Electrochemical hydrogenation cathode electrolyte and electrochemical hydrogenation method

Abstract

The invention discloses an electrochemical hydrogenation cathode electrolyte and an electrochemical hydrogenation method. The electrochemical hydrogenation cathode electrolyte is used for the electrochemical hydrogenation of nitrogen heterocyclic compounds. The electrochemical hydrogenation cathode electrolyte comprises: a strong base, an organic solvent and water; in the electrochemical hydrogenation cathode electrolyte, OH ‑ The molar concentration is 0.2 mol / L to 5 mol / L, and the organic solvent and the water are mutually soluble or partially soluble, so that the electrochemical hydrogenation cathode electrolyte forms a uniform and stable solution. Combined with the test results of the specific embodiments, the electrochemical hydrogenation cathode electrolyte of the present invention can effectively increase the reaction current of nitrogen heterocyclic compounds in the electrochemical hydrogenation process by adding an organic solvent, thereby effectively improving the reaction efficiency and reducing energy consumption.

Description

Technical Field

[0001] The invention relates to the field of electrochemical hydrogenation, and in particular to an electrochemical hydrogenation cathode electrolyte and an electrochemical hydrogenation method. Background Art

[0002] Hydrogen energy is a green and efficient energy source. After hydrogen is burned, only water is produced, and water can be regenerated into hydrogen through electrolysis, realizing the green cycle of hydrogen energy. However, as the lightest element on earth, hydrogen has a very low density whether it exists in gaseous or liquid form. As a fuel, the utilization of hydrogen energy has the characteristics of dispersion and intermittence, so its storage and transportation problems need to be solved urgently. In the development of hydrogen energy technology, how to store hydrogen with high density and safety is the key to the real practical application of hydrogen energy technology.

[0003] At present, the commonly used hydrogen storage technologies include high-pressure gaseous hydrogen storage, low-temperature liquid hydrogen storage, metal hydride hydrogen storage, metal organic framework compound hydrogen storage and organic liquid hydrogen storage. Among them, organic liquid hydrogen storage materials are an effective means to achieve large-scale hydrogen storage and long-distance transportation of hydrogen energy due to their safe and efficient hydrogen storage methods. Compared with traditional hydrogen storage methods, organic liquids have high hydrogen storage capacity and density, good reversibility, and recyclable reactants and products. They have similar properties to gasoline and can be transported and stored in accordance with existing infrastructure such as pipelines and gas stations.

[0004] Nitrogen heterocyclic compounds such as quinoline and quinoxaline can be hydrogenated and reduced through electrochemical reactions, thereby achieving electrochemical hydrogenation. In the commonly used electrochemical reaction system, potassium hydroxide aqueous solution is generally used as the cathode electrolyte, and nitrogen heterocyclic compounds such as quinoline and quinoxaline are dissolved in the cathode electrolyte for electrochemical hydrogenation. Increasing the electrode current density of the electrochemical hydrogenation reaction can effectively improve the reaction efficiency and reduce energy consumption. Summary of the invention

[0005] Based on this, it is necessary to provide an electrochemical hydrogenation cathode electrolyte that can increase the electrode current density of the electrochemical hydrogenation reaction.

[0006] In addition, it is also necessary to provide an electrochemical hydrogenation method using the above electrochemical hydrogenation cathode electrolyte.

[0007] An electrochemical hydrogenation cathode electrolyte, used for electrochemical hydrogenation of nitrogen heterocyclic compounds, the electrochemical hydrogenation cathode electrolyte comprising: a strong base, an organic solvent and water;

[0008] In the electrochemical hydrogenation cathode electrolyte, OH - The molar concentration is 0.2 mol / L to 5 mol / L, and the organic solvent and the water are mutually soluble or partially soluble in each other, so that the electrochemical hydrogenation cathode electrolyte forms a uniform and stable solution.

[0009] In one embodiment, the volume ratio of the organic solvent to the water is 1:16-1:4.

[0010] In one embodiment, the organic solvent is selected from at least one of acetonitrile, tetrahydrofuran and DMF.

[0011] In one embodiment, the strong base is selected from at least one of KOH and NaOH.

[0012] In one embodiment, in the electrochemical hydrogenation cathode electrolyte, OH - The molar concentration is 1 mol / L.

[0013] In one embodiment, the nitrogen heterocyclic compound is at least one selected from quinoline, quinoxaline, a quinoline derivative containing an alkyl group, a quinoxaline derivative containing an alkyl group, a quinoline derivative containing a benzyl group, and a quinoxaline derivative containing a benzyl group.

[0014] In one embodiment, the nitrogen heterocyclic compound has less than 24 carbon atoms.

[0015] An electrochemical hydrogenation method uses the electrochemical hydrogenation cathode electrolyte.

