A method for synthesizing 1,2,3,4-tetrahydroquinoline by using copper-based bimetallic electrocatalytic hydrogenation of quinoline
The synthesis of 1,2,3,4-tetrahydroquinoline by means of Cu-based bimetallic electrocatalysts under electrochemical conditions solves the problems of high reaction risk and poor selectivity of existing chemical catalytic methods, and realizes efficient, green and selective hydrogenation synthesis of quinoline.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV OF TECH
- Filing Date
- 2023-05-15
- Publication Date
- 2026-06-05
AI Technical Summary
The existing chemical catalytic quinoline hydrogenation method has problems such as harsh reaction conditions, high risk, large equipment investment, poor product selectivity, and low conversion rate of single metal electrode catalysts.
Using a Cu-based bimetallic (CuCo or CuNi) electrocatalyst as the cathode, quinoline was hydrogenated to synthesize 1,2,3,4-tetrahydroquinoline via an electrochemical method at room temperature. An H-type electrolytic cell was used, with a Nafion N117 cation exchange membrane separating the anode and cathode chambers. A platinum sheet was used as the anode, and the Cu-based bimetallic catalyst was used as the cathode. The electrocatalytic reaction was carried out in a constant-temperature water bath and at a constant-potential electrolysis.
It achieves efficient conversion of quinoline under mild conditions with a product selectivity of up to 99.9%. The catalyst is simple to prepare, inexpensive, and suitable for industrial production.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of organic electrosynthesis, and particularly relates to a method for the electrocatalytic hydrogenation of quinoline to synthesize 1,2,3,4-tetrahydroquinoline using copper-based bimetallic materials. Background Technology
[0002] Quinoline exists naturally in coal tar fractions and can also be synthesized artificially through various methods. It is widely distributed and inexpensive. 1,2,3,4-Tetrahydroquinoline is an important hydrogenation product of quinoline, a significant N-heterocyclic compound with various biological activities. It is a crucial pharmaceutical intermediate used for the prevention and treatment of diseases such as arteriosclerosis, hyperlipidemia, and arrhythmia. The main synthetic methods for 1,2,3,4-tetrahydroquinoline include catalytic cyclization, the Beckmann rearrangement, and catalytic hydrogenation. Among these, chemically catalytic hydrogenation is currently the commonly used method for the industrial synthesis of 1,2,3,4-tetrahydroquinoline. Although this method has a simple reaction pathway, the reaction conditions are harsh, requiring H2 as the hydrogen source and a high pressure of 1–4 MPa and a high temperature of 60–200 °C. The use of H2 increases the reaction risk and requires significant equipment investment. Furthermore, chemically catalytic hydrogenation of quinoline is usually not unidirectional, resulting in poor product selectivity and low conversion and yield.
[0003] In light of this, the electrochemical catalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline exhibits significant advantages. Utilizing electrochemical reduction technology at room temperature, electrons are used as the reactants; the reactants are reduced by losing electrons at the electrodes, eliminating the need for additional reducing agents. Compared to traditional chemical catalysis, which requires the addition of a catalyst before the reaction, electrochemical catalysis allows for control of the current density based on the actual consumption of the substrate, improving the conversion rate of the reactants and the selectivity of the products. Furthermore, compared to conventional chemical methods, it offers advantages such as easy product separation, safe equipment operation, simple process flow, and environmental friendliness, making it an important component of "green chemical synthesis."
[0004] Currently, there are relatively few research reports on the electrochemical catalytic hydrogenation of quinolines to 1,2,3,4-tetrahydroquinoline. Only one report has documented the use of an F-doped Co(OH)₂ electrode for the electrocatalytic hydrogenation of quinolines (Nature Communications, 2022, 13(1):5297). Furthermore, the performance of single-metal catalysts used is relatively low; the highest conversion rate achieved using cobalt nanowires is only around 50%. Therefore, there is an urgent need to develop more catalysts for the efficient electrocatalytic hydrogenation of quinolines to prepare 1,2,3,4-tetrahydroquinoline. Summary of the Invention
[0005] To address the aforementioned problems in the existing technology, this invention proposes a method for the electrocatalytic hydrogenation synthesis of 1,2,3,4-tetrahydroquinoline using a Cu-based bimetallic (CuCo or CuNi) electrocatalyst as the cathode.
