Self-supporting cop nanowire catalytic electrode, preparation method thereof and application of the electrode in electrocatalytic quinoline hydrogenation synthesis of 1,2,3,4-tetrahydroquinoline

Abstract

The application discloses a self-supporting CoP nanowire catalytic electrode and a preparation method and application of the self-supporting CoP nanowire catalytic electrode in electrocatalytic quinoline hydrogenation synthesis of 1,2,3,4-tetrahydroquinoline. The self-supporting CoP nanowire catalytic electrode is composed of a carrier and an active component grown on the carrier. The carrier is a graphite felt, and the active component is a CoP nanowire structure. The preparation process of the electrode material is simple, raw materials are low in price and easy to obtain, and the electrode material has a good industrial application prospect. Moreover, the CoP nanomaterial performs very well in an electrolytic reaction, and selectivity and conversion rate of the CoP nanomaterial are quite ideal, which means that the material has good application potential in many chemical reactions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic electrocatalytic synthesis, and particularly relates to a CoP nanowire catalytic electrode loaded on a graphite felt, a preparation method thereof, and application in electrocatalytic hydrogenation of quinoline to synthesize 1,2,3,4-tetrahydroquinoline. BACKGROUND

[0002] Nitrogen-containing heterocyclic compounds with high added value play an important role in the fields of pharmaceuticals and fine chemicals. These compounds, mostly natural products, have unique structures and properties and can be artificially synthesized in various ways. Quinoline and its derivatives, as an important part of nitrogen-containing heterocyclic compounds, are one of the hydrogenation products of quinoline, 1,2,3,4-tetrahydroquinoline, which is an important pharmaceutical intermediate and has a wide range of applications in the synthesis of drugs with antibacterial activity, neuroprotective agents, and immunomodulators. And due to the unique molecular structure of 1,2,3,4-tetrahydroquinoline, it has a good electron-donating chromophore, which can be used as an important intermediate in the field of dye synthesis. In industrial production, 1,2,3,4-tetrahydroquinoline, as an important organic compound, is mainly prepared by chemical catalytic quinoline hydrogenation process. However, this process has very harsh reaction conditions, usually requires external hydrogen source, and is carried out under high temperature and high pressure. Moreover, the chemical catalytic quinoline hydrogenation reaction is usually not one-way, and there are many problems such as more side reactions, poor product selectivity, and low conversion rate.

[0003] In order to solve these problems, in recent years, electrochemical reduction hydrogenation as a very promising method has attracted people's attention. Compared with traditional chemical hydrogenation method, electrochemical reduction hydrogenation is more mild and green in nature, because it does not need the use of high temperature and high pressure container, nor does it need additional hydrogen source, but through electron transfer to reduce the compound, thereby generating the desired product, reducing the occurrence of side reactions, improving the product selectivity, and improving the conversion rate and yield. Electrochemical synthesis method also has many other advantages, such as easy separation of product, simple process flow and easy realization of automatic production. Therefore, electrochemical reduction hydrogenation is expected to become an important method for industrial production of 1,2,3,4-tetrahydroquinoline in the future.

[0004] At present, some patent documents, such as CN117143015A, report the reaction example of thermal catalytic reduction of quinoline to generate 1,2,3,4-tetrahydroquinoline, and the product separation yield reaches 82%, but the reaction condition is harsh and needs to add multiple organic matters in the reaction process. Considering the complexity of this process, we envisage synthesizing a new material that can effectively promote the activation of quinoline and water, and used for electrochemical method to realize efficient and high-selectivity quinoline hydrogenation reaction.

[0005] Specifically, we envision that the synthetic new type of electrocatalytic material, the structural design and preparation process should be able to ensure that in the process of electrochemical reaction, it can effectively capture and transfer electrons, thereby promoting the hydrogenation of quinoline. This new material should have high catalytic activity, and can realize the efficient conversion of quinoline at normal temperature and pressure, while also maintaining high selectivity. In the field of organic electrochemical synthesis, transition metals show many unique characteristics. Especially in the electrochemical reduction process of nitrate and organic matter, Co-based catalysts are widely studied due to their low cost and high stability. These catalysts can achieve efficient electron transfer in electrochemical reactions, promoting the reaction. The application of Co-based catalysts in organic electrochemical synthesis not only lies in their catalytic performance, but also in their controllable coordination environment and reaction conditions. For example, Co-based phosphides exhibit high electrical conductivity and high stability, which can enhance the electrocatalytic performance. Flexible carbon carrier graphite felt (GF) has the characteristics of electrical conductivity close to metal, high volume porosity, excellent corrosion resistance, etc., which makes GF a very attractive catalyst carrier for the field of organic electrochemical synthesis.

