Method for preparing 2, 6-dichlorotoluene with high selectivity

Abstract

The invention relates to a method for preparing 2, 6-dichlorotoluene with high selectivity, which comprises the following steps: (1) reacting toluene with olefin in the presence of a catalyst Cat1 to generate 3, 5-dialkyl toluene; (2) reacting the 3, 5-dialkyl toluene with chlorine in the presence of a catalyst Cat2 and a catalytic promoter to generate 2, 6-dichloro-3, 5-dialkyl toluene; and (3) the 2, 6-dichloro-3, 5-dialkyl toluene is subjected to a dealkylation reaction in the presence of a catalyst Cat3 to generate 2, 6-dichlorotoluene and olefin, and the olefin generated in the step (3) is the same as the olefin used in the step (1). The conversion rate of the reaction in each step is up to 100%, the selectivity exceeds 90%, the selectivity of the final target product 2, 6-dichlorotoluene reaches 90% or above, and the total yield exceeds 90%. The olefin obtained in the step (3) can be recycled.

Description

Technical Field

[0001] The present application belongs to the field of organic synthesis and relates to a method for preparing 2,6-dichlorotoluene with high selectivity, and specifically relates to a method for preparing 2,6-dichlorotoluene by alkylation, chlorination and dealkylation of toluene. Background Art

[0002] 2,6-Dichlorotoluene is a colorless transparent liquid at room temperature. It is soluble in alcohol, ether, benzene, etc., but insoluble in water. It is an important fine chemical raw material for the manufacture of fungicides, insecticides, herbicides, dyes, pigments, medicines and other chemical products. It can be further used in the production of chemical intermediates such as 2,6-dichlorobenzoic acid and 2,6-dichlorobenzonitrile.

[0003] At present, the industrial synthesis of 2,6-dichlorotoluene usually uses toluene as the starting material, chlorine gas as the chlorine source, Lewis acids such as antimony trichloride, ferric chloride or aluminum trichloride as catalysts, and auxiliary catalysts to obtain the product by catalytic chlorination under appropriate conditions. The selectivity of 2,6-dichlorotoluene in this process route is low, and the product contains a large number of by-products, especially other isomers such as 2,5-dichlorotoluene, 2,4-dichlorotoluene and 2,3-dichlorotoluene, which are difficult to separate. The obtained 2,6-dichlorotoluene product is often mixed with other dichlorotoluenes and is usually only used as a solvent, which is less economical.

[0004] Japanese patent application JP2002145810 discloses a method for synthesizing 2,6-dichlorotoluene by continuous catalytic chlorination using toluene as a raw material. While generating 2,6-dichlorotoluene, four other dichlorotoluene isomers are also generated, namely 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene and 3,4-dichlorotoluene. The selectivity of 2,6-dichlorotoluene is only 20-25%.

[0005] Chen Qun et al. reported in "Synthesis of 2,6-Dichlorotoluene" (Chemical Industry Progress, Vol. 21, No. 9, 2002, pp. 656-759) a method for preparing 2,6-dichlorotoluene using toluene as raw material through three steps of alkylation with tert-butyl chloride, chlorination catalyzed by aluminum chloride, and dealkylation. This method can achieve a chlorination yield of 78% by introducing a localization effect of a tert-butyl group on the benzene ring. However, toluene is used as solvent in the dealkylation step, and the boiling point of the product mono-tert-butyltoluene is slightly different from that of 2,6-dichlorotoluene. The separation process is long, difficult, and energy-intensive.

[0006] Chen Qun et al. reported a route for synthesizing 2,6-dichlorotoluene using toluene, isobutylene and chlorine as raw materials in "A Review of the Uses and Synthesis Routes of 2,6-Dichlorotoluene" (Journal of Jiangsu Petrochemical University, March 1997, pp. 47-54). First, isobutylene reacts with concentrated hydrochloric acid to generate tert-butyl chloride, which reacts with toluene in the presence of aluminum chloride to generate 3,5-di-tert-butyltoluene by Friedel-Crafts alkylation, and then 3,5-di-tert-butyltoluene reacts with chlorine at room temperature to generate 2,6-dichloro-3,5-di-tert-butyltoluene by benzene ring substitution reaction. After purification, 2,6-dichloro-3,5-di-tert-butyltoluene reacts with toluene to generate 2,6-dichlorotoluene, and finally the product is purified by distillation. The product yield of this method can reach 68-70% based on toluene, but the dealkylation reaction also uses toluene as a solvent, and it is difficult to separate mono-tert-butyltoluene and 2,6-dichlorotoluene in the reaction product.

