A method for electrocatalytic reaction of carbon dioxide with amine compounds to achieve aminomethylation

Abstract

The present invention discloses a method for realizing aminomethylation by electrochemically catalyzing the reaction of CO2 with amine compounds. This method uses a CuNi x Al-MMO catalyst / electrode composite material, an electrolyte, and an H-type electrolytic cell device to form an electrocatalytic system. The present invention innovatively designs a CuNi x Al-MMO catalyst / electrode composite material and uses it as the cathode material to electrochemically catalyze the aminomethylation reaction of CO2 with amine compounds with high Faraday efficiency. The electrochemistry system of the present invention is simple to operate, the cathode catalyst has good stability, is easy to recycle, and has the value of industrial development. The present invention has great practical application value for the resource utilization of CO2 and is an important breakthrough in the fields of electrocatalytic conversion of CO2 and aminomethylation.

Description

Technical Field

[0001] The present invention belongs to the field of chemical engineering, and particularly relates to a method for electrocatalytically reacting CO2 with amine compounds to achieve aminomethylation. Background Art

[0002] Since the Industrial Revolution, the demand for fossil energy in industrial activities has been increasing day by day. Fossil energy dominates the entire energy structure, resulting in a sharp rise in the concentration of CO2 in the atmosphere. The current atmospheric CO2 concentration has increased by about 50% compared with that before the Industrial Revolution. CO2 is a greenhouse gas that has caused a series of environmental problems such as global warming. Reducing CO2 emissions is extremely urgent. Therefore, the research on the conversion and utilization of CO2 is of great significance. A large number of researchers have developed various methods for the conversion and utilization of CO2, including traditional thermal catalysis, electrocatalysis, photocatalysis, biological conversion, etc. Among them, electrocatalysis has received extensive attention due to its mild reaction conditions, simple reaction conditions, and green and clean reaction process. At present, researchers have successfully converted CO2 into various products such as CO, formic acid, methanol, acetic acid, ethylene, and ethanol. From the perspective of the reaction essence, these all belong to the "hydrogenation" process of CO2. In addition to hydrogenation, another method for CO2 fixation is to react with organic substances to obtain higher-value-added chemicals. Currently, the existing organic electrochemical reactions of CO2 mainly focus on electrocarboxylation with organic halides, electrocarboxylation with aldehydes and ketones, and the reaction with alcohols or epoxides to synthesize carbonates. Although some important progress has been made in the research on the organic electrochemical reaction of CO2, it is still in its infancy, and more new reaction routes and reaction systems need to be designed and constructed.

[0003] The aminomethylation reaction is a very important reaction in chemical production and is widely used in the fields of pharmaceutical and pesticide synthesis, chemical raw material preparation, surfactant synthesis, biomolecule intermediate synthesis, etc. At present, the aminomethylation reaction is mainly carried out by thermal catalysis, with relatively harsh reaction conditions and high energy consumption and high pollution. Using CO2 as a carbon source and coupling it with other small molecules through an electrochemical method can not only obtain new high-value-added products but also develop a new path for the conversion and utilization of CO2. Therefore, electrocatalytic coupling of CO2 with amine compounds for aminomethylation reaction has broad development prospects. In order to achieve efficient electrocatalytic aminomethylation reaction of CO2 with amine compounds, a highly active, efficient and stable electrocatalyst needs to be designed. Summary of the Invention

[0004] One object of the present invention is to provide an electrode material.

[0005] The electrode material provided by the present invention is a CuNi x Al metal oxide (CuNi x Al-MMO) catalyst / electrode composite material.

[0006] Among them, the CuNi x Al-MMO catalyst is obtained by high-temperature calcination after obtaining the precursor by the co-precipitation method. The specific preparation method is as follows:

[0007] 1) Dissolve copper compounds, nickel compounds and aluminum compounds in water to obtain an aqueous solution of metal compounds; prepare an aqueous sodium hydroxide solution as the alkali solution; add the aqueous solution of metal compounds and the aqueous sodium hydroxide solution into the reaction vessel at the same time, maintain the pH value stable between 8.0 and 9.5, and heat and stir the reaction. After the reaction is completed, wash and dry the obtained precipitate to obtain CuNi x Al hydrotalcite (CuNi x Al-LDH) powder;

[0008] 2) Calcinate the obtained CuNi x Al-LDH powder at high temperature to obtain it.

