Method for realizing electrocatalytic acetylene coupling by using copper-based small organic molecule catalyst

Abstract

The invention provides a method for realizing electrocatalytic acetylene coupling by using a copper-based small organic molecule catalyst, which comprises the following steps of: carrying out bidentate coordination on a copper source and organic ligands such as carboxylic acid or carboxylate with different functional groups to controllably construct the copper-based small organic molecule catalyst, and taking a gas diffusion electrode prepared from the copper-based small organic molecule catalyst as a cathode to realize electrocatalytic acetylene coupling by using the copper-based small organic molecule catalyst. A current collector anode material matched with a supported metal is isolated by an exchange membrane in the middle to form a three-electrode flowing electrolytic tank, and efficient conversion of 1, 3-butadiene is realized through coupling reaction of electro-catalytic acetylene.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of novel electrocatalytic materials, and particularly relates to a method for realizing electrocatalytic coupling of acetylene by using a copper-based organic small-molecule catalyst. BACKGROUND

[0002] Based on the resource characteristics of rich coal, less oil and gas in China, the development of acetylene chemical industry taking coal as raw material occupies an important position in China. Combined with the electrocatalytic technology driven by renewable electric energy, acetylene raw materials can be converted into higher value-added organic compounds under milder reaction conditions, improving the energy utilization efficiency and sustainability of production, and meeting the development trend of the future chemical industry. However, so far, the research on electrocatalytic acetylene reaction mainly focuses on the semi-hydrogenation synthesis of ethylene, and it is urgent to promote the exploration of other potential applications of this process to realize the green synthesis of more kinds of organic compounds.

[0003] Chinese patent CN112342562B first discloses a method for preparing 1,3-butadiene by electrocatalytic coupling of acetylene, and the catalyst powder includes oxides, alloys and single-atom catalysts. Through the electrocatalytic coupling reaction of acetylene, the Faraday efficiency of 1,3-butadiene can reach 71% at a potential of-0.2V (vs. RHE), and the by-products are only ethylene and a small amount of hydrogen, which reduces the dependence of 1,3-butadiene production on traditional chemical reagents and complex process flow. However, the types of catalysts that can be selected in this process are very limited, the reaction current density is low, and the coupling intermediates are easily hydrogenated and desorbed from the catalyst surface as ethylene at high potential, so the Faraday efficiency of the target product needs to be improved.

[0004] Therefore, it is necessary to seek a catalyst that can realize electrocatalytic coupling of acetylene and a method for improving the Faraday efficiency of the target product. SUMMARY

[0005] The purpose of the present application is to solve the problems of the prior art method for preparing 1,3-butadiene by electrocatalytic coupling of acetylene, such as limited types of catalysts, low reaction current density, and easy hydrogenation of coupling intermediates and desorption from the catalyst surface as ethylene at high potential, and low Faraday efficiency of the target product, and to provide a method for realizing electrocatalytic coupling of acetylene by using a copper-based organic small-molecule catalyst, so as to realize efficient conversion of 1,3-butadiene by electrocatalytic coupling reaction of acetylene by using a controllably constructed copper-based organic small-molecule as a catalyst, a gas diffusion electrode made of the catalyst as a cathode, and a current collector anode material matching the supported metal.

[0006] To achieve the above-mentioned purpose, the technical solution provided by the present application is as follows:

[0007] The application of copper-based organic small molecules as catalysts in electrocatalytic acetylene coupling to prepare 1,3-butadiene, wherein the copper-based organic small molecules are formed by bidentate coordination of carboxylic acids or carboxylate salts with different functional groups and copper sources, i.e., the copper-based organic small molecules contain two carboxyl-copper active sites.

[0008] Further, the different functional groups refer to tert-butyl (-C(CH3)3), isopropyl (-CH(CH3)2), ethyl (-CH2CH3), methyl (-CH3), trichloromethyl (-CCl3) or trifluoromethyl (-CF3); for example, the carboxylic acid is propionic acid (CH3CH2COOH), acetic acid (CH3COOH), trichloroacetic acid (CCl3COOH), trifluoroacetic acid (CF3COOH) or isobutyric acid ((CH3)2CHCOOH), and the carboxylate salt is potassium trimethylacetate ((CH3)3CCOOK).

[0009] The copper source is copper nitrate (Cu(NO3)2), copper sulfate (CuSO4), basic copper carbonate (Cu2(OH)2CO3), copper oxide (CuO) or copper hydroxide (Cu(OH)2).

[0010] That is, the copper-based organic small molecules described above are ((CH3)3CCOO)4Cu2, ((CH3)2CHCOO)4Cu2, (CH3CH2COO)4Cu2, (CH3COO)4Cu2, (CCl3COO)4Cu2, (CF3COO)4Cu2, etc.

[0011] Based on the above application, the application provides a method for realizing electrocatalytic acetylene coupling by using a copper-based organic small molecule catalyst, and the special feature of the method is as follows:

[0012] 1) Dispersing copper-based organic small molecule powder in a good solvent, adding 5% Nafion solution, and obtaining a catalyst slurry after ultrasonic dispersion;

[0013] 2) Uniformly spraying the catalyst slurry obtained in step 1) on a gas diffusion flat plate material until the catalyst loading is 0.1-10 mg cm -2 , and obtaining a gas diffusion electrode after sufficient drying (which can be dried by infrared lamp baking);

[0014] 3) Using the gas diffusion electrode obtained in step 2) as a cathode, using a conductive current collector or a conductive current collector loaded with a metal-based material as an anode, and using an exchange membrane to separate the cathode chamber and the anode chamber to form a three-electrode flow electrolytic cell, and performing an electrocatalytic acetylene coupling reaction to prepare 1,3-butadiene.

[0015] Further, in step 1), the ratio of copper-based organic small molecules, good solvent and 5% Nafion solution is 1-20:0.1-5:0.1-15, mg:mL:μL.

