Electrolytic tank cathode solid electrolyte interface self-growth method and application thereof in aniline production

Abstract

The invention belongs to the field of electrochemistry, and discloses a self-growing solid electrolyte interface in an electrolysis process and application of the self-growing solid electrolyte interface in aniline production. The method comprises the following steps: dissolving nitrobenzene, 2-piperidone, lithium bromide and tris (N, N-tetramethylene) phosphamide in an organic solvent to obtain an electrolyte, and placing the electrolyte in a single-chamber electrolytic tank provided with an anode and a cathode for electrolysis, so that a solid electrolyte interface automatically grows on the cathode along with electrolysis and generates electrocatalytic activity. According to the method, hydrogen is not used, so that the risks of combustion and explosion are avoided; the device can be coupled with clean energy power generation, and is environment-friendly and sustainable; the device is simple, the size of the device is obviously reduced, and an exchange membrane does not need to be used for separating a cavity; a catalyst does not need to be loaded on an electrode, and the cost and technical difficulty of synthesizing and loading the catalyst are avoided; the price is low and operation is easy; the problems of inactivation and shedding of the catalyst do not need to be considered, and the long-term stability is good.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemistry technology, and specifically relates to a method for self-growing the solid electrolyte interface of the cathode of an electrolytic cell and its application in aniline production. Background Art

[0002] Aniline has important applications in the dye, pharmaceutical, and polymer industries, while nitrobenzene is an important precursor for synthesizing various derivatives. Currently, the main methods for synthesizing aniline are the traditional method, thermal catalysis method, photocatalysis method, and electrocatalysis method. The traditional method for synthesizing aniline relies on stoichiometric metal reducing agents (such as zinc, tin, iron), which does not conform to the sustainable development concept of modern chemistry; the thermal catalysis method has limitations in economy and safety because it uses noble metal catalysis and uses hydrogen to provide protons under high temperature and high pressure conditions; although the photocatalysis method is a sustainable strategy, its energy utilization rate and reaction rate are relatively low, so its practicality is currently low.

[0003] The electrocatalysis method is a clean and effective method for synthesizing high-value chemicals. During electrochemical transfer hydrogenation, electrons directly or indirectly come from an external electric field, avoiding the participation of sacrificial reducing agents. In addition, non-hydrogen hydrogen supply and mild reaction conditions not only reduce the additional storage and transportation costs but also avoid the risks of fire and explosion. In recent years, the technology for high-value utilization of organic compounds by electrochemical reduction has been widely studied, and it has become a method with broad prospects for synthesizing aniline due to its sustainability and safety.

[0004] However, the current electrocatalytic system still has its limitations. The existing methods for loading catalysts on electrodes include the drop coating method, electrodeposition method, and photodeposition method. These methods load electrocatalysts on electrodes physically or chemically, thereby generating catalytic activity on the electrodes. After a period of electrolysis, the catalyst may undergo changes in surface morphology and become inactivated, or fall off the electrode and become ineffective. Therefore, it is difficult for these methods to maintain stability during the electrolysis process. Summary of the Invention

[0005] The present invention aims to solve the problem of the long-term stability of electrocatalysts during the electrocatalysis process. By introducing additives into the electrolyte, the SEI layer grows on the cathode of the electrolytic cell automatically, changing the cathode morphology and electrochemical activity, and then generating catalytic activity. At the same time, the in-situ grown SEI can maintain its surface morphology and activity for a long time, preventing inactivation.

[0006] Aiming at the shortcomings of the unsustainability and high danger of the existing aniline synthesis technology, the present invention provides an improved scheme for electrochemical synthesis, which not only has sustainability and safety but also overcomes the stability problems such as inactivation and shedding of traditional electrocatalysts. The device of this scheme is simple and the operation is convenient, and it is expected to become an effective method for electrocatalytic synthesis of aniline.

[0007] The technical solution provided by the present invention is as follows:

[0008] A method for self-growing a solid electrolyte interface at the cathode of an electrolytic cell, comprising the following steps: dissolving nitrobenzene, 2-piperidone, lithium bromide, and tris(N,N-tetramethylene)phosphoramide in an organic solvent to obtain an electrolyte solution, and placing the electrolyte solution in a single-chamber electrolytic cell equipped with an anode and a cathode for electrolysis, so that the solid electrolyte interface grows on the cathode by itself during electrolysis and generates electrocatalytic activity.

[0009] Further, the current for electrolysis is 4 - 6 mA, and the electrolysis time is 2 - 4 h.

[0010] Further, the cathode electrode material is one of C, Mg, Al, stainless steel, Co, Ni, Cu, Zn, and Sn.

[0011] Further, the anode electrode material is Al or Mg.