[0009] In step 1) of the above method, the copper compound can be one of copper sulfate (CuSO4), copper nitrate (CuNO3), copper chloride (CuCl2), copper acetate (Cu(CH3COO)2) and their hydrates, specifically CuSO4·5H2O;

[0010] The nickel compound can be selected from at least one of nickel chloride (NiCl2), nickel nitrate (Ni(NO3)2) and their hydrates, specifically NiCl2;

[0011] The aluminum compound can be selected from at least one of aluminum chloride (AlCl3), aluminum nitrate (Al(NO3)3) and their hydrates, and specifically Al(NO3)3·9H2O is used;

[0012] The molar ratio of Cu in the copper compound, Ni in the nickel compound to Al in the aluminum compound can be 1:X:Y, where X can be 0.5 - 2 and Y is (1 + X) / 3, specifically 1:2:1;

[0013] When preparing hydrotalcite, control the molar ratio of divalent metal ions (Cu 2+ and Ni 2+ ) to trivalent metal ions (Al 3+ ) between 2:1 and 4:1, specifically 3:1; The molar ratio of Cu 2+ to Ni 2+ is denoted as 1:X, where X = 0.5 - 2, specifically can be 0.5, 1 or 2;

[0014] The concentration of the aqueous sodium hydroxide solution can be 0.01 - 10M, specifically 1M.

[0015] The heating temperature can be 50 - 80 °C, specifically 70 °C;

[0016] The stirring reaction time can be 10 min - 60 min, specifically 30 min. <s

[0017] After the reaction, the precipitate is collected by centrifugation. The centrifugation speed is 5000 - 10000 rpm and the time is 1 - 30 min; specifically 8000 rpm for 5 min.

[0018] The solvent for washing can be deionized water, ethanol, acetone, and their mixed solutions. The specific washing steps are to wash 3 times with deionized water first, then 2 times with ethanol, and finally 1 time with acetone.

[0019] The drying temperature can be 30 - 150 °C and the time can be 1 - 50 h; the specific steps are to place it in a vacuum drying oven and dry at 60 °C for 12 h.

[0020] In step 2) of the above method, the high - temperature calcination is carried out in a muffle furnace. The calcination temperature can be 300 - 600 °C and the time can be 2 - 8 h. The specific calcination temperature is 500 °C and the time is 4 h.

[0021] The CuNi x The CuNiAl - MMO catalyst / electrode composite material is prepared by a method comprising the following steps: dispersing the CuNiAl - MMO catalyst into an organic solvent, adding a Nafion D - 521 dispersion as a binder, and dropping the resulting dispersion onto a hydrophobic conductive support to obtain it.

[0022] Among them, the organic solvent can be selected from at least one of the following: acetone, ethanol, isopropanol, methanol, specifically acetone;

[0023] In the dispersion, the concentration of the CuNi x Al - MMO catalyst is 1 - 10 mg / mL -1 , specifically 10 mg / mL -1 .

[0024] The mass fraction of the Nafion D - 521 dispersion is 5 - 20 wt%.

[0025] [[ID=3C]]The ratio of the Nafion D - 521 dispersion to the catalyst is 5 - 100 μL∶10 mg, such as 50 μL∶10 mg.

[0026] The hydrophobic conductive support can be carbon fiber paper, carbon fiber woven cloth, non - woven fabric, carbon black paper, specifically carbon fiber paper.

[0027] The CuNi xThe loading amount of the Al-MMO catalyst on the hydrophobic conductive support can be 0.1-10 mg·cm -2 , specifically it can be 2 mg·cm -2 .

[0028] The second object of the present invention is to provide an electrochemical catalytic system.

[0029] The electrochemical catalytic system provided by the present invention includes the above electrode material, reaction electrolyte and reaction device;

[0030] The reaction electrolyte includes an anode electrolyte and a cathode electrolyte. Among them, the anode electrolyte is selected from at least one of the following: aqueous KOH solution, aqueous KHCO3 solution, aqueous NaOH solution, aqueous NaHCO3 solution; the cathode electrolyte includes a reaction substrate, a mixed solution of LiI and KHCO3.

[0031] The concentration of the anode electrolyte can be 0.1-10 M; specifically it can be 1 M aqueous KHCO3 solution.

