Method for preparing halogenated xylene with high selectivity and halogenated xylene prepared by using method

Abstract

The invention provides a method for preparing halogenated xylene with high selectivity and halogenated xylene prepared by using the method. The preparation method comprises the following steps: a diazotization reaction step: carrying out diazotization reaction on diazonium salt and 3, 4-dimethylaniline or 3, 5-dimethylaniline to obtain diazonium liquid; and a Sandmeyer reaction step: mixing the diazonium liquid with cuprous halide, and then carrying out Sandmeyer reaction to obtain a reaction product containing halogenated xylene. The method for preparing halogenated xylene with high selectivity is simple and easy to implement, high in conversion rate, few in by-products, high in selectivity, easy to separate and purify and low in toxicity.

Description

Technical Field

[0001] The invention relates to a method for preparing halogenated xylene with high selectivity and halogenated xylene prepared by the method, and belongs to the field of organic synthesis. Background Art

[0002] Halogenated xylenes are an important class of chemical intermediates, widely used in the fields of pesticides, medicines, and dyes, such as 4-chloro-o-xylene, 4-bromo-o-xylene, or 3,5-dimethylchlorobenzene.

[0003] 4-Chlorophthalic anhydride, the oxidation product of 4-chloro-o-xylene, is an important raw material for the synthesis of polyimide engineering plastics. 4-Chloro-o-xylene is currently mainly prepared by chlorination of o-xylene, which generates isomers and polychlorinated side reaction products with low conversion rate and difficulty in separation, resulting in low yield.

[0004] It has been reported in the prior art that Lewis acid, molecular sieve, etc. can be used as catalysts to optimize the ratio of 4-chloro-o-xylene to 3-chloro-o-xylene and inhibit the formation of polychlorinated by-products. However, the following problems still exist: (1) low single-pass conversion rate, 75-80%; (2) high polychlorinated content, 3%-5%; (3) poor selectivity, 1-3.3:1; (4) difficult to separate and purify.

[0005] Reference 1 discloses the chlorination reaction of o-xylene catalyzed by ferric chloride, which mainly controls the generation of dichlorides. The single-pass conversion rate can only be controlled at 75% to 80%. At this time, the content of dichlorides has reached 3% to 4%, but the ratio of isomers in the chlorination reaction is not studied.

[0006] References 2 and 3 disclose feasibility studies on continuous chlorination reactions in autoclave and microchannel reactors in the presence of Lewis acids (including FeCl3, AlCl3, SnCl4, SbCl6, etc.). Continuous chlorination of xylene dissolved in saturated ferric chloride or antimony pentachloride can effectively reduce the production of dichloro compounds, but do not involve research on how to improve the isomer ratio and increase the single-pass conversion rate.

[0007] Reference 4 discloses the direct chlorination of o-xylene in liquid phase using FeCl3 as the main catalyst and a homemade thianthrene compound as a co-catalyst. The selectivity of the 4-isomer is improved from 1.370 to 3.313, the chlorination reaction rate is reduced, and a large amount of polychlorinated products are generated.

[0008] Reference 5 discloses that NH4 + , Li + , K +When modified NaX, NaY, and ZSM-5 molecular sieves were used as catalysts, the Y molecular sieve showed better para-selectivity. When the KY molecular sieve was used as catalyst, the molar ratio of 4-chloro-o-xylene to 3-chloro-o-xylene was only above 1.6, and no higher selectivity of 4-chloro-o-xylene was obtained.

[0009] Therefore, developing a method for preparing halogenated xylenes with high selectivity has become a technical problem that needs to be solved urgently.

[0010] References:

[0011] Document 1: CN1080278A

[0012] Document 2: CN108752161A

[0013] Document 3: CN113563153A

[0014] Reference 4: Lü Hongfei, Zhang Hui, Shan Zhipeng. Study on Selective Chlorination of o-Xylene[J]. Progress in Fine Petrochemicals, 2002, 3(5):3.

[0015] Reference 5: Lü Hongfei, Zhang Hui. Selective chlorination of o-xylene catalyzed by modified molecular sieve catalysts[J]. Petrochemicals, 2004, 33(11):4. Summary of the invention

[0016] Problem that the invention aims to solve

[0017] In view of the technical problems existing in the prior art, the present invention first provides a method for preparing halogenated xylenes with high selectivity. The method of the present invention is simple and easy to operate, has high conversion rate, few by-products, high selectivity, is easy to separate and purify, and has low toxicity.