[0007] In the existing technology for preparing 2,6-dichlorotoluene, the continuous chlorination method of toluene produces more byproducts, has very low selectivity and poor economic efficiency. The chlorination selectivity of the alkyltoluene chlorination method is low, and toluene and the like are introduced as solvents in the dealkylation step. The byproduct mono-tert-butyltoluene increases the difficulty of subsequent separation and production costs, and the generated mono-tert-butyltoluene needs to be further converted into 3,5-di-tert-butyltoluene, which has problems such as complicated process flow and great difficulty in separation. Summary of the invention

[0008] The purpose of the present application is to provide a method for preparing 2,6-dichlorotoluene, which has high product selectivity, reduces process steps, avoids the introduction of aromatic solvents such as toluene during deprotection, reduces the difficulty of product separation, and improves the economy of the process route. Through in-depth research, the inventors of the present application found that using toluene and olefins as raw materials, preparing 2,6-dichlorotoluene through alkylation, chlorination, and dealkylation not only has a localization effect in the chlorination reaction and improves product selectivity, but also the olefins produced by dealkylation can be recycled as raw materials for alkylation, thereby achieving the above purpose.

[0009] Therefore, the present application provides a method for preparing 2,6-dichlorotoluene, comprising the following steps:

[0010] (1) Toluene reacts with olefins in the presence of catalyst Cat1 to produce 3,5-dialkyltoluene;

[0011] (2) 3,5-dialkyltoluene reacts with chlorine in the presence of catalyst Cat2 and a catalyst promoter to generate 2,6-dichloro-3,5-dialkyltoluene;

[0012] (3) 2,6-dichloro-3,5-dialkyltoluene undergoes dealkylation reaction in the presence of catalyst Cat3 to produce 2,6-dichlorotoluene and olefins.

[0013] The olefin produced in step (3) is the same as the olefin used in step (1).

[0014] In some embodiments, the olefin has the formula wherein R1 and R2 are independently selected from H and a linear or branched C1-C4 alkyl group.

[0015] In some embodiments, the 3,5-dialkyltoluene has the formula

[0016] In some embodiments, in step (1), the molar ratio of toluene to olefin is 1:1.5 to 1:6, preferably 1:2 to 1:4.

[0017] In some embodiments, in step (1), the reaction temperature is 30-150°C.

[0018] In some embodiments, in step (1), the reaction time is 0.5-10 hours.

[0019] In some embodiments, in step (1), the reaction pressure is 0.1-5 MPa.

[0020] In some embodiments, in step (1), the catalyst Cat1 is selected from one or more of the following groups: anhydrous aluminum chloride, p-toluenesulfonic acid, benzenesulfonic acid, phosphoric acid, HY, HZSM-5, HZSM-12, ZSM-5, Hβ zeolite, HY zeolite, MCM-22, phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, silicotungstic acid.

[0021] In some embodiments, in step (1), the amount of catalyst Cat1 used is 0.5-15% by mass, preferably 1-10% by mass, of the amount of toluene used.

[0022] In some embodiments, the reaction of step (2) is carried out in an organic solvent, and the organic solvent is selected from one or more of the following groups: ethylene dichloride, carbon tetrachloride, chloroform, and dichloromethane.

[0023] In some embodiments, in step (2), the catalyst Cat2 is selected from one or more of the following groups: anhydrous aluminum chloride, ferrous sulfide, ferrous disulfide, anhydrous ferric chloride, antimony trichloride, tin tetrachloride, titanium tetrachloride, and zirconium tetrachloride.

[0024] In some embodiments, in step (2), the amount of catalyst Cat2 used is 0.5-10% of the amount of 3,5-dialkyltoluene used, by mass.

[0025] In some embodiments, in step (2), the catalyst promoter is a sulfur-containing promoter.

[0026] In some embodiments, in step (2), the catalyst promoter is selected from one or more of the following groups: diphenyl disulfide, diphenyl sulfide, dibutyl sulfide, methyl sulfide, sulfur, polyphenylene sulfide resin, methyl mercaptan resin, isothiourea resin, zinc sulfide, copper sulfide, cobalt sulfide, and cadmium sulfide.

[0027] In some embodiments, in step (2), the amount of the catalyst promoter used is 0.5-10% by mass, preferably 0.8-8% by mass, of the amount of 3,5-dialkyltoluene used.

[0028] In some embodiments, in step (2), the molar ratio of chlorine to 3,5-dialkyltoluene is 1.5:1 to 4:1, preferably 1.8:1 to 2.5:1.

[0029] In some embodiments, in step (2), the reaction temperature is 30-70°C.