[0032] The concentration of the cathode electrolyte can be 0.1-10 M KHCO3 / KOH, 1-20 mM LiI and 20-500 mM reaction substrate; specifically it can be 1 M KHCO3, 5 mM LiI and 100 mM amine compound.

[0033] The reaction device can be an H-type electrolytic cell.

[0034] The application of the above electrode material and electrochemical catalytic system in the electrochemical aminomethylation reaction also belongs to the protection scope of the present invention. Specifically, the electrode material and electrochemical catalytic system catalyze the reaction of carbon dioxide and amine compound to achieve aminomethylation.

[0035] The present invention also provides a method for electrochemical catalytic aminomethylation reaction.

[0036] The method provided by the present invention for electrochemically catalyzing the aminomethylation reaction of CO2 and amine compound includes the following steps: using the above electrochemical catalytic system, introducing CO2 gas into the cathode cell, using the amine compound as the reaction substrate, and under the action of the electrode material and electrolyte, performing electrocatalytic aminomethylation reaction.

[0037] In the above method, the above electrode material is used as the working electrode, the Ag / AgCl electrode is used as the reference electrode, and the platinum mesh is used as the counter electrode;

[0038] The reaction potential can be -1.0 to -2.0 V vs. Ag / AgCl; the specific reaction potential is -1.3 to -1.7 V vs. Ag / AgCl.

[0039] The reaction time can be 0.5 - 120 h (such as 0.5 - 5 h, 2 - 4 h), and the specific reaction time is 3 h.

[0040] The amine compound can be alkylamine, cycloalkylamine, aromatic amine and their derivatives, specifically methylamine, dimethylamine, diethylamine, piperidine, 4 - hydroxypiperidine, aniline, and more specifically dimethylamine, 4 - hydroxypiperidine, aniline (the corresponding reaction products are trimethylamine, 4 - hydroxy - 1 - methylpiperidine, 1 - methylaniline in sequence).

[0041] In the present invention, by combining Cu with transition metal elements or noble metal elements and precisely controlling the size, composition, morphology and structure of the catalyst, an electrocatalyst with high activity, high efficiency and stability is achieved for the electrocatalytic coupling of CO2 with amine compounds for aminomethylation reaction.

[0042] The present invention provides a method for aminomethylation reaction of amine compounds with CO2 under electrochemical catalysis using CO2 as a carbon source. This reaction can be efficiently carried out in an H - type electrolytic cell system using a CuNi x Al - MMO catalyst / electrode composite material as the electrode material, which is an important breakthrough in the field of electrochemical catalytic conversion of CO2 and the field of aminomethylation. The products of the aminomethylation reaction play important roles in various fields, opening a new path for the electrochemical catalytic conversion of CO2. In addition, the catalyst of the present invention has excellent cyclic use performance, laying a solid foundation for its industrial development. The synthesis of the catalytic material uses cheap and easily available metal compound raw materials, having large - scale practical application value for the resource - based reuse of CO2. The present invention has far - reaching significance in solving energy crisis and environmental problems. Description of the Drawings

[0043] Figure 1 is the scanning electron microscope (SEM) image and transmission electron microscope (TEM) image of CuNi2Al - MMO;

[0044] Figure 2 is the X - ray diffraction analysis (XRD) pattern of CuNi2Al - MMO;

[0045] Figure 3 is the high - resolution TEM (HRTEM) image and elemental distribution map (EDS Mapping) of CuNi2Al - MMO;

[0046] Figure 4 is the Faraday efficiency diagram of the electrochemical catalysis of CO2 and aminomethylation by CuNi2Al - MMO;

[0047] Figure 5 is the stability test result diagram of the electrochemical catalysis of CO2 and aminomethylation by CuNi2Al - MMO. Detailed Embodiments

[0048] The present invention will be further described in detail below in conjunction with specific embodiments. The provided embodiments are only for clarifying the present invention, rather than limiting the scope of the present invention. The following provided embodiments can be used as a guide for those of ordinary skill in the art to make further improvements, and do not constitute any limitation to the present invention in any way.

