Method for preparing 2, 6-dichloro-3, 5-di-tert-butyltoluene with high selectivity

Abstract

The invention provides a method for preparing an intermediate 2, 6-dichloro-3, 5-di-tert-butyl toluene for synthesizing 2, 6-dichlorotoluene, and the method comprises the following steps: (1) first-stage chlorination reaction: in the presence of a solvent, a first catalyst and a first auxiliary agent, reacting 3, 5-di-tert-butyl toluene with chlorine to obtain 2-chloro-3, 5-di-tert-butyl toluene; and (2) a second-stage chlorination reaction: in the presence of a second catalyst and a second auxiliary agent, carrying out a reaction on the 2-chloro-3, 5-di-tert-butyl toluene and chlorine to obtain the 2, 6-dichloro-3, 5-di-tert-butyl toluene.

Description

Technical Field

[0001] The invention relates to a method for preparing 2,6-dichlorotoluene, in particular to a method for preparing 2,6-dichloro-3,5-di-tert-butyltoluene, an intermediate for synthesizing 2,6-dichlorotoluene. The method is carried out through a step-by-step chlorination reaction. Background Art

[0002] 2,6-Dichlorotoluene is an important fine chemical intermediate, which can be further used to produce 2,6-dichlorobenzoic acid, 2,6-dichlorobenzaldehyde, 2,6-dichlorobenzonitrile and 2,6-dichloroaniline, etc. It is an important fine chemical raw material for the manufacture of fungicides, insecticides, herbicides, dyes and pigments, medicines and other chemical products.

[0003] There are four main methods for synthesizing 2,6-dichlorotoluene: (1) continuous chlorination of toluene. This method has simple steps, but produces a large number of isomers, low yield, and difficulty in separating and purifying the product; (2) directional chlorination of p-toluenesulfonyl chloride. This process has unstable product quality and produces a large amount of three wastes, making it unsuitable for industrial production; (3) o- / p-nitrotoluene. This process has a long process flow, many steps, a high risk factor for diazotization reaction, a large amount of three wastes, high cost, high pollution, low yield, and little industrial value; (4) alkyltoluene chlorination. This process introduces a tert-butyl directing group into toluene, has mild reaction conditions, and high product selectivity.

[0004] In the art, there are increasing studies on the chlorination of 3,5-di-tert-butyltoluene to synthesize 2,6-dichlorotoluene. In the prior art, aluminum trichloride and composite catalysts containing aluminum trichloride are mostly used for the chlorination reaction of 3,5-di-tert-butyltoluene. Aluminum trichloride is a common highly active Lewis acid that can be used as a catalyst for both Friedel-Crafts alkylation and dealkylation. Therefore, when aluminum trichloride is added during the chlorination of alkyltoluene, dealkylation is likely to occur, and the functional group localization effect is reduced, resulting in poor selectivity of the chlorination reaction. The prior art method for solving this problem is to add a sulfur-containing auxiliary agent to form a coordination with aluminum trichloride, reduce the activity of aluminum trichloride, and inhibit the dealkylation side reaction. However, due to problems such as the solubility of the auxiliary agent in the system, the selectivity of the target product is still not high, the reaction yield is usually no more than 80%, and the amount of catalyst and auxiliary agent added is too much, resulting in high cost of use.

[0005] Therefore, there is an urgent need in the art to develop an improved method for preparing 2,6-dichloro-3,5-di-tert-butyltoluene with high selectivity. Summary of the invention

[0006] A first aspect of the present invention provides a method for preparing 2,6-dichloro-3,5-di-tert-butyltoluene, the method comprising the following steps:

[0007] (1) a first-stage chlorination reaction: reacting 3,5-di-tert-butyltoluene with chlorine in the presence of a solvent, a first catalyst, and a first auxiliary agent to obtain 2-chloro-3,5-di-tert-butyltoluene;

[0008] (2) Two-stage chlorination reaction: In the presence of a second catalyst and a second auxiliary agent, 2-chloro-3,5-di-tert-butyltoluene is reacted with chlorine to obtain 2,6-dichloro-3,5-di-tert-butyltoluene.

[0009] In one embodiment of the present invention, the first catalyst and the second catalyst are Lewis acid catalysts, and the Lewis acid strength of the first catalyst is smaller than that of the second catalyst.