[0016] The ultrasonic time is 1-30 min.

[0017] Further, in step 1), the good solvent is acetone, anhydrous ethanol, isopropanol or a mixed solution of deionized water and ethanol or isopropanol mixed in any volume ratio.

[0018] Further, in step 2), the gas diffusion plate material is carbon fiber paper, carbon fiber woven cloth, non-woven fabric or carbon black paper.

[0019] Further, in step 3), the metal-based material is a non-noble metal such as Fe, Co, Ni and a noble metal such as Ir, Ru or an alloy or composite thereof.

[0020] The conductive current collector adopts a titanium current collector (titanium mesh, titanium felt, etc.), a nickel current collector (nickel plate, nickel sheet or foamed nickel, etc.), a copper current collector (copper foil, foamed copper, etc.), carbon paper, carbon cloth, etc. 2 with a thickness of 0.05-1 mm and an area of 1-40 cm

[0021] Further, in step 3), the exchange membrane is an anion exchange membrane, a proton exchange membrane or a bipolar membrane.

[0022] Further, in step 3), high-purity acetylene is used as the raw material, and is introduced into the electrolytic cell at a flow rate of 5-50 sccm from the gas chamber inlet of the electrolytic cell, and the electrolysis product is collected by flowing out from the gas chamber outlet of the electrolytic cell, while the cathode electrolyte and the anode electrolyte are pumped in at a peristaltic speed of 5-10 rpm from the cathode chamber inlet and the anode chamber inlet, respectively, and are pumped out from the cathode chamber outlet and the anode chamber outlet, respectively.

[0023] Further, in step 3), the electrolyte (anode electrolyte and cathode electrolyte) is 1M KOH solution, 1M KHCO3 solution, 0.5M K2SO4 solution, 1M KI solution, 1M KBr solution or 1M KCl solution.

[0024] Advantages of the present application:

[0025] 1. The present application selects copper-based organic small molecules as catalysts, which not only have the advantages of low price and precise structure control, but also help to reveal the structure-function relationship of the catalysts, providing key insights for the rational design of catalysts. Functionalization of metal catalysts by organic ligands can effectively regulate the catalytic active sites and the microenvironment (such as electronic affinity) of the catalyst surface, thereby changing the selectivity of the product.

[0026] 2.The copper-based organic small molecule catalyst of the application achieves the performance of oxide, alloy and its single-atom catalyst coupling 1,3-butadiene, especially the catalyst modified by a strong electron-donating group, which can achieve 90% 1,3-butadiene faradic efficiency at -0.55 V (vs. RHE), effectively inhibiting the occurrence of acetylene semi-hydrogenation and hydrogen evolution side reactions at high potential (mainly because the modification group changes the electron cloud density of the metal active site, especially the strong electron-donating group increases the electron cloud density of the copper atom, which is more conducive to the adsorption and activation of electrophilic acetylene, thereby facilitating the occurrence of coupling reaction and inhibiting side reactions), and the current density of the reaction can reach nearly -50 mA cm -2 The faradic efficiency of the target product is still maintained at 70%, which significantly improves the technical effect of the reaction and expands the practical application prospect of the acetylene chemical route. More importantly, the application involves copper-based small molecule catalysts functionalized by different organic ligands, which reveals that the effect of electrocatalytic acetylene coupling increases first and then decreases with the increase of the electronegativity of the modified functional group, which provides effective guidance and new ideas for the design of high-efficiency electro-coupling acetylene catalysts. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Performance results of the ((CH3)3CCOO)4Cu2 copper-based organic small molecule catalyst for electrocatalytic acetylene coupling to form 1,3-butadiene using a three-electrode flow cell: (a) polarization curve; (b) product distribution diagram at each potential.

[0028] Figure 2 Performance comparison of different functional group modified copper-based organic small molecule catalysts for electrocatalytic acetylene coupling to form 1,3-butadiene at -0.75 V (vs. RHE). DETAILED DESCRIPTION

[0029] The content of the application is further described in detail below in combination with the drawings and specific examples:

[0030] The application proposes a method for realizing electrocatalytic acetylene coupling by using a copper-based organic small molecule catalyst, which is prepared by using carboxylic acid or carboxylic acid salt with different functional groups (including but not limited to t-butyl, isopropyl, ethyl, methyl, trichloromethyl, trifluoromethyl, etc.) as an organic ligand, bidentate coordination with a copper source, and then loading the copper-based organic small molecule catalyst on a gas diffusion flat plate material to prepare a gas diffusion electrode, which is used as a cathode, matching a current collector anode material loaded with metal, and being separated by an exchange membrane to form a three-electrode flow electrolytic cell, thereby realizing efficient conversion of 1,3-butadiene through electrocatalytic acetylene coupling reaction.

[0031] 1, Controllable construction of copper-based organic small molecule catalyst

[0032] (1) Synthesis route of tert-butyl-modified copper-based organic small molecule catalyst:

[0033] Take potassium trimethylacetate as the organic ligand and copper nitrate as the copper source; weigh them according to the molar ratio of 2:1, then add them into a round-bottom flask, and add 25 mL of deionized water; magnetically stir at a speed of 1000 r / min for 5 h under an oil bath temperature of 30 °C; after the reaction is completed, collect the solid-phase product by suction filtration using a Buchner funnel, and finally obtain the tert-butyl-modified copper-based organic small molecule ((CH3)3CCOO)4Cu2 powder after vacuum drying at 60 °C for 12 h.

[0034] (2) Synthesis route of isopropyl-modified copper-based organic small molecule catalyst:

[0035] Take isobutyric acid as the organic ligand and copper oxide as the copper source; weigh them according to the molar ratio of 2:1, then add them into a round-bottom flask, and add 25 mL of deionized water; condense and reflux at a speed of 1000 r / min for 5 h under an oil bath temperature of 100 °C; after the reaction is completed, collect the liquid by suction filtration using a Buchner funnel, then remove the solvent by rotary evaporation to obtain a solid product, and finally obtain the isopropyl-modified copper-based organic small molecule ((CH3)2CHCOO)4Cu2 powder after vacuum drying at 60 °C for 12 h.

