Method for preparing 1, 2, 3, 4-tetrahydroquinoline by electro-catalysis of quinoline hydrogenation in acidic system through chlorine-doped copper-silver bimetallic catalyst

Abstract

The invention discloses a method for preparing 1, 2, 3, 4-tetrahydroquinoline by electro-catalysis of quinoline hydrogenation in an acidic system through a chlorine-doped copper-silver bimetallic catalyst. Two steps of simple electro-deposition reaction are carried out on foamy copper, the copper cubic nano array and the silver nano particles are grown respectively, the performance of the catalyst is further improved through chlorine doping, the catalyst is simple in preparation process and low in cost, the reaction selectivity can reach 99.9%, and the yield can reach 97.8%; the method provided by the invention realizes synthesis of 1, 2, 3, 4-tetrahydroquinoline by electrocatalytic hydrogenation of high-concentration quinoline in an acidic environment, is green and environment-friendly, is efficient and energy-saving, and has industrial production prospects.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic electrocatalytic synthesis, and particularly relates to a method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline in an acidic system through a chlorine-doped copper-silver bimetallic catalyst. BACKGROUND

[0002] 1,2,3,4-tetrahydroquinoline (THQ) is an important nitrogen-containing heterocyclic compound and has various biological activities, and is widely used in the fields of medicine, pesticide, fuel, etc. As a pharmaceutical intermediate, THQ can be applied to the synthesis of various high-demand drugs such as antibacterial, antithrombotic, treatment of schizophrenia, heart failure, etc. At present, the catalytic hydrogenation of quinoline is usually selected as the most efficient and simplest method for synthesizing 1,2,3,4-tetrahydroquinoline in industry, but the chemical catalysis method faces many challenges, such as harsh reaction conditions, high temperature and high pressure, and external hydrogen source, which has certain danger and increases the economic cost. In addition, the chemical catalytic hydrogenation of quinoline often has other side reactions, and the product has poor selectivity, low conversion rate and low yield. Compared with this, electrochemical hydrogenation as a technology with mild reaction conditions, safe and simple operation, easy separation of products and environmental friendliness has attracted widespread attention, and the product selectivity can be improved by adjusting the electrochemical parameters, and the conversion rate and product yield can also be improved.

[0003] At present, there have been some reports on the preparation of 1,2,3,4-tetrahydroquinoline by electrochemical catalytic hydrogenation of quinoline, but they are mainly concentrated in alkaline systems, which has the challenge of low solubility of quinoline, and additional organic cosolvents need to be added, which not only increases the economic cost but also brings trouble to the subsequent product separation. Quinoline has high solubility in acidic solution, which undoubtedly reduces the production cost and is expected to improve the production efficiency. There has been a report CN 118854361 A that uses Pd / Ni5P4 defect nanosheet for electrocatalytic hydrogenation of quinoline in an acidic system to prepare 1,2,3,4-tetrahydroquinoline, but the concentration of the substrate quinoline is basically less than 20 mmol / L, which is still far from industrial application. Therefore, it is urgent to develop a new type of catalyst suitable for electrocatalytic hydrogenation of high-concentration quinoline in an acidic system to synthesize 1,2,3,4-tetrahydroquinoline. SUMMARY

[0004] The application provides a method for preparing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline in an acidic system through a chlorine-doped copper-silver bimetallic catalyst, which has not been reported at present.

[0005] In the application, a two-step simple electrodeposition reaction is carried out on the foam copper to grow copper cubic nanometer array and silver nanoparticles, respectively, and the electrocatalytic reaction rate is enhanced by chlorine doping to further improve the catalyst performance, and the process is simple and low in cost.

[0006] In the electrocatalytic reaction system of the application, quinoline accepts a proton through the lone pair of electrons of the nitrogen atom on the nitrogen-containing heterocycle to form a positively charged ion, while the molecular skeleton and conjugated system remain unchanged. After the protonation reaction of quinoline, the polarity is significantly increased, thereby the solubility in an acidic solution is significantly improved compared with an alkaline solution, so that the electrocatalytic hydrogenation conversion of high-concentration substrate quinoline is realized, and the industrial production prospect is possessed.