[0006] Bimetallic catalysts often exhibit superior catalytic performance compared to their single-component counterparts. This is due to the synergistic effect between dissimilar elements in bimetallic catalysts, resulting in excellent activity and high selectivity. However, when using other copper-based catalysts, such as CuFe and CuMn, as cathodes for the electrocatalytic hydrogenation of quinoline to synthesize 1,2,3,4-tetrahydroquinoline, the conversion rate is only around 30%. Therefore, the Cu-based bimetallic catalyst (CuCo or CuNi) of this invention demonstrates excellent catalytic performance in the electrocatalytic hydrogenation of quinoline, and its preparation is simple and inexpensive, which is beneficial for industrial production.
[0007] The technical solution of the present invention is as follows:
[0008] A method for synthesizing 1,2,3,4-tetrahydroquinoline by copper-based bimetallic electrocatalytic hydrogenation of quinoline, the method comprising:
[0009] The current and voltage were controlled by an electrochemical power source, and an H-type electrolytic cell was used as the reaction apparatus. The anode and cathode reaction cells were separated by a Nafion N117 cation exchange membrane. In the anode chamber, a platinum sheet was used as the anode, and an alkaline solution was used as the anolyte. In the cathode chamber, a Cu-based bimetallic catalyst was used as the cathode, and an alkaline solution containing the reaction substrates quinoline and 1,4-dioxane was used as the catholyte. The electrocatalytic hydrogenation reaction was carried out for 1 to 6 hours under the conditions of constant temperature water bath 25 to 55℃, constant potential electrolysis potential -1.0 to -3.5V, and constant current electrolysis current -5 to -1000mA to obtain the product 1,2,3,4-tetrahydroquinoline.
[0010] The reaction formula is as follows:
[0011]
[0012] Typically, the volume of the cathode chamber and the anode chamber is 10–800 mL, preferably 20–700 mL.
[0013] The alkaline solutions in the cathode and anode chambers are aqueous solutions of potassium hydroxide, sodium hydroxide, dipotassium hydrogen phosphate, or disodium hydrogen phosphate, preferably potassium hydroxide solution, with a concentration of 0.1–2 mol / L, more preferably 0.1–1 mol / L;
[0014] In the preferred cathode solution, the concentration of the reaction substrate quinoline is 1-2 g / L, and the volume ratio of 1,4-dioxane to alkaline solution is 1:5-150.
[0015] The preferred electrocatalytic hydrogenation reaction has a constant potential electrolysis potential of -1.0 to -1.4V, a constant current electrolysis current of -5 to -500mA, and a reaction time of 3 to 6h.
[0016] In this invention, the Cu-based bimetallic catalyst is prepared by the following method:
[0017] (1) Sonicate the copper foam with acetone, ethanol, hydrochloric acid and water for 3 to 10 minutes respectively to remove impurities from the surface of the copper foam and set aside.
[0018] (2) Weigh sodium hydroxide and ammonium persulfate, dissolve them in deionized water to obtain a mixed solution; at 10-35°C, soak the copper foam prepared in step (1) in the mixed solution for 10-40 minutes, and then take it out to obtain the copper hydroxide precursor;
[0019] In the preferred mixed solution, the concentration of sodium hydroxide is 1 mol / L and the concentration of ammonium persulfate is 0.0114 g / mL;
[0020] (3) Add the 2-methylimidazole solution to the metal salt solution and stir to mix well to obtain a mixed system;
[0021] The metal salt is selected from cobalt nitrate hexahydrate or nickel nitrate hexahydrate, preferably with a concentration of 0.5 mM and anhydrous methanol as the solvent;
[0022] The preferred concentration of the 2-methylimidazole solution is 1 mM, and the solvent is anhydrous methanol;
[0023] The preferred volume ratio of 2-methylimidazole solution to metal salt solution is 1:3 to 2:1;
[0024] (4) Place the copper hydroxide precursor obtained in step (2) into the mixed system obtained in step (3) and react at 120-160℃ for 2-6 hours. Then, cool naturally to room temperature, take it out and rinse with deionized water to obtain Cu-based bimetallic catalyst.
[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0026] (1) The present invention adopts an electrocatalytic reduction process, which is mild, green and pollution-free, with high conversion rate of raw materials and good selectivity for 1,2,3,4-tetrahydroquinoline;
[0027] (2) This invention is the first to propose the use of copper-based bimetallic materials as cathodes to electrocatalytically hydrogenate quinoline to 1,2,3,4-tetrahydroquinoline. The catalyst preparation process is simple, and the electrocatalytic hydrogenation of quinoline to synthesize 1,2,3,4-tetrahydroquinoline is achieved. It has good catalytic performance, high conversion rate of raw materials, and good selectivity of products, with a selectivity of up to 99.9%. Attached Figure Description
[0028] Figure 1 Diagram of an electrolytic apparatus for the electrocatalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline.