[0036] (3) Synthesis route of ethyl-modified copper-based organic small molecule catalyst:

[0037] Take propionic acid as the organic ligand and copper hydroxide as the copper source; weigh them according to the molar ratio of 2:1, then add them into a round-bottom flask, and add 40 mL of ethanol; condense and reflux at a speed of 1000 r / min for 16 h under an oil bath temperature of 100 °C; after the reaction is completed, collect the liquid by suction filtration using a Buchner funnel, then remove the solvent by rotary evaporation to obtain a solid product, and finally obtain the ethyl-modified copper-based organic small molecule (CH3CH2COO)4Cu2 powder after vacuum drying at 60 °C for 12 h.

[0038] (4) Synthesis route of methyl-modified copper-based organic small molecule catalyst:

[0039] Take acetic acid as the organic ligand and basic copper carbonate as the copper source; weigh them according to the molar ratio of 2:1, then add them into a round-bottom flask, and add 100 mL of deionized water; magnetically stir at a speed of 1000 r / min for 5 h under an oil bath temperature of 40 °C; after the reaction is completed, collect the liquid by suction filtration using a Buchner funnel, then remove the solvent by rotary evaporation to obtain a solid product, and finally obtain the methyl-modified copper-based organic small molecule (CH3COO)4Cu2 powder after vacuum drying at 60 °C for 12 h.

[0040] (5) Synthesis route of copper-based organic small molecule catalyst modified by trichloromethyl:

[0041] Trichloroacetic acid was used as the organic ligand and basic copper carbonate as the copper source. The two were weighed according to a molar ratio of 2:1 and added to a round-bottom flask, and 25 mL of deionized water was added. The mixture was stirred at a speed of 1000 r / min under an oil bath temperature of 40 °C for 12 h. After the reaction was completed, the liquid was collected by suction filtration using a Buchner funnel, and then the solvent was removed by rotary evaporation to obtain a solid product. Finally, the product was dried under vacuum at 80 °C for 24 h to obtain copper-based organic small molecule powder (CCl3COO)4Cu2 modified by trichloromethyl.

[0042] (6) Synthesis route of copper-based organic small molecule catalyst modified by trifluoromethyl:

[0043] Trifluoroacetic acid was used as the organic ligand and copper oxide as the copper source. The two were weighed according to a molar ratio of 2:1 and added to a round-bottom flask, and 25 mL of deionized water was added. The mixture was stirred at a speed of 1000 r / min under an oil bath temperature of 30 °C for 5 h. After the reaction was completed, the liquid was collected by suction filtration using a Buchner funnel, and then the solvent was removed by rotary evaporation to obtain a solid product. Finally, the product was dried under vacuum at 80 °C for 24 h to obtain copper-based organic small molecule powder (CF3COO)4Cu2 modified by tert-butyl.

[0044] Since the synthesis of the above copper-based organic small molecules is known to those skilled in the art, only a brief description is given here and no specific description is provided.

[0045] 2. Preparation of gas diffusion electrode

[0046] The above-synthesized copper-based organic small molecule was used as the catalyst, 1-20 mg of catalyst powder was weighed, dispersed in 0.1-5 mL of solvent, and 0.1-15 μL of 5% Nafion solution was added. After ultrasonic dispersion for 1-30 min, a catalyst slurry was obtained. 0.001-50 mL of the catalyst slurry was measured, and 0.1-10 mg cm-2of the catalyst was uniformly loaded on the gas diffusion flat material by an air compressor. After being dried sufficiently, a gas diffusion electrode was prepared. -2

[0047] The solvent is a good solvent for the catalyst, including but not limited to acetone, anhydrous ethanol, isopropanol, or a mixed solution of deionized water and ethanol or isopropanol in any volume ratio.

[0048] The gas diffusion flat material includes but is not limited to carbon fiber paper, carbon fiber woven cloth, non-woven fabric, or carbon black paper, etc.

[0049] 3. Preparation of metal anode

[0050] ​The metal-based material is loaded on a conductive current collector with a thickness of 0.05-1 mm and an area of 1-40 cm 2 as an anode material by calcination, electrodeposition, impregnation or spraying, or directly using the conductive current collector as the anode.

[0051] The metal-based material includes but is not limited to non-noble metals such as Fe, Co and Ni, noble metals such as Ir and Ru or alloys and composites thereof.

[0052] The conductive current collector includes but is not limited to titanium current collectors (titanium mesh, titanium felt, etc.), nickel current collectors (nickel plate, nickel sheet or nickel foam, etc.), copper current collectors (copper foil, copper foam, etc.), carbon paper, carbon cloth, etc.

[0053] 4. Assembly and performance test of flow electrolytic cell

[0054] The gas diffusion electrode and the metal anode prepared above are used as the cathode and the anode respectively, and a silver / silver chloride (Ag / AgCl) electrode, a saturated calomel electrode (SCE), a mercury / mercurous sulfate (Hg / Hg2SO4) electrode or a mercury / mercuric oxide (Hg / HgO) electrode is selected as the reference electrode to form a three-electrode flow electrolytic cell; the cathode chamber and the anode chamber are respectively circulated with the cathode electrolyte and the anode electrolyte, and the two chambers are separated by an exchange membrane; during the electrolysis reaction, high-purity gaseous acetylene flows into the gas chamber of the electrolytic cell from the inlet, and the gas flow rate is controlled to be 5-50 sccm by a gas mass flow meter, and the electrolysis product flows out of the outlet of the gas chamber of the electrolytic cell for collection; the cathode electrolyte and the anode electrolyte are pumped into the cathode chamber inlet and the anode chamber inlet respectively at a peristaltic speed of 5-10 rpm by a peristaltic pump, and pumped out from the cathode chamber outlet and the anode chamber outlet; the reaction activity of different copper-based organic small molecule catalysts in the electrocatalytic acetylene coupling to produce 1,3-butadiene and the Faraday efficiency of the target product are evaluated by using a constant potential test method, and the gas composition and content flowing out of the gas chamber outlet are detected by using an online gas chromatograph.