[0007] The technical solution of the application is as follows:

[0008] A method for electrocatalytically synthesizing 1,2,3,4-tetrahydroquinoline by hydrogenation of quinoline in an acidic system by using a chlorine-doped copper-silver bimetallic catalyst, comprising:

[0009] An electrochemical workstation is used as a power supply, an H-type electrolytic tank is used as a reaction device, and a NaFion N117 proton membrane is used to separate the cathode chamber and the anode chamber. A platinum sheet is used as a counter electrode and an acidic solution is used as an anode liquid in the anode chamber, a chlorine-doped copper-silver bimetallic catalyst is used as a working electrode and a Hg2SO4 electrode is used as a reference electrode in the cathode chamber, and an acidic solution containing quinoline is used as a cathode liquid. Under the conditions of stirring and room temperature, the electrocatalytic hydrogenation reaction of quinoline is carried out by constant-voltage electrolysis.

[0010] In the application,

[0011] The working electrode chlorine-doped copper-silver bimetallic catalyst is obtained by growing copper cubic nanometer arrays and silver nanoparticles through two-step electrodeposition reactions based on a foamed copper substrate.

[0012] The acidic solution in the cathode chamber and the anode chamber is selected from sulfuric acid aqueous solution, acetic acid aqueous solution and hydrochloric acid aqueous solution, and preferably 1 mol / L sulfuric acid aqueous solution or 1 mol / L acetic acid aqueous solution.

[0013] Preferably, the concentration of the reaction substrate quinoline in the cathode liquid is 15-150 mmol / L.

[0014] Preferably, the constant-voltage electrolysis condition parameters are: voltage-1.0 to-1.2 V, and reaction time 1-4 h.

[0015] Specifically, the preparation method of the chlorine-doped copper-silver bimetallic catalyst in the application is as follows:

[0016] (1) A copper sulfate anhydrous is weighed and dissolved in hydrochloric acid aqueous solution to obtain a mixed solution A; silver nitrate is weighed and dissolved in boric acid aqueous solution to obtain a mixed solution B.

[0017] The concentration of the hydrochloric acid aqueous solution is 0.1-0.3 mol / L, and preferably 0.3 mol / L; in the mixed solution A, the concentration of the copper sulfate anhydrous is 0.1-0.3 mol / L, and preferably 0.15 mol / L.

[0018] The concentration of the aqueous boric acid solution is 0.1-0.3 mol / L, preferably 0.3 mol / L; in the mixed solution B, the concentration of silver nitrate is 5-20 mmol / L, preferably 10 mmol / L;

[0019] The "mixed solution A" and the "mixed solution B" have no special meaning, and the labels "A" and "B" are only used to distinguish the mixed solutions in different operation steps;

[0020] (2) In a single-tank three-electrode system, the foam copper substrate is immersed in the mixed solution A to perform an electrodeposition reaction, and then taken out, washed and dried to obtain a catalyst precursor;

[0021] Before use, the foam copper substrate is pretreated by ultrasonic cleaning with acetone, ethanol, hydrochloric acid and deionized water respectively to remove the oxide layer on the surface of the foam copper substrate, and is ready for use;

[0022] The three-electrode system uses the foam copper as the working electrode, the Ag / AgCl electrode as the reference electrode, and the Pt sheet as the counter electrode;

[0023] The electrodeposition reaction conditions are: current -0.01 to -0.25 A, time 100-400 s; preferably, the current is -0.05 A, and the time is 300 s;

[0024] (3) In a single-tank three-electrode system, the catalyst precursor obtained in step (2) is immersed in the mixed solution B to perform an electrodeposition reaction, and then taken out, washed and dried to obtain the chlorine-doped copper-silver bimetallic catalyst;

[0025] The three-electrode system uses the catalyst precursor as the working electrode, the Ag / AgCl electrode as the reference electrode, and the Pt sheet as the counter electrode;

[0026] The electrodeposition reaction conditions are: current -0.1 to -0.25 A, time 30 s; preferably, the current is -0.2 A, and the time is 30 s.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] 1. Considering the solubility characteristics of quinoline, the electrocatalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline is realized in an acidic environment, which avoids the use of organic cosolvents, reduces production costs, and greatly improves the solubility of quinoline, enabling the preparation of 1,2,3,4-tetrahydroquinoline from high-concentration quinoline, and effectively improving production efficiency.