[0029] Figure 2 This is an X-ray diffraction pattern of the CuCo bimetallic electrocatalyst obtained in Example 1.
[0030] Figure 3 This is a scanning electron microscope image of the CuCo bimetallic electrocatalyst obtained in Example 1.
[0031] Figure 4 The image shows the liquid chromatography results before and after 4 hours of electrolysis of CuCo bimetallic electrocatalytic hydrogenation to 1,2,3,4-tetrahydroquinoline obtained in Example 1. Detailed Implementation
[0032] The technical content of the present invention will be illustrated below with some specific examples, but the scope of protection of the present invention is not limited thereto.
[0033] The technical terms used are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention.
[0034] All raw materials and reagents used in the following examples were of analytical grade, purchased commercially, and required no further processing. Copper foam (Cyber Electrochemical, 200*300*1.5mm, areal density 500g / m³) 2 ).
[0035] Example 1: Electrocatalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline using a CuCo bimetallic electrocatalyst
[0036] (1) Take a piece of foamed copper (1×3cm) and ultrasonically clean it for 3 minutes each with acetone, ethanol, hydrochloric acid and water. Change the solution in the middle and rinse with deionized water to remove impurities from the surface of the foamed copper.
[0037] (2) Prepare a 1 mol / L sodium hydroxide solution. Take 25 mL of sodium hydroxide solution, weigh 0.285 g of ammonium persulfate and add it to the sodium hydroxide solution. Stir to dissolve. Under room temperature conditions, immerse the pretreated foam copper carrier (1×3 cm) in the solution and react for 30 minutes to obtain the copper hydroxide precursor.
[0038] (3) According to the feeding ratio, weigh 0.5mM cobalt nitrate and stir to dissolve in anhydrous methanol to obtain solution A; weigh 1mM 2-methylimidazole and stir to dissolve in anhydrous methanol to obtain solution B; add 10mL of solution B to 30mL of solution A and stir to mix to obtain solution C.
[0039] (4) Transfer the solution C from step 3) to a polytetrafluoroethylene hydrothermal reactor, place the precursor obtained in step 2) in the reactor and react at 120°C for 120 minutes. After the reaction is completed, cool naturally to room temperature and rinse the surface solvent with deionized water to obtain CuCo bimetallic electrocatalyst.
[0040] X-ray diffraction observation was performed on the CuCo bimetallic electrocatalyst obtained in Example 1, and the results are shown in the figure. Figure 2 The CuCo bimetallic electrocatalyst obtained in Example 1 was observed using scanning electron microscopy, and the results are shown in the figure below. Figure 3 .Depend on Figure 2 As can be seen, the CuCo bimetallic electrocatalyst obtained in Example 1, compared with the PDF card, showed no other impurity peaks, indicating that the prepared CuCo bimetallic electrocatalyst has good purity; Figure 3 It can be seen that the CuCo bimetallic electrocatalyst obtained in Example 1 has a uniform array of nanosheets growing on copper hydroxide nanowires.
[0041] The catalytic performance of the CuCo bimetallic electrocatalyst obtained in Example 1 was tested using the following method: The CuCo bimetallic electrocatalyst was cut into pieces approximately 1×1 cm in size. 2 The size of the electrode was used as the working electrode. Electrochemical tests were controlled by an electrochemical workstation, and the reaction was carried out in an H-type electrolytic cell. The volume of both the anode and cathode chambers was 28 mL, separated by an N117 cation exchange membrane. 28 mL of 1 mol / L KOH aqueous solution was used as the electrolyte in the anode chamber, and 24 mL of 1 mol / L KOH aqueous solution and 4 mL of 1,4-dioxane were used as the electrolyte in the cathode chamber. In the anode chamber of the H-type electrolytic cell, a platinum electrode was used as the anode electrode; in the cathode chamber of the H-type electrolytic cell, a CuCo bimetallic electrocatalyst was used as the cathode electrode.