[0055] The cathode electrolyte and the anode electrolyte are alkaline or neutral electrolytes, including but not limited to 1M KOH solution, 1M KHCO3 solution, 0.5M K2SO4 solution, 1M KI solution, 1M KBr solution or 1M KCl solution.

[0056] The exchange membrane is an anion exchange membrane, a proton exchange membrane or a bipolar membrane.

[0057] The performance of the copper-based organic small molecule catalyst in the electrocatalytic acetylene coupling to produce 1,3-butadiene is tested in combination with specific catalysts and reaction conditions.

[0058]

Example 1

[0059] (1) The gas diffusion electrode loaded with ((CH3)3CCOO)4Cu2 copper-based organic small molecule catalyst was used as the cathode, the titanium felt coated with ruthenium and iridium was used as the anode, and the bipolar membrane was used to separate the middle part to form a three-electrode flow electrolysis cell. 1M KCl was pumped into the cathode chamber, and 1M KOH was pumped into the anode chamber.

[0060] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30sccm by using a gas mass flow meter.

[0061] (3) The flow rate of the electrolyte flowing through the cathode chamber and the anode chamber was controlled to be 10rpm by using a peristaltic pump.

[0062] (4) The performance of ((CH3)3CCOO)4Cu2 copper-based organic small molecule electrocatalysis acetylene coupling was evaluated by using linear sweep voltammetry and constant potential test at-0.55V (vs. RHE) by using an electrochemical workstation, and the content of the target product was analyzed by using online gas chromatography.

[0063] Example 2

[0064] (1) The gas diffusion electrode loaded with ((CH3)3CCOO)4Cu2 copper-based organic small molecule catalyst was used as the cathode, the titanium felt coated with ruthenium and iridium was used as the anode, and the bipolar membrane was used to separate the middle part to form a three-electrode flow electrolysis cell. 1M KBr was pumped into the cathode chamber, and 1M KOH was pumped into the anode chamber.

[0065] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30sccm by using a gas mass flow meter.

[0066] (3) The flow rate of the electrolyte flowing through the cathode chamber and the anode chamber was controlled to be 10rpm by using a peristaltic pump.

[0067] (4) The performance of ((CH3)3CCOO)4Cu2 copper-based organic small molecule electrocatalysis acetylene coupling was evaluated by using linear sweep voltammetry and constant potential test at-0.55V (vs. RHE) by using an electrochemical workstation, and the content of the target product was analyzed by using online gas chromatography.

[0068] Example 3

[0069] (1) The gas diffusion electrode loaded with ((CH3)3CCOO)4Cu2 copper-based organic small molecule catalyst was used as the cathode, the titanium felt coated with ruthenium and iridium was used as the anode, and the bipolar membrane was used to separate the middle part to form a three-electrode flow electrolysis cell. 1M KI was pumped into the cathode chamber, and 1M KOH was pumped into the anode chamber.

[0070] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30sccm by using a gas mass flow meter.

[0071] (3) The flow rate of electrolyte through the cathode and anode chambers was controlled by a peristaltic pump at 10 rpm.

[0072] (4) The performance of ((CH3)3CCOO)4Cu2 copper-based small organic molecule for electrocatalysis of acetylene coupling was evaluated by linear sweep voltammetry and constant potential test at -0.55 V (vs. RHE) using an electrochemical workstation, and the content of the target product was analyzed using online gas chromatography.

[0073]

Example 4

[0074] (1) A three-electrode flow electrolysis cell was formed with a gas diffusion electrode loaded with ((CH3)3CCOO)4Cu2 copper-based small organic molecule catalyst as the cathode, a titanium felt coated with ruthenium and iridium as the anode, and an anion exchange membrane in between, 1M KHCO3 was pumped into the cathode chamber, and 1M KOH was pumped into the anode chamber.

[0075] (2) The flow rate of high-purity gaseous acetylene was controlled at 30 sccm by a gas mass flow meter.

[0076] (3) The flow rate of electrolyte through the cathode and anode chambers was controlled by a peristaltic pump at 10 rpm.

[0077] (4) The performance of ((CH3)3CCOO)4Cu2 copper-based small organic molecule for electrocatalysis of acetylene coupling was evaluated by linear sweep voltammetry and constant potential test at -0.55 V (vs. RHE) using an electrochemical workstation, and the content of the target product was analyzed using online gas chromatography.

[0078]

Example 5

[0079] (1) A three-electrode flow electrolysis cell was formed with a gas diffusion electrode loaded with ((CH3)3CCOO)4Cu2 copper-based small organic molecule catalyst as the cathode, a titanium felt coated with ruthenium and iridium as the anode, and an anion exchange membrane in between, 0.5M K2SO4 was pumped into the cathode chamber, and 1M KOH was pumped into the anode chamber.

[0080] (2) The flow rate of high-purity gaseous acetylene was controlled at 30 sccm by a gas mass flow meter.

[0081] (3) The flow rate of electrolyte through the cathode and anode chambers was controlled by a peristaltic pump at 10 rpm.

[0082] (4) The performance of ((CH3)3CCOO)4Cu2 copper-based small organic molecule for electrocatalysis of acetylene coupling was evaluated by linear sweep voltammetry and constant potential test at -0.55 V (vs. RHE) using an electrochemical workstation, and the content of the target product was analyzed using online gas chromatography.