[0030] In some embodiments, in step (3), the catalyst Cat3 is selected from one or more of the following groups: p-toluenesulfonic acid, benzenesulfonic acid, phosphoric acid, sulfuric acid, tin tetrachloride, anhydrous antimony trichloride, aluminum trichloride, titanium tetrachloride, zirconium tetrachloride, trifluoromethanesulfonic acid, trifluoroacetic acid, phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, and silicotungstic acid.

[0031] In some embodiments, in step (3), the amount of catalyst Cat3 used is 0.5-10% by mass of the amount of 2,6-dichloro-3,5-dialkyltoluene used.

[0032] In some embodiments, in step (3), the reaction temperature is 80-200°C.

[0033] In some embodiments, in step (3), the reaction is carried out under a negative pressure of -0.1 MPa to -0.05 MPa, preferably -0.1 MPa to -0.07 MPa. DETAILED DESCRIPTION

[0034] "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.

[0035] 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.

[0036] 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.

[0037] In the present application, unless otherwise specified or there is no inherent sequence relationship, 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.

[0038] 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.

[0039] 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.

[0040] 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).

[0041] Herein, unless otherwise specified, percentage (%) or part refers to percentage by weight or part by weight relative to the composition.

[0042] If not specifically stated, the terms "a" or "an" used in the present specification means "at least one".

[0043] The present application provides a method for preparing 2,6-dichlorotoluene, comprising the following steps:

[0044] (1) Toluene reacts with olefins in the presence of catalyst Cat1 to produce 3,5-dialkyltoluene;

[0045] (2) 3,5-dialkyltoluene reacts with chlorine in the presence of catalyst Cat2 and a catalyst promoter to generate 2,6-dichloro-3,5-dialkyltoluene;

[0046] (3) 2,6-dichloro-3,5-dialkyltoluene undergoes dealkylation reaction in the presence of catalyst Cat3 to produce 2,6-dichlorotoluene and olefins.

[0047] The olefin produced in step (3) is the same as the olefin used in step (1).

[0048] Since the olefin produced in step (3) is the same as the olefin used in step (1), the olefin produced in step (3) can be recycled into step (1) as an alkylation raw material, thereby greatly saving material consumption.

[0049] The olefin may be represented by the chemical formula It means that R1 and R2 are independently selected from H and straight or branched C1-C4 alkyl. Specifically, the straight or branched C1-C4 alkyl includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl. Preferably, R1 and R2 are not both H. More preferably, neither R1 nor R2 is H. For example, the olefin can be selected from propylene, n-butene, isobutylene, 1-pentene, 3-methyl-1-pentene, 2-methyl-1-butene, etc. However, it should be understood that other olefins that can achieve the purpose of the present application also fall within the scope of the present application.

[0050] 3,5-Dialkyltoluene can be used with the chemical formula It means that 2,6-dichloro-3,5-dialkyltoluene can be expressed by the chemical formula , wherein R1 and R2 are as defined above. For example, when one of R1 and R2 is H and the other is methyl, the corresponding olefin is propylene, the corresponding 3,5-dialkyltoluene is 3,5-diisopropyltoluene, and 2,6-dichloro-3,5-dialkyltoluene is 2,6-dichloro-3,5-diisopropyltoluene; when both R1 and R2 are methyl, the corresponding olefin is isobutylene, the corresponding 3,5-dialkyltoluene is 3,5-di-tert-butyltoluene, and 2,6-dichloro-3,5-dialkyltoluene is 2,6-dichloro-3,5-di-tert-butyltoluene.

[0051] Step (1) of the method described in the present application is an alkylation reaction, which uses toluene and olefins in a certain molar ratio as raw materials, and replaces the meta position of toluene to generate a group with steric hindrance under a certain temperature and a catalyst. The reaction can be carried out in a reactor. After toluene and the catalyst are put into the reactor, the reactor can be replaced with nitrogen, and olefins are introduced into the reactor after the replacement. After the reaction is completed, the temperature is lowered, the unreacted olefins are emptied and recovered, and the reaction solution is post-treated to obtain 3,5-dialkyltoluene. The reaction can be represented by the following chemical reaction formula (I):

[0052]

[0053] In step (1), the molar ratio of toluene to olefin may be 1:1.5 to 1:6, preferably 1:1.6 to 1:5.5, more preferably 1:1.7 to 1:5, for example 1:1.8 to 1:4.5, 1:1.9 to 1:4, 1:2 to 1:3.5, 1:2.1 to 1:3, 1:2.2 to 1:2.5, 1:2.3 to 1:2.4.

[0054] In step (1), the reaction temperature may be 30-150°C, preferably 40-140°C, for example 50-130°C, 60-120°C, 70-110°C, 80-100°C, 90-95°C.

