CN115449829A

CN115449829A - Electrochemical preparation method of chlorobenzene

Info

Publication number: CN115449829A
Application number: CN202210975671.4A
Authority: CN
Inventors: 雷爱文; 胡精诚; 何浩宇
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2022-08-15
Filing date: 2022-08-15
Publication date: 2022-12-09

Abstract

The invention discloses an electrochemical preparation method of chlorobenzene, which comprises the following steps: mixing organic solvent, benzene, hydrochloric acid and electrolyte uniformly, and carrying out electrolytic reaction in a constant current mode to obtain chlorobenzene. The invention takes hydrochloric acid as a chlorine source, performs chlorination reaction by electrooxidation of benzene, and obtains chlorobenzene with high Faraday efficiency. The method directly uses cheap and easily obtained benzene and hydrochloric acid as raw materials, and the only byproduct is hydrogen, so the method meets the requirement of green synthesis. And the Faraday efficiency of the reaction is high, and the method has a good industrial application prospect.

Description

Electrochemical preparation method of chlorobenzene

Technical Field

The invention relates to the technical field of organic synthesis, in particular to an electrochemical preparation method of chlorobenzene.

Background

Chlorobenzene is used for the production of the agricultural chemicals dicofos, DDT, etc., and for the synthesis of dyes, pharmaceuticals and other organic chemicals, as well as solvents for ethylcellulose and many resins and for the production of various intermediates, such as p-dichlorobenzene, p-chlorobenzenesulfonic acid, 2,4-dinitrochlorobenzene, o-nitrochlorobenzene, p-nitrochlorobenzene, nitrophenol, etc.

The traditional synthesis of chlorobenzene is catalyzed by iron, and chlorine is directly used for carrying out chlorination reaction with benzene. The process releases a large amount of hydrogen chloride, and the environmental pollution and the corrosion to the device are serious. Therefore, the traditional chlorobenzene synthesis method has the defects of complicated steps, environmental pollution and the like.

Therefore, it is necessary to develop an electrochemical method for preparing chlorobenzene to solve the above technical problems.

Disclosure of Invention

The invention aims to provide an electrochemical preparation method of chlorobenzene, which realizes the conversion from benzene to chlorobenzene by one step and has simple steps and environmental protection.

In order to achieve the above object, the present invention provides a method for electrochemically preparing chlorobenzene, the method comprising:

mixing organic solvent, benzene, hydrochloric acid and electrolyte uniformly, and carrying out electrolytic reaction in a constant current mode to obtain chlorobenzene.

Further, the volume ratio of the benzene to the hydrochloric acid is (1-2.5): 3.

further, the organic solvent is one of dichloroethane, dimethyl sulfoxide, N, N-dimethylformamide and hexafluoroisopropanol; the volume ratio of the organic solvent to chlorobenzene is 10: (2-3).

Further, the electrolyte comprises at least one of tetrabutylammonium tetrafluoroborate (TBABF 4) and tetraethylammonium tetrafluoroborate, and the concentration of the electrolyte is in a range from 0.1M to 0.5M.

In the electrolytic reaction, an integrated electrolytic cell equipped with a stirrer and an electrode is used.

Further, in the electrolytic reaction, the adopted anode comprises one of a carbon sheet, a graphite felt and a carbon cloth; the cathode is one of a carbon sheet, an iron sheet, a stainless steel sheet, a platinum sheet and a nickel sheet.

Further, the hydrochloric acid is commercially available concentrated hydrochloric acid.

Further, the current of the electrolytic reaction is 20 to 800mA.

Furthermore, the temperature of the electrolytic reaction is 0-40 ℃, and the time of the electrolytic reaction is 0.25-4 h.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

according to the electrochemical preparation method of chlorobenzene, hydrochloric acid is used as a chlorine source, chlorination reaction is carried out on benzene through electrooxidation, and chlorobenzene is obtained with high Faraday efficiency under high current density. Compared with the traditional benzene chlorination method, the method has the advantages of less pollution, no need of using highly toxic chlorine gas, high atom utilization rate and weak corrosivity to devices, and meets the requirements of green and safe production. Simple, high-efficiency and easy to operate. The method directly uses cheap and easily obtained benzene and hydrochloric acid as raw materials, and the only byproduct is hydrogen, so the method meets the requirement of green synthesis. And the Faraday efficiency of the reaction is high, and the method has a good industrial application prospect.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a chemical reaction equation in an electrochemical preparation method of chlorobenzene according to an embodiment of the present invention.

Detailed Description

The embodiments of the present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the embodiments of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that the present embodiments and examples are illustrative of the present invention and are not to be construed as limiting the present invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood in accordance with the meanings commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the invention belong. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the examples of the present invention are commercially available or can be prepared by an existing method.

In order to solve the technical problems, the embodiment of the invention provides the following general ideas:

according to an exemplary embodiment of the present invention, there is provided a method for electrochemical preparation of chlorobenzene, the method comprising:

The chemical equation for this reaction is:

in the technical proposal, the device comprises a base,

the volume ratio of the benzene to the hydrochloric acid is (1-2.5): 3. this volume ratio range is advantageous for the reaction to be sufficiently completed. If the volume ratio is outside the range of the present invention, which is unfavorable for the conversion of benzene, it is liable that the faradaic efficiency is lowered or chlorine gas is emitted.

The organic solvent is one of dichloroethane, dimethyl sulfoxide, N, N-dimethylformamide and hexafluoroisopropanol. The volume ratio of the chlorobenzene to chlorobenzene is 10: (2-3).

The electrolyte comprises at least one of tetrabutylammonium tetrafluoroborate and tetraethylammonium tetrafluoroborate, and the electrolyte is relatively stable and is not easy to generate side reaction. The concentration range of the electrolyte is 0.1-0.5M.