[0010] In one embodiment of the present invention, in step (1), the solvent comprises a C1-C6 alkane substituted with a halogen atom.

[0011] In one embodiment of the present invention, the mass ratio of the solvent to 3,5-di-tert-butyltoluene is (0-8):1.

[0012] In one embodiment of the present invention, the first catalyst comprises at least one Lewis acid catalyst selected from the group consisting of: FeCl 3 、ZnCl 2 、ZrCl 4 ,FeS,FeS 2 , ZnS, CoS and CdS.

[0013] In one embodiment of the present invention, the amount of the first catalyst used is 0.1-2 mass % of 3,5-di-tert-butyltoluene.

[0014] In one embodiment of the present invention, the first auxiliary agent comprises at least one auxiliary agent selected from the group consisting of insoluble sulfur, polyphenylene sulfide resin, methyl mercaptan resin, isothiourea resin and mercapto resin.

[0015] In one embodiment of the present invention, the amount of the first auxiliary agent is 1-10 mass % of 3,5-di-tert-butyltoluene.

[0016] In one embodiment of the present invention, the chlorination reaction temperature in step (1) is 20-60°C.

[0017] In one embodiment of the present invention, the amount of chlorine used in step (1) is 0.9-1.1 times the molar amount of 3,5-di-tert-butyltoluene.

[0018] In one embodiment of the present invention, the second catalyst comprises at least one Lewis acid catalyst selected from the group consisting of: AlCl 3 、TiCl 4 、SbCl3 and SnCl 4 .

[0019] In one embodiment of the present invention, the amount of the second catalyst used is 0.2-2% by mass of 3,5-di-tert-butyltoluene.

[0020] In one embodiment of the present invention, the second adjuvant comprises at least one sulfur-containing organic sulfur compound.

[0021] In one embodiment of the present invention, the amount of the second auxiliary agent is 0.1-5% by mass of 3,5-di-tert-butyltoluene.

[0022] In one embodiment of the present invention, the chlorination reaction temperature in step (2) is 40-80°C.

[0023] In one embodiment of the present invention, the total amount of chlorine used in step (1) and step (2) is 1.9-2.2 times the molar amount of 3,5-di-tert-butyltoluene.

[0024] The second aspect of the present invention provides a 2,6-dichloro-3,5-di-tert-butyltoluene product prepared by the method for preparing 2,6-dichloro-3,5-di-tert-butyltoluene according to the present invention.

[0025] The third aspect of the present invention provides a method for preparing 2,6-dichlorotoluene, which comprises subjecting 2,6-dichloro-3,5-di-tert-butyltoluene prepared by the method according to the present invention to a dealkylation reaction.

[0026] The fourth aspect of the present invention provides a 2,6-dichlorotoluene product prepared by the method for preparing 2,6-dichlorotoluene according to the present invention.

[0027] The advantages of this application are:

[0028] According to the substrate characteristics of the chlorinated raw materials, the invention adopts segmented chlorination, accurately controls the chlorination conditions and the types of catalysts, and improves the selectivity of the target product. The selectivity of 2,6-dichloro-3,5-di-tert-butyltoluene reaches more than 95%, and the impurity 2,4-dichlorotoluene products (including four impurities, namely, 2,4-dichloro-3,5-di-tert-butyltoluene, 2,4,6-trichloro-3-tert-butyltoluene, 2,4-dichloro-3-tert-butyltoluene and 4-chloro-3,5-di-tert-butyltoluene) does not exceed 3%.

[0029] The raw materials used in the method of the present invention are simple and easy to obtain, the amount of high-activity catalyst and auxiliary agent added is small, and the first-stage chlorination auxiliary agent can be recycled, which effectively reduces the auxiliary agent use cost and improves the economic efficiency of the process route. DETAILED DESCRIPTION

[0030] "Scope" disclosed herein is defined in the form of lower limit and upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The scope defined in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a particular parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0031] In this application, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0032] In this application, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0033] In the present application, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0034] In this application, unless otherwise specified, the terms "include" and "comprising" mentioned herein may be open-ended or closed-ended. For example, the terms "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0035] In the description of this article, it should be noted that, unless otherwise specified, "above" and "below" are inclusive of the number itself, and "several" in "one or several" means two or more.