[0012] Further, the lithium bromide is dried at 160 - 200 °C for 40 - 80 min before preparing the electrolyte solution.

[0013] Further, the organic solvent is tetrahydrofuran.

[0014] Further, the tetrahydrofuran is pretreated tetrahydrofuran, and the pretreatment method of the tetrahydrofuran includes: pre-putting tetrahydrofuran with flaky potassium hydroxide overnight, pouring the liquid part into the device, adding sodium metal flakes and benzophenone in sequence, then filling nitrogen into the device, heating under stirring conditions until the solution shows dark blue, and then performing condensation treatment to obtain pretreated tetrahydrofuran.

[0015] Further, the heating temperature is 90 - 95 °C, and the heating time is 3 - 5 h.

[0016] Further, the condensation treatment time is 1 - 3 h.

[0017] The present invention also provides a single-chamber electrolytic cell system for generating SEI, including a cathode electrode, an anode electrode, a solvent, an electrolyte salt, an additive, a substrate, and a hydrogen donor.

[0018] The cathode electrode material includes: one of C, Mg, Al, stainless steel, Co, Ni, Cu, Zn, and Sn.

[0019] The anode electrode material includes: one of Al and Mg.

[0020] The solvent is tetrahydrofuran.

[0021] The electrolyte salt is LiBr.

[0022] The additive is tris(N,N-tetramethylene)phosphoramide (CAS: 6415-07-2).

[0023] The substrate is nitrobenzene.

[0024] The hydrogen donor is 2-piperidone (CAS: 675-20-7)

[0025] The method for forming the SEI is as follows: dissolving a substrate (30 mmol / L), a hydrogen donor (0.18 mmol / L), an electrolyte salt (0.2 mol / L), and an additive (0.3 mol / L) in a solvent, tetrahydrofuran. The solution is electrolyzed at a current of 5 mA in a single-chamber electrolytic cell equipped with the anode and cathode. The SEI will grow on the cathode.

[0026] The present invention also provides the application of the above-mentioned electrolytic cell cathode solid electrolyte interface self-growth method in aniline production, and nitrobenzene is reduced while the solid electrolyte interface self-grows to obtain aniline.

[0027] At a current of 5 mA, the substrate nitrobenzene was converted simultaneously with the formation of SEI. At 3 h, the conversion of nitrobenzene reached 100%, and the selectivity of aniline reached 75.48%.

[0028] Beneficial Effects

[0029] Solid Electrolyte Interphase (SEI) is a passivation layer formed on the surface of the negative electrode during the battery charging and discharging process. This interface is formed by the reaction of electrolytes, solutions and additives. It is a good conductor of lithium ions but does not allow the passage of electrons. SEI was first used in lithium battery technology to extend the life of lithium batteries and prevent the growth of dendrites due to excessive charging and discharging. Since lithium batteries need to undergo thousands of charge and discharge cycles during their life, SEI has extremely strong long-term stability.

[0030] The method of self - growth of the solid electrolyte interface at the cathode of the electrolytic cell is applied to aniline production for the first time in the present invention. The method of the present invention does not use hydrogen, without the risks of its combustion and explosion; electrocatalysis can be coupled with clean energy power generation, which is environmentally friendly and sustainable; a single - chamber electrolytic cell is used to synthesize aniline, the device is simple. Compared with the H - type electrolytic cell, while significantly reducing the volume of the device, there is no need to use an expensive exchange membrane to separate the chambers; there is no need to load a catalyst on the electrode, and SEI is self - generated to produce activity, without the cost and technical difficulties of synthesizing and loading the catalyst; due to the simple device, the device cost and the cost of the exchange membrane are reduced. At the same time, there is no need to consider the synthesis and loading costs of the catalyst, which is cheap and easy to operate; there is no need to consider the problems of catalyst deactivation and shedding, and SEI grows in situ on the cathode, which can maintain long - term stability. This method has good potential and prospects for industrial application. Description of the Drawings

[0031] Figure 1 It is the scanning electron microscope imaging diagram of the solid electrolyte interface described in Example 1, 1 mm (left) and 50 μm (right).

[0032] Figure 2 It is the X - ray photoelectron spectroscopy diagram of the solid electrolyte interface prepared by the method of Example 1. Detailed Embodiments

[0033] Example 1

[0034] The self - growth of SEI and the production of aniline in the present invention occur simultaneously. The specific steps are as follows:

[0035] 1. Drying of tetrahydrofuran:

[0036] Use a reflux device to dry tetrahydrofuran. Approximately 250 mL of THF is pre - charged with flake potassium hydroxide overnight, then the liquid part is poured into the reflux device, and sodium metal flakes and benzophenone are added in turn. Then, nitrogen is filled into the device through a Schlenk tube. Subsequently, the device is heated to 92 °C with stirring for about 4 hours until the solution turns dark blue, and then condensation treatment is carried out for about 2 hours. The cooled THF can be drawn out for use with a long needle. The dried THF will not change color after dropping into a 10% potassium iodide solution.

