JPH0491045A - Production of 2, 6-dichlorotoluene - Google Patents

Abstract

PURPOSE:To simplify operation in producing the title compound from 3, 5-d-tert. butyltoluene through chlorination, transalkylation, dispropotionaton and alkylation processes by separating the objective compound after the disproportionation and alkylation. CONSTITUTION:In producing the title compound useful as an intermediate for medicines, agricultural chemicals, etc., by using 3, 5-d-tert. butyltoluene (DBT) as a raw material and passing through (i) a process of chlorinating DBT to give 3, 5-di-tert. butyl-2,6-dichlorotoluene, (ii) a process of transalkylating 3, 5-di-tert. butyl-2, 6-dichlorotoluene with toluene in the presence of a catalyst to give the title compound and tert. butyltoluene(BT) and (iii) a process of disproportionating BT in the presence of the same catalyst as that of the process (ii) to give DBT and a process of alkylation after the disproportionaton of BT and the alkylation, the objective compound is separated and the disproportionaton ration in the process (iii) is made 0-60% to simplify operation, to miniaturize a distillation device and to reduce energy cost.

Description

[Detailed Description of the Invention] The present invention provides 2.6 useful as synthetic intermediates for pharmaceuticals, agricultural chemicals, etc.
-Dichlorotoluene (hereinafter abbreviated as 2.6-DCT)
Relating to a manufacturing method. More specifically, 3.5 gL from 3.5-di-t-butyltoluene (hereinafter abbreviated as DBT)
-butyl-2,6-dichlorotoluene (hereinafter referred to as DBDC)
2.6-DCT (abbreviated as T).

Poor Rice ■ Limb Blood 2.6-OCT cannot be produced by simply chlorinating toluene or 0-chlorotoluene, which produces various isomers such as 2,4-dichlorotoluene, and 2.6-OCT. DCT cannot be obtained selectively. Therefore, conventionally, in order to suppress the production of isomers and improve the yield of 2.6-DCT, alkyltoluene was chlorinated to produce 2.6-dichloroalkyltoluene, and then the alkyl group was eliminated. 2.6
- A method for manufacturing OCT has been proposed (Special Public Interest Publication in 1977)
-26495, JP-A-62-5930).

The method described in Japanese Patent Publication No. 47-26495 describes the method of D
After chlorinating BT to form DBDCT, 1 in the presence of a catalyst.
A catalytic dealkylation reaction is performed at 00 to 500'C to remove the butyl group of the protecting group as isobutyne, and 2.6
- A method of obtaining OCT. This method has the disadvantage that the life of the dealkylation catalyst is short, and the productivity of 2.6-DCT is poor. In addition, since the t-butyl group is eliminated as isobutyl, a recovery process is required, etc. 2.6-
There were points that needed to be improved in the industrial production of OCT.

JP-A-62-5930 has been proposed as an improvement method of the above-mentioned Japanese Patent Publication No. 47-26495. This method is (1)
DOT from t-phthyltoluene (hereinafter abbreviated as BT)
and toluene, (2) chlorinating DBT to obtain DBDCT, and (3) adding toluene and a t-butylating agent to DBOCT to obtain 2.6-[]CT and BT.
This method consists of the steps of obtaining . However, even with this method, there are several problems in implementing it industrially.
For example, 2.6-DCT and BT are separated by distillation after removing the catalyst from a reaction solution obtained by transalkylation of DBDCT and alkylation of toluene (t-butylation). 2.6 of the reaction solution to be subjected to distillation
-The ratio of OCT to BT is approximately 1:3.7 Since the amount of BTO is large, large-scale distillation equipment and an enormous amount of energy are required.

Further, DBT is produced by a disproportionation reaction of separated BT, but unless the disproportionation reaction rate is increased, the amount of BT recycled will increase and the size of the disproportionation reactor and DBT distillation column will increase. Furthermore, it requires two catalyst separation operations, one for decatalyst after the transalkylation and alkylation reactions and one for decatalyst after the disproportionation reaction, making the process complicated.

■ In the method of producing 6-OCT via IIBT and IIBDCT, the above-mentioned problem of distillation operation,
Operations such as disproportionation reaction and decatalysis are necessary for wood quality, but there is a need to simplify these operations. It is an object of the present invention to meet such demands.