[0036] In the description herein, unless otherwise specified, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0037] Herein, unless otherwise specified, percentage (%) or part refers to percentage by weight or part by weight relative to the composition.

[0038] Herein, if there is no contrary description, the sum of the contents of the various components in the composition is 100%.

[0039] Herein, if there is no contrary description, the sum of the parts of each component in the composition may be 100 parts by weight.

[0040] In this context, unless otherwise specified, "a combination thereof" means a multi-component mixture of the elements described, for example a mixture of two, three, four and up to the maximum possible multi-component mixture.

[0041] If not specifically stated, the terms "a" or "an" used in the present specification means "at least one".

[0042] Herein, unless otherwise stated, all reactions are carried out at normal temperature and pressure.

[0043] Herein, unless otherwise specified, the term "alkyl" refers to a straight or branched chain saturated hydrocarbon group having one or more carbon atoms, including a C1-C20 alkyl group, preferably a C1-C6 alkyl group.

[0044] Herein, the term "contains" or "includes" or "uses" indicates that various components can be used together in the mixture or composition of the present disclosure. It should be understood that the degree of "high", "low", etc. used in the present disclosure is well known in the art.

[0045] In the present invention, the chlorination reaction of 3,5-di-tert-butyltoluene can be divided into two steps, namely, main reaction 1 and main reaction 2, wherein the first stage chlorination reaction produces 2-chloro-3,5-di-tert-butyltoluene, and the second stage chlorination reaction produces 2,6-dichloro-3,5-di-tert-butyltoluene:

[0046] Main reaction 1:

[0047]

[0048] Main reaction 2:

[0049]

[0050] During the chlorination process, the following side reaction occurs, namely, the removal of a tert-butyl group under the catalysis of aluminum chloride to generate para- and meta-position impurities:

[0051] Side reaction 1:

[0052]

[0053] Side reaction 2:

[0054]

[0055] Side reaction 3:

[0056]

[0057] At the same time, a small amount of 4-chloro-3,5-dichlorotoluene is also produced, and chlorination continues to produce 2,4-dichloro-3,5-dichlorotoluene:

[0058] Side reaction 4:

[0059]

[0060] The main impurities include 2,4-dichloro-3,5-di-tert-butyltoluene, 2,4,6-trichloro-3-tert-butyltoluene, 2,4-dichloro-3-tert-butyltoluene and 4-chloro-3,5-di-tert-butyltoluene.

[0061] The present invention adopts a step-by-step chlorination method. Since the activity of the chlorinated substrate in the first stage is high, the Lewis acid used in the chlorination in the first stage is weaker than the Lewis acid used in the chlorination in the second stage; the auxiliary agent used in the first stage is a sulfur-containing polymer; and the auxiliary agent used in the second stage is an organic sulfide. According to the different activities of the two-step chlorinated substrates, the different reaction conditions of the two-step chlorination are controlled, and the types and amounts of catalysts and auxiliary agents are added to achieve high-selectivity preparation of 2,6-dichloro-3,5-di-tert-butyltoluene, and the present invention is realized on this basis.

[0062] The present invention provides a method for preparing 2,6-dichloro-3,5-di-tert-butyltoluene, the method comprising the following steps:

[0063] (1) a first-stage chlorination reaction: reacting 3,5-di-tert-butyltoluene with chlorine in the presence of a solvent, a first catalyst, and a first auxiliary agent to obtain 2-chloro-3,5-di-tert-butyltoluene;

[0064] (2) Two-stage chlorination reaction: In the presence of a second catalyst and a second auxiliary agent, 2-chloro-3,5-di-tert-butyltoluene is reacted with chlorine to obtain 2,6-dichloro-3,5-di-tert-butyltoluene.

[0065] In a specific embodiment of the present invention, the first catalyst and the second catalyst are Lewis acid catalysts. Due to the different activities of the two-stage chlorinated substrates, the Lewis acid strength of the first catalyst is smaller than that of the second catalyst.