[0037] 2. Drying of LiBr

[0038] Weigh LiBr in a 20 mL glass sample bottle and dry it at a temperature of 180 °C in a drying oven for 1 hour. After the sample bottle is taken out of the drying oven, it is immediately sealed with a headspace bottle cap with a PTFE diaphragm. The sample bottle is placed at room temperature to cool.

[0039] 3. Self - growth of SEI and production of aniline

[0040] Weigh 0.1 mmol of nitrobenzene, 0.6 mmol of 2-piperidone, 0.2 mmol of LiBr, and 1.0 mmol of tris(N,N-tetramethylene)phosphoramide and place them in a single-chamber electrolytic cell, and dissolve them in 3.5 mL of tetrahydrofuran. Assemble the electrolytic cell. The electrodes using an Sn cathode and an Mg anode have the best reaction effect. Electrolyze at a constant current of 5 mA at normal temperature and pressure for 3 hours. The SEI will self-grow on the cathode during the process and continuously reduce nitrobenzene to produce aniline. The conversion rate of nitrobenzene reaches 100%, and the selectivity of aniline reaches 75.48%.

[0041] Figure 1 This is the scanning electron microscope imaging diagram of the solid electrolyte interface described in this example, Figure 2 This is the X-ray photoelectron spectroscopy diagram of the solid electrolyte interface described in this example. The composition of this interface does not change significantly after long-term operation.

[0042] Example 2

[0043] The self-growth of the SEI of the present invention and the production of aniline occur simultaneously. The specific steps are as follows:

[0044] 1. Drying of tetrahydrofuran:

[0045] Use a reflux device to dry tetrahydrofuran. Approximately 250 mL of THF is pre-loaded with flaky potassium hydroxide overnight, then the liquid part is poured into the reflux device, and sodium metal flakes and benzophenone are added in sequence. Then, nitrogen is filled into the device through a Schlenk tube. Subsequently, the device is heated to 92 °C with stirring for about 4 hours until the solution turns dark blue, and then a condensation treatment is carried out for about 2 hours. The cooled THF can be drawn out for use with a long needle. The dried THF will not change color after dropping into a 10% potassium iodide solution.

[0046] 2. Drying of LiBr

[0047] Weigh LiBr in a 20 mL glass sample bottle and dry it in an oven at a temperature of 180 °C for 1 hour. Immediately seal the sample bottle with a headspace cap with a PTFE diaphragm after taking it out of the oven. Place the sample bottle to cool at room temperature.

[0048] 3. Self-growth of SEI and production of aniline

[0049] Weigh 0.1 mmol of nitrobenzene, 0.6 mmol of 2-piperidone, 0.2 mmol of LiBr, and 1.0 mmol of tris(N,N-tetramethylene)phosphoramide and place them in a single-chamber electrolytic cell, and dissolve them with 3.5 mL of tetrahydrofuran. Assemble the electrolytic cell. Electrodes using C, Mg, Al, stainless steel, Co, Ni, Cu, or Zn as the cathode and Al as the anode have non-optimal but equally feasible reaction effects. Electrolyze at a constant current of 5 mA at normal temperature and pressure for more than 3 hours. The SEI will grow spontaneously on the cathode during the process and continuously reduce nitrobenzene to produce aniline, with a relatively high nitrobenzene conversion rate and aniline selectivity, but the efficiency is lower than that of the preferred reaction conditions described in Example 1.

[0050] Examples 3 - 9

[0051] Table 1 Comparison of nitrobenzene conversion rate and aniline selectivity after replacing different substances

[0052]

[0053] The purpose of Examples 3 - 8 is to study the influence of changing the reaction system on the nitrobenzene conversion rate and aniline selectivity. It can be seen from Examples 3 - 5 that tris(N,N-tetramethylene)phosphoramide is a key additive. When tris(N,N-tetramethylene)phosphoramide is not added, the reaction cannot proceed, and there is no conversion of nitrobenzene and formation of aniline. When using hexakis(ethyl)phosphorous triamide with the same groups and similar structure as tris(N,N-tetramethylene)phosphoramide, the aniline selectivity can only reach 25.94%. Even when using tris(2,2,2-trifluoroethyl) phosphate applied to the SEI of lithium batteries, the aniline selectivity does not increase significantly. It can be seen from Example 6 that lithium bromide is a key electrolyte because its lithium ions need to dissolve in tetrahydrofuran and be reduced to reducing species at the cathode, and then nitrobenzene can be converted. The sodium ions in sodium chloride cannot dissolve in tetrahydrofuran and cannot generate corresponding reducing species. It can be seen from Example 7 that tetrahydrofuran is a key solvent. It can not only dissolve the electrolyte, substrate, and additive in this system, but also remain stable during electrolysis and improve the aniline yield. Ethylene glycol dimethyl ether easily becomes gel-like during the reaction and hinders the continuation of the reaction, resulting in a nitrobenzene conversion rate of only 7.01%. It can be seen from Example 8 that hexamethyl disilazone with the same groups and similar structure as 2-piperidone can also be used as the hydrogen donor in this system, but the effect is inferior to that of 2-piperidone.