In view of the above-mentioned current situation, the inventors of the present invention have decided to use DB rather than DBT.
As a result of intensive research on a method for producing 2,6-DCT via OCT, we found that 2,6-DCT obtained by transalkyl reaction of DBOCT is subjected to disproportionation reaction and alkylation reaction without separation. The present invention was achieved by successfully simplifying the manufacturing process.

The structure of the present invention consists of a chlorination step in which DBT is chlorinated to obtain DBOCT, and the obtained DBDCT and toluene are transalkylated in the presence of a catalyst. -DCT and B
2,6- consisting of a transalkylation step to obtain T, a disproportionation step in which BT is disproportioned in the presence of the same catalyst as the transalkylation catalyst to obtain DBT, and an alkylation step.
In the method for producing OCT, 2,6-O is used to separate 2,6-OCT after the disproportionation reaction and alkylation reaction of BY.
CT manufacturing method and 2,6- consisting of the above steps
In the method for producing OCT, the reaction rate of the disproportionation step for obtaining DBT from BT is kept at 10 to 60%, and 2.6-OCT is separated after the disproportionation reaction and the alkylation reaction2.
6-Method for manufacturing DCT.

The present invention will be explained in detail below.

) Chlorination step and transalkylation step Chlorination reaction to chlorinate DBT to obtain DBOCT and DBDCT
A known method can be applied to the transalkylation reaction.

That is, DBT is chlorinated by blowing 2.0 to 2.2 times the mole of chlorine gas to DBT using Lewis acid and elemental sulfur as catalysts. If the amount of chlorine gas is less than 2.0 moles, the production of dichloride is not sufficient, and if it is more than 2.2 moles, the amount of trichloride produced increases, which is not preferable. After removing the catalyst, the chlorination reaction solution is subjected to distillation and crystallization operations to obtain DBDCT with a purity of 99% or more.

The transalkylation reaction of DBOCT is DBDCT 1
2 to 30 moles of toluene, preferably 10 to 30 moles per mole
20 moles were reacted in the presence of a Lewis acid catalyst to give 2,60
Obtain CT and BT. As the Lewis acid of the catalyst, aluminum chloride, iron chloride, titanium chloride, etc. can be used, and the amount used is 1 to 20 mol%, preferably 5% by mole based on DBDCT.
~15 mol%. The reaction temperature is 0 to 100''C1, preferably 30 to 70C.

1i) Disproportionation and alkylation reaction of BT Transalkylation of DBDCT to obtain the desired 2,6-DCT
When BT is produced, the BT produced at the same time is subjected to a disproportionation reaction in order to return it to DBT, which is a raw material for the chlorination reaction. Conventionally, after separating the target object 2.6-DCT, that is, 2.6-DCT
BT was subjected to the disproportionation reaction in a system without the presence of
This required catalyst removal and distillation operations from the transalkylation reaction solution.

Removal of the catalyst from the reaction solution requires pickling, neutralization, and water washing, and these operations are complicated. In addition, 2.
Distillation separation of 6-DCT and BT also becomes more difficult as the BT content increases. Usually, in the transalkylation liquid 02.6
- The ratio of OCT and BT is approximately 1:2 (weight ratio). According to the research conducted by the present inventors, the disproportionation reaction and alkylation reaction of BT are not affected by the presence of 2,6-OCT, and the catalyst used in the transalkylation reaction is directly used in the disproportionation reaction and alkylation reaction. Can be used as a catalyst for alkylation reactions. Therefore, in the present invention, the transalkylation reaction liquid is used as it is in a vacuum distillation apparatus to disproportionate BT under the conditions of a degree of vacuum of 20 to 200↑orr and a temperature of 40 to 100"C, preferably 50 to 70°C. The reaction is carried out, and the generated toluene is successively taken out of the system.The disproportionation reaction of BT proceeds relatively quickly until the disproportionation reaction rate reaches about 50%, but after that the reaction rate becomes extremely slow. In order to further increase the disproportionation reaction rate, a higher degree of vacuum and a longer reaction time are required. Therefore, in the present invention, the disproportionation reaction rate is kept at 10 to 60%, preferably 15 to 40%,
The remaining BT is reacted with an alkylating agent to form DBT. Incidentally, the disproportionation reaction rate is expressed by the following formula.