[0055] In step (1), the reaction time may be 0.5-10 hours, preferably 1-9 hours, more preferably 2-8 hours, such as 2-7 hours, 3-6 hours, 4-5 hours.

[0056] In step (1), the reaction pressure may be 0.1-5 MPa, preferably 0.2-4.5 MPa, more preferably 0.3-4 MPa, for example 0.4-3.5 MPa, 0.5-3 MPa, 0.6-2.5 MPa, 0.7-2 MPa, 0.8-1.5 MPa, 0.9-1 MPa.

[0057] In step (1), the catalyst Cat1 can be selected from one or more of the following groups: anhydrous aluminum chloride, p-toluenesulfonic acid, benzenesulfonic acid, phosphoric acid, HZSM-5, Hβ zeolite, HY zeolite, MCM-22, phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, silicotungstic acid. In some embodiments, the catalyst Cat1 can be selected from one or more of the following groups: anhydrous aluminum chloride, p-toluenesulfonic acid, HZSM-5.

[0058] In step (1), the amount of catalyst Cat1 used can be 0.5-15% of the amount of toluene used, preferably 1-10%, more preferably 1-8%, such as 2-7%, 3-6%, 4-5%, by mass.

[0059] Step (2) of the method described in the present application is a chlorination reaction. The reaction system can be purged with a certain flow rate of nitrogen. After the purging is completed, the 3,5-dialkyltoluene obtained in step (1), the organic solvent, the catalyst, and the catalytic promoter are sequentially added to the reactor. After the feeding is completed, the temperature is raised to a certain temperature, and chlorine gas is introduced to react. After the chlorine gas reacts for a certain period of time at a certain flow rate, the chlorine introduction is terminated, the temperature is lowered, and the chlorine is driven out with nitrogen. The collected material is subjected to acid washing, alkali washing, solvent removal, and decoking treatment to obtain 2,6-dichloro-3,5-dialkyltoluene. The reaction can be represented by the following chemical reaction formula (II):

[0060]

[0061] The reaction in step (2) is carried out in an organic solvent, and the organic solvent can be selected from one or more of the following groups: dichloromethane, dichloroethane, carbon tetrachloride, and chloroform.

[0062] In step (2), the catalyst Cat2 can be selected from one or more of the following groups: anhydrous aluminum chloride, ferrous sulfide, ferrous disulfide, anhydrous ferric chloride, antimony trichloride, tin tetrachloride, titanium tetrachloride, zirconium tetrachloride. In some embodiments, the catalyst Cat2 can be selected from one or more of the following groups: anhydrous aluminum chloride, ferrous sulfide, anhydrous ferric chloride.

[0063] In step (2), the amount of catalyst Cat2 used can be 0.5-10% of the amount of 3,5-dialkyltoluene, preferably 0.5-8%, more preferably 0.5-6%, for example 0.6-5%, 0.7-4%, 0.8-3.5%, 0.9-3%, 1-2.5%, 1.5-2%, by mass.

[0064] In step (2), the catalyst promoter is a sulfur-containing promoter. In some embodiments, the catalyst promoter may be selected from one or more of the following groups: diphenyl disulfide, diphenyl sulfide, dibutyl sulfide, methyl sulfide, sulfur, polyphenylene sulfide resin, methyl mercaptan resin, isothiourea resin, zinc sulfide, copper sulfide, cobalt sulfide, cadmium sulfide. In some embodiments, the catalyst promoter may be selected from one or more of the following groups: diphenyl disulfide, dibutyl sulfide, sulfur, polyphenylene sulfide resin, zinc sulfide. In terms of mass, the amount of the catalyst promoter may be 0.5-10% of the amount of 3,5-dialkyltoluene, preferably 0.8-8%, more preferably 1-7%, for example 1.5-6%, 2-5%, 3-4%.

[0065] In step (2), the molar ratio of chlorine to 3,5-dialkyltoluene may be 1.5:1 to 4:1, preferably 1.6:1 to 3.5:1, for example 1.7:1 to 3:1, 1.8:1 to 2.5:1, 1.9:1 to 2.4:1, 2:1 to 2.3:1, 2.1:1 to 2.2:1.

[0066] In step (2), the reaction temperature may be 30-70°C, preferably 35-65°C, such as 40-60°C, 45-55°C.