[0054] Examples 9 - 14

[0055] Table 2 Comparison of nitrobenzene conversion rate and aniline selectivity at different 2-piperidone equivalents

[0056]

[0057] The purpose of Examples 9-14 was to study the effects of different 2-piperidone equivalents on the conversion rate of nitrobenzene and the selectivity of aniline. It can be seen from Example 9 that in the absence of 2-piperidone, aniline could not be effectively produced because protons could not be generated to participate in the reaction, and nitrobenzene would be converted into azobenzene. The formation of trace amounts of aniline was due to the protons generated from the residual moisture in the solution. It can be seen from Examples 10-14 that when the 2-piperidone equivalent was 6 equivalents, both the conversion rate of nitrobenzene and the selectivity of aniline reached the maximum, but more 2-piperidone led to a decrease in the selectivity of aniline. This was because the increase in the equivalent initially caused more protons to be generated in the system, shifting the chemical equilibrium to the right and facilitating the formation of aniline; when the equivalent continued to increase, too much 2-piperidone adsorbed on the cathode, competing with the decoupling of azobenzene, resulting in the inability of azobenzene to be hydrogenolyzed into aniline quickly and effectively. Therefore, 6 equivalents of 2-piperidone was the optimal condition.

[0058] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any changes or modifications made within the spirit and principle of the present invention using the above-disclosed technical content are equivalent implementation cases and should be included within the protection scope of the present invention.

Claims

1. A method for self - growth of a solid electrolyte interface at the cathode of an electrolytic cell, characterized in that, It includes the following steps: Dissolve nitrobenzene, 2-piperidone, lithium bromide, and tris(N,N-tetramethylene) phosphamide in an organic solvent to obtain an electrolyte solution. Place the electrolyte solution in a single-chamber electrolytic cell equipped with an anode and a cathode for electrolysis, so that a solid electrolyte interface grows on the cathode spontaneously during electrolysis and generates electrocatalytic activity.

2. The method for self-growing the solid electrolyte interface of the cathode of the electrolytic cell according to claim 1, characterized in that, The current for electrolysis is 4 - 6 mA, and the electrolysis time is 2 - 4 h.

3. The method for self-growing the cathode solid electrolyte interface of an electrolytic cell according to claim 1, characterized in that The cathode electrode material is one of C, Mg, Al, stainless steel, Co, Ni, Cu, Zn, Sn.

4. The method for self - growth of the solid electrolyte interface of the electrolytic cell cathode according to claim 1, wherein, The anode electrode material is Al or Mg.

5. The method for self-growing the solid electrolyte interface of the cathode of the electrolytic cell according to claim 1, characterized in that The lithium bromide is dried at 160 - 200 °C for 40 - 80 min before preparing the electrolyte solution.

6. The method for self - growth of the solid electrolyte interface of the electrolytic cell cathode according to claim 1, wherein, The organic solvent is tetrahydrofuran.

7. The method for self - growth of the solid electrolyte interface of the electrolytic cell cathode according to claim 6, wherein The tetrahydrofuran is pretreated tetrahydrofuran. The pretreatment method of the tetrahydrofuran includes: pre-putting tetrahydrofuran into flaky potassium hydroxide overnight, then pouring the liquid part into the device, adding sodium metal flakes and benzophenone in sequence, then filling nitrogen into the device, heating under stirring conditions until the solution shows a dark blue color, and then performing condensation treatment to obtain pretreated tetrahydrofuran.

8. The method for self - growth of the solid electrolyte interface of the electrolytic cell cathode according to claim 7, wherein The heating temperature is 90 - 95 °C, and the heating time is 3 - 5 h.

9. The method for self-growing an electrolytic cell cathode solid electrolyte interface according to claim 7, characterized in that, The condensation treatment time is 1 - 3 h.

10. Use of the method for self-growing the solid electrolyte interface of the electrolytic cell cathode according to any one of claims 1 to 9 in the production of aniline, characterized in that, During the spontaneous growth of the solid electrolyte interface, the reduction of nitrobenzene occurs to obtain aniline.

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