An electrochemical preparation method of dichlorobenzene

Abstract

The present invention discloses an electrochemical method for preparing dichlorobenzene. The method comprises: uniformly mixing an organic solvent, chlorobenzene, hydrochloric acid, and an electrolyte, and conducting an electrolytic reaction in a constant current mode to obtain dichlorobenzene. The method uses hydrochloric acid as a chlorine source, and electrooxidizes chlorobenzene to produce dichlorobenzene with high Faradaic efficiency. Because the method directly uses inexpensive and readily available chlorobenzene 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, 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 dichlorobenzene. Background Art

[0002] Dichlorobenzene is an intermediate for the insecticide carbofuran, the herbicides dicamba and quizalofop-p-ethyl, as well as an intermediate for dyes and pharmaceuticals. It can also be used as a household insecticide and moth repellent.

[0003] The traditional synthesis of dichlorobenzene is separated from the by-products obtained by the direct chlorination reaction of chlorine with benzene using iron catalysis. This process releases a large amount of hydrogen chloride, which seriously pollutes the environment and corrodes the equipment. Therefore, the traditional dichlorobenzene synthesis method has the disadvantages of being cumbersome and not environmentally friendly.

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

[0005] The present invention aims to provide an electrochemical preparation method for dichlorobenzene, which realizes the conversion of chlorobenzene to dichlorobenzene in one step, with simple steps and environmental protection.

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

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

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

[0009] Furthermore, the organic solvent is one of N,N-dimethylformamide, dichloromethane, dichloroethane, and hexafluoroisopropanol, and the volume ratio of the organic solvent to the chlorobenzene is 10:(1-3).

[0010] Furthermore, the electrolyte includes at least one of tetrabutylammonium tetrafluoroborate (TBABF4) and tetraethyltetrafluoroboric acid, and the concentration 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 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 0.5-4 h.

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

[0017] The electrochemical preparation method of a kind of dichlorobenzene provided in the embodiment of the present invention, with hydrochloric acid as chlorine source, chlorobenzene is carried out chlorination reaction by electro-oxidation, under large current density, with high Faradaic efficiency, dichlorobenzene (including p-dichlorobenzene and o-dichlorobenzene) is obtained. Compared with the chlorination method of traditional benzene, this method is less polluting, does not need to use highly toxic chlorine, has high atom utilization rate, is weak to device corrosiveness, meets the requirements of green, safe production. Simple, efficient, easy to operate. Because this method directly uses cheap and easily available chlorobenzene and hydrochloric acid as raw materials, and the only by-product is hydrogen, it meets the requirements of green synthesis. And the Faradaic efficiency of the reaction is high, with good industrial application prospects. 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 dichlorobenzene. 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 present invention relates. 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 dichlorobenzene is provided, the method comprising:

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

[0026] The chemical equation for this reaction is:

[0027]

[0028] In the above technical solution,

[0029] The volume ratio of chlorobenzene to hydrochloric acid is (1-3):1. This volume ratio range is conducive to the complete completion of the reaction. Volume ratios outside the range of the present invention are not conducive to the conversion of chlorobenzene, and are likely to reduce Faradaic efficiency or release chlorine gas.

[0030] The organic solvent is one of N,N-dimethylformamide, dichloromethane, dichloroethane, and hexafluoroisopropanol. The volume ratio of the organic solvent to the dichlorobenzene is 10:(1-3). This volume ratio is conducive to the electrochemical reaction and improves the Faradaic efficiency of the product.

[0031] The electrolyte includes at least one of tetrabutylammonium tetrafluoroborate and tetraethyltetrafluoroboric acid. Such electrolytes are relatively stable and are not prone to side reactions.

[0032] The molar concentration of the electrolyte in the electrolytic solvent is in the range of 0.1 to 0.5M.

[0033] The hydrochloric acid is commercially available concentrated hydrochloric acid.

[0034] As a specific embodiment, in the electrolysis reaction, an integrated electrolytic cell equipped with a stirrer and electrodes is used.

[0035] 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 and a nickel sheet.

[0036] The current of the electrolysis reaction is 20-800 mA. This current range is conducive to the progress of the electrochemical reaction and is conducive to improving the Faradaic efficiency of the product.

[0037] The electrolysis reaction temperature is 0-40° C., and the electrolysis reaction time is 0.5-4 hours. The temperature of 0-40° C. can ensure the activity of the reaction without causing the hydrochloric acid or chlorine generated by electrolysis to volatilize due to excessively high temperature, thereby reducing the Faraday efficiency.

[0038] 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 dichlorobenzene, or performing distillation on the electrolyte and collecting the product dichlorobenzene through low-temperature condensation.

[0039] In summary, the present invention utilizes hydrochloric acid as a chlorine source to electrooxidize chlorobenzene to produce dichlorobenzene at a high current density and high Faradaic efficiency. This one-step conversion of chlorobenzene to dichlorobenzene is simple and environmentally friendly.

[0040] The following is a detailed description of the electrochemical preparation method of dichlorobenzene of the present application with reference to examples and comparative experimental data.

[0041] Example 1

[0042]

[0043] TBABF4 (1 mmol), concentrated hydrochloric acid (1 mL), chlorobenzene (1 mL), and hexafluoroisopropanol (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 3 hours at a constant current of 20.0 mA. At the end of the reaction, biphenyl was added as an internal standard, and GC quantification was performed. The Faradaic efficiency of the product, para-dichlorobenzene, was 30%, and that of o-dichlorobenzene was 16%.

[0044] Example 2

[0045]

[0046] 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 3 hours at a constant current of 20.0 mA. At the end of the reaction, biphenyl was added as an internal standard, and GC quantification was performed. The Faradaic efficiency of the product, para-dichlorobenzene, was 42%, and that of o-dichlorobenzene was 20%.

