A kind of electrochemical preparation method of chlorobenzene

Abstract

The present invention discloses an electrochemical method for preparing chlorobenzene. The method comprises: uniformly mixing an organic solvent, benzene, hydrochloric acid, and an electrolyte, and conducting an electrolytic reaction in a constant current mode to obtain chlorobenzene. The method uses hydrochloric acid as a chlorine source, electrooxidizing benzene to carry out a chlorination reaction, thereby obtaining chlorobenzene with a high Faradaic efficiency. Because the method directly uses inexpensive and readily available benzene and hydrochloric acid as raw materials, and the only byproduct is hydrogen, it meets the requirements of green synthesis. Furthermore, the reaction has a high Faradaic efficiency, suggesting promising prospects for industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and in particular to an electrochemical preparation method of chlorobenzene. Background Art

[0002] Chlorobenzene is used to produce pesticides such as trichlorosulfone and DDT, and is also used in the synthesis of dyes, medicines and other organic chemical products. It is also used as a solvent for ethyl cellulose and many resins, and in the production of various intermediates, such as p-dichlorobenzene, p-chlorobenzenesulfonic acid, 2,4-dinitrochlorobenzene, o-nitrochlorobenzene, p-nitrochlorobenzene, nitrophenol, etc.

[0003] Traditional chlorobenzene synthesis involves a direct chlorination reaction between chlorine and benzene using iron as a catalyst. This process releases large amounts of hydrogen chloride, causing significant environmental pollution and corrosion to the equipment. Consequently, traditional chlorobenzene synthesis methods suffer from complex procedures and environmental concerns.

[0004] Therefore, it is necessary to develop an electrochemical preparation method for chlorobenzene to solve the above technical problems. Summary of the Invention

[0005] The present invention aims to provide an electrochemical preparation method for chlorobenzene, which realizes the conversion of benzene into chlorobenzene in one step, has simple steps and is environmentally friendly.

[0006] In order to achieve the above object, the present invention provides an electrochemical preparation method of chlorobenzene, which comprises:

[0007] An organic solvent, benzene, hydrochloric acid and electrolyte are mixed and electrolytic reaction is carried out in a constant current mode to obtain chlorobenzene.

[0008] Furthermore, the volume ratio of the benzene to the hydrochloric acid is (1-2.5):3.

[0009] Furthermore, the organic solvent is one of dichloroethane, dimethyl sulfoxide, N,N-dimethylformamide, and hexafluoroisopropanol; and the volume ratio of the organic solvent to chlorobenzene is 10:(2-3).

[0010] Furthermore, the electrolyte includes at least one of tetrabutylammonium tetrafluoroborate (TBABF4) and tetraethyltetrafluoroboric acid, and the concentration range of the electrolyte is 0.1 to 0.5M.

[0011] Furthermore, in the electrolysis reaction, an integrated electrolytic cell equipped with a stirrer and electrodes is used.

[0012] Furthermore, in the electrolysis reaction, the anode used includes one of a carbon sheet, graphite felt, and carbon cloth; and the cathode used is one of a carbon sheet, an iron sheet, a stainless steel sheet, a platinum sheet, and a nickel sheet.

[0013] Furthermore, the hydrochloric acid is commercially available concentrated hydrochloric acid.

[0014] Furthermore, the current of the electrolysis reaction is 20 to 800 mA.

[0015] Furthermore, the temperature of the electrolysis reaction is 0-40° C., and the time of the electrolysis reaction is 0.25-4 h.

[0016] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0017] An electrochemical preparation method of chlorobenzene provided in an embodiment of the present invention uses hydrochloric acid as a chlorine source, and chlorinates benzene by electrooxidation. Chlorobenzene is obtained at a high current density with a high Faradaic efficiency. Compared with traditional benzene chlorination methods, this method has low pollution, does not require the use of highly toxic chlorine, has a high atomic utilization rate, is weakly corrosive to the device, and meets the requirements of green and safe production. It is simple, efficient, and easy to operate. Since the method directly uses cheap and readily available benzene and hydrochloric acid as raw materials, and the only by-product is hydrogen, it meets the requirements of green synthesis. In addition, the reaction has a high Faradaic efficiency and has good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 The present invention provides a chemical reaction equation for an electrochemical method for preparing chlorobenzene. DETAILED DESCRIPTION

[0020] The following will be combined with specific implementation methods and examples to specifically describe embodiments of the present invention, and the advantages and various effects of the embodiments of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific implementation methods and examples are used to illustrate embodiments of the present invention, rather than to limit the embodiments of the present invention.

[0021] Throughout this specification, unless otherwise specified, the terms used herein should be understood to have the same meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the embodiments of the present invention belong. In the event of any conflict, the present specification shall take precedence.

[0022] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0023] The technical solution provided by the embodiments of the present invention is to solve the above technical problems, and the overall idea is based on the following:

[0024] According to a typical embodiment of the present invention, a method for electrochemically preparing chlorobenzene is provided, the method comprising:

[0025] An organic solvent, benzene, hydrochloric acid and electrolyte are mixed and electrolytic reaction is carried out in a constant current mode to obtain chlorobenzene.

[0026] The chemical equation for this reaction is:

[0027]

[0028] In the above technical solution,

[0029] The volume ratio of benzene to hydrochloric acid is (1-2.5):3. This volume ratio is conducive to the complete completion of the reaction. If the volume ratio is not within the range of the present invention, it is not conducive to the conversion of benzene, and is likely to reduce the Faradaic efficiency or release chlorine gas.