[0029] 2, the chloro-doped CuAg bimetallic catalyst is used to electrocatalytically hydrogenate quinoline to synthesize 1,2,3,4-tetrahydroquinoline in an acidic environment, the catalyst has high specific surface area and rich active sites, the strong electronegativity of chlorine changes the electron density of the catalytically active sites, and the intrinsic activity is improved. The catalyst has simple preparation process, low cost, good catalytic performance, reaction selectivity can reach 99.9%, and yield can reach 97.8%.

[0030] 3, compared with the traditional thermal catalytic method, the electrochemical method is used to directly hydrogenate 1,2,3,4-tetrahydroquinoline in one step, which has the advantages of environmental friendliness, green pollution-free and high efficiency and energy saving, and has wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 X-ray diffraction observation chart of the chloro-doped CuAg bimetallic catalyst obtained in example 1.

[0032] Figure 2 Scanning electron microscope chart of the chloro-doped CuAg bimetallic catalyst obtained in example 1.

[0033] Figure 3 Conversion rate chart of the chloro-doped CuAg bimetallic catalyst obtained in example 1 in electrolysis in different electrode solutions.

[0034] Figure 4 Yield chart of the chloro-doped CuAg bimetallic catalyst obtained in example 1 under different substrate concentrations. DETAILED DESCRIPTION

[0035] The technical content of the present application will be described below in combination with some specific examples, but the protection scope of the present application is not limited thereto. The professional terms used are only for the purpose of describing the specific examples, and are not intended to limit the protection scope of the present application.

[0036] Example 1: chloro-doped CuAg bimetallic catalyst electrocatalytically hydrogenates quinoline to prepare 1,2,3,4-tetrahydroquinoline

[0037] (1) The foamed copper (Sai Bo electrochemistry, 200*300*1.5mm, surface density 500g / m 2 ) is ultrasonically cleaned with acetone, ethanol, hydrochloric acid and water respectively to remove the surface oxide layer, and is ready for use;

[0038] (2) Weigh anhydrous copper sulfate (1.4365 g, 0.009 mol) and dissolve it in 60 mL of 0.3 mol / L aqueous hydrochloric acid solution, stir for 15 min to obtain a uniform blue electrodeposition solution, in a three-electrode system, use clean foamed copper as the working electrode, Ag / AgCl electrode as the reference electrode, and Pt sheet as the counter electrode, constant current -0.05 A electrodeposition at room temperature for 300 s, the obtained catalyst precursor is washed with water and ethanol and then dried with nitrogen, and is ready for use;

[0039] (3) Weigh silver nitrate (0.1019 g, 0.0006 mol) and dissolve it in 60 mL of 0.3 mol / L aqueous boric acid solution, stir for 15 min to obtain a uniform colorless electrodeposition solution, in the same three-electrode system as above, use the catalyst precursor as the working electrode, constant current -0.2 A electrodeposition at room temperature for 30 s, the obtained catalyst is washed with water and ethanol and then dried with nitrogen to obtain a chlorine-doped CuAg bimetallic catalyst CuAg-Cl.

[0040] The chlorine-doped CuAg bimetallic catalyst obtained in Example 1 is observed by X-ray diffraction, and the results are shown in Figure 1 The chlorine-doped CuAg bimetallic catalyst obtained in Example 1 is observed by scanning electron microscope, and the results are shown in Figure 2 . Figure 1 It is shown that the chlorine-doped CuAg bimetallic electrode CuAg-Cl prepared in Example 1 shows obvious diffraction peaks of Ag, CuCl and Cu2O; Figure 2 It is shown that the chlorine-doped CuAg bimetallic electrode CuAg-Cl grows silver nanoparticles on the copper cubic nanometer array.

[0041] The chlorine-doped CuAg bimetallic catalyst obtained in Example 1 is tested for quinoline electrocatalytic hydrogenation performance, and the specific method is as follows:

[0042] The area of the chlorine-doped CuAg bimetallic catalyst as the working electrode in the cathode chamber is controlled to be 1×1 cm 2 , a Hg2SO4 electrode is used as the reference electrode in the cathode chamber, and a platinum sheet electrode is used as the counter electrode in the anode chamber, the reaction is carried out in an H-type electrolytic cell by controlling the electrochemical workstation, the anode liquid is 28 mL of 1 mol / L H2SO4 aqueous solution, the cathode liquid is 28 mL of 1 mol / L H2SO4 and 15 mmol / L quinoline mixed aqueous solution, the electrolysis potential is controlled at -1.1 V, and the electrolysis is carried out at room temperature (25℃) for 4 h.