[0047] Example 3

[0048] In this example, the solvent was changed to ethylene dichloride, and other conditions were the same as in Example 2. The faradaic efficiency of the product p-dichlorobenzene was 40%, and the faradaic efficiency of o-dichlorobenzene was 17%.

[0049] Example 4

[0050] In this example, the solvent was changed to N,N-dimethylformamide, and other conditions were the same as those in Example 2. The faradaic efficiency of the product p-dichlorobenzene was 54%, and the faradaic efficiency of o-dichlorobenzene was 26%.

[0051] Example 5

[0052]

[0053] TBABF4 (1 mmol), concentrated hydrochloric acid (1 mL), chlorobenzene (1 mL), and dimethyl sulfoxide (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 Faradaic efficiency of the product, para-dichlorobenzene, was 52%, and that of o-dichlorobenzene was 26%.

[0054] Example 6

[0055] In this embodiment, the current is changed to 800.0 mA, the reaction time is changed to 30 min, and other conditions are the same as those in Example 5. The faradaic efficiency of the product p-dichlorobenzene is 54%, and the faradaic efficiency of o-dichlorobenzene is 26%.

[0056] Example 7

[0057] In this example, the temperature was changed to 0° C. Other conditions were the same as those in Example 5, and the faradaic efficiency of the product p-dichlorobenzene was 44%, and the faradaic efficiency of o-dichlorobenzene was 22%.

[0058] Example 8

[0059] In this example, the temperature was changed to 40° C. Other conditions were the same as those in Example 5, and the faradaic efficiency of the product p-dichlorobenzene was 53%, and the faradaic efficiency of o-dichlorobenzene was 26%.

[0060] Comparative Example 1

[0061] In Comparative Example 1, the hydrochloric acid was replaced with sodium chloride. The other steps were the same as those in Example 5, and the faradaic efficiency of the product p-dichlorobenzene was 2%, and the faradaic efficiency of o-dichlorobenzene was 1%.

[0062] Comparative Example 2

[0063] In Comparative Example 2, the volume ratio of chlorobenzene to hydrochloric acid was changed to 1:2. The other steps were the same as those in Example 5. The faradaic efficiency of the product p-dichlorobenzene was 25%, and the faradaic efficiency of o-dichlorobenzene was 13%.

[0064] Comparative Example 3

[0065] In Comparative Example 3, the organic solvent was replaced with DMSO. The other steps were the same as those in Example 5. The faradaic efficiency of the product p-dichlorobenzene was 8%, and the faradaic efficiency of o-dichlorobenzene was 5%.

[0066] Experimental Example 1

[0067] For the convenience of comparison, the experimental parameters of each embodiment and each comparative example are statistically analyzed as shown in Table 1.

[0068] Table 1

[0069]

[0070]

[0071] From the data in Table 1, we can see that:

[0072] In Comparative Example 1, hydrochloric acid was replaced with sodium chloride, and the faradaic efficiency of the product p-dichlorobenzene was as low as 2%, and the faradaic efficiency of o-dichlorobenzene was as low as 1%;

[0073] The volume ratio of chlorobenzene to hydrochloric acid is changed to 1:2, which is not within the range of 1:1 in Examples (1 to 3) of the present invention. This is not conducive to the conversion of chlorobenzene and is likely to reduce the Faradaic efficiency or release chlorine gas, resulting in a low Faradaic efficiency.

[0074] In Comparative Example 3, the organic solvent was replaced with DMSO, and the faradaic efficiency of the product p-dichlorobenzene was as low as 8%, and the faradaic efficiency of o-dichlorobenzene was as low as 5%.

[0075] In the embodiment of the present invention, the faradaic efficiency of the product p-dichlorobenzene is 30%-53%, and the faradaic efficiency of o-dichlorobenzene is 16-26%.

[0076] In Examples 1 to 6 of the present invention, the Faradaic efficiencies of the products p-dichlorobenzene and o-dichlorobenzene are both better than those of the comparative example, indicating that the product dichlorobenzene can be synthesized only when the reaction conditions are within the scope of the present invention.

[0077] 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.

[0078] 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.

[0079] 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 dichlorobenzene, characterized in that: The method comprises: An organic solvent, chlorobenzene, hydrochloric acid and an electrolyte are mixed and electrolytically reacted in a constant current mode to obtain dichlorobenzene; The volume ratio of the chlorobenzene to the hydrochloric acid is (1-3):1, the organic solvent is one of N,N-dimethylformamide, dichloromethane, dichloroethane, and hexafluoroisopropanol, the volume ratio of the organic solvent to the chlorobenzene is 10:(1-3), the current of the electrolysis reaction is 20-800 mA, the temperature of the electrolysis reaction is 0-40°C, and the time of the electrolysis reaction is 0.5-4 h.

2. The electrochemical preparation method of dichlorobenzene according to claim 1, characterized in that: The electrolyte includes at least one of tetrabutylammonium tetrafluoroborate and tetraethyltetrafluoroboric acid, and the concentration of the electrolyte is 0.1-0.5M.

3. The electrochemical preparation method of dichlorobenzene according to claim 1, characterized in that: In the electrolytic reaction, an integrated electrolytic cell equipped with a stirrer and electrodes is used.

4. The electrochemical preparation method of dichlorobenzene according to claim 1, characterized in that: 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 and a nickel sheet.

5. The electrochemical preparation method of dichlorobenzene according to claim 1, characterized in that: The hydrochloric acid is commercially available concentrated hydrochloric acid.

6. The electrochemical preparation method of dichlorobenzene 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 dichlorobenzene, or performing distillation on the electrolyte and collecting the product dichlorobenzene through low-temperature condensation.

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