[0049] The experimental methods in the following embodiments are all conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0050] Example 1: Preparation and Characterization of Catalysts:

[0051] Preparation of CuNi2Al-MMO Catalyst

[0052] First, 20 mL of CuSO4·5H2O (100 mM), 40 mL of NiCl2 (100 mM), and 20 mL of Al(NO3)3·9H2O (100 mM) were mixed to obtain Solution A. A 1 M NaOH solution was prepared and denoted as Solution B. The flask was heated by an oil bath and stabilized at 70 °C. Solution A and Solution B were slowly added to the flask and stirred well. At the same time, a pH meter was used to monitor in real time to ensure that the pH value of the solution was always between 8.0 and 9.5 during the mixing reaction. After all of Solution A was added, the addition of Solution B was stopped. The flask was kept heated and stirred at 70 °C for 30 min and then stopped. The reaction mixture was centrifuged at 8000 rpm for 5 min to obtain a precipitate. It was washed 3 times with deionized water, 2 times with ethanol, and finally 1 time with acetone. The washed precipitate was placed in a vacuum drying oven and dried at 60 °C for 12 h. The dried powder was transferred to a muffle furnace and calcined at 500 °C for 4 h to obtain a CuNi2Al-MMO (the atomic ratio of each element was obtained by XPS elemental analysis) catalyst, with Cu:Ni:Al = 1:2:1.

[0053] Preparation of Cu2NiAl-MMO Catalyst

[0054] First, 40 mL of CuSO4·5H2O (100 mM), 20 mL of NiCl2 (100 mM), and 20 mL of Al(NO3)3·9H2O (100 mM) were mixed to obtain Solution A. A 1 M NaOH solution was prepared and denoted as Solution B. The flask was heated by an oil bath and stabilized at 70 °C. Solution A and Solution B were slowly added to the flask and stirred well. At the same time, a pH meter was used for real-time monitoring to ensure that the pH value of the solution was always between 8.0 and 9.5 during the mixing reaction. After all of Solution A was added, the addition of Solution B was stopped. The flask was kept heated at 70 °C and stirred for 30 min and then stopped. The reaction mixture was centrifuged at 8000 rpm for 5 min to obtain a precipitate. The precipitate was washed 3 times with deionized water, then 2 times with ethanol, and finally 1 time with acetone. The washed precipitate was placed in a vacuum drying oven and dried at 60 °C for 12 h. The dried powder was transferred to a muffle furnace and calcined at 500 °C for 4 h to obtain the Cu2Nil-MMO (the atomic ratios of each element were obtained by XPS elemental analysis) catalyst, with Cu:Ni:Al = 2:1:1.

[0055] Preparation of CuNiAl-MMO Catalyst

[0056] First, 30 mL of CuSO4·5H2O (100 mM), 30 mL of NiCl2 (100 mM), and 20 mL of Al(NO3)3·9H2O (100 mM) were mixed to obtain Solution A. A 1 M NaOH solution was prepared and denoted as Solution B. The flask was heated by an oil bath and stabilized at 70 °C. Solution A and Solution B were slowly added to the flask and stirred well. At the same time, a pH meter was used for real-time monitoring to ensure that the pH value of the solution was always between 8.0 and 9.5 during the mixing reaction. After all of Solution A was added, the addition of Solution B was stopped. The flask was kept heated at 70 °C and stirred for 30 min and then stopped. The reaction mixture was centrifuged at 8000 rpm for 5 min to obtain a precipitate. The precipitate was washed 3 times with deionized water, then 2 times with ethanol, and finally 1 time with acetone. The washed precipitate was placed in a vacuum drying oven and dried at 60 °C for 12 h. The dried powder was transferred to a muffle furnace and calcined at 500 °C for 4 h to obtain the CuNiAl-MMO (the atomic ratios of each element were obtained by XPS elemental analysis) catalyst. Cu:Ni:Al = 3:3:2

[0057] Preparation of CuAl-MMO Catalyst

[0058] First, 60 mL of CuSO4·5H2O (100 mM) was mixed with 20 mL of Al(NO3)3·9H2O (100 mM) to obtain solution A. 1 M NaOH solution was prepared and denoted as solution B. The flask was heated by an oil bath and stabilized at 70 °C. Solution A and solution B were slowly added to the flask and stirred well. At the same time, a pH meter was used for real-time monitoring to ensure that the pH value of the solution was always between 8.0 and 9.5 during the mixing reaction. After all of solution A was added, the addition of solution B was stopped. The flask was kept heated at 70 °C and stirred for 30 min and then stopped. The resulting mixture was centrifuged at 8000 rpm for 5 min to obtain a precipitate. It was washed 3 times with deionized water, then 2 times with ethanol, and finally 1 time with acetone. The washed precipitate was placed in a vacuum drying oven and dried at 60 °C for 12 h. The dried powder was transferred to a muffle furnace and calcined at 500 °C for 4 h to obtain the CuAl-MMO (the atomic ratios of each element were obtained by XPS elemental analysis) catalyst. Cu:Al = 3:1.