[0066] The present invention uses halogenated hydrocarbons as solvents, and the "halogenated hydrocarbons" refer to compounds in which hydrogen atoms in hydrocarbon molecules are replaced by halogen atoms, preferably C1-C6 alkanes substituted by chlorine atoms. Preferably, the solvent includes at least one halogenated hydrocarbon selected from the group consisting of dichloromethane, chloroform, carbon tetrachloride, ethyl chloride, dichloroethane, trichloroethane, tetrachloroethane, chloropropane and chlorobutane, and the solvent preferably includes at least one halogenated hydrocarbon selected from the group consisting of dichloroethane, chloroform, carbon tetrachloride, dichloromethane and chlorobutane.

[0067] In a specific embodiment of the present invention, the mass ratio of the solvent to 3,5-di-tert-butyltoluene is (0-8):1, preferably (2-5):1, and more preferably (3-4):1.

[0068] In one embodiment of the present invention, the first catalyst comprises at least one Lewis acid catalyst selected from the group consisting of: FeCl 3 、ZnCl 2 、ZrCl 4 ,FeS,FeS 2 , ZnS, CoS and CdS; preferably, the first catalyst comprises at least one Lewis acid catalyst selected from the group consisting of: FeCl 3 、ZnCl 2 、ZrCl 4 and FeS.

[0069] In a specific embodiment of the present invention, the amount of the first catalyst used is 0.1-2% by mass, preferably 0.5-1% by mass, of 3,5-di-tert-butyltoluene.

[0070] In a specific embodiment of the present invention, the first auxiliary agent includes at least one auxiliary agent selected from the group consisting of insoluble sulfur, polyphenylene sulfide resin, methyl mercaptan resin, isothiourea resin and mercapto resin. Preferably, the first auxiliary agent includes insoluble sulfur or polyphenylene sulfide resin.

[0071] In a specific embodiment of the present invention, the amount of the first auxiliary agent is 1-10% by mass, preferably 5-10% by mass, of 3,5-di-tert-butyltoluene.

[0072] In a specific embodiment of the present invention, the chlorination reaction temperature in step (1) is 20-60°C.

[0073] In a specific embodiment of the present invention, the amount of chlorine used in step (1) is 0.9-1.1 times the molar amount of 3,5-di-tert-butyltoluene.

[0074] In one embodiment of the present invention, the second catalyst comprises at least one Lewis acid catalyst selected from the group consisting of: AlCl 3 、TiCl 4 、SbCl 3 and SnCl 4 .

[0075] In a specific embodiment of the present invention, the amount of the second catalyst used is 0.2-2% by mass, preferably 0.3-1% by mass, and more preferably 0.5-0.8% by mass of 3,5-di-tert-butyltoluene.

[0076] In a specific embodiment of the present invention, the second auxiliary agent includes a sulfur-containing organic sulfur compound. Preferably, the second auxiliary agent includes at least one organic sulfide selected from the group consisting of methyl mercaptan, thiophenol, dibutyl sulfide, methyl sulfide, diphenyl disulfide, diphenyl sulfide and disulfur dichloride.

[0077] In a specific embodiment of the present invention, the dosage of the second auxiliary agent is 0.1-5% by mass, preferably 0.2-5% by mass, and more preferably 2-5% by mass of 3,5-di-tert-butyltoluene.

[0078] In a specific embodiment of the present invention, the chlorination reaction temperature in step (2) is 40-80°C.

[0079] In a specific embodiment of the present invention, the total amount of chlorine used in step (1) and step (2) is 1.9-2.2 times the molar amount of 3,5-di-tert-butyltoluene.

[0080] In a specific embodiment of the present invention, the first stage chlorination reaction is carried out as follows: under nitrogen protection conditions, a certain amount of 3,5-di-tert-butyltoluene and a solvent are added to the reactor, and then a certain amount of the first catalyst and the first auxiliary agent are added, and a certain chlorination reaction temperature is controlled, chlorine is introduced, and the amount of chlorine introduced is controlled. After the reaction is completed, the chlorination auxiliary agent is filtered and recovered to obtain a monochlorinated product; the second stage chlorination reaction is carried out as follows: the second catalyst and the second auxiliary agent are added to the monochlorinated product in step 1, a certain reaction temperature is controlled, chlorine is continued to be introduced, and the amount of chlorine introduced is controlled. After the conversion rate of the monochlorinated product is greater than 99%, the reaction is stopped.