[0067] Step (3) of the method described in the present application is a dealkylation reaction, which uses the product 2,6-dichloro-3,5-dialkyltoluene obtained in step (2) as a raw material, and undergoes a dealkylation reaction under a certain temperature and a catalyst to obtain the target product 2,6-dichlorotoluene. No solvent is used in this reaction. The reaction can be represented by the following chemical reaction formula (III):

[0068]

[0069] In step (3), the catalyst Cat3 can be selected from one or more of the following groups: p-toluenesulfonic acid, benzenesulfonic acid, phosphoric acid, sulfuric acid, tin tetrachloride, antimony trichloride, anhydrous aluminum chloride, titanium tetrachloride, zirconium tetrachloride, trifluoromethanesulfonic acid, trifluoroacetic acid, phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, silicotungstic acid. In some embodiments, the catalyst Cat3 can be selected from one or more of the following groups: trifluoromethanesulfonic acid, anhydrous aluminum chloride, zirconium tetrachloride.

[0070] In step (3), the amount of catalyst Cat3 used can be 0.1-10% of the amount of 2,6-dichloro-3,5-dialkyltoluene, preferably 0.2-9%, for example 0.3-8%, 0.4-7%, 0.5-6%, 0.6-5%, 0.7-4%, 0.8-3%, 0.9-2.5%, 1-2%, by mass.

[0071] In step (3), the reaction temperature may be 80-200°C, preferably 90-190°C, for example 100-180°C, 110-170°C, 120-160°C, 130-155°C, 140-150°C.

[0072] In step (3), the reaction may be carried out under a negative pressure of -0.1 MPa to -0.05 MPa, preferably -0.1 MPa to -0.06 MPa, for example -0.1 MPa to -0.07 MPa, -0.1 MPa to -0.08 MPa, or -0.1 MPa to -0.09 MPa.

[0073] In step (3), the reaction time may be 1-6 hours, preferably 2-5 hours, for example 3-4 hours.

[0074] Compared with the prior art, the method for preparing 2,6-dichlorotoluene in the present application has at least the following beneficial effects:

[0075] (1) The conversion rate of each step of the reaction can reach 100%, the selectivity exceeds 90%, the selectivity of the final target product 2,6-dichlorotoluene is high, reaching more than 90%, and the total yield exceeds 90%;

[0076] (2) The method of the present application adopts a solvent-free method for dealkylation reaction, the reaction conditions are mild, and the produced olefins can be recycled as raw materials, which reduces the process flow and improves the economic efficiency of the process route;

[0077] (3) The process flow of the present application method is short, there is no difficult-to-separate substance such as mono-tert-butyltoluene, the separation energy consumption is low, and the product purity is above 99.9%.

[0078] 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.

[0079] Example

[0080] The present invention will be further described below in conjunction with specific embodiments.

[0081] The sources of reagents or gases used in the following examples are as follows:

[0082] p-Toluenesulfonic acid: purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0083] Toluene: purchased from Sinopharm Chemical Reagent Co., Ltd.

[0084] Nitrogen: purchased from Yangzhou Chunhui Gas Co., Ltd.

[0085] Propylene: purchased from Nanjing Special Gas Co., Ltd.

[0086] Ethylene dichloride: purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0087] Diphenyl disulfide: purchased from Shanghai Haohong Biopharmaceutical Technology Co., Ltd.;

[0088] Anhydrous aluminum chloride: purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0089] Chlorine: purchased from China Salt Changzhou Chemical Co., Ltd.

[0090] Trifluoromethanesulfonic acid: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0091] HZSM-5: purchased from Nankai Molecular Sieve Catalyst Factory

[0092] Isobutylene: purchased from Nanjing Special Gas Co., Ltd.

[0093] Carbon tetrachloride: purchased from Sinopharm Chemical Reagent Co., Ltd.

[0094] Sulfur: purchased from Yanggu Huatai Chemical Co., Ltd.;

[0095] Dibutyl sulfide: purchased from Shanghai Haohong Biopharmaceutical Technology Co., Ltd.

[0096] Anhydrous ferric chloride: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0097] Chloroform: purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0098] Polyphenylene sulfide resin: purchased from Zhejiang Xinhecheng Co., Ltd.

[0099] Zinc sulfide: purchased from Shanghai Leyan Biopharmaceutical Technology Co., Ltd.

[0100] Ferrous sulfide: purchased from Tianjin Xiensi Biochemical Technology Co., Ltd.

[0101] Zirconium tetrachloride: purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0102] The reaction kettle used in the following examples is a Yantai Songling 2L316L autoclave purchased from Yantai Songling Chemical Equipment Co., Ltd., and the gas chromatograph used is an Agilent 7890.