[0018] The invention also provides a halogenated xylene product, the yield of which can reach more than 85% and the purity of which can reach more than 95%.

[0019] Solutions for solving problems

[0020] The present invention provides a method for preparing halogenated xylenes with high selectivity, which comprises the following steps:

[0021] Diazotization reaction step: subjecting the diazonium salt to diazotization reaction with 3,4-dimethylaniline or 3,5-dimethylaniline to obtain a diazo liquid;

[0022] Sandmeyer reaction step: the diazo liquid is mixed with cuprous halide and then subjected to Sandmeyer reaction to obtain a reaction product containing halogenated xylene.

[0023] According to the method of the present invention, before the diazotization reaction, the method further comprises the step of preparing a 3,4-dimethylaniline hydrochloride solution or a 3,5-dimethylaniline hydrochloride solution;

[0024] Preferably, the 3,4-dimethylaniline or the 3,5-dimethylaniline is mixed with a hydrochloric acid solution to obtain the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution;

[0025] More preferably, the temperature of the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is controlled to be 40-50°C.

[0026] According to the method of the present invention, the molar ratio of hydrogen chloride in the hydrochloric acid solution to the 3,4-dimethylaniline or the 3,5-dimethylaniline is 2 to 5:1; and / or,

[0027] The mass concentration of the hydrochloric acid solution is 10% to 15%.

[0028] According to the method of the present invention, a diazonium salt aqueous solution is mixed with the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution, and the diazonium salt is subjected to a diazotization reaction with the 3,4-dimethylaniline or the 3,5-dimethylaniline to obtain a diazo liquid;

[0029] Preferably, the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is added dropwise to the diazonium salt aqueous solution;

[0030] More preferably, the time for adding the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution dropwise to the diazonium salt aqueous solution is 0.5 to 1.5 hours;

[0031] Further preferably, the diazonium salt comprises sodium nitrite and / or potassium nitrite.

[0032] According to the method of the present invention, the molar ratio of the diazonium salt to the 3,4-dimethylaniline or the 3,5-dimethylaniline is 1.03 to 1.2:1; and / or,

[0033] The temperature of the diazotization reaction is -20 to 10°C, and the time of the diazotization reaction is 1 to 5 hours.

[0034] According to the method of the present invention, the cuprous halide is dissolved to obtain a cuprous halide solution, the cuprous halide solution is mixed with the diazo solution and subjected to a Sandmeyer reaction to obtain a reaction product containing halogenated xylene;

[0035] Preferably, the cuprous halide includes one or a combination of two or more of cuprous chloride, cuprous bromide, cuprous fluoride and cuprous iodide.

[0036] According to the method of the present invention, the cuprous halide is dissolved by an acidic substance to obtain the cuprous halide solution;

[0037] Preferably, the molar ratio of the acidic substance to the 3,4-dimethylaniline or the 3,5-dimethylaniline is 0.5-5:1.

[0038] According to the method of the present invention, the diazo liquid is added dropwise to the cuprous halide solution to carry out a Sandmeyer reaction. Preferably, the diazo liquid is added dropwise to the cuprous halide solution for a time of 0.5 to 3 hours.

[0039] According to the method of the present invention, the molar ratio of the cuprous halide to the 3,4-dimethylaniline or the 3,5-dimethylaniline is 0.2 to 1.0:1; and / or,

[0040] The temperature of the Sandmeyer reaction is 20-70° C., and the time of the Sandmeyer reaction is 0.1-2 hours.

[0041] The present invention provides a halogenated xylene, which is prepared by the preparation method of the present invention; preferably, the purity of the halogenated xylene is above 95%, preferably above 98%; the yield of the halogenated xylene is above 70%, preferably above 90%.

[0042] Effects of the Invention

[0043] The method for preparing halogenated xylene with high selectivity of the present invention is simple and easy to operate, has high conversion rate, few by-products, high selectivity, is easy to separate and purify, and has low toxicity.