[0081] The present invention also provides a method for preparing 2,6-dichlorotoluene, which comprises carrying out a dealkylation reaction on 2,6-dichloro-3,5-di-tert-butyltoluene prepared by the method according to the present invention.

[0082] In a specific embodiment of the present invention, the method for preparing 2,6-dichlorotoluene is carried out as follows: 500 kg of 2,6-dichloro-3,5-di-tert-butyltoluene and 1000 kg of toluene are taken, and two tert-butyltoluenes are removed at room temperature for 3-4 hours under the action of 5 kg of catalyst to obtain a reaction liquid containing 2,6-dichlorotoluene. After post-treatment and distillation of the reaction liquid, 285 kg of 2,6-dichlorotoluene with a purity of more than 99.9% is separated.

[0083] Unless otherwise specified, the various raw materials of the present application can be obtained from the market; or prepared according to conventional methods in the art. Unless otherwise defined or specified, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein can be applied to the methods disclosed herein. Other aspects of the present disclosure are obvious to those skilled in the art due to the disclosure herein.

[0084] Example

[0085] The present disclosure will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present disclosure and are not intended to limit the scope of the present disclosure. The experimental methods for which specific conditions are not specified in the following examples are usually measured in accordance with national standards. If there is no corresponding national standard, then it is carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer. Unless otherwise stated, all parts are parts by weight, all percentages are percentages by weight, and the polymer molecular weight is the number average molecular weight.

[0086] Raw material sources and preparation

[0087] 3,5-di-tert-butyltoluene was purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.;

[0088] Ethylene dichloride was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0089] Ammonia water, concentration 25-28%, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0090] Polyphenylene sulfide resin was purchased from Xinhecheng Co., Ltd.

[0091] Ferric chloride was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0092] Diphenyl disulfide was purchased from Shanghai Haohong Biopharmaceutical Technology Co., Ltd.;

[0093] Anhydrous aluminum chloride was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0094] Chloroform was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0095] Insoluble sulfur was purchased from Yanggu Huatai Chemical Co., Ltd.;

[0096] Zirconium tetrachloride was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0097] Dibutyl sulfide was purchased from Shanghai Haohong Biopharmaceutical Technology Co., Ltd.;

[0098] Anhydrous titanium tetrachloride was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0099] Example 1

[0100] Prepare 2,6-dichloro-3,5-di-tert-butyltoluene by the following steps:

[0101] Add 500kg 3,5-di-tert-butyltoluene, 1000kg dichloroethane, 25kg polyphenylene sulfide resin and 5kg ferric chloride to the reactor, heat it to 50°C, and introduce chlorine. When the molar amount of chlorine is 0.9 times that of 3,5-dichloro-tert-butyltoluene, the first stage of chlorination is completed. Liquid filter the reaction liquid to remove the resin and transfer it to the second stage chlorination reactor. Add 5kg diphenyl disulfide and 2.5kg anhydrous aluminum chloride, heat it to 50°C, introduce chlorine until the total molar amount of chlorine is 2.05 times that of 3,5-dichloro-tert-butyltoluene. The second stage of chlorination is completed. Nitrogen is introduced into the reactor to purge the unreacted chlorine. Samples are taken for gas chromatography analysis. According to the gas spectrum normalization results, 3,5-di-tert-butyltoluene is not detected in the chlorinated liquid, and 2,6-dichloro-3- The content of tert-butyltoluene is 0.53%, the content of 2,6-dichloro-3,5-di-tert-butyltoluene is 95.14%, the content of 2,4-dichloro-3-tert-butyltoluene is 0.76%, the content of 2,4-dichloro-3,5-di-tert-butyltoluene is 0.57%, the content of 2,4,6-trichloro-3-tert-butyltoluene is 0.28%, the selectivity of 2,6-dichloro-3,5-di-tert-butyltoluene is 96.5%, and the total selectivity of the main impurity 2,4-dichlorotoluene impurities is 1.5%.