[0016] In one embodiment, the cathode catalyst of the electrochemical hydrogenation method is nickel powder.

[0017] In one embodiment, the nickel powder is prepared from nickel nitrate by NaOH co-precipitation-hydrogen reduction.

[0018] Combined with the test results of the specific embodiments, the electrochemical hydrogenation cathode electrolyte of the present invention can effectively increase the reaction current of nitrogen heterocyclic compounds in the electrochemical hydrogenation process by adding an organic solvent, thereby effectively improving the reaction efficiency and reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] in:

[0021] Figure 1 This is a comparison graph of the linear sweep voltammetry (LSV) of 1-1 and 1-2 in Example 1.

[0022] Figure 2This is the current difference curve diagram of the linear sweep voltammetry (LSV) of 1-1 and 1-2 in Example 1.

[0023] Figure 3 This is a comparison curve of the linear sweep voltammetry (LSV) of 2-1 and 2-2 in Example 1.

[0024] Figure 4 This is the current difference curve diagram of the linear sweep voltammetry (LSV) of 2-1 and 2-2 in Example 1.

[0025] Figure 5 This is a comparison curve of the linear sweep voltammetry (LSV) of 3-1 and 3-2 in Example 1.

[0026] Figure 6 This is the current difference curve diagram of the linear sweep voltammetry (LSV) of 3-1 and 3-2 in Example 1.

[0027] Figure 7 This is a comparison graph of the linear sweep voltammetry (LSV) of 4-1 and 4-2 in Example 1.

[0028] Figure 8 This is the current difference curve diagram of the linear sweep voltammetry (LSV) of 4-1 and 4-2 in Example 1.

[0029] Fig. 9 This is the chromatogram of the cathode electrolyte 1-2 in Example 1 after 8 hours of electrochemical hydrogenation reaction.

[0030] Fig.10 This is the chromatogram of the 3-2 cathode electrolyte in Example 1 after 8 hours of electrochemical hydrogenation reaction. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The invention discloses an electrochemical hydrogenation cathode electrolyte according to an embodiment of the invention, which is used for the electrochemical hydrogenation of nitrogen heterocyclic compounds.

[0033] The cathode electrolyte of the electrochemical hydrogenation includes: a strong base, an organic solvent and water.

[0034] In the catholyte of electrochemical hydrogenation, OH -The molar concentration is 0.2 mol / L~5 mol / L, and the organic solvent and water are miscible or partially miscible, so that the electrochemical hydrogenation cathode electrolyte forms a uniform and stable solution.

[0035] Combined with the test results of the specific embodiments, the electrochemical hydrogenation cathode electrolyte of the present invention can effectively increase the reaction current of nitrogen heterocyclic compounds in the electrochemical hydrogenation process by adding an organic solvent, thereby effectively improving the reaction efficiency and reducing energy consumption.

[0036] Preferably, the volume ratio of the organic solvent to water is 1:16 to 1:4.

[0037] Specifically, the volume ratio of the organic solvent to water may be 1:16, 1:8 or 1:4.

[0038] In combination with the specific embodiment, when the volume ratio of the organic solvent to water is too high (1:2), the reaction current of the nitrogen heterocyclic compound during the electrochemical hydrogenation process does not increase significantly.

[0039] Specifically, in this embodiment, the organic solvent is selected from at least one of acetonitrile, tetrahydrofuran and DMF.

[0040] In this embodiment, the strong base is selected from at least one of KOH and NaOH.

[0041] In other embodiments, other types of strong bases can also be selected, as long as OH - The molar concentration can be 0.2mol / L~5mol / L.

[0042] Preferably, in this embodiment, in the electrochemical hydrogenation cathode electrolyte, OH - The molar concentration is 1 mol / L.

[0043] Specifically, the nitrogen heterocyclic compound is at least one selected from quinoline, quinoxaline, a quinoline derivative containing an alkyl group, a quinoxaline derivative containing an alkyl group, a quinoline derivative containing a benzyl group, and a quinoxaline derivative containing a benzyl group.

[0044] Preferably, in this embodiment, the number of carbon atoms in the nitrogen heterocyclic compound is less than 24.

[0045] The present invention also discloses an electrochemical hydrogenation method according to an embodiment, which adopts the electrochemical hydrogenation cathode electrolyte.

[0046] Preferably, the cathode catalyst of the electrochemical hydrogenation method is nickel powder.

[0047] Specifically, the nickel powder is prepared using nickel nitrate as a raw material through NaOH co-precipitation-hydrogen reduction.

[0048] The following are specific embodiments.

[0049] Example 1

[0050] Nickel nitrate was used as raw material, and Ni powder prepared by NaOH coprecipitation-hydrogen reduction was used as cathode catalyst. The cathode was bonded to nickel foam with Nafion solution, and the cathode area was 1 cm 2 , a 6mm diameter carbon rod was used as the anode.