[0044] The yield of the halogenated xylene product of the invention can reach more than 70%, and the purity can reach more than 95%. DETAILED DESCRIPTION

[0045] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0046] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0047] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0048] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0049] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0050] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0051] The present invention first provides a method for preparing halogenated xylenes with high selectivity, which comprises the following steps:

[0052] Diazotization reaction step: subjecting the diazonium salt to diazotization reaction with 3,4-dimethylaniline or 3,5-dimethylaniline to obtain a diazo liquid;

[0053] Sandmeyer reaction step: the diazo liquid is mixed with cuprous halide and then subjected to Sandmeyer reaction to obtain a reaction product containing halogenated xylene.

[0054] The method for preparing halogenated xylene with high selectivity of the present invention is simple and easy to operate, has high conversion rate, few by-products, high selectivity, is easy to separate and purify, and has low toxicity.

[0055] In some specific embodiments, before the diazotization reaction, the step of preparing 3,4-dimethylaniline hydrochloride solution or 3,5-dimethylaniline hydrochloride solution is also included. By preparing 3,4-dimethylaniline hydrochloride solution or 3,5-dimethylaniline hydrochloride solution, the reaction with the diazonium salt can be better performed.

[0056] Specifically, taking 3,4-dimethylaniline as an example, 3,4-dimethylaniline is mixed with a hydrochloric acid solution to obtain a 3,4-dimethylaniline hydrochloride solution. The hydrochloric acid solution can be an aqueous solution of hydrochloric acid, and concentrated hydrochloric acid can be first mixed with water and then mixed with 3,4-dimethylaniline.

[0057] At room temperature, 3,4-dimethylaniline is partially dissolved in a hydrochloric acid solution. When heated to 40-50°C at a suitable hydrochloric acid concentration, for example, 42°C, 44°C, 46°C, 48°C, etc., 3,4-dimethylaniline can be effectively dissolved, so that the 3,4-dimethylaniline hydrochloride solution is in a uniform phase, and when the diazotization reaction is carried out, it can fully react to form a diazo liquid, and the dripping of the 3,4-dimethylaniline hydrochloride solution can also prevent the decomposition of the diazo liquid. Therefore, the present invention can promote the dissolution of 3,4-dimethylaniline by using a hydrochloric acid solution, thereby forming a stable 3,4-dimethylaniline hydrochloride solution; and the hydrochloric acid solution can also promote the diazotization reaction and form a stable diazo liquid.

[0058] Similarly, 3,5-dimethylaniline can also be mixed with a hydrochloric acid solution to obtain a 3,5-dimethylaniline hydrochloride solution. The hydrochloric acid solution can be an aqueous solution of hydrochloric acid, and concentrated hydrochloric acid can be first mixed with water and then mixed with 3,5-dimethylaniline.

[0059] Specifically, in the present invention, the molar ratio of hydrogen chloride to 3,4-dimethylaniline or 3,5-dimethylaniline in the hydrochloric acid solution is 2 to 5:1, preferably 2.5 to 3.5:1, for example: 2.2:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, etc.

[0060] The present invention does not specifically limit the concentration of the hydrochloric acid solution, as long as 3,4-dimethylaniline hydrochloride or 3,5-dimethylaniline hydrochloride can be obtained. Preferably, the mass concentration of the hydrochloric acid solution is 10% to 15%, preferably 10% to 12%, for example: 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, etc.

[0061] In some specific embodiments, in order to make the reaction proceed better, the temperature of the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is controlled to 40-50°C, for example: 42°C, 44°C, 46°C, 48°C, etc. By controlling the temperature of the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution, 3,4-dimethylaniline or 3,5-dimethylaniline can be effectively dissolved, so that the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is a uniform phase. When the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is mixed with a diazonium salt aqueous solution, it can fully react to generate a diazonium liquid. If the temperature of the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is controlled too low, the 3,4-dimethylaniline or the 3,5-dimethylaniline will not be completely dissolved or solid will be precipitated; if the temperature of the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is controlled too high, it will be unfavorable for the generation of the diazo solution.

[0062] Specifically, water and concentrated hydrochloric acid are mixed and stirred evenly to obtain a hydrochloric acid solution, and then 3,4-dimethylaniline or 3,5-dimethylaniline is added to the hydrochloric acid solution to obtain a 3,4-dimethylaniline hydrochloride solution or a 3,5-dimethylaniline hydrochloride solution. Then, the temperature of the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is controlled to 40-50° C. by heating in a water bath and then kept warm.