[0102] 2,6-dichloro-3,5-di-tert-butyltoluene selectivity = (normalized content of 2,6-dichloro-3-tert-butyltoluene in reaction solution + normalized content of 2,6-dichloro-3-tert-butyltoluene) / (content of 3,5-di-tert-butyltoluene in raw material - content of 3,5-di-tert-butyltoluene in reaction solution)

[0103] 2,4-Dichlorotoluene impurity selectivity = (normalized content of 2,4-dichloro-3-tert-butyltoluene in the reaction solution + normalized content of 2,4-dichloro-3,5-di-tert-butyltoluene + normalized content of 2,4,6-trichloro-3-tert-butyltoluene + normalized content of 4-chloro-3,5-di-tert-butyltoluene) / (3,5-di-tert-butyltoluene content in the raw material - 3,5-di-tert-butyltoluene content in the reaction solution)

[0104] Example 2

[0105] Using the same reaction apparatus as in Example 1, 500 kg of 3,5-di-tert-butyltoluene, 1500 kg of chloroform, 50 kg of insoluble sulfur and 2.5 g of zirconium tetrachloride were added to the reactor, the temperature was raised to 30° C., chlorine was introduced, and the first stage of chlorination was completed when the molar amount of chlorine was 1.1 times that of 3,5-dichloro-tert-butyltoluene. The reaction liquid was filtered to remove the insoluble sulfur and transferred to the second stage chlorination reactor. 1 kg of dibutyl sulfide and 4 kg of anhydrous titanium tetrachloride were added, the temperature was raised to 45° C., chlorine was introduced, and the second stage of chlorination was completed when the total molar amount of chlorine was 2.1 times that of 3,5-dichloro-tert-butyltoluene. Nitrogen was introduced into the reactor to purge unreacted chlorine, and sampling was performed for gas chromatography analysis. 3,5-dichlorotoluene was completely converted, the selectivity of 2,6-dichloro-3,5-di-tert-butyltoluene was 98%, and the selectivity of the main impurity 2,4-dichlorotoluene was 1.5%.

[0106] Examples 3-6 all used the same reaction apparatus as Example 1, and were carried out according to the steps and conditions of Example 1, with only the amount and type of solvent being changed. The type, amount and chlorination effect of the solvent used are shown in Table 1:

[0107] Table 1 Chlorination effect of Examples 3-6

[0108]

[0109] It can be seen from the data in Table 1 that according to the method of the present invention, 2,6-dichloro-3,5-di-tert-butyltoluene can be prepared with high selectivity without using a solvent, and the use of a solvent can further improve the selectivity of preparing 2,6-dichloro-3,5-di-tert-butyltoluene.

[0110] Examples 7-11 all use the same reaction apparatus as Example 1, and are carried out according to the steps and conditions of Example 1, except that only the amount and type of the second-stage chlorination aid are changed. The type, amount and chlorination effect of the second-stage chlorination aid used are shown in Table 2:

[0111] Table 2: Chlorination effects of Examples 7-11

[0112]

[0113] It can be seen from the data in Table 2 that the use of organic sulfur compounds containing divalent sulfur as the second-stage auxiliary agent can prepare 2,6-dichloro-3,5-di-tert-butyltoluene with higher selectivity.

[0114] Examples 12-16 all used the same reaction apparatus as Example 1, and were carried out according to the steps and conditions of Example 1, with only the catalysts and types of the first and second stages being changed. The types of catalysts used and the chlorination effects are shown in Table 3:

[0115] Table 3: Chlorination Effects of Examples 12-16

[0116]

[0117] Comparative Example 1-2: According to the steps and conditions of Example 1, a one-stage method is adopted. The types of catalysts, types of additives and chlorination effects used are shown in Table 4:

[0118] Table 4: Chlorination effect of comparative example 1-2

[0119]

[0120] It can be seen from the data in Table 4 that, compared with the use of a single Lewis acid catalyst and auxiliary agent, the use of different Lewis acid catalysts and auxiliary agents in the two-stage chlorination reaction can significantly improve the selectivity of preparing 2,6-dichloro-3,5-di-tert-butyltoluene. In addition, the method of the present invention can significantly improve the selectivity of preparing 2,6-dichloro-3,5-di-tert-butyltoluene by using a small amount of catalyst and auxiliary agent.