[0103] The conversion rate and selectivity calculation formulas in the following examples are as follows:

[0104] Step (1):

[0105] Toluene conversion rate = (number of moles of toluene fed - number of moles of toluene remaining in the reaction solution) / number of moles of toluene fed × 100%

[0106] 3,5-diisopropyl (or di-tert-butyl) toluene selectivity = number of moles of 3,5-diisopropyl (or di-tert-butyl) toluene produced / (number of moles of toluene input - number of moles of toluene remaining in the reaction solution) × 100%

[0107] Step (2):

[0108] 3,5-diisopropyl (or di-tert-butyl) toluene conversion rate = (3,5-diisopropyl (or di-tert-butyl) toluene input moles - 3,5-diisopropyl (or di-tert-butyl) toluene remaining moles in the reaction solution) / 3,5-diisopropyl (or di-tert-butyl) toluene input moles × 100%

[0109] Selectivity of 2,6-dichloro-3,5-diisopropyl (or di-tert-butyl) toluene = number of moles of 2,6-dichloro-3,5-diisopropyl (or di-tert-butyl) toluene produced / (number of moles of 3,5-diisopropyl (or di-tert-butyl) toluene input - number of moles of 3,5-diisopropyl (or di-tert-butyl) toluene remaining in the reaction solution) × 100%

[0110] Step (3):

[0111] 2,6-dichloro-3,5-diisopropyl (or di-tert-butyl) toluene conversion rate = (number of moles of 2,6-dichloro-3,5-diisopropyl (or di-tert-butyl) toluene input - number of moles of 2,6-dichloro-3,5-diisopropyl (or di-tert-butyl) toluene remaining in the reaction liquid) / number of moles of 2,6-dichloro-3,5-diisopropyl (or di-tert-butyl) toluene input × 100%

[0112] 2,6-Dichlorotoluene selectivity = 2,6-Dichlorotoluene produced moles / (2,6-Dichloro-3,5-diisopropyl (or di-tert-butyl) toluene input moles - 2,6-Dichloro-3,5-diisopropyl (or di-tert-butyl) toluene remaining moles in the reaction solution) × 100%

[0113] Total yield of 2,6-dichlorotoluene = toluene conversion × 3,5-diisopropyl (or di-tert-butyl) toluene selectivity × 3,5-diisopropyl (or di-tert-butyl) toluene conversion × 2,6-dichloro-3,5-diisopropyl (or di-tert-butyl) toluene selectivity × 2,6-dichloro-3,5-diisopropyl (or di-tert-butyl) toluene conversion × 2,6-dichloro-3,5-diisopropyl (or di-tert-butyl) toluene selectivity

[0114] Example 1

[0115] Step (1): 3 g of p-toluenesulfonic acid and 300 g of toluene are put into a reactor, and the reactor is replaced with nitrogen. After the replacement is completed, propylene is introduced into the reactor, and a total of 412 g of propylene is introduced. The reaction is carried out at 40° C. and 0.5 MPa for 4 hours, and the temperature is lowered. The unreacted propylene is emptied and recovered, and the reaction liquid is post-treated to obtain 3,5-diisopropyltoluene. The conversion rate of toluene and the selectivity of 3,5-diisopropyltoluene are analyzed and calculated by gas chromatography, as shown in Table 1 below.

[0116] Step (2): chlorinate the 3,5-diisopropyltoluene obtained in step (1). Connect a brown four-necked reaction flask to a condenser, a water absorption device and an alkali absorption device, turn on the nitrogen, purge the system with nitrogen at a flow rate of 5-10L / min for 10 minutes, then add 300g of 3,5-diisopropyltoluene and 1000g of dichloroethane solvent into the reaction flask, add 3g of auxiliary agent diphenyl disulfide and 2.5g of catalyst anhydrous aluminum chloride under stirring. After the feeding is completed, the temperature is raised to 50°C and chlorine is introduced for reaction. After a total of 254g of chlorine is introduced, the chlorine is stopped, the temperature is lowered, and the chlorine is driven out with nitrogen for 30 minutes. The reacted material is collected, and after acid washing, alkali washing, solvent removal, and decoking, 2,6-dichloro-3,5-diisopropyltoluene is obtained. The conversion rate of 3,5-diisopropyltoluene and the selectivity of 2,6-dichloro-3,5-diisopropyltoluene were analyzed and calculated by gas chromatography and are shown in Table 1 below.

[0117] Step (3): 400 g of 2,6-dichloro-3,5-diisopropyltoluene obtained in step (2) was placed in a reaction bottle, 10 g of trifluoromethanesulfonic acid was added, and the mixture was reacted at a temperature of 150° C. and a negative pressure of −0.09 MPa for 4 hours to obtain 2,6-dichlorotoluene and propylene, and the propylene was collected as the olefin raw material in step (1) for recycling. The conversion rate of 2,6-dichloro-3,5-diisopropyltoluene and the selectivity of 2,6-dichlorotoluene were analyzed and calculated by gas chromatography, as shown in Table 1 below.