[0059] Preparation of NiAl-MMO catalyst

[0060] First, 60 mL of NiCl2 (100 mM) was mixed with 20 mL of Al(NO3)3·9H2O (100 mM) to obtain solution A. 1 M NaOH solution was prepared and denoted as solution B. The flask was heated by an oil bath and stabilized at 70 °C. Solution A and solution B were slowly added to the flask and stirred well. At the same time, a pH meter was used for real-time monitoring to ensure that the pH value of the solution was always between 8.0 and 9.5 during the mixing reaction. After all of solution A was added, the addition of solution B was stopped. The flask was kept heated at 70 °C and stirred for 30 min and then stopped. The resulting mixture was centrifuged at 8000 rpm for 5 min to obtain a precipitate. It was washed 3 times with deionized water, then 2 times with ethanol, and finally 1 time with acetone. The washed precipitate was placed in a vacuum drying oven and dried at 60 °C for 12 h. The dried powder was transferred to a muffle furnace and calcined at 500 °C for 4 h to obtain the NiAl-MMO (the atomic ratios of each element were obtained by XPS elemental analysis) catalyst. Ni:Al = 3:1.

[0061] Preparation of CuCo-MMO catalyst

[0062] First, 60 mL of CuSO4·5H2O (100 mM) was mixed with 20 mL of CoCl2·6H2O (100 mM) to obtain Solution A. 1 M NaOH solution was prepared and denoted as Solution B. The flask was heated by an oil bath and stabilized at 70 °C. Solution A and Solution B were slowly added to the flask and stirred well. At the same time, a pH meter was used to monitor in real time to ensure that the pH value of the solution was always between 8.0 and 9.5 during the mixing reaction. After all of Solution A was added, the addition of Solution B was stopped. The flask was kept heated and stirred at 70 °C for 30 min and then stopped. The reaction mixture was centrifuged at 8000 rpm for 5 min to obtain a precipitate. It was washed 3 times with deionized water, 2 times with ethanol, and finally 1 time with acetone. The washed precipitate was placed in a vacuum drying oven and dried at 60 °C for 12 h. The dried powder was transferred to a muffle furnace and calcined at 500 °C for 4 h to obtain the CuCo-MMO (the atomic ratio of each element was obtained by XPS elemental analysis) catalyst. Cu:Co = 3:1.

[0063] Preparation of ZnAl-MMO catalyst

[0064] First, 60 mL of ZnCl2·2H2O (100 mM) was mixed with 20 mL of Al(NO3)3·9H2O (100 mM) to obtain Solution A. 1 M NaOH solution was prepared and denoted as Solution B. The flask was heated by an oil bath and stabilized at 70 °C. Solution A and Solution B were slowly added to the flask and stirred well. At the same time, a pH meter was used to monitor in real time to ensure that the pH value of the solution was always between 8.0 and 9.5 during the mixing reaction. After all of Solution A was added, the addition of Solution B was stopped. The flask was kept heated and stirred at 70 °C for 30 min and then stopped. The reaction mixture was centrifuged at 8000 rpm for 5 min to obtain a precipitate. It was washed 3 times with deionized water, 2 times with ethanol, and finally 1 time with acetone. The washed precipitate was placed in a vacuum drying oven and dried at 60 °C for 12 h. The dried powder was transferred to a muffle furnace and calcined at 500 °C for 4 h to obtain the ZnAl-MMO (the atomic ratio of each element was obtained by XPS elemental analysis) catalyst. Cu:Co = 3:1

[0065] Systematic characterization of the CuNi2Al-MMO catalyst. Scanning electron microscopy (SEM) images and transmission electron microscopy (TEM) images showed that CuNi2Al-MMO presented an irregular flaky structure with a diameter of about 500 nm ( Figure 1 ). X-ray diffraction analysis (XRD) showed that Cu, Ni, and Al in the CuNi2Al-MMO catalyst existed in the forms of copper oxide, nickel oxide, and aluminum oxide respectively ( Figure 2)。The spacing of lattice fringes in high-resolution TEM (HRTEM) is 0.27 nm, 0.25 nm, and 0.22 nm, which can be attributed to the (110) crystal plane of CuO, the (101) crystal plane of NiO, and the (222) crystal plane of Al2O3, respectively. Figure 2 )。Element distribution map (EDS Mapping) studies show that Cu, Ni, Al, and O elements are uniformly distributed on the catalyst surface. Figure 3 )。