[0063] In some specific embodiments, the aqueous diazonium salt solution is mixed with a 3,4-dimethylaniline hydrochloride solution or a 3,5-dimethylaniline hydrochloride solution to allow the diazonium salt to undergo a diazotization reaction with 3,4-dimethylaniline or 3,5-dimethylaniline to obtain a diazo liquid.

[0064] In some specific embodiments, 3,4-dimethylaniline hydrochloride solution or 3,5-dimethylaniline hydrochloride solution is added dropwise to the diazonium salt aqueous solution. More preferably, the time for adding 3,4-dimethylaniline hydrochloride solution or 3,5-dimethylaniline hydrochloride solution to the diazonium salt aqueous solution is 0.5 to 1.5 h, for example: 0.7 h, 0.9 h, 1.1 h, 1.3 h, etc.

[0065] In the present invention, in order to make the reaction safe and effective, before the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is added dropwise to the diazonium salt aqueous solution, the diazonium salt aqueous solution needs to be cooled. Specifically, the diazonium salt aqueous solution can be cooled to -20 to 10°C in an ice water bath, for example: -18°C, -15°C, -12°C, -10°C, -8°C, -5°C, -2°C, 0°C, 2°C, 5°C, 8°C, etc.

[0066] In some specific embodiments, the molar ratio of the diazonium salt to 3,4-dimethylaniline or 3,5-dimethylaniline is 1.03 to 1.2:1, for example: 1.05:1, 1.08:1, 1.1:1, 1.12:1, 1.15:1, 1.18:1, etc. When the molar ratio of the diazonium salt to 3,4-dimethylaniline or 3,5-dimethylaniline is 1.03 to 1.2:1, a chemical reaction can be carried out to prepare the required diazo solution. In addition, the mass concentration of the diazonium salt in the diazonium salt aqueous solution is not particularly limited in the present invention, and can generally be 1-50%, preferably 2-30%, for example: 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc.

[0067] The present invention does not particularly limit the conditions of the diazotization reaction, as long as the diazotization reaction can be carried out in an orderly manner. Preferably, the temperature of the diazotization reaction is -20 to 10°C, preferably -10 to 5°C, for example:, for example: -18°C, -15°C, -12°C, -10°C, -8°C, -5°C, -2°C, 0°C, 2°C, 5°C, 8°C, etc.; the time of the diazotization reaction is 1 to 5 hours, preferably 2 to 3 hours, for example: 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, etc.

[0068] In the present invention, the diazonium salt is not particularly limited. In order to better prepare the desired diazo liquid, nitrite can be used as the diazonium salt, for example, sodium nitrite and / or potassium nitrite.

[0069] Specifically, 3,4-dimethylaniline hydrochloride solution or 3,5-dimethylaniline hydrochloride solution is slowly added dropwise to a diazonium salt aqueous solution cooled in an ice water bath, and after the addition is completed, the solution is kept warm for reaction to obtain a diazonium solution.

[0070] In some specific embodiments, cuprous halide is dissolved to obtain a cuprous halide solution, the cuprous halide solution is mixed with the diazo solution and subjected to a Sandmeyer reaction to obtain a reaction product containing halogenated xylene.

[0071] Preferably, the cuprous halide includes one or a combination of two or more of cuprous chloride, cuprous bromide, cuprous fluoride and cuprous iodide.

[0072] In some specific embodiments, the cuprous halide is dissolved by an acidic substance to obtain a cuprous halide solution. Specifically, the cuprous halide can be dissolved by an aqueous solution of an acidic substance to obtain a cuprous halide solution.

[0073] The inventors of the present invention have found that after using an acidic substance to dissolve cuprous halide, the reaction process when the diazo liquid reacts with the cuprous halide is relatively stable and the reaction is more thorough. When the cuprous halide is directly added to the diazo liquid, or the diazo liquid is directly added dropwise to the cuprous halide, due to the uneven solid-liquid contact, there are many side reactions in the reaction process.

[0074] Preferably, the molar ratio of the acidic substance to 3,4-dimethylaniline or 3,5-dimethylaniline is 0.5-5:1, preferably 1-3:1, for example: 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, etc.

[0075] In some specific embodiments, the diazo liquid is added dropwise to the cuprous halide solution to carry out a Sandmeyer reaction. Preferably, the diazo liquid is added dropwise to the cuprous halide solution for 0.5 to 3 h, preferably 0.5 to 1.5 h, for example 1 h, 1.5 h, 2 h, 2.5 h, etc.