[0118] The total yield of the reaction was calculated and is shown in Table 1 below.

[0119] Example 2

[0120] Step (1): 15 g HZSM-5 and 300 g toluene are put into a reactor, and the reactor is replaced with nitrogen. After the replacement is completed, isobutylene is introduced into the reactor, and a total of 457 g of isobutylene is introduced. The reaction is carried out at 140° C. and 1.5 MPa for 2 hours, and the temperature is lowered. The unreacted isobutylene is discharged and recovered, and the reaction liquid is post-treated to obtain 3,5-di-tert-butyltoluene. The conversion rate of toluene and the selectivity of 3,5-di-tert-butyltoluene are analyzed and calculated by gas chromatography, as shown in Table 1 below.

[0121] Step (2): chlorinate the 3,5-di-tert-butyltoluene obtained in step (1). Connect a brown four-necked reaction flask to a condenser, a water absorption device and an alkali absorption device, turn on the nitrogen, purge the system with nitrogen at a flow rate of 5-10L / min for 10 minutes, then add 300g 3,5-di-tert-butyltoluene and 600g carbon tetrachloride solvent into the reaction flask, add 1.5g sulfur and 3g dibutyl sulfide as auxiliary agents and 6g catalyst anhydrous ferric chloride under stirring. After the feeding is completed, the temperature is raised to 35°C and chlorine is introduced for reaction. After a total of 220g of chlorine is introduced, the chlorine is stopped, the temperature is lowered, and the chlorine is driven out with nitrogen for 30 minutes. The reacted material is collected, and after acid washing, alkali washing, solvent removal, and decoking, 2,6-dichloro-3,5-di-tert-butyltoluene is obtained. The conversion rate of 3,5-di-tert-butyltoluene and the selectivity of 2,6-dichloro-3,5-di-tert-butyltoluene were analyzed and calculated by gas chromatography, and are shown in Table 1 below.

[0122] Step (3): 350 g of 2,6-dichloro-3,5-di-tert-butyltoluene obtained in step (2) was placed in a reaction bottle, 20 g of anhydrous aluminum chloride was added, and the mixture was reacted at a temperature of 120° C. and a negative pressure of −0.0 MPa for 4 hours to obtain 2,6-dichlorotoluene and isobutylene, and the isobutylene was collected and recycled as the olefin raw material in step (1). The conversion rate of 2,6-dichloro-3,5-di-tert-butyltoluene and the selectivity of 2,6-dichlorotoluene were analyzed and calculated by gas chromatography, as shown in Table 1 below.

[0123] The total yield of the reaction was calculated and is shown in Table 1 below.

[0124] Example 3

[0125] Step (1): 24 g of anhydrous aluminum chloride and 300 g of toluene are put into a reactor, and the reactor is replaced with nitrogen. After the replacement is completed, propylene is introduced into the reactor, and a total of 275 g of propylene is introduced. The reaction is carried out at 100° C. and 1.0 MPa for 5 hours, and the temperature is lowered. The unreacted propylene is discharged and recovered, and the reaction liquid is post-treated to obtain 3,5-diisopropyltoluene. The conversion rate of toluene and the selectivity of 3,5-diisopropyltoluene are analyzed and calculated by gas chromatography, as shown in Table 1 below.

[0126] Step (2): chlorinate the 3,5-diisopropyltoluene obtained in step (1). Connect a brown four-necked reaction flask to a condenser, a water absorption device and an alkali absorption device, turn on the nitrogen, purge the system with nitrogen at a flow rate of 5-10L / min for 10 minutes, then add 300g of 3,5-diisopropyltoluene and 300g of chloroform solvent into the reaction flask, add 10g of polyphenylene sulfide resin and 9g of zinc sulfide as an auxiliary agent and 9g of catalyst ferrous sulfide under stirring. After the feeding is completed, the temperature is raised to 40°C and chlorine is introduced for reaction. After a total of 242g of chlorine is introduced, the chlorine is stopped, the temperature is lowered, and the chlorine is driven out with nitrogen for 30 minutes. The reacted material is collected, and after acid washing, alkali washing, solvent removal, and decoking, 2,6-dichloro-3,5-diisopropyltoluene is obtained. The conversion rate of 3,5-diisopropyltoluene and the selectivity of 2,6-dichloro-3,5-diisopropyltoluene were analyzed and calculated by gas chromatography and are shown in Table 1 below.