[0083] Example 6

[0084] (1) A three-electrode flow cell was assembled with a gas diffusion electrode loaded with ((CH3)3CCOO)4Cu2copper-based organometallic catalyst as cathode, a titanium felt coated with ruthenium and iridium as anode, and a cation exchange membrane in between. 0.5 M K2SO4was pumped into the cathode chamber and 1 M KOH was pumped into the anode chamber.

[0085] (2) The flow rate of high purity gaseous acetylene was controlled at 30 seem by a mass flow meter.

[0086] (3) The flow rate of electrolyte through the cathode and anode chambers was controlled at 10 rpm by a peristaltic pump.

[0087] (4) The performance of ((CH3)3CCOO)4Cu2copper-based organometallic catalyst for electrocatalysis of acetylene coupling was evaluated by linear sweep voltammetry and constant potential testing at -0.75 V (vs. RHE) using an electrochemical workstation, and the content of target product was analyzed by online gas chromatography.

[0088] Example 7

[0089] (1) A three-electrode flow cell was assembled with a gas diffusion electrode loaded with ((CH3)2CHCOO)4Cu2copper-based organometallic catalyst as cathode, a titanium felt coated with ruthenium and iridium as anode, and a cation exchange membrane in between. 0.5 M K2SO4was pumped into the cathode chamber and 1 M KOH was pumped into the anode chamber.

[0090] (2) The flow rate of high purity gaseous acetylene was controlled at 30 seem by a mass flow meter.

[0091] (3) The flow rate of electrolyte through the cathode and anode chambers was controlled at 10 rpm by a peristaltic pump.

[0092] (4) The performance of ((CH3)2CHCOO)4Cu2copper-based organometallic catalyst for electrocatalysis of acetylene coupling was evaluated by linear sweep voltammetry and constant potential testing at -0.55 V (vs. RHE) using an electrochemical workstation, and the content of target product was analyzed by online gas chromatography.

[0093] Example 8

[0094] (1) A three-electrode flow cell was assembled with a gas diffusion electrode loaded with ((CH3)2CHCOO)4Cu2copper-based organometallic catalyst as cathode, a titanium felt coated with ruthenium and iridium as anode, and a cation exchange membrane in between. 0.5 M K2SO4was pumped into the cathode chamber and 1 M KOH was pumped into the anode chamber.

[0095] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30 seem by using a gas mass flow meter.

[0096] (3) The flow rate of electrolyte flowing through the cathode chamber and the anode chamber was controlled to be 10 rpm by using a peristaltic pump.

[0097] (4) The performance of the ((CH3)2CHCOO)4Cu2 copper-based organic small molecule in electrocatalyzing acetylene coupling was evaluated by using a linear sweep voltammetry and a constant potential test of -0.75 V (vs. RHE) by using an electrochemical workstation, and the content of the target product was analyzed by using an online gas chromatography.

[0098]

Example 9

[0099] (1) A three-electrode flow electrolysis cell was formed by taking a gas diffusion electrode loaded with a (CH3CH2COO)4Cu2 copper-based organic small molecule catalyst as a cathode, taking a titanium felt coated with ruthenium and iridium as an anode, and separating the middle by using an anion exchange membrane, and 0.5M K2SO4 was pumped into the cathode chamber and 1M KOH was pumped into the anode chamber.

[0100] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30 seem by using a gas mass flow meter.

[0101] (3) The flow rate of electrolyte flowing through the cathode chamber and the anode chamber was controlled to be 10 rpm by using a peristaltic pump.

[0102] (4) The performance of the (CH3CH2COO)4Cu2 copper-based organic small molecule in electrocatalyzing acetylene coupling was evaluated by using a linear sweep voltammetry and a constant potential test of -0.55 V (vs. RHE) by using an electrochemical workstation, and the content of the target product was analyzed by using an online gas chromatography.

[0103]

Example 10

[0104] (1) A three-electrode flow electrolysis cell was formed by taking a gas diffusion electrode loaded with a (CH3CH2COO)4Cu2 copper-based organic small molecule catalyst as a cathode, taking a titanium felt coated with ruthenium and iridium as an anode, and separating the middle by using an anion exchange membrane, and 0.5M K2SO4 was pumped into the cathode chamber and 1M KOH was pumped into the anode chamber.

[0105] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30 seem by using a gas mass flow meter.

[0106] (3) The flow rate of electrolyte flowing through the cathode chamber and the anode chamber was controlled to be 10 rpm by using a peristaltic pump.

[0107] (4) The performance of (CH3CH2COO)4Cu2 copper-based organic small molecule electrocatalysis of acetylene coupling was evaluated by linear sweep voltammetry and constant potential test at -0.75 V (vs. RHE) using an electrochemical workstation, and the content of the target product was analyzed using online gas chromatography.

[0108] Example 11

[0109] (1) A three-electrode flow electrolysis cell was formed with a gas diffusion electrode loaded with (CH3COO)4Cu2 copper-based organic small molecule catalyst as the cathode, a titanium felt coated with ruthenium and iridium as the anode, and an anion exchange membrane in between, 0.5 M K2SO4 was pumped into the cathode chamber, and 1 M KOH was pumped into the anode chamber.

[0110] (2) The flow rate of high-purity gaseous acetylene was controlled at 30 sccm using a gas mass flow meter.

[0111] (3) The flow rate of the electrolyte flowing through the cathode chamber and the anode chamber was controlled at 10 rpm using a peristaltic pump.

[0112] (4) The performance of (CH3COO)4Cu2 copper-based organic small molecule electrocatalysis of acetylene coupling was evaluated by linear sweep voltammetry and constant potential test at -0.55 V (vs. RHE) using an electrochemical workstation, and the content of the target product was analyzed using online gas chromatography.

[0113] Example 12

[0114] (1) A three-electrode flow electrolysis cell was formed with a gas diffusion electrode loaded with (CH3COO)4Cu2 copper-based organic small molecule catalyst as the cathode, a titanium felt coated with ruthenium and iridium as the anode, and an anion exchange membrane in between, 0.5 M K2SO4 was pumped into the cathode chamber, and 1 M KOH was pumped into the anode chamber.