[0076] In some specific embodiments, the molar ratio of cuprous halide to 3,4-dimethylaniline or 3,5-dimethylaniline is 0.2-1.0:1, preferably 0.2-0.8:1, for example: 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, etc.

[0077] The temperature of the Sandmeyer reaction is 20-70°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, etc.; the time of the Sandmeyer reaction is 0.1-2 hours, for example, 0.5h, 1h, 1.5h, 2h, etc.

[0078] Specifically, cuprous halide is dissolved in an aqueous solution of an acidic substance, and a diazo solution is slowly added dropwise to the cuprous halide solution. After the addition is completed, a heat preservation reaction (i.e., Sandmeyer reaction) is performed, and after cooling, a post-treatment is performed to obtain halogenated xylene.

[0079] The present invention does not specifically limit the acidic substance, and it can be a common inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, etc., preferably hydrochloric acid. The present invention does not specifically limit the concentration of the acidic substance in the aqueous solution of the acidic substance, as long as it can dissolve the cuprous halide.

[0080] Finally, the present invention does not impose any particular limitation on post-treatment, as long as the desired halogenated xylene can be obtained. After the Sandmeyer reaction is completed, the halogenated xylene can be obtained by toluene extraction, liquid separation, and reduced pressure distillation.

[0081] The conditions for toluene extraction and reduced pressure distillation are not particularly limited in the present invention, and can be carried out by methods commonly used in the art.

[0082] In some specific embodiments, taking the reaction of 3,4-dimethylaniline as an example, the reaction formula of the relevant chemical reaction of the present invention can be shown as follows:

[0083]

[0084] The present invention also provides a halogenated xylene, such as 4-chloro-o-xylene, 4-bromo-o-xylene or 3,5-dimethylchlorobenzene, etc. The halogenated xylene can be prepared by the preparation method of the present invention; preferably, the purity of the halogenated xylene is above 95%, preferably above 98%, more preferably above 99%; the yield of the halogenated xylene is above 70%, preferably above 80%, more preferably above 85%.

[0085] Example

[0086] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0087] Example 1

[0088] (1) Hydrochloride solution: Weigh 95.2 g of 11.5% hydrochloric acid aqueous solution and add it into a reaction kettle. Add 12.1 g of 3,4-dimethylaniline while stirring. Heat the mixture in a water bath at 50°C and dissolve until it becomes clear.

[0089] (2) Diazotization: Weigh 7.2 g of sodium nitrite and dissolve it in 40 g of water, cool it in an ice-water bath, and stir it to obtain a sodium nitrite solution. Then slowly add 3,4-dimethylaniline hydrochloride solution to the sodium nitrite solution, control the temperature at -5°C, and complete the addition in about 1 hour. Keep the temperature for 2.5 hours to obtain a diazo solution.

[0090] (3) Sandmeyer reaction: 5.0 g of cuprous chloride was weighed and dissolved in 12.2 g of 30% hydrochloric acid solution at 40° C. by stirring, and the diazo solution was slowly added dropwise to the cuprous chloride solution. The addition was completed in about 1 hour. The reaction was kept warm for 0.5 hour. After cooling, a reaction product containing 4-chloro-o-xylene was obtained.

[0091] (4) The reaction product containing 4-chloro-o-xylene was extracted and separated by toluene, specifically, 25 g of toluene (twice) was added for extraction, and the separation obtained toluene organic phase 1, toluene organic phase 2 and aqueous phase 1; the toluene organic phase 1 and toluene organic phase 2 were combined, 50 mL of saturated sodium bicarbonate aqueous solution was added for neutralization, and the toluene organic phase 3 and aqueous phase 2 were separated; 3 g of anhydrous magnesium sulfate was added to the toluene organic phase 3 for drying, and the dried toluene organic phase 4 was obtained by filtration; the aqueous phase 1 and the aqueous phase 2 were combined and extracted by adding 20 g of toluene, and the toluene organic phase 5 and aqueous phase 3 were obtained by separation; the toluene organic phase 4 and the toluene organic phase 5 were combined. The purity of the control sample was 96.67% and the o-xylene was 1.37% by gas chromatography of the organic phase. Then, the toluene was distilled off and recovered at room temperature by reduced pressure distillation at 10 mmHg, and 4-chloro-o-xylene was obtained by saturated steam at about 59°C. The purity of 4-chloro-o-xylene was 99.8% by gas chromatography of the organic phase, and the yield was 92.21%.