The hydrochloric acid is commercially available concentrated hydrochloric acid.

In the electrolytic reaction, an integrated electrolytic cell with a stirrer and an electrode is adopted.

In the electrolytic reaction, the adopted anode comprises one of a carbon sheet, a graphite felt and a carbon cloth; the cathode is one of a carbon sheet, an iron sheet, a stainless steel sheet, a platinum sheet and a nickel sheet.

The current of the electrolytic reaction is 20-800 mA. The current is beneficial to more easily capture chlorine free radicals and chlorine positive ions in benzene and simultaneously prevent hydrogen chloride from being lost due to overhigh temperature.

The temperature of the electrolytic reaction is 0-40 ℃, and the time of the electrolytic reaction is 0.25-4 h. The reason that the temperature is 0-40 ℃ is that the activity of the reaction can be ensured, and the volatilization of hydrochloric acid or chlorine generated by electrolysis due to too high temperature can be avoided, so that the Faraday efficiency is reduced.

The method further comprises the following steps: after the reaction is finished, organic solvent is used for carrying out organic extraction on the electrolyte, and then separation and purification are carried out to obtain the chlorobenzene product, or the electrolyte is distilled and condensed at low temperature to obtain the chlorobenzene product.

In summary, the present invention provides a method for producing chlorobenzene with high faradaic efficiency at a high current density by performing a chlorination reaction of benzene by electrooxidation using hydrochloric acid as a chlorine source. The method realizes the conversion from chlorobenzene to chlorobenzene by one step, and has simple steps and environmental protection.

The electrochemical preparation of chlorobenzene according to the present application will now be described in more detail with reference to the following examples and comparative experimental data.

Example 1

Adding TBABF into a reaction tube under an air atmosphere ₄ (1 mmol), concentrated hydrochloric acid (3 mmol), benzene (2 mmol) and dimethyl sulfoxide (10 mL); the carbon felt serves as an anode and the iron sheet serves as a cathode. The mixture was stirred at room temperature for 3 hours at a constant current of 25.0 mA. At the end of the reaction, biphenyl was added as an internal standard for GC quantification and the faradaic efficiency of the product was 78%.

Example 2

In this example, the solvent was changed to dichloroethane, and the other conditions were the same as in example 1, and the product faradaic efficiency was 85%.

Example 3

Adding TBABF into a reaction tube under an air atmosphere ₄ (1 mmol), concentrated hydrochloric acid (1 mL), chlorobenzene (1 mL) and dichloromethane (10 mL); carbon felt was used as the anode and stainless steel as the cathode. The mixture was stirred at room temperature for 1 hour at a constant current of 200.0 mA. At the end of the reaction, biphenyl was added as an internal standard for GC quantification, the product faraday efficiency was 85%.

Example 4

In this example, the current was changed to 800.0mA, the reaction time was changed to 30min, and the other conditions were the same as in example 3, and the product Faraday efficiency was 82%.

Example 5

In this example, the temperature becomes 40 ℃. The other conditions were the same as in example 3, and the faradaic efficiency of the product was 90%.

Comparative example 1

In comparative example 1, the hydrochloric acid was changed to sodium chloride. The other steps are as in example 15, and the faradaic efficiency of the product is 2%.

Comparative example 2

In comparative example 2, the current was 1200mA. The other steps are as in example 15, and the faradaic efficiency of the product is 54%.

Experimental example 1

For comparison, the experimental parameters of each example and each comparative example are shown in Table 1.

TABLE 1

As can be seen from the data in Table 1:

in examples 1 to 5 of the present invention, the faradaic efficiency of the product chlorobenzene was superior to that of the comparative example. Indicating that the reaction conditions are within the scope of the present invention to synthesize the product chlorobenzene.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the embodiments of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, provided that such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the embodiments of the present invention and their equivalents, the embodiments of the present invention are intended to include such modifications and variations as well.

Claims

1. A method for the electrochemical production of chlorobenzene, comprising:

2. The electrochemical preparation method of chlorobenzene according to claim 1, wherein the volume ratio of benzene to hydrochloric acid is (1-2.5): 3.

3. the electrochemical preparation method of chlorobenzene according to claim 1, wherein the organic solvent is one of dichloroethane, dimethylsulfoxide, N-dimethylformamide, and hexafluoroisopropanol; the volume ratio of the organic solvent to chlorobenzene is 10: (2-3).

4. The method of claim 1, wherein the electrolyte comprises at least one of tetrabutylammonium tetrafluoroborate and tetraethyl tetrafluoroborate, and the concentration of the electrolyte is in the range of 0.1 to 0.5M.

5. The method of claim 1, wherein the electrolysis reaction is carried out in an integrated electrolytic cell equipped with a stirrer and an electrode.

6. The method of claim 1, wherein the anode used in the electrolysis comprises one of carbon sheet, graphite felt and carbon cloth; the cathode is one of a carbon sheet, an iron sheet, a stainless steel sheet, a platinum sheet and a nickel sheet.

7. The process of claim 1, wherein the hydrochloric acid is commercially available concentrated hydrochloric acid.

8. The method of claim 1, wherein the current of the electrolysis reaction is 20-800 mA.

9. The electrochemical preparation method of chlorobenzene according to claim 1, wherein the temperature of the electrolysis reaction is 0 to 40 ℃ and the time of the electrolysis reaction is 0.25 to 4 hours.

10. The method of claim 1, further comprising: after the reaction is finished, organic solvent is used for carrying out organic extraction on the electrolyte, and then separation and purification are carried out to obtain the chlorobenzene product, or the electrolyte is distilled and condensed at low temperature to obtain the chlorobenzene product.