[0115] (2) The flow rate of high-purity gaseous acetylene was controlled at 30 sccm using a gas mass flow meter.

[0116] (3) The flow rate of the electrolyte flowing through the cathode chamber and the anode chamber was controlled at 10 rpm using a peristaltic pump.

[0117] (4) The performance of (CH3COO)4Cu2 copper-based organic small molecule electrocatalysis of acetylene coupling was evaluated by linear sweep voltammetry and constant potential test at -0.75 V (vs. RHE) using an electrochemical workstation, and the content of the target product was analyzed using online gas chromatography.

[0118] Example 13

[0119] (1) The three-electrode flow cell was assembled with the gas diffusion electrode loaded with (CC13COO)4Cu2copper-based organic small molecule catalyst as the cathode, the titanium felt coated with ruthenium and iridium as the anode, and the anion exchange membrane in between. 0.5 M K2SO4 was pumped into the cathode chamber, and 1 M KOH was pumped into the anode chamber.

[0120] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30 seem by using a gas mass flow meter.

[0121] (3) The flow rate of the electrolyte flowing through the cathode chamber and the anode chamber was controlled to be 10 rpm by using a peristaltic pump.

[0122] (4) The performance of (CC13COO)4Cu2copper-based organic small molecule electrocatalysis of acetylene coupling was evaluated by using linear sweep voltammetry and constant potential testing at -0.55 V (vs. RHE) by using an electrochemical workstation, and the content of the target product was analyzed by using online gas chromatography.

[0123] [Example 14]

[0124] (1) The three-electrode flow cell was assembled with the gas diffusion electrode loaded with (CC13COO)4Cu2copper-based organic small molecule catalyst as the cathode, the titanium felt coated with ruthenium and iridium as the anode, and the anion exchange membrane in between. 0.5 M K2SO4 was pumped into the cathode chamber, and 1 M KOH was pumped into the anode chamber.

[0125] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30 seem by using a gas mass flow meter.

[0126] (3) The flow rate of the electrolyte flowing through the cathode chamber and the anode chamber was controlled to be 10 rpm by using a peristaltic pump.

[0127] (4) The performance of (CC13COO)4Cu2copper-based organic small molecule electrocatalysis of acetylene coupling was evaluated by using linear sweep voltammetry and constant potential testing at -0.75 V (vs. RHE) by using an electrochemical workstation, and the content of the target product was analyzed by using online gas chromatography.

[0128] [Example 15]

[0129] (1) The three-electrode flow cell was assembled with the gas diffusion electrode loaded with (CC13COO)4Cu2copper-based organic small molecule catalyst as the cathode, the titanium felt coated with ruthenium and iridium as the anode, and the anion exchange membrane in between. 0.5 M K2SO4 was pumped into the cathode chamber, and 1 M KOH was pumped into the anode chamber.

[0130] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30 seem by using a gas mass flow meter.

[0131] (3) The flow rate of electrolyte through the cathode and anode chambers was controlled by a peristaltic pump at 10 rpm.

[0132] (4) The performance of (CF3COO)4Cu2 copper-based organic small molecule for electrocatalysis of ethyne coupling was evaluated by linear sweep voltammetry and constant potential test at -0.55 V (vs. RHE) using an electrochemical workstation, and the content of the target product was analyzed using online gas chromatography.

[0133] [Example 16]

[0134] (1) A three-electrode flow electrolysis cell was formed with a gas diffusion electrode loaded with (CF3COO)4Cu2 copper-based organic small molecule catalyst as the cathode, a titanium felt coated with ruthenium and iridium as the anode, and an anion exchange membrane in between, 0.5 M K2SO4 was pumped into the cathode chamber, and 1 M KOH was pumped into the anode chamber.

[0135] (2) The flow rate of high-purity gaseous ethyne was controlled at 30 sccm by a gas mass flow meter.

[0136] (3) The flow rate of electrolyte through the cathode and anode chambers was controlled by a peristaltic pump at 10 rpm.

[0137] (4) The performance of (CF3COO)4Cu2 copper-based organic small molecule for electrocatalysis of ethyne coupling was evaluated by linear sweep voltammetry and constant potential test at -0.75 V (vs. RHE) using an electrochemical workstation, and the content of the target product was analyzed using online gas chromatography.

[0138] [Comparative Example 1]

[0139] (1) A three-electrode flow electrolysis cell was formed with a gas diffusion electrode loaded with commercial cuprous oxide (Cu2O) catalyst as the cathode, a titanium felt coated with ruthenium and iridium as the anode, and an anion exchange membrane in between, 0.5 M K2SO4 was pumped into the cathode chamber, and 1 M KOH was pumped into the anode chamber.

[0140] (2) The flow rate of high-purity gaseous ethyne was controlled at 30 sccm by a gas mass flow meter.

[0141] (3) The flow rate of electrolyte through the cathode and anode chambers was controlled by a peristaltic pump at 10 rpm.

[0142] (4) The performance of commercial Cu2O for electrocatalysis of ethyne coupling was evaluated by linear sweep voltammetry and constant potential test at -0.55 V (vs. RHE) using an electrochemical workstation, and the content of the target product was analyzed using online gas chromatography.

[0143] [Comparative Example 2]

[0144] (1) The gas diffusion electrode loaded with commercial cuprous oxide (Cu2O) catalyst was used as cathode, the titanium felt coated with ruthenium iridium was used as anode, and the three-electrode flow electrolysis cell was composed by separating the middle with anion exchange membrane. 0.5M K2SO4 was pumped into the cathode chamber, and 1M KOH was pumped into the anode chamber.

[0145] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30sccm by using a gas mass flow meter.

[0146] (3) The flow rate of electrolyte flowing through the cathode chamber and the anode chamber was controlled to be 10rpm by using a peristaltic pump.