[0127] Step (3): 380 g of 2,6-dichloro-3,5-diisopropyltoluene obtained in step (2) was placed in a reaction bottle, 3 g of zirconium tetrachloride was added, and the mixture was reacted at a temperature of 180° C. and a negative pressure of −0.09 MPa for 3 hours to obtain 2,6-dichlorotoluene and propylene, and the propylene was collected and used as the olefin raw material in step (1) for recycling. The conversion rate of 2,6-dichloro-3,5-diisopropyltoluene and the selectivity of 2,6-dichlorotoluene were analyzed and calculated by gas chromatography, as shown in Table 1 below.

[0128] The total yield of the reaction was calculated and is shown in Table 1 below.

[0129] Table 1 Conversion rate, selectivity and total yield of each reaction step in Examples 1-3

[0130]

[0131] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing 2,6-dichlorotoluene, comprising the following steps: (1) Toluene reacts with olefins in the presence of catalyst Cat1 to produce 3,5-dialkyltoluene; (2) 3,5-dialkyltoluene reacts with chlorine in the presence of catalyst Cat2 and a catalyst promoter to generate 2,6-dichloro-3,5-dialkyltoluene; (3) 2,6-dichloro-3,5-dialkyltoluene undergoes dealkylation reaction in the presence of catalyst Cat3 to produce 2,6-dichlorotoluene and olefins. The olefin produced in step (3) is the same as the olefin used in step (1).

2. The method according to claim 1, characterized in that The olefin has the formula wherein R1 and R2 are independently selected from H and straight chain or branched C1-C4 alkyl.

3. The method according to claim 2, characterized in that 3,5-Dialkyltoluene has the chemical formula 4. The method according to claim 1, characterized in that In step (1): The molar ratio of toluene to olefin is from 1:1.5 to 1:6, preferably from 1:2 to 1:4; and / or The reaction temperature is 30-150°C; and / or The reaction time is 0.5-10 hours; and / or The reaction pressure is 0.1-5MPa.

5. The method according to claim 1, characterized in that In step (1): Catalyst Cat1 is selected from one or more of the following groups: anhydrous aluminum chloride, p-toluenesulfonic acid, benzenesulfonic acid, phosphoric acid, HZSM-5, Hβ zeolite, HY zeolite, MCM-22, phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, silicotungstic acid; and / or The amount of catalyst Cat1 used is 0.5-15% of the amount of toluene used, preferably 1-10% by mass.

6. The method according to claim 1, characterized in that The reaction in step (2) is carried out in an organic solvent, and the organic solvent is selected from one or more of the following groups: ethylene dichloride, carbon tetrachloride, chloroform, and dichloromethane.

7. The method according to claim 1, characterized in that In step (2): Catalyst Cat2 is selected from one or more of the following groups: anhydrous aluminum chloride, ferrous sulfide, ferrous disulfide, anhydrous ferric chloride, antimony trichloride, tin tetrachloride, titanium tetrachloride, zirconium tetrachloride; and / or The amount of catalyst Cat2 used is preferably 0.5-10% of the amount of 3,5-dialkyltoluene used by mass; and / or The catalyst promoter is a sulfur-containing promoter, preferably one or more of the following: diphenyl disulfide, diphenyl sulfide, dibutyl sulfide, methyl sulfide, sulfur, polyphenylene sulfide resin, methyl mercaptan resin, isothiourea resin, zinc sulfide, copper sulfide, cobalt sulfide, cadmium sulfide; and / or The amount of the catalyst aid used is 0.5-10% of the amount of 3,5-dialkyltoluene used, preferably 0.8-8% by mass.

8. The method according to claim 1, characterized in that In step (2): The molar ratio of chlorine to 3,5-dialkyltoluene is from 1.5:1 to 4:1, preferably from 1.8:1 to 2.5:1; and / or The reaction temperature is 30-70°C.

9. The method according to claim 1, characterized in that In step (3): Catalyst Cat3 is selected from one or more of the following groups: p-toluenesulfonic acid, benzenesulfonic acid, phosphoric acid, sulfuric acid, tin tetrachloride, antimony trichloride, anhydrous aluminum chloride, titanium tetrachloride, zirconium tetrachloride, trifluoromethanesulfonic acid, trifluoroacetic acid, phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, silicotungstic acid; and / or The amount of catalyst Cat3 used is 0.5-10% of the amount of 2,6-dichloro-3,5-dialkyltoluene used by mass.

10. The method according to claim 1, characterized in that In step (3): The reaction is carried out in the absence of a solvent; and / or The reaction is carried out under a negative pressure of -0.1 MPa to -0.05 MPa, preferably -0.1 MPa to -0.07 MPa; and / or The reaction temperature is 80-200°C.

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