[0092] Example 2

[0093] (1) Hydrochloride solution: Weigh 102.7 g of 10.7% hydrochloric acid aqueous solution and add it to a reaction kettle. Add 12.1 g of 3,4-dimethylaniline while stirring. Heat the mixture in a water bath at 40°C and dissolve until it becomes clear.

[0094] (2) Diazotization: Weigh 7.2 g of sodium nitrite and dissolve it in 58.7 g of water, cool it in an ice-water bath, and stir it to obtain a sodium nitrite solution. Then slowly add 3,4-dimethylaniline hydrochloride solution to the sodium nitrite solution, control the temperature at 5°C, and complete the addition in about 1 hour. Keep the temperature for 2.5 hours to obtain a diazo solution.

[0095] (3) Sandmeyer reaction: Weigh 5.0 g of cuprous chloride and dissolve it in 12.2 g of 30% hydrochloric acid aqueous solution at 40° C. with stirring. Slowly add the diazo solution dropwise to the cuprous chloride solution within 1 hour. Keep the temperature for 2 hours and cool to obtain a reaction product containing 4-chloro-o-xylene.

[0096] (4) The reaction product containing 4-chloro-o-xylene was extracted and separated by toluene, specifically, 25 g of toluene (twice) was added for extraction, and the separation obtained a toluene organic phase 1, a toluene organic phase 2 and an aqueous phase 1; the toluene organic phase 1 and the toluene organic phase 2 were combined, 50 mL of saturated sodium bicarbonate aqueous solution was added for neutralization, and the toluene organic phase 3 and the aqueous phase 2 were separated; 3 g of anhydrous magnesium sulfate was added to the toluene organic phase 3 for drying, and the dried toluene organic phase 4 was obtained by filtration; the aqueous phase 1 and the aqueous phase 2 were combined and extracted by adding 20 g of toluene, and the toluene organic phase 5 and the aqueous phase 3 were obtained by separation; the toluene organic phase 4 and the toluene organic phase 5 were combined. The purity of the control sample was 95.11% and the o-xylene was 2.68% by gas chromatography of the organic phase. Then, the toluene was distilled off and recovered at room temperature by reduced pressure distillation at 10 mmHg, and 4-chloro-o-xylene was obtained by saturated steam at about 59°C. The purity of 4-chloro-o-xylene was 99.6% by gas chromatography of the organic phase, and the yield was 88.49%.

[0097] Example 3

[0098] (1) Hydrochloride solution: Weigh 102.7 g of 10.7% hydrochloric acid aqueous solution and add it to a reaction kettle. Add 12.1 g of 3,4-dimethylaniline while stirring. Heat the mixture in a water bath at 40°C and dissolve until it becomes clear.

[0099] (2) Diazotization: Weigh 7.2 g of sodium nitrite and dissolve it in 58.7 g of water, cool it in an ice-water bath, and stir it to obtain a sodium nitrite solution. Then slowly add 3,4-dimethylaniline hydrochloride solution to the sodium nitrite solution, control the temperature at 5°C, and complete the addition in about 1 hour. Keep the temperature for 2.5 hours to obtain a diazo solution.

[0100] (3) Sandmeyer reaction: Weigh 3.0 g of cuprous chloride and dissolve it in 51.8 g of 4.4% hydrochloric acid solution at 40° C. with stirring. Slowly add the diazo solution dropwise to the cuprous chloride solution within 1 hour. Keep the temperature for reaction for 1 hour. After cooling, obtain a reaction product containing 4-chloro-o-xylene.

[0101] (4) The reaction product containing 4-chloro-o-xylene was extracted and separated by toluene, specifically, 25 g of toluene (twice) was added for extraction, and the separation obtained toluene organic phase 1, toluene organic phase 2 and aqueous phase 1; the toluene organic phase 1 and toluene organic phase 2 were combined, 50 mL of saturated sodium bicarbonate aqueous solution was added for neutralization, and the toluene organic phase 3 and aqueous phase 2 were separated; 3 g of anhydrous magnesium sulfate was added to the toluene organic phase 3 for drying, and the dried toluene organic phase 4 was obtained by filtration; the aqueous phase 1 and the aqueous phase 2 were combined and extracted by adding 20 g of toluene, and the toluene organic phase 5 and aqueous phase 3 were obtained by separation; the toluene organic phase 4 and the toluene organic phase 5 were combined. The purity of the control sample was 92.57% and the purity of o-xylene was 1.69% by gas chromatography of the organic phase. Then, the toluene was distilled off and recovered at room temperature by reduced pressure distillation at 10 mmHg, and 4-chloro-o-xylene was obtained by saturated steam at about 59°C. The purity of 4-chloro-o-xylene was 99.7% by gas chromatography of the organic phase, and the yield was 87.15%.