[0147] (4) The performance of commercial Cu2O in electrocatalytic acetylene coupling was evaluated by using linear sweep voltammetry and constant potential test at-0.75V (vs. RHE) by using an electrochemical workstation, and the content of target product was analyzed by using online gas chromatography.

[0148]

Comparative Example 3

[0149] (1) The gas diffusion electrode loaded with commercial cupric oxide (CuO) catalyst was used as cathode, the titanium felt coated with ruthenium iridium was used as anode, and the three-electrode flow electrolysis cell was composed by separating the middle with anion exchange membrane. 0.5M K2SO4 was pumped into the cathode chamber, and 1M KOH was pumped into the anode chamber.

[0150] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30sccm by using a gas mass flow meter.

[0151] (3) The flow rate of electrolyte flowing through the cathode chamber and the anode chamber was controlled to be 10rpm by using a peristaltic pump.

[0152] (4) The performance of commercial CuO in electrocatalytic acetylene coupling was evaluated by using linear sweep voltammetry and constant potential test at-0.55V (vs. RHE) by using an electrochemical workstation, and the content of target product was analyzed by using online gas chromatography.

[0153]

Comparative Example 4

[0154] (1) The gas diffusion electrode loaded with commercial cupric oxide (CuO) catalyst was used as cathode, the titanium felt coated with ruthenium iridium was used as anode, and the three-electrode flow electrolysis cell was composed by separating the middle with anion exchange membrane. 0.5M K2SO4 was pumped into the cathode chamber, and 1M KOH was pumped into the anode chamber.

[0155] (2) The flow rate of high-purity gaseous acetylene was controlled to be 30sccm by using a gas mass flow meter.

[0156] (3) The flow rate of electrolyte flowing through the cathode chamber and the anode chamber was controlled to be 10rpm by using a peristaltic pump.

[0157] (4) The performance of commercial CuO in electrocatalytic acetylene coupling was evaluated by linear sweep voltammetry and constant potential test at-0.75 V (vs. RHE) using an electrochemical workstation, and the content of the target product was analyzed using online gas chromatography.

[0158] The specific evaluation results are shown in Table 1.

[0159] Table 1

[0160]

[0161]

[0162]

[0163] During the experiment, the performance of the foam nickel and titanium felt as an anode in electrocatalytic acetylene coupling was mainly explored. It was found that the foam nickel would be etched when a halogen-containing electrolyte was used, thereby causing a decrease in performance. Considering the stability of the reaction system and the comparison between different reaction systems, the titanium felt with better corrosion resistance was used as the anode in the embodiments of the present application.

[0164] As shown in Table 1, the performance of copper-based organic small molecule catalysts and inorganic catalysts such as oxides and metals in electrocatalytic acetylene coupling was compared. Among them, cases 1 to 3 of the comparative document correspond to three different copper-based catalysts (oxide catalysts with different valence states and metal single-atom catalysts) in the background technology CN112342562B.

[0165] As can be seen from the data of Examples 1-5 in Table 1, the performance of electrocatalytic acetylene coupling is best in 0.5M K2SO4 electrolyte. It should be noted that the electrocatalytic acetylene coupling reaction is easier to proceed at a low potential, that is, the faradaic efficiency of the target product is higher at a low applied potential. As the potential increases, the copper-based catalyst for electrocatalysis using acetylene as the raw material is more prone to semi-hydrogenation to generate ethylene byproducts. The potential range of the electrocatalytic acetylene coupling of the present application is -0.55 to -0.85 V (vs. RHE), and the lowest reaction potential is also higher than -0.2 V (vs. RHE) used in the background technology CN112342562B; even so, the copper-based small organic molecule catalyst used in the present application can achieve more excellent coupling performance: at -0.55 V (vs. RHE), the faradaic efficiency of the target product can achieve more than 80%, and the highest can even reach 90%; at -0.75 V (vs. RHE), the faradaic efficiency of the best sample for 1,3-butadiene can still be maintained at 70%. Specifically, as can be seen from the data of Examples 1-5, 7, 9, 11, 13, and 15, when acetylene is used as the reaction gas, the copper-based small organic molecule proposed in the present application exhibits more excellent coupling performance at a higher applied potential (-0.55 V vs. RHE), and the faradaic efficiency for the coupling product 1,3-butadiene is basically more than 80%; in particular, the faradaic efficiency of the copper-based small organic molecule modified by tert-butyl at this potential is as high as 90%. As can be seen from the data of Examples 5, 8, 10, 11, 14, and 16, the copper-based small organic molecule catalyst used in the present application can still achieve a relatively high faradaic efficiency even at a high potential of -0.75 V (vs. RHE), and can reach about 60% except for -CH3, -CH3CH2, and -CCl3; in particular, the faradaic efficiency of the copper-based small organic molecule modified by tert-butyl at this potential is as high as 70%, and has a relatively high current density (-46 mA cm -2 ). It can be seen that the catalytic effect of the present application is obviously better than that of the background technology CN112342562B, which can effectively inhibit the semi-hydrogenation of acetylene and the hydrogen evolution side reaction at a high applied potential, widen the application field of acetylene industry, and help the green and sustainable synthesis of more high-value organic compounds.