[0030] The organic solvent is one of dichloroethane, dimethyl sulfoxide, N,N-dimethylformamide, and hexafluoroisopropanol, and the volume ratio of the organic solvent to chlorobenzene is 10:(2-3).

[0031] The electrolyte comprises at least one of tetrabutylammonium tetrafluoroborate and tetraethyltetrafluoroboric acid, which are relatively stable and less prone to side reactions. The electrolyte concentration range is 0.1 to 0.5M.

[0032] The hydrochloric acid is commercially available concentrated hydrochloric acid.

[0033] In the electrolytic reaction, an integrated electrolytic cell equipped with a stirrer and electrodes is used.

[0034] In the electrolysis reaction, the anode used includes one of a carbon sheet, graphite felt, and carbon cloth; the cathode used is one of a carbon sheet, an iron sheet, a stainless steel sheet, a platinum sheet, and a nickel sheet.

[0035] The current of the electrolysis reaction is 20-800 mA, which is conducive to easier capture of chlorine radicals and chloride ions by benzene while preventing hydrogen chloride from being lost due to excessive temperature.

[0036] The electrolysis reaction temperature is 0-40° C., and the electrolysis reaction time is 0.25-4 hours. The reason for the temperature being 0-40° C. is to ensure the activity of the reaction without volatilizing the hydrochloric acid or chlorine generated by electrolysis due to the high temperature, thereby reducing the Faraday efficiency.

[0037] The method further comprises: after the reaction is completed, performing organic extraction on the electrolyte with an organic solvent and then separating and purifying to obtain the product chlorobenzene, or performing distillation on the electrolyte and collecting the product chlorobenzene by low-temperature condensation.

[0038] In summary, the present invention uses hydrochloric acid as a chlorine source to electrooxidize benzene to produce chlorobenzene at a high current density and high Faradaic efficiency. The conversion of chlorobenzene to chlorobenzene is achieved in a single step, which is simple and environmentally friendly.

[0039] The following is a detailed description of the electrochemical preparation method of chlorobenzene in the present application with reference to examples and comparative experimental data.

[0040] Example 1

[0041]

[0042] TBABF4 (1 mmol), concentrated hydrochloric acid (3 mmol), benzene (2 mmol), and dimethyl sulfoxide (10 mL) were added to a reaction tube under air atmosphere; carbon felt served as the anode and an iron sheet served as the 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, and GC quantification was performed. The product Faradaic efficiency was 78%.

[0043] Example 2

[0044] In this example, the solvent was changed to ethylene dichloride, and other conditions were the same as in Example 1. The Faradaic efficiency of the product was 85%.

[0045] Example 3

[0046]

[0047] TBABF4 (1 mmol), concentrated hydrochloric acid (1 mL), chlorobenzene (1 mL), and dichloromethane (10 mL) were added to a reaction tube under air atmosphere; carbon felt served as the anode and stainless steel served 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, and GC quantification was performed. The product Faradaic efficiency was 85%.

[0048] Example 4

[0049] In this embodiment, the current was changed to 800.0 mA, the reaction time was changed to 30 min, and other conditions were the same as those in Example 3. The Faradaic efficiency of the product was 82%.

[0050] Example 5

[0051] In this example, the temperature was changed to 40° C. Other conditions were the same as those in Example 3, and the Faradaic efficiency of the product was 90%.

[0052] Comparative Example 1

[0053] In Comparative Example 1, the hydrochloric acid was replaced with sodium chloride. The other steps were the same as those in Example 15, and the Faradaic efficiency of the product was 2%.

[0054] Comparative Example 2

[0055] In Comparative Example 2, the current was 1200 mA. The other steps were the same as in Example 15, and the Faradaic efficiency of the product was 54%.

[0056] Experimental Example 1

[0057] For the convenience of comparison, the experimental parameters of each embodiment and each comparative example are statistically analyzed as shown in Table 1.

[0058] Table 1

[0059]

[0060]

[0061] From the data in Table 1, we can see that:

[0062] In Examples 1 to 5 of the present invention, the Faradaic efficiency of the product chlorobenzene is better than that of the comparative example, indicating that the product chlorobenzene can be synthesized only when the reaction conditions are within the scope of the present invention.

[0063] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0064] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0065] Obviously, those skilled in the art may make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the embodiments of the present invention. Thus, if such changes and modifications 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 changes and modifications.

Claims

1. A method for electrochemically preparing chlorobenzene, characterized in that: The method comprises: An organic solvent, benzene, hydrochloric acid and an electrolyte are mixed and electrolytically reacted in a constant current mode to obtain chlorobenzene. The volume ratio of the benzene to the hydrochloric acid is (1-2.5):

3. 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). The electrolyte includes at least one of tetrabutylammonium tetrafluoroborate and tetraethyltetrafluoroboric acid. The concentration range of the electrolyte is 0.1-0.5 M. In the electrolytic reaction, an integrated electrolytic cell equipped with a stirrer and an electrode is used. In the electrolytic reaction, the anode used includes one of a carbon sheet, graphite felt and carbon cloth. The cathode used is one of a carbon sheet, an iron sheet, a stainless steel sheet, a platinum sheet and a nickel sheet. The hydrochloric acid is commercially available concentrated hydrochloric acid. The current of the electrolytic reaction is 20-800 mA. The temperature of the electrolytic reaction is 0-40° C. and the time of the electrolytic reaction is 0.25-4 h.

2. The electrochemical preparation method of chlorobenzene according to claim 1, characterized in that: The method further comprises: after the reaction is completed, performing organic extraction on the electrolyte with an organic solvent and then separating and purifying to obtain the product chlorobenzene, or performing distillation on the electrolyte and collecting the product chlorobenzene by low-temperature condensation.

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