[0042] S1: Using quinoline as the reaction substrate, add 54.75 mg of quinoline to the electrolyte in the cathode chamber;
[0043] S2: Place the entire electrolysis device in a water bath stirring device, stir at a constant temperature of 25℃, maintain a constant voltage between the anode and cathode of -1.3V, a current of -30mA, and an electrolysis time of 4h.
[0044] S3: After removing the electrolyte from the cathode chamber in step S2, quantitative detection was performed using liquid chromatography. The reaction results are shown in the figure below as the reaction time progresses. Figure 4 As shown, the amount of quinoline as the raw material gradually decreases, while the amount of 1,2,3,4-tetrahydroquinoline as the product gradually increases. When the reaction reaches 4 hours, the conversion rate of quinoline is 97.64%, and the selectivity of 1,2,3,4-tetrahydroquinoline is 99.9%.
[0045] Example 2: Electrocatalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline using a CuNi bimetallic electrocatalyst
[0046] (1) CuCo bimetallic electrocatalyst was prepared by hydrothermal method. The preparation method was the same as in Example 1, except that cobalt nitrate hexahydrate was replaced with nickel nitrate hexahydrate to prepare CuNi bimetallic electrocatalyst.
[0047] (2) The catalytic performance of the CuNi bimetallic electrocatalyst obtained in Example 2 was tested, with the CuNi bimetallic electrocatalyst as the cathode. The specific testing method was the same as in Example 1. The conversion rate of quinoline was determined to be 70.6%, and the selectivity reached 99.9%.
[0048] Example 3: Electrocatalyst for the electrocatalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline using CuCo bimetallic electrocatalysts.
[0049] (1) CuCo bimetallic electrocatalyst was prepared by hydrothermal method, the preparation method being the same as in Example 1.
[0050] (2) The catalytic performance of the CuCo bimetallic electrocatalyst obtained in Example 3 was tested. The test method was the same as in Example 1, except that the potential between the anode and cathode was constant at -1.2V, the current was -20mA, and the electrolysis time was 4h. After measurement and calculation, the conversion rate of quinoline was 85.28%, and the selectivity reached 99.9%.
[0051] Example 4: Electrocatalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline using a CuCo bimetallic electrocatalyst
[0052] (1) CuCo bimetallic electrocatalyst was prepared by hydrothermal method, the preparation method being the same as in Example 1.
[0053] (2) The catalytic performance of the CuCo bimetallic electrocatalyst obtained in Example 4 was tested using the same method as in Example 1, except that a constant current of -20mA was used for electrolysis for 4 hours. Measurements and calculations showed that the conversion rate of quinoline was 96.8%, and the selectivity reached 99.9%.
[0054] Example 5: Electrocatalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline using a CuCo bimetallic electrocatalyst
[0055] The CuCo bimetallic electrocatalyst was prepared by a hydrothermal method, using the same method as in Example 1. The difference from Example 1 was that the surface area of the CuCo bimetallic electrocatalyst was increased from 1×1 cm to 14×8 cm.
[0056] The electrocatalytic performance testing method differs from that in Example 1. The electrochemical test is controlled by a galvanometer. The volumes of the cathode and anode chambers are increased from 28 mL to 700 mL and separated by a perfluorosulfonic acid cation exchange membrane. 700 mL of 1 mol / L KOH aqueous solution is used as the electrolyte in the anode chamber, and 700 mL of 1 mol / L KOH aqueous solution and 5 mL of 1,4-dioxane are used as the electrolyte in the cathode chamber. Electrolysis is performed in a plate-and-frame flow electrolyzer, with a peristaltic pump controlling the liquid flow rate and a flow meter controlling the flow velocity. In the anode chamber of the plate-and-frame electrolyzer, stainless steel is used as the anode electrode, and a CuCo bimetallic electrocatalyst is used as the cathode electrode.
[0057] S1: Using quinoline as the reaction substrate, add 1.4g of quinoline to the electrolyte in the cathode chamber;
[0058] S2: Electrolysis at a constant current of -1000mA, a potential of -2.5V, and an electrolysis time of 3h at room temperature;
[0059] S3: After removing the electrolyte from the cathode chamber in step S2, quantitative detection was performed using liquid chromatography. As the reaction time progressed, the amount of quinoline in the raw material gradually decreased, while the amount of 1,2,3,4-tetrahydroquinoline in the product gradually increased. When the reaction reached 3 hours, the conversion rate of quinoline was 88.9%, and the selectivity of 1,2,3,4-tetrahydroquinoline was 99%.