[0006] Based on the research of such electrocatalytic materials, the present application designs a CoP catalytic electrode, which uses electrode materials and reaction microenvironment to control the selectivity and conversion rate of the reaction. Currently, there is no report on the use of GF to improve the electrochemical selective hydrogenation conversion system of CoP for quinoline. SUMMARY

[0007] In view of the problems of "difficult reaction, low yield and poor selectivity" in the quinoline hydrogenation reaction in the prior art, the present application provides a self-supporting CoP nanowire catalytic electrode and a preparation method thereof, and an application of the electrode as a cathode electrode for electrocatalytic hydrogenation of quinoline to synthesize 1,2,3,4-tetrahydroquinoline.

[0008] The technical scheme of the present application is as follows:

[0009] A self-supporting CoP nanowire catalytic electrode is composed of a carrier and an active ingredient grown on the carrier; wherein the carrier is graphite felt (GF), and the active ingredient is a CoP nanowire structure.

[0010] The catalytic electrode of the present application has the following characteristics: the CoP nanowires are uniformly distributed on the substrate, which makes the catalyst have a larger specific surface area and electrochemical active area; this nanostructure provides more active sites for the active substance, promotes the diffusion of the active substance, and also helps the transmission of protons in the electrolyte, which makes the catalyst exhibit higher reaction speed and lower reaction activation energy in the electrochemical reaction.

[0011] The preparation method of the self-supporting CoP nanowire catalytic electrode of the present application is as follows:

[0012] Co(NO3)2·6H2O, NH4F and urea are dissolved in deionized water to obtain a mixed solution; the obtained mixed solution and graphite felt are added into an autoclave, kept at 120℃ for 6h, and then cooled to room temperature; the graphite felt is taken out, washed and dried to obtain a catalytic electrode precursor; the catalytic electrode precursor and a porcelain boat containing NaH2PO2 are placed into a muffle furnace, calcined at 300℃ for 2h in an Ar atmosphere to obtain the self-supporting CoP nanowire catalytic electrode;

[0013] Preferably, the mass ratio of Co(NO3)2·6H2O, NH4F, urea and NaH2PO2 is 0.291:0.093:0.30:0.5;

[0014] The graphite felt is pretreated before use: the graphite felt is immersed in an HNO3 solution (40wt%) and then transferred into an autoclave, kept at 120℃ for 2h, and then sequentially ultrasonicated in acetone, H2O and ethanol, and dried for standby use.

[0015] The self-supporting CoP nanowire catalytic electrode can be used in the reaction of electrocatalytic hydrogenation of quinoline to synthesize 1,2,3,4-tetrahydroquinoline; the specific method is as follows:

[0016] The electrocatalytic reaction device adopts an H-shaped electrolytic cell (as shown in Figure 2 ), the electrolyte is separated by an N117 cation membrane between the cathode and anode reaction tanks, the anode is a platinum electrode, the cathode is a self-supporting CoP nanowire catalytic electrode, and the reference electrode is a Hg / HgO electrode; the electrolyte is added into the cathode and anode reaction tanks, and the electrocatalytic reaction is carried out in a constant voltage electrolysis mode under the conditions of room temperature and stirring;

[0017] The reaction equation is as shown in Figure 1 ;

[0018] The electrolyte in the anode reaction tank: 1mol / L KOH solution;

[0019] The electrolyte in the cathode reaction tank: a mixed solution of quinoline, 1mol / L KOH solution and 1,4-dioxane; wherein the concentration of quinoline is 14.14mmol / L, and the volume ratio of 1mol / L KOH solution to 1,4-dioxane is 26:4;

[0020] The constant voltage bias of the electrocatalytic reaction is set to-1.1 to-1.3V;

[0021] The electrolysis time is 3 to 6h.

[0022] The beneficial effects of the present application mainly include:

[0023] Firstly, compared with the thermo-chemical catalytic method, the electrochemical method has the characteristics of green environmental protection and mild efficiency. The process of the present application is more simple, and is also conducive to reducing the production cost. Secondly, the satisfactory conversion rate and selectivity are achieved in the process of realizing the selective electrochemical catalytic hydrogenation reduction of quinoline, which shows that the process of the present application can effectively convert quinoline into the required product, and at the same time avoid the generation of by-products.

[0024] Compared with other materials reported previously, the CoP nanomaterial prepared by us has significant advantages. The preparation process is very simple, the metal Co is cheap and easy to obtain in the market, and has good industrial application prospect. Moreover, the CoP nanomaterial also performs very well in the electrolysis reaction, and the selectivity and conversion rate are quite ideal, which means that the material may have good application potential in many chemical reactions. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 : The electrochemical reaction equation of quinoline in the present application.

[0026] Figure 2 : The electrolytic cell device in the embodiment of the present application.