[0121] Examples 17-21 all used the same reaction apparatus as Example 1, and were carried out according to the steps and conditions of Example 1, except that the polyphenylene sulfide resin of the first stage was repeatedly applied. The chlorination effects are shown in Table 5:

[0122] Table 5: Chlorination Effects of Examples 17-21

[0123]

[0124] It can be seen from the data in Table 5 that the chlorination auxiliary agent in the first stage of the present invention can be recycled for multiple times, and a relatively high selectivity of 2,6-dichloro-3,5-di-tert-butyltoluene can still be achieved after being recycled for 5 times, which effectively reduces the cost of using the auxiliary agent and improves the economy of the process route.

[0125] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the scope of the substantial technical content of the present disclosure. The substantial technical content of the present disclosure is broadly defined in the scope of the claims of the application. Any technical entity or method completed by others, if it is exactly the same as that defined in the scope of the claims of the application or an equivalent variation, will be deemed to be included in the scope of the claims.

[0126] All documents mentioned in this disclosure are cited as references in this application, just as each document is cited as reference individually. In addition, it should be understood that after reading the above content of this disclosure, those skilled in the art may make various changes or modifications to this disclosure, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for preparing 2,6-dichloro-3,5-di-tert-butyltoluene, the method comprising the following steps: (1) a first-stage chlorination reaction: reacting 3,5-di-tert-butyltoluene with chlorine in the presence of a solvent, a first catalyst, and a first auxiliary agent to obtain 2-chloro-3,5-di-tert-butyltoluene; (2) Two-stage chlorination reaction: In the presence of a second catalyst and a second auxiliary agent, 2-chloro-3,5-di-tert-butyltoluene is reacted with chlorine to obtain 2,6-dichloro-3,5-di-tert-butyltoluene.

2. The method according to claim 1, characterized in that The first catalyst and the second catalyst are Lewis acid catalysts, and the Lewis acid strength of the first catalyst is smaller than that of the second catalyst.

3. The method according to claim 1 or 2, characterized in that In step (1), the solvent comprises a C1-C6 alkane substituted with a halogen atom, and / or The mass ratio of the solvent to 3,5-di-tert-butyltoluene is (0-8):

1.

4. The method according to claim 1 or 2, characterized in that: The first catalyst comprises at least one Lewis acid catalyst selected from the group consisting of FeCl3, ZnCl2, ZrCl4, FeS, FeS2, ZnS, CoS and CdS, and / or The amount of the first catalyst is 0.1-2% by mass of 3,5-di-tert-butyltoluene, and / or The first auxiliary agent comprises at least one auxiliary agent selected from the group consisting of insoluble sulfur, polyphenylene sulfide resin, methyl mercaptan resin, isothiourea resin and mercapto resin, and / or The amount of the first auxiliary agent used is 1-10 mass % of 3,5-di-tert-butyltoluene.

5. The method according to claim 1 or 2, characterized in that: The chlorination reaction temperature in step (1) is 20-60°C, and / or The amount of chlorine used is 0.9-1.1 times the molar amount of 3,5-di-tert-butyltoluene.

6. The method according to claim 1 or 2, characterized in that: The second catalyst comprises at least one Lewis acid catalyst selected from the group consisting of AlCl3, TiCl4, SbCl3 and SnCl4, and / or The amount of the second catalyst is 0.2-2% by mass of 3,5-di-tert-butyltoluene, and / or The second auxiliary agent comprises at least one sulfur-containing organic sulfur compound, and / or The dosage of the second auxiliary agent is 0.1-5 weight percent of 3,5-di-tert-butyltoluene.

7. The method according to claim 1 or 2, characterized in that: The chlorination reaction temperature in step (2) is 40-80°C, and / or The total amount of chlorine used in step (1) and step (2) is 1.9-2.2 times the molar amount of 3,5-di-tert-butyltoluene.

8. The 2,6-dichloro-3,5-di-tert-butyltoluene product prepared according to the method described in any one of claims 1 to 7.

9. A method for preparing 2,6-dichlorotoluene, the method comprising subjecting 2,6-dichloro-3,5-di-tert-butyltoluene prepared by the method according to any one of claims 1 to 7 to a dealkylation reaction.

10. The 2,6-dichlorotoluene product prepared according to the method of claim 9.

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