[0102] Example 4

[0103] (1) Hydrochloride solution: Weigh 102.7 g of 10.7% hydrochloric acid aqueous solution and add it to a reaction kettle. Add 12.1 g of 3,4-dimethylaniline while stirring. Heat the mixture in a water bath at 40°C and dissolve until it becomes clear.

[0104] (2) Diazotization: Weigh 7.2 g of sodium nitrite and dissolve it in 58.7 g of water, cool it in an ice-water bath, and stir it to obtain a sodium nitrite solution. Then slowly add 3,4-dimethylaniline hydrochloride solution to the sodium nitrite solution, control the temperature at 5°C, and complete the addition in about 1 hour. Keep the temperature for 2.5 hours to obtain a diazo solution.

[0105] (3) Sandmeyer reaction: Weigh 5.0 g of cuprous chloride, add it to 40°C diazo solution with stirring, keep the temperature to react for 2 h, and after cooling, obtain a reaction product containing 4-chloro-o-xylene.

[0106] (4) The reaction product containing 4-chloro-o-xylene was extracted and separated by toluene, specifically, 25 g of toluene (twice) was added for extraction, and the toluene organic phase 1, toluene organic phase 2 and aqueous phase 1 were obtained by separation; (2) the toluene organic phase 1 and toluene organic phase 2 were combined, 50 mL of saturated sodium bicarbonate aqueous solution was added for neutralization, and the toluene organic phase 3 and aqueous phase 2 were obtained by separation; (3) the toluene organic phase 3 was dried by adding 3 g of anhydrous magnesium sulfate, and the dried toluene organic phase 4 was obtained by filtration; (4) the aqueous phase 1 and the aqueous phase 2 were combined and extracted by adding 20 g of toluene, and the toluene organic phase 5 and the aqueous phase 3 were obtained by separation; (5) the toluene organic phase 4 and the toluene organic phase 5 were combined. The purity of the control sample was 84.36% and the purity of o-xylene was 2.10% by gas chromatography of the organic phase. Then, the toluene was distilled off and recovered at room temperature by reduced pressure distillation at 10 mmHg, and 4-chloro-o-xylene was obtained by saturated steam at about 59°C. The purity of 4-chloro-o-xylene detected by organic phase gas chromatography was 99.5%, and the yield was 79.56%.

[0107] Example 5

[0108] (1) Hydrochloride solution: Weigh 102.7 g of 10.7% hydrochloric acid aqueous solution and add it to a reaction kettle. Add 12.1 g of 3,4-dimethylaniline while stirring. Heat the mixture in a water bath at 40°C and dissolve until it becomes clear.

[0109] (2) Diazotization: Weigh 7.2 g of sodium nitrite and dissolve it in 58.7 g of water, cool it in an ice-water bath, and stir it to obtain a sodium nitrite solution. Then slowly add the sodium nitrite solution dropwise to the 3,4-dimethylaniline hydrochloride solution, control the temperature at 5°C, complete the addition in about 1 hour, and keep the temperature for 2.5 hours to obtain a diazo solution.

[0110] (3) Sandmeyer reaction: Weigh 5.0 g of cuprous chloride, add it to 40°C diazo solution with stirring, keep the temperature for reaction for 2 h, and after cooling, obtain a reaction product containing 4-chloro-o-xylene.