[0166] More importantly, the present application also discloses that the effect of electrocatalytic acetylene coupling presents a structure-function relationship of first decreasing and then rising with the increase of the electronegativity of the modified functional group. Specifically, the data of Examples 4-16 in the table and Figure 2It can be concluded that the performance of the catalysts in electrocatalyzing the coupling of acetylene to 1,3-butadiene at -0.55 and -0.75 V (vs. RHE) presents a trend of first decreasing and then increasing with the increase of the electronegativity of the modified functional groups (i.e. electron-withdrawing ability, the functional groups contained in the copper-based organic small molecule catalysts (CH3)3CCOO)4Cu2, ((CH3)2CHCOO)4Cu2, (CH3CH2COO)4Cu2, (CH3COO)4Cu2, (CCl3COO)4Cu2 and (CF3COO)4Cu2 are -C(CH3)3, -CH(CH3)2, -CH2CH3, -CH3, -CCl3 and -CF3, respectively, and the electronegativity presents a trend of increasing monotonously), and this trend is more significant at -0.75 V (vs. RHE), i.e. 50-70% (at -0.55 V (vs. RHE), the faradaic efficiency of each catalyst for 1,3-butadiene is 80-90%), which provides an effective guidance and new ideas for the design of high-efficiency acetylene coupling catalysts.

[0167] Figure 1 In (a), the tert-butyl-modified catalyst can achieve a higher current density (about 155 mA cm-2) and exhibits good catalytic activity in the acetylene reaction gas; -2 Figure 1 (b) is the product faradaic distribution of the tert-butyl-modified organic small molecule catalyst at -0.55 to -0.85 V (vs. RHE), and the faradaic efficiency of the catalyst for 1,3-butadiene is maintained at more than 60% in the whole test range, and almost no hydrogen by-product is generated. Overall, the ((CH3)3CCOO)4Cu2 copper-based organic small molecule catalyst exhibits excellent performance in the process of electrocatalyzing acetylene coupling.

[0168] On the other hand, the structure of the organic small molecule can be precisely controlled by functional group modification and the like, and the present application mentions six functional groups, i.e. -C(CH3)3, -CH(CH3)2, -CH2CH3, -CH3, -CCl3 and -CF3, the electron-withdrawing and electron-donating abilities of which are different, which causes the electron cloud density of the catalyst surface (especially the Cu atom) to change, thereby affecting the adsorption of acetylene raw material and the desorption of product and the like, and further affecting the catalytic performance. The electron-withdrawing abilities of the above six functional groups present a trend of monotonous increasing, and the performance of the organic small molecule modified by the functional groups in electrocatalyzing acetylene coupling (including the faradaic efficiency for the target product and the partial current density) presents a trend of first decreasing and then increasing with the increase of the electron-withdrawing ability of the modified group, as shown in FIG. 1 (as the difference in the performance of each catalyst in electrocatalyzing acetylene coupling is more significant at a high applied potential, the data at a high potential are selected to draw the graph). Figure 2 Figure 2 ​​), which is helpful for guiding the design of catalysts.

[0169] The scope of the claims of the present application is not limited to the above-mentioned embodiments, and all other embodiments obtained by those skilled in the art based on the embodiments in the present application without making creative efforts are within the scope of protection of the present application.

Claims

1. Use of copper-based organic small molecules as catalysts in electrocatalytic acetylene coupling to prepare 1,3-butadiene, wherein the copper-based organic small molecules are formed by bidentate coordination of carboxylic acids or carboxylate salts with different functional groups and copper sources.

2. The use according to claim 1, wherein: the different functional groups are tert-butyl, isopropyl, ethyl, methyl, trichloromethyl or trifluoromethyl; and the copper source is copper nitrate, copper sulfate, basic copper carbonate, copper oxide or copper hydroxide. The method comprises the following steps: 1) dispersing copper-based organic small molecule powder in a good solvent, adding a 5% Nafion solution, and obtaining a catalyst slurry after ultrasonic dispersion; 3. A method for electrocatalytic coupling of acetylene by a copper-based small organic molecule catalyst, characterized in that: 3) using the gas diffusion electrode obtained in step 2) as a cathode, using a conductive current collector or a conductive current collector loaded with a metal-based material as an anode, and using an exchange membrane to separate the cathode chamber and the anode chamber to form a three-electrode flow electrolysis cell, and then performing electrocatalytic acetylene coupling to prepare 1,3-butadiene.

4. The method according to claim 3, wherein: in step 1), the ratio of copper-based organic small molecules, good solvent and 5% Nafion solution is 1-20:0.1-5:0.1-15, mg:mL:μL; and the ultrasonic time is 1-30 min. 2) The catalyst slurry obtained in step 1) is uniformly sprayed on a gas diffusion flat sheet material until the catalyst loading is 0.1-10 mg cm -2 , and a gas diffusion electrode is prepared after sufficient drying; 5. The method according to claim 4, wherein: in step 1), the good solvent is acetone, anhydrous ethanol, isopropanol or a mixed solution of deionized water and ethanol or isopropanol in any volume ratio.

6. The method according to claim 5, wherein: in step 2), the gas diffusion flat material is carbon fiber paper, carbon fiber woven cloth, non-woven fabric or carbon black paper.

7. The method according to claim 6, wherein: in step 3), the metal-based material is Fe, Co, Ni, Ir, Ru or an alloy or composite thereof.

8. The method according to claim 7, wherein: in step 3), the exchange membrane is an anion exchange membrane, a proton exchange membrane or a bipolar membrane.

9. The method according to claim 8, wherein: in step 3), high-purity acetylene is used as the raw material, and is introduced into the electrolysis cell at a flow rate of 5-50 sccm through the gas chamber inlet, and the electrolysis product is collected by flowing out of the gas chamber outlet, while the cathode electrolyte and the anode electrolyte are pumped into the cathode chamber inlet and the anode chamber inlet at a peristaltic speed of 5-10 rpm, and pumped out of the cathode chamber outlet and the anode chamber outlet.

10. The method according to claim 9, wherein: ​ ​ ​ ​ The conductive current collector adopts titanium current collector, nickel current collector, copper current collector, carbon paper or carbon cloth with thickness of 0.05-1mm and area of 1-40cm 2 . ​ ​ ​ ​ ​ In step 3), the electrolyte is a 1 M KOH solution, a 1 M KHCO3 solution, a 0.5 M K2SO4 solution, a 1 M KI solution, a 1 M KBr solution, or a 1 M KCl solution.

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