[0043] High performance liquid chromatography is used for analysis and detection, and the results show that the conversion rate of quinoline after 4 h of reaction is 97.32%, and the selectivity of 1,2,3,4-tetrahydroquinoline is higher than 99%.

[0044] Example 2: Electrocatalytic Hydrogenation of Quinoline to 1,2,3,4-Tetrahydroquinoline over Chlorine-Doped CuAg Bimetallic Catalyst in Different Electrode Solutions

[0045] (1) A chlorine-doped CuAg bimetallic catalyst was prepared by a two-step electrodeposition method, the method being the same as that in Example 1.

[0046] (2) The electrocatalytic performance of quinoline over the chlorine-doped CuAg bimetallic catalyst was tested. The test method was the same as in Example 1, except that different acidic electrolytes were used as the cathode and anode solutions: 0.01 mol / L H2SO4, 0.5 mol / L H2SO4, 1 mol / L CH3COOH, and 1 mol / L HCl. The selectivity of 1,2,3,4-tetrahydroquinoline was greater than 99.9%. Figure 3 As shown, the quinoline conversion rate is 39.25% in 0.01 mol / L H2SO4 solution, the quinoline conversion rate is 80.34% in 0.5 mol / L H2SO4 solution, the quinoline conversion rate is 94.47% in 1 mol / L CH3COOH, and the quinoline conversion rate is 13.27% in 1 mol / L HCl, demonstrating the adaptability and excellent catalytic performance of the chlorine-doped CuAg bimetallic catalyst prepared by the present invention for the electrocatalytic hydrogenation of quinoline to prepare 1,2,3,4-tetrahydroquinoline in acidic solution.

[0047] Example 3: Electrocatalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline over chlorine-doped CuAg bimetallic catalyst at different substrate concentrations

[0048] (1) A chlorine-doped CuAg bimetallic catalyst was prepared by a two-step electrodeposition method, the method being the same as that in Example 1.

[0049] (2) The electrocatalytic performance of quinoline on the chlorine-doped CuAg bimetallic catalyst was tested. The test method was the same as in Example 1, except that different quinoline substrate concentrations were used. Figure 4 The results show that quinoline has high solubility in 1 mol / L H2SO4 solution in an acidic environment. The chlorine-doped CuAg bimetallic catalyst prepared by the present invention has excellent catalytic performance for high-concentration quinoline. Under the catalytic conditions in Example 1 and a quinoline concentration of 150 mmol / L, the yield reaches 0.292 mmol·h -1 cm -2 , which is higher than the currently reported optimal yield of 0.18 mmol·h in alkaline systems. -1 cm -2 (Small 2025,21,2412626), showing good catalytic ability and broad application potential.

Claims

1. A method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline using a chlorine-doped copper-silver bimetallic catalyst in an acidic system, characterized in that: include: An electrochemical workstation was used as the power source, an H-type electrolyzer was used as the reaction apparatus, and a NaFion N117 proton membrane was used to separate the anode and cathode chambers. In the anode chamber, a platinum sheet was used as the counter electrode and an acidic solution was used as the anolyte. In the cathode chamber, a chlorine-doped copper-silver bimetallic catalyst was used as the working electrode, an Hg2SO4 electrode was used as the reference electrode, and an acidic solution containing quinoline was used as the catholyte. Quinoline electrocatalytic hydrogenation was carried out by constant-voltage electrolysis under stirring and room temperature conditions. in, The chlorine-doped copper-silver bimetallic catalyst for the working electrode is prepared by growing copper cubic nanoarrays and silver nanoparticles on a foam copper substrate through a two-step electrodeposition reaction. The acidic solution in the cathode chamber and the anode chamber is selected from a sulfuric acid aqueous solution, an acetic acid aqueous solution, and a hydrochloric acid aqueous solution.