[0066] Example 2: Electrochemical catalytic amination methylation reaction of CO2 with amine compounds

[0067] Preparation of working electrode: First, disperse 10 mg of CuNi2Al-MMO catalyst (prepared in Example 1) and 50 μL of Nafion D-521 dispersion (5 wt%) in 1 mL of acetone, and ultrasonicate for 30 min to make it evenly dispersed. Take 200 μL of the dispersion and evenly drop-coat it on the surface of hydrophobic carbon paper (1×0.5 cm -2 ), and dry it at room temperature. The loading amount of the catalyst for each electrode is 2 mg·cm -2 .

[0068] All electrochemical experiments were completed on an electrochemical workstation (CHI 660E, Shanghai Chenhua Instrument Co., Ltd.). The electrolysis experiment was carried out at 25 °C. The electrolytic cell device used was a three-electrode H-type electrolytic cell system. The three electrodes included the above working electrode, nickel foam counter electrode, and Ag / AgCl reference electrode, with saturated KCl aqueous solution added inside. Before the experiment, the reference electrode was calibrated according to the method in the literature. During the experiment, Nafion 117 membrane was used as the proton exchange membrane to separate the cathode and anode. The cathode used 5 mM LiI, 1 M KHCO3, and 100 mM 4-hydroxypiperidine as the electrolyte, and the anode used 1 M KHCO3 aqueous solution as the electrolyte. The amount of electrolyte used for each experiment at both the cathode and anode was 30 ml, and the CO2 flow rate was 20 sccm for electrolysis. The gas products were collected using an air bag and analyzed by a gas chromatograph (GC, HP4890D), and the liquid products were analyzed by nuclear magnetic resonance (1H NMR, Bruker Avance III 400HD).

[0069] The test results of the electrochemical catalytic amination methylation reaction of CO2 with amine compounds under different catalytic conditions by CuNi2Al-MMO are as follows Figure 4As shown. It can be seen from the figure that the catalytic system of the present invention has excellent Faraday efficiency for aminomethylation. At 25 °C and under the condition of reacting for 3 hours, the Faraday efficiency of 4-hydroxy-1-methylpiperidine produced by the electrochemical catalysis of 4-hydroxypiperidine and CO2 can reach 29.28% at a potential of -1.5 V vs. Ag / AgCl. This is much higher than the data reported in J. Am. Chem. Soc. 2021, 143, 19983-19991. Compared with other materials, CuNi2Al-MMO has the highest catalytic activity under the conditions of 25 °C, a working potential of -1.5 V vs. RHE, and a reaction time of 3 hours (Table 1). Table 2 shows that CuNi2Al-MMO has high generality for the electrochemical catalytic aminomethylation reaction of CO2 and amine compounds under the conditions of 25 °C, a working potential of -1.5 V vs. RHE, and a reaction time of 3 hours.

[0070] Table 1. Faraday efficiency of electrocatalytic coupling of 4-hydroxypiperidine and CO2 to synthesize 4-hydroxy-1-methylpiperidine by different materials.

[0071] Catalytic material FE of 4-hydroxypiperidine CuAl-MMO - <![CDATA[Cu2NiAl-MMO]]> 12.36％ CuNiAl-MMO 21.13％ <![CDATA[CuNi2Al-MMO]]> 29.28％ NiAl-MMO - CuCo-MMO 13.21％ ZnAl-MMO -

[0072] Table 2. Faraday efficiency of different types of amine compounds in the process of electrocatalytic aminomethylation.

[0073] Amine compound FE Dimethylamine 13.55％ Aniline 8.79％ 4-hydroxypiperidine 21.52％

[0074] Example 3. Study on the stability performance of the catalyst

[0075] Under the conditions of 25 °C, a working potential of -1.5 V vs. RHE, and a reaction time of 3 hours, the reaction was repeated 4 times to evaluate the long-term stability of CuNi2Al-MMO. The results are as Figure 5 shown. We found that the current density and the Faraday efficiency of 4-hydroxy-1-methylpiperidine did not show obvious decrease, indicating that the catalyst has good electrochemical stability and potential industrial value.