[0027] Figure 3 : The SEM image of CoP-GF prepared in the embodiment of the present application. DETAILED DESCRIPTION

[0028] The present application will be further described below through specific embodiments, but the protection scope of the present application is not limited to this.

[0029] The graphite felt used in the following embodiments is from scientific material station (carbon felt GF 030).

[0030] Example 1

[0031] 1. Preparation of CoP nanowire material grown on GF.

[0032] GF pretreatment: immerse GF (40x10x3mm) into 40mL HNO3 solution (40%) and then transfer to a stainless steel autoclave with a polytetrafluoroethylene liner, keep at 120℃ for 2h, and then ultrasonic in acetone, H2O and ethanol for 30min respectively.

[0033] CoP material preparation: Co(N03)2-6H20 (0.291 g), NH4F (0.093 g) and urea (0.30 g) were dissolved in deionized water (20 mL). After stirring for ten minutes, the solution was transferred into a Teflon-lined stainless steel autoclave with one piece of pretreated GF. The autoclave was kept at 120 °C for 6 h, then cooled to room temperature. The precursor was washed several times with deionized water to remove free particles and residual reactants. Finally, the precursor was calcined in a porcelain boat with 0.5 g NaH2P02 under Ar atmosphere at 300 °C for 2 h to obtain CoP nanowire material. The morphology of the material is shown in Figure 1. The Co content of the material prepared by this method is 44.67% and the P content is 55.33%. CoP retains the nanowire array feature and is well dispersed on the GF, ensuring that it has abundant active sites, which is an important reason why the material can achieve good catalytic performance. Figure 3

[0034] 2. Using CoP nanowires grown on GF as the cathode, quinoline was subjected to electrocatalytic hydrogenation. An H-type electrolysis cell was used, with a N117 cation membrane separating the anolyte and catholyte. Platinum was used as the anode, and Hg / HgO was used as the reference electrode. The anolyte was a 1 mol / L potassium hydroxide solution (30 mL, same below); the catholyte was a mixture of 14.14 mmol / L quinoline, 26 mL of 1 M KOH, and 4 mL of 1,4-dioxane (30 mL, same below). The electrolysis potential was controlled at -1.2 V, and the electrolysis was carried out at room temperature (25 °C, same below) with constant stirring at 500 r / min for 6 h. High-performance liquid chromatography was used for detection, and the results showed that the selectivity of 1,2,3,4-tetrahydroquinoline was 99.99%, and the yield was 86.81%.

[0035] Table 1: Effect of different thicknesses of GF on the hydrogenation reduction of quinoline

[0036]

[0037] All experiments in Table 1 were the same as in Example 1, except for the different thicknesses of the graphite felt. The amount of catalyst grown on GF of different thicknesses was different, resulting in some differences in catalytic performance. However, the performance of the 6.5 mm GF was lower due to its large thickness, which reduced the permeability of the solution and the efficiency of proton transfer.

[0038] Example Two

[0039] 1. CoP nanowire material grown on GF was prepared.

[0040] GF pretreatment: GF (40 x 10 x 3 mm) was sequentially ultrasonicated in HNO3 solution (40%), acetone, H2O, and ethanol for 30 min. ​

[0041] CoP material preparation: material preparation is the same as example one.

[0042] 2. CoP nanowires grown on GF were used as cathode to electrocatalytically hydrogenate quinoline. H-type electrolytic cell was used, N117 cation membrane was used to separate the anolyte and catholyte, platinum electrode was used as anode, and Hg / HgO was used as reference electrode. Figure 2 The H-type electrolytic cell diagram, the electrolyte in the anode reaction tank was 1 mol / L concentration of potassium hydroxide solution; the catholyte was a mixed solution of 14.14 mmol / L concentration of quinoline, 26 ml of 1M KOH and 4 ml of 1,4-dioxane, the electrolytic potential was controlled at -1.2V, and the electrolysis was carried out at room temperature for 6 hours with constant speed stirring. High performance liquid chromatography was used for detection, the results showed that the selectivity of 1,2,3,4-tetrahydroquinoline was 99.99%, and the yield was 58.41%. The insufficient hydrophobic surface properties of GF and the insufficient electrochemical activity in the electrolyte were the main reasons for the decline of the performance of the catalyst material in this example.

[0043] Example three

[0044] 1. CoP nanowires grown on GF were prepared.

[0045] GF pretreatment: graphite felt (40x10x3mm) was put into deionized water for ultrasonic cleaning for 10 min, dried, and then put into a tube furnace for calcination under argon atmosphere at 400℃ for two hours, taken out, and put into HNO3 solution (40%) for ultrasonic treatment for 30 min, and then sequentially treated with acetone, deionized water and ethanol by ultrasonic treatment for 15 min.

[0046] CoP material preparation: material preparation is the same as example one.

