chamber.

[0012] 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.

[0013] 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.%.

[0014] 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.%.

[0015] 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 .

[0016] Optionally, the electrolysis temperature described in the above technical solution is 50~60℃.

[0017] The high-purity hydrogen produced by the cathode described in the above technical solution is connected to a 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.

[0018] Beneficial effects of the present invention: 1. The present invention adopts an active cathode with low hydrogen evolution overpotential and a dimensionally stable anode with high catalytic activity, and utilizes constant current electrolysis to improve the selective electrocatalytic oxidation performance of monomethyl adipate, thereby achieving efficient electrocatalytic conversion of monomethyl adipate to dimethyl sebacate. At the same time, the cathode hydrogen evolution overpotential is greatly reduced, and the cell voltage is reduced.

[0019] 2. The present invention couples the anodic oxidation coupling of monomethyl adipate with the cathode electrolysis of water to produce hydrogen, which solves a series of problems faced in the traditional production process of dimethyl sebacate, such as unstable raw material supply, poor atomic economy, serious pollution, and high energy consumption, and also solves the problems of high energy consumption, low added value of oxygen production, and potential safety hazards in the traditional electrolysis of water to produce hydrogen. In short, the effective coupling of the anionic and anodic reactions improves the atomic economy of the overall reaction, reduces energy consumption, improves the overall economic benefits, and has good industrial value. DETAILED DESCRIPTION

[0020] The invention provides a method for coupling hydrogen production by electro-oxidation of monomethyl adipate to dimethyl sebacate. In order to make the purpose, technical scheme and effect of the invention clearer and more specific, the following examples further describe the invention in detail. It should be understood that the invention is not limited to the listed embodiments, but also includes any other known changes within the scope of the claims of the invention.

[0021] The term noble metal in the present invention refers specifically to Ru, Rh, Ir and Pt.

[0022] 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.

[0023] In the embodiment, a series of active electrodes with low hydrogen evolution overpotential are used as cathodes, and the cathode includes 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 selected from any one or more of Pt, Pd, Au, and Ag noble metal single substance, alloy, or carbon complex, Fe compound, Co compound, Ni compound, Mo compound, W compound, and Bi compound.

[0024] In the embodiment, 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 rise (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.

[0025] In the embodiment, 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 electrolysis of water.

[0026] Example 1 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 15.0 wt.% monomethyl adipate, 1.0 wt.% water, 5.0 wt.% potassium hydroxide, and 79.0 wt.% methanol 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 as the catholyte. Constant current electrolysis was performed at 40 °C with a current density of 1 A / dm 2 , the electrolysis time is 4h. 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%.

[0027] In this embodiment, the NiMo / Ni cathode is prepared by the following method: 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 a platinum sheet. 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.

[0028] Example 2 A plate-and-frame flow diaphragm electrolyzer was used, with a graphite electrode as the anode, 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 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 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 68.9%, and the coulombic efficiency of hydrogen at the cathode is 96.9%.

[0029] In this embodiment, the method for preparing the NiMo / Ni cathode is the same as that in Embodiment 1.

[0030] Example 3 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 is 4 h. In this embodiment, the selectivity of dimethyl sebacate synthesized at the anode is 82.2%, and the coulombic efficiency of hydrogen at the cathode is 98.9%.

[0031] In this embodiment, the method for preparing the NiMo / Ni cathode is the same as that in Example 1.

[0032] Example 4 A plate-and-frame flow diaphragm electrolyzer was used, with a RuO2 / IrO2-coated titanium electrode as the anode, 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 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 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%.

[0033] In this embodiment, the Pt / NiCoOH / Ni cathode is prepared by the following method: First, 50 mL of a mixed electrolyte solution of cobalt nitrate, nickel nitrate, and chloroplatinic acid with a suitable concentration ratio was prepared. Then, a three-electrode system was constructed with clean nickel foam as the cathode, Ag / AgCl electrode as the reference electrode, and platinum sheet as the anode; nickel cobalt hydroxide / platinum catalytic material was constructed on the nickel foam substrate by constant voltage deposition, where the deposition voltage was -1.0 V and the deposition time was 500 s.