2. The method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline using a chlorine-doped copper-silver bimetallic catalyst in an acidic system as claimed in claim 1, characterized in that: The acidic solution in the cathode chamber and the anode chamber is a 1 mol / L sulfuric acid aqueous solution or a 1 mol / L acetic acid aqueous solution.

3. The method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline using a chlorine-doped copper-silver bimetallic catalyst in an acidic system as claimed in claim 1, characterized in that: In the cathode liquid, the concentration of the reaction substrate quinoline is 15 to 150 mmol / L.

4. The method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline using a chlorine-doped copper-silver bimetallic catalyst in an acidic system as claimed in claim 1, characterized in that: The condition parameters of constant voltage electrolysis are: voltage -1.0 to -1.2 V, reaction time 1 to 4 h.

5. The method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline using a chlorine-doped copper-silver bimetallic catalyst in an acidic system as claimed in claim 1, characterized in that: The preparation method of the chlorine-doped copper-silver bimetallic catalyst is as follows: (1) Weigh anhydrous copper sulfate and dissolve it in aqueous hydrochloric acid to obtain a mixed solution A; weigh silver nitrate and dissolve it in aqueous boric acid to obtain a mixed solution B; The concentration of the hydrochloric acid aqueous solution is 0.1 to 0.3 mol / L; in the mixed solution A, the concentration of anhydrous copper sulfate is 0.1 to 0.3 mol / L; The concentration of the boric acid aqueous solution is 0.1 to 0.3 mol / L; in the mixed solution B, the concentration of silver nitrate is 5 to 20 mmol / L; (2) In a single-tank three-electrode system, the foam copper substrate is immersed in the mixed solution A for electrodeposition reaction, and then removed, washed, and dried to obtain a catalyst precursor; The three-electrode system uses copper foam as the working electrode, Ag / AgCl electrode as the reference electrode, and Pt sheet as the counter electrode; The electrodeposition reaction conditions were: current -0.01 to -0.25 A, time 100 to 400 s; (3) In a single-tank three-electrode system, immersing the catalyst precursor obtained in step (2) in the mixed solution B for electrodeposition reaction, and then taking it out, washing, and drying it to obtain the chlorine-doped copper-silver bimetallic catalyst; The three-electrode system uses the catalyst precursor as the working electrode, the Ag / AgCl electrode as the reference electrode, and the Pt sheet as the counter electrode; The electrodeposition reaction conditions are: current -0.1 to -0.25 A, time 30 s.

6. The method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline using a chlorine-doped copper-silver bimetallic catalyst in an acidic system as claimed in claim 5, characterized in that: In step (1) of the preparation method of the chlorine-doped copper-silver bimetallic catalyst, the concentration of the hydrochloric acid aqueous solution is 0.3 mol / L; and the concentration of anhydrous copper sulfate in the mixed solution A is 0.15 mol / L.

7. The method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline using a chlorine-doped copper-silver bimetallic catalyst in an acidic system as claimed in claim 5, characterized in that: In step (1) of the preparation method of the chlorine-doped copper-silver bimetallic catalyst, the concentration of the boric acid aqueous solution is 0.3 mol / L; and the concentration of silver nitrate in the mixed solution B is 10 mmol / L.

8. The method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline using a chlorine-doped copper-silver bimetallic catalyst in an acidic system as claimed in claim 5, characterized in that: In step (2) of the preparation method of the chlorine-doped copper-silver bimetallic catalyst, the foam copper substrate is pretreated as follows before use: ultrasonic cleaning with acetone, ethanol, hydrochloric acid, and deionized water respectively to remove the oxide layer on the surface of the foam copper substrate and set aside.

9. The method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline using a chlorine-doped copper-silver bimetallic catalyst in an acidic system as claimed in claim 5, characterized in that: In step (2) of the preparation method of the chlorine-doped copper-silver bimetallic catalyst, the electrodeposition reaction conditions are: current -0.05A, time 300s.

10. The method for synthesizing 1,2,3,4-tetrahydroquinoline by electrocatalytic hydrogenation of quinoline using a chlorine-doped copper-silver bimetallic catalyst in an acidic system as claimed in claim 5, characterized in that: In step (2) of the preparation method of the chlorine-doped copper-silver bimetallic catalyst, the electrodeposition reaction conditions are: current -0.2A, time 30s.

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