[0111] (4) The reaction product containing 4-chloro-o-xylene was extracted and separated by toluene, specifically, 25 g of toluene (twice) was added for extraction, and the separation obtained a toluene organic phase 1, a toluene organic phase 2 and an aqueous phase 1; the toluene organic phase 1 and the toluene organic phase 2 were combined, 50 mL of saturated sodium bicarbonate aqueous solution was added for neutralization, and the toluene organic phase 3 and the aqueous phase 2 were separated; 3 g of anhydrous magnesium sulfate was added to the toluene organic phase 3 for drying, and the dried toluene organic phase 4 was obtained by filtration; the aqueous phase 1 and the aqueous phase 2 were combined and extracted with 20 g of toluene, and the toluene organic phase 5 and the aqueous phase 3 were obtained by separation; the toluene organic phase 4 and the toluene organic phase 5 were combined. The purity of the control sample was 78.56% and the purity of o-xylene was 2.38% by gas chromatography of the organic phase. Then, the toluene was distilled off and recovered at room temperature by reduced pressure distillation at 10 mmHg, and 4-chloro-o-xylene was obtained by saturated steam at about 59°C. The purity of 4-chloro-o-xylene was 99.4% by gas chromatography of the organic phase, and the yield was 73.51%.

[0112] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0113] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing halogenated xylenes with high selectivity, characterized in that: The following steps are involved: Diazotization reaction step: subjecting the diazonium salt to diazotization reaction with 3,4-dimethylaniline or 3,5-dimethylaniline to obtain a diazo liquid; Sandmeyer reaction step: the diazo liquid is mixed with cuprous halide and then subjected to Sandmeyer reaction to obtain a reaction product containing halogenated xylene.

2. The method according to claim 1, characterized in that Before the diazotization reaction, the step of preparing a 3,4-dimethylaniline hydrochloride solution or a 3,5-dimethylaniline hydrochloride solution is also included; Preferably, the 3,4-dimethylaniline or the 3,5-dimethylaniline is mixed with a hydrochloric acid solution to obtain the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution; More preferably, the temperature of the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is controlled to be 40-50°C.

3. The method according to claim 2, characterized in that The molar ratio of hydrogen chloride in the hydrochloric acid solution to the 3,4-dimethylaniline or the 3,5-dimethylaniline is 2 to 5:1; and / or, The mass concentration of the hydrochloric acid solution is 10% to 15%.

4. The method according to claim 2 or 3, characterized in that: Mixing a diazonium salt aqueous solution with the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution to allow the diazonium salt to undergo a diazotization reaction with the 3,4-dimethylaniline or the 3,5-dimethylaniline to obtain a diazo liquid; Preferably, the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution is added dropwise to the diazonium salt aqueous solution; More preferably, the time for adding the 3,4-dimethylaniline hydrochloride solution or the 3,5-dimethylaniline hydrochloride solution dropwise to the diazonium salt aqueous solution is 0.5 to 1.5 hours; Further preferably, the diazonium salt comprises sodium nitrite and / or potassium nitrite.

5. The method according to claim 4, characterized in that The molar ratio of the diazonium salt to the 3,4-dimethylaniline or the 3,5-dimethylaniline is 1.03 to 1.2:1; and / or, The temperature of the diazotization reaction is -20 to 10°C, and the time of the diazotization reaction is 1 to 5 hours.

6. The method according to any one of claims 1 to 5, characterized in that: After dissolving the cuprous halide, a cuprous halide solution is obtained, and the cuprous halide solution is mixed with the diazo solution and subjected to a Sandmeyer reaction to obtain a reaction product containing halogenated xylene; Preferably, the cuprous halide includes one or a combination of two or more of cuprous chloride, cuprous bromide, cuprous fluoride and cuprous iodide.

7. The method according to claim 6, characterized in that Dissolving the cuprous halide by using an acidic substance to obtain the cuprous halide solution; Preferably, the molar ratio of the acidic substance to the 3,4-dimethylaniline or the 3,5-dimethylaniline is 0.5-5:

1.

8. The method according to claim 6 or 7, characterized in that: The diazo liquid is added dropwise to the cuprous halide solution to carry out a Sandmeyer reaction. Preferably, the diazo liquid is added dropwise to the cuprous halide solution for a time period of 0.5 to 3 hours.

9. The method according to any one of claims 1 to 8, characterized in that: The molar ratio of the cuprous halide to the 3,4-dimethylaniline or the 3,5-dimethylaniline is 0.2 to 1.0:1; and / or, The temperature of the Sandmeyer reaction is 20-70° C., and the time of the Sandmeyer reaction is 0.1-2 hours.

10. A halogenated xylene prepared by the preparation method according to any one of claims 1 to 9; preferably, the purity of the halogenated xylene is above 95%, preferably above 98%; the yield of the halogenated xylene is above 70%, preferably above 90%.

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