[0051] Take 25 mL of 1 mol / L KOH solution as the electrolyte, and dissolve 0.05 mol of quinoxaline as the reaction substrate. The formula of KOH solution is shown in Table 1, and electrolytes No. 1 to No. 4 are prepared according to the volume ratio of acetonitrile to water of 0, 1 / 16, 1 / 8, 1 / 4, and 1 / 2.

[0052] Table 1

[0053]

[0054] The electrochemical reaction was carried out in a three-port electrolytic cell separated by a sand core, and the cathode electrolytic cell was filled with 8 electrolytes shown in Table 1, and the effects of different acetonitrile contents in the cathode electrolyte on the hydrogenation reaction current were compared. The electrolyte with suffix -1 did not contain substrate, and the electrolyte with suffix -2 contained substrate.

[0055] The anolyte was 1 mol / L KOH aqueous solution, and the calomel electrode was used as the reference electrode.

[0056] Linear voltage scanning was performed on different cathode electrolytes to observe the reaction current at different potentials. Figure 1 to Figure 8 .

[0057] Among them, 1-1 and 1-2 electrolytes were used as comparison objects when no acetonitrile was added, and the cathode electrolyte needed to be mechanically stirred during the reaction.

[0058] Results Analysis

[0059] Combination Figure 1 and Figure 2 It can be seen that without adding acetonitrile, a reaction current peak of about 0.0005 A appears near -1.2V after the addition of the reactants.

[0060] Combination Figure 3 and Figure 4 It can be seen that when acetonitrile is added, a reaction current peak of about 0.0005A appears near -1.25V after the addition of the reactant.

[0061] Combination Figure 5 and Figure 6It can be seen that when acetonitrile is added, a reaction current peak of about 0.0025 A appears near -1.25 V after the addition of the reactant.

[0062] Combination Figure 1 to Figure 6 It can be seen that after adding acetonitrile, the reaction current of quinoxaline hydrogenation has a significant increase.

[0063] It can be seen that adding an appropriate amount of acetonitrile to the cathode electrolyte can greatly increase the reaction current of quinoxaline hydrogenation, especially Figure 5 and Figure 6 It can be seen that the reaction current at -1.2V increases from about 0.0005A to about 0.0025A.

[0064] Combination Figure 7 and Figure 8 It can be seen that when acetonitrile: water = 1:2, no significant increase in reaction current was observed after the addition of the substrate.

[0065] Reaction product verification

[0066] To verify the effect of hydrogenation reaction, 1-2 and 3-2 electrolytes were reacted at -1.25V for 8 hours, and then the reaction products in the electrolyte were extracted with ethyl acetate and analyzed by gas chromatography-mass spectrometry. The test results are as follows: Fig. 9 and Fig.10 shown.

[0067] Combination Fig. 9 and Fig.10 It can be seen that the mass spectrum shows that the product separated at around 9.3 min is quinoxaline, and the product separated at around 14.3 min is tetrahydroquinoxaline, which are products of electrochemical hydrogenation of quinoxaline. The content of tetrahydroquinoxaline detected in the 3-2 solution sample is much higher than that in the 1-2 solution.

[0068] This proves that the scheme effectively improves the yield of electrochemical hydrogenation products.

[0069] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An electrochemical hydrogenation cathode electrolyte, characterized in that For electrochemical hydrogenation of nitrogen heterocyclic compounds, the electrochemical hydrogenation cathode electrolyte comprises: a strong base, an organic solvent and water; In the electrochemical hydrogenation cathode electrolyte, OH - The molar concentration is 0.2 mol / L to 5 mol / L, the organic solvent and the water are mutually soluble or partially soluble in each other, so that the electrochemical hydrogenation cathode electrolyte forms a uniform and stable solution; The volume ratio of the organic solvent to the water is 1:8 to 1:4; The organic solvent is selected from acetonitrile; The nitrogen heterocyclic compound is selected from quinoxaline.

2. The electrochemical hydrogenation cathode electrolyte according to claim 1, characterized in that The strong base is selected from at least one of KOH and NaOH.

3. The electrochemical hydrogenation cathode electrolyte according to claim 2, characterized in that In the electrochemical hydrogenation cathode electrolyte, OH - The molar concentration is 1 mol / L.

4. An electrochemical hydrogenation method, characterized in that: The electrochemical hydrogenation cathode electrolyte as claimed in any one of claims 1 to 3 is used.

5. The electrochemical hydrogenation method according to claim 4, characterized in that: The cathode catalyst of the electrochemical hydrogenation method is nickel powder.

6. The electrochemical hydrogenation method according to claim 5, characterized in that: The nickel powder is prepared by using nickel nitrate as raw material through NaOH co-precipitation-hydrogen reduction.

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