[0047] 2. CoP nanowires grown on GF were used as cathode to electrocatalytically hydrogenate quinoline. H-type electrolytic cell was used, N117 cation membrane was used to separate the anolyte and catholyte, platinum electrode was used as anode, and Hg / HgO was used as reference electrode. Figure 2 The H-type electrolytic cell diagram, the electrolyte in the anode reaction tank was 1 mol / L concentration of potassium hydroxide solution; the catholyte was a mixed solution of 14.14 mmol / L concentration of quinoline, 26 ml of 1M KOH and 4 ml of 1,4-dioxane, the electrolytic potential was controlled at -1.2V, and the electrolysis was carried out at room temperature for 6 hours with constant speed stirring. High performance liquid chromatography was used for detection, the results showed that the selectivity of 1,2,3,4-tetrahydroquinoline was 99.99%, and the yield was 59.61%. The reason for the decrease in yield was the same as in example two.

[0048] Example four

[0049] 1. CoP nanowires grown on GF were prepared.

[0050] GF pretreatment: GF (40 x 10 x 3 mm) was immersed in a mixed acid solution (1:3) of HNO3 (65%) and H2SO4 (98%) for 12 hours, then washed with deionized water and dried in vacuum.

[0051] CoP material preparation: The material was prepared as in Example One.

[0052] 2. The CoP nanowires grown on GF were used as the cathode to electrocatalytically hydrogenate quinoline. An H-type electrolysis cell was used, with a N117 cation membrane separating the anolyte and catholyte. Platinum was used as the anode, and Hg / HgO as the reference electrode. Figure 2 The H-type electrolysis cell diagram is shown in Figure 1. The anolyte was a 1 mol / L potassium hydroxide solution, and the catholyte was a mixture of 14.14 mmol / L quinoline, 26 mL of 1 M KOH, and 4 mL of 1,4-dioxane. The electrolysis potential was controlled at -1.2 V, and the electrolysis was carried out at room temperature with constant stirring for 6 hours. High performance liquid chromatography was used for detection, and the results showed that the selectivity of 1,2,3,4-tetrahydroquinoline was 99.99%, and the yield was 42.65%. The reason for the reduced yield is the same as in Example Two.

Claims

1. Application of a self-supporting CoP nanowire catalytic electrode in the electrocatalytic hydrogenation of quinoline to synthesize 1,2,3,4-tetrahydroquinoline; The self-supporting CoP nanowire catalytic electrode consists of a support and active components grown on the support; wherein... The carrier is graphite felt, and the active ingredient is a CoP nanowire structure.

2. The application as described in claim 1, characterized in that, The preparation method of the self-supporting CoP nanowire catalytic electrode is as follows: Co(NO3)2·6H2O, NH4F, and urea were dissolved in deionized water to obtain a mixed solution. The resulting mixed solution and graphite felt were added to an autoclave and kept at 120 °C for 6 h. After cooling to room temperature, the graphite felt was removed, rinsed, and dried to obtain a catalytic electrode precursor. The catalytic electrode precursor and a ceramic boat containing NaH2PO2 were placed in a muffle furnace and calcined at 300 °C for 2 h under an Ar atmosphere to obtain the self-supporting CoP nanowire catalytic electrode.

3. The application as described in claim 2, characterized in that, The mass ratio of Co(NO3)2·6H2O, NH4F, urea, and NaH2PO2 is 0.291:0.093:0.30:0.

5.

4. The application as described in claim 2, characterized in that, The graphite felt undergoes the following pretreatment before use: the graphite felt is immersed in HNO3 solution, then transferred to an autoclave and kept at 120 °C for 2 h, followed by ultrasonic treatment in acetone, H2O and ethanol in sequence, and then dried for later use.

5. The application as described in claim 1, characterized in that, The application method is as follows: The electrocatalytic reaction device uses an H-type electrolytic cell. The electrolyte is separated between the cathode and anode reaction cells by an N117 cation membrane. The anode is a platinum electrode, the cathode is a self-supporting CoP nanowire catalytic electrode, and the reference electrode is an Hg / HgO electrode. Electrolyte is added to the cathode and anode reaction cells, and the electrocatalytic reaction is carried out by constant voltage electrolysis under room temperature and stirring conditions. Electrolyte in the anode reaction cell: 1 mol / L KOH solution; The electrolyte in the cathode reactor is a mixed solution of quinoline, 1 mol / L KOH solution, and 1,4-dioxane.

6. The application as described in claim 5, characterized in that, The electrolyte in the cathode reaction cell contained quinoline at a concentration of 14.14 mmol / L, and the volume ratio of 1 mol / L KOH solution to 1,4-dioxane was 26:

4.

7. The application as described in claim 5, characterized in that, The constant voltage bias for the electrocatalytic reaction was set to -1.1 to -1.3V, and the electrolysis time was 3 to 6 hours.

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