[0034] Example 5 A plate-and-frame flow diaphragm electrolyzer was used, with a RuO2 / IrO2-coated titanium electrode as the anode, 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 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 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%.

[0035] In this embodiment, the Ni2P / Ni cathode is prepared by the following method: 50 mL of 0.2 mol L -1 The nickel nitrate aqueous solution was stirred vigorously, and 500 mg CO(NH2)2 and 120 mg NH4F were added to the above solution. Then the solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene, and a piece of nickel foam was immersed in the reaction solution. The reactor was heated at 120°C for 16 hours to obtain nickel foam with Ni(OH)2 loaded on the surface, which was washed and dried. Then, it was placed in a tube furnace with NaH2PO2 at the same time, heated at 300°C in an argon atmosphere for 1 hour, and Ni2P / Ni was obtained after cooling.

[0036] Example 6 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. Constant current electrolysis was performed at 40 °C with a current density of 1 A / dm2 , the electrolysis time is 4h. 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%.

[0037] In this embodiment, the (NiCo)P / Ni cathode is prepared by the following method: Dissolve nickel nitrate and cobalt nitrate in a molar ratio of 1:1 in water and stir vigorously to ensure that the total ion concentration is 0.2 mol / L -1 , add 500 mg CO(NH2)2 and 120 mg NH4F to the above solution. Then transfer the solution to a stainless steel autoclave lined with polytetrafluoroethylene, immerse a piece of nickel foam in the reaction solution, heat the autoclave at 120 °C for 16 h, and obtain nickel foam with Ni(OH)2 and Co(OH)2 loaded on the surface, which is washed and dried. Then, place it and NaH2PO2 in a tube furnace at the same time, heat it at 300 °C in an argon atmosphere for 1 h, and obtain NiCoP / Ni after cooling.

[0038] In summary, the present invention provides a method for coupling hydrogen production by electro-oxidation of monomethyl adipate to dimethyl sebacate, which not only solves the problems of unstable raw material supply, poor atomic economy, serious pollution and high energy consumption faced by the thermochemical process for preparing dimethyl sebacate, but also solves the problems of high energy consumption, low added value of oxygen production and potential safety hazards in traditional hydrogen production by electrolysis of water. The effective coupling of anionic and anodic reactions improves the current efficiency of the entire reaction, reduces energy consumption, and improves the comprehensive economic benefits of the reaction, and has good industrial value.

[0039] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of protection of this patent should not be determined with reference to the above description, but should be determined with reference to the full scope of the preceding claims.

Claims

1. A method for preparing dimethyl sebacate by electro-oxidation of monomethyl adipate, characterized in that: The method adopts a diaphragm electrolyzer, wherein the anolyte is composed of 1.0-40.0 wt.% monomethyl adipate, 47.0-97.5 wt.% lower alcohols, 0.5-3.0 wt.% water and 1.0-10.0 wt.% supporting electrolyte, and the catholyte is composed of 60.0-98.5 wt.% lower alcohols, 0.5-30.0 wt.% water and 1.0-10.0 wt.% 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, and the hydrogen evolution overpotential is less than 200 mV; Through constant current electrolysis, adipic acid monoester 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 electro-oxidation 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 a proton exchange membrane.

3. The method for preparing dimethyl sebacate by electro-oxidation 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 electro-oxidation of monomethyl adipate according to claim 1, characterized in that: The active cathode with low hydrogen evolution overpotential is a loaded catalytic cathode, comprising a substrate and a loaded 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 composites with carbon, Fe compounds, Co compounds, Ni compounds, Mo compounds, W compounds, and Bi compounds.

5. The method for preparing dimethyl sebacate by electro-oxidation 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 electro-oxidation 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 electro-oxidation 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 electro-oxidation 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 electro-oxidation 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 electro-oxidation of monomethyl adipate according to claim 1, characterized in that: The cathode chamber of the electrolyzer is connected to a hydrogen separation device 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.

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