[0076] The above has described the present invention in detail. For those skilled in the art, without departing from the purpose and scope of the present invention and without unnecessary experiments, the present invention can be implemented within a relatively wide range under equivalent parameters, concentrations and conditions. Although specific embodiments of the present invention are given, it should be understood that the present invention can be further improved. In short, according to the principle of the present invention, this application intends to include any changes, uses or improvements to the present invention, including changes made by using conventional techniques known in the art that depart from the scope disclosed in this application.

Claims

1. An electrochemical catalytic system, comprising an electrode material, a reaction electrolyte solution, and a reaction device; The electrode material is CuNi x Al metal oxide CuNi x Al-MMO catalyst / electrode composite material; In the electrode material, CuNi x The Al-MMO catalyst is prepared by a method comprising the following steps: 1) Dissolve a copper compound, a nickel compound and an aluminum compound in water to obtain an aqueous solution of a metal compound; prepare an aqueous sodium hydroxide solution as an alkali solution; simultaneously add the aqueous solution of the metal compound and the aqueous sodium hydroxide solution into a reaction vessel, maintain the pH value at weakly alkaline and heat with stirring for reaction. After the reaction is completed, wash and dry the obtained precipitate to obtain CuNi x Al hydrotalcite powder; 2) Calcinate the obtained CuNi x Al-LDH powder at high temperature to obtain it; The molar ratio of Cu in the copper compound, Ni in the nickel compound, and Al in the aluminum compound is 1:X:Y, where X is 0.5 - 2 and Y is (1 + X) / 3; When preparing hydrotalcite, control the molar ratio of divalent metal ions to trivalent metal ions to be between 2:1 and 4:1; Cu 2+ and Ni 2+ The molar ratio of is denoted as 1:X, where X = 0.5 - 2; The reaction electrolyte includes an anolyte and a catholyte, wherein, The anolyte is selected from at least one of the following: aqueous KOH solution, aqueous KHCO3 solution, aqueous NaOH solution, aqueous NaHCO3 solution; The catholyte comprises a reaction substrate, LiI, and a KHCO3 / KOH mixed solution; The reaction substrate is an amine compound; The concentration of the anolyte is 0.1 - 10 M; The concentration of the catholyte is 0.1 - 10 M KHCO3 / KOH, 1 - 20 mM LiI, and 20 - 500 mM reaction substrate.

2. The electrochemical catalytic system according to claim 1, wherein The heating temperature is 50 - 80 °C; The stirring reaction time is 10 min - 60 min; The calcination temperature is 300 - 600 °C, and the time is 2 - 8 h.

3. The electrochemical catalytic system according to claim 1, characterized in that, The electrode material is prepared by a method comprising the following steps: dispersing a CuNi x Al-MMO catalyst in an organic solvent, adding a Nafion D-521 dispersion as a binder, and drop-coating the resulting dispersion onto a hydrophobic conductive support, thereby obtaining the electrode material; Among them, in the dispersion liquid, CuNi x The concentration of the Al-MMO catalyst is 1-10 mg / mL -1 ; The mass fraction of the Nafion D - 521 dispersion is 5 - 20 wt%; The ratio of the Nafion D - 521 dispersion to the catalyst is 5 - 100 μL∶10 mg; The hydrophobic conductive carrier is any one of carbon fiber paper, carbon fiber woven cloth, non - woven fabric, and carbon black paper; The described CuNi x The loading amount of the Al-MMO catalyst on the hydrophobic conductive carrier is 0.1-10 mg·cm -2 .

4. Use of the electrochemical catalytic system according to any one of claims 1 - 3 in an electrochemical aminomethylation reaction.

5. A method for an electrochemical catalytic aminomethylation reaction, comprising the following steps: using the electrochemical catalytic system according to any one of claims 1 - 3, using CO2 as a carbon source, using an amine compound as a reaction substrate, and performing an electrocatalytic aminomethylation reaction under the action of an electrode material and an electrolyte solution.

6. The method according to claim 5, characterized in that: In the method, the reaction potential is -1.0~ - 2.0V vs. Ag / AgCl; the reaction time is 0.5 - 120 h.

7. The method according to claim 5, wherein: The amine compound is selected from: alkylamine, cycloalkylamine, aromatic amine.

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