Claims
1. A method for synthesizing 1,2,3,4-tetrahydroquinoline by copper-based bimetallic electrocatalytic hydrogenation of quinoline, characterized in that, The method is as follows: The current and voltage were controlled by an electrochemical power source, and an H-type electrolytic cell was used as the reaction apparatus. The anode and cathode reaction cells were separated by a Nafion N117 cation exchange membrane. In the anode chamber, a platinum sheet was used as the anode, and an alkaline solution was used as the anolyte. In the cathode chamber, a Cu-based bimetallic catalyst was used as the cathode, and an alkaline solution containing the reaction substrates quinoline and 1,4-dioxane was used as the catholyte. The electrocatalytic hydrogenation reaction was carried out for 1 to 6 h under the conditions of constant temperature water bath 25~55 ℃, constant potential electrolysis potential -1.0~-3.5 V, and constant current electrolysis current -5~-1000 mA to obtain the product 1,2,3,4-tetrahydroquinoline. The reaction formula is as follows: in, The Cu-based bimetallic catalyst is either a CuCo bimetallic electrocatalyst or a CuNi bimetallic electrocatalyst; The Cu-based bimetallic catalyst was prepared by the following method: (1) Sonicate the copper foam with acetone, ethanol, hydrochloric acid and water for 3-10 minutes respectively to remove impurities from the surface of the copper foam and set aside. (2) Weigh sodium hydroxide and ammonium persulfate, dissolve them in deionized water to obtain a mixed solution; at 10~35 ℃, soak the copper foam prepared in step (1) in the mixed solution for 10~40 minutes, and then take it out to obtain the copper hydroxide precursor; (3) Add the 2-methylimidazole solution to the metal salt solution and stir to mix well to obtain a mixed system; The metal salt is selected from cobalt nitrate hexahydrate or nickel nitrate hexahydrate; (4) Place the copper hydroxide precursor obtained in step (2) into the mixed system obtained in step (3) and react at 120~160 °C for 2~6 h. Then, cool naturally to room temperature, take it out and rinse with deionized water to obtain Cu-based bimetallic catalyst.
2. The method for synthesizing 1,2,3,4-tetrahydroquinoline by copper-based bimetallic electrocatalytic hydrogenation of quinoline as described in claim 1, characterized in that, The alkaline solutions in the cathode and anode chambers are aqueous solutions of potassium hydroxide, sodium hydroxide, dipotassium hydrogen phosphate, or disodium hydrogen phosphate.
3. The method for synthesizing 1,2,3,4-tetrahydroquinoline by copper-based bimetallic electrocatalytic hydrogenation of quinoline as described in claim 2, characterized in that, The alkaline solutions in the cathode and anode chambers are potassium hydroxide solutions with a concentration of 0.1–2 mol / L.
4. The method for synthesizing 1,2,3,4-tetrahydroquinoline by copper-based bimetallic electrocatalytic hydrogenation of quinoline as described in claim 1, characterized in that, In the catholy solution, the concentration of the reaction substrate quinoline is 1~2 g / L, and the volume ratio of 1,4-dioxane to alkaline solution is 1:5~150.
5. The method for synthesizing 1,2,3,4-tetrahydroquinoline by copper-based bimetallic electrocatalytic hydrogenation of quinoline as described in claim 1, characterized in that, The electrocatalytic hydrogenation reaction has a constant potential electrolysis potential of -1.0 to -1.4 V, a constant current electrolysis current of -5 to -500 mA, and a reaction time of 3 to 6 h.
6. The method for synthesizing 1,2,3,4-tetrahydroquinoline by copper-based bimetallic electrocatalytic hydrogenation of quinoline as described in claim 1, characterized in that, In the preparation method of Cu-based bimetallic catalyst, step (2) states that the concentration of sodium hydroxide in the mixed solution is 1 mol / L and the concentration of ammonium persulfate is 0.0114 g / mL.
7. The method for synthesizing 1,2,3,4-tetrahydroquinoline by copper-based bimetallic electrocatalytic hydrogenation of quinoline as described in claim 1, characterized in that, In step (3) of the preparation method of Cu-based bimetallic catalyst, the concentration of the metal salt solution is 0.5 mM and the solvent is anhydrous methanol; the concentration of the 2-methylimidazole solution is 1 mM and the solvent is anhydrous methanol; the volume ratio of the 2-methylimidazole solution to the metal salt solution is 1:3~2:1.