Weight of BT after disproportionation (However, if an alkylating agent is added at the time of disproportionation, the weight of BT after reaction plus 148 times the number of moles of alkylating agent added is the weight of BT after disproportionation. By the above-mentioned disproportionation reaction, a reaction solution having a BT content of 40 to 60% by weight is obtained. This reaction solution was used as it was, that is, without separating 26-DCT and the catalyst, to perform alkylation of BT, that is, DBT.
used in the production of Alkylation of BT involves adding an alkylating agent such as t-butyl chloride or isobutylene;
The reaction is carried out at a reaction temperature of 10 to 40°C for 3 to 6 hours. The amount of the alkylating agent used is equimolar to the amount of BT to be alkylated or used in slightly excess amount. This reaction reduces the ratio of BT to 2.6-OCT in the alkylation reaction solution to approximately 1:0.1 to 0.3 (weight ratio), which facilitates the subsequent distillation separation of 2.6-OCT. The BT disproportionation reaction and the alkylation reaction can of course proceed simultaneously by adding an alkylating agent during disproportionation. can.

In this case, a part of the alkylating agent tends to flow out of the system unreacted, and the preferred reaction temperature for the disproportionation reaction and the preferred reaction temperature for the alkylation reaction are not the same, so the alkylation reaction is not carried out. It is preferable to carry out this separately after the equalization reaction is completed.

ij) After the separation alkylation reaction of 2.6-OCT, after removing the catalyst from the reaction solution,
2.6-DCT is separated by distillation. In the distillation, BT, 2.6-DCT, and DBT fractions may be separated in order of boiling point, but as another method, first BT and 2.6-OC are separated.
It is divided into a mixed fraction of T and a DBT fraction, and then BT and 2.6
It is also possible to adopt a method of distilling and separating a mixed fraction of -OCT. The separated DBT may be used as a raw material for a chlorination reaction, and the BT may be subjected to a disproportionation reaction or an alkylation reaction.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example ■, chlorination process 1 equipped with stirring device, chlorine blowing pipe, thermometer, and cooler
DBT with a purity of 98.80% in a five-hole flask with a purity of 4
64.4g (2,249moj2), 3.0g (0,023moj2) of aluminum chloride and 1.5g (0,047moj2) of elemental sulfur were charged as a catalyst, and 2.1 times mo!2 of chlorine was added at a reaction temperature of 50°C. It was chlorinated using

The obtained chlorinated liquid was subjected to distillation and crystallization to perform DBDCT.
377.5g (purity 99.5%, DBDCT 1.3
Obtained 75 AO.

Il,) Rance Alkylation Step 377.5 g of the above DBOCT (1,3
75 moffi), aluminum chloride 18.4 g (0
, 138mo R), toluene 1898.0g (20,
632mo IV,) was charged and reacted at 50°C for 5 hours to obtain a reaction product. As a result of compositional analysis by gas chromatography, this product was found to be 2.6-DCT 203
．． 5g (1,264M0ri, BT 386.5g (2,
611mo I! ).

(2) Disproportionation step 37.5 g of BT recovered in the subsequent step (BT 88.27% by weight, OCT 11.73%) is added to the above reaction solution.
% by weight) and the reaction temperature was 60°C under reduced pressure (200~
This state was maintained for 6 hours while toluene was distilled off at 20 Torr). The toluene distilled at this time was 1677
．． It was 6g. This operation produced a reaction product of 622.9
I got g. As a result of composition analysis by gas chromatography, this product weighed 335.8 g of BT (2,269
mo E ), 2.6-DCT 207.9 g (1
, 291mo I! ) and DBT 53.3g (
It contained 0,261 mof.

The disproportionation rate at this time was 20.0%.

(2) Return the pressure inside the alkylation chemical system to normal pressure, and add 214.0 g (2,314 mo!) of t-butyl chloride to the above reaction solution at 30°C.
In C, the solution was added dropwise over 1 hour while stirring. After the dropwise addition, stirring was continued for 3 hours, and then nitrogen gas was blown at a rate of 50 mm/min for 1 hour to remove residual unreacted t-butyl chloride.

After adding 1000 d of water to the reaction mixture and continuing stirring at 30°C for 0.5 hour, the liquid was allowed to stand and was separated into an aqueous layer and an organic layer. The organic layer was dried using anhydrous sodium sulfate to obtain 744.5 g of a reaction product. As a result of compositional analysis by gas chromatography, this product was BT4
3.1g (0,291Wloffi), 2.6-OCT
207.9 g (1,291 mof), DBT 4
It contained 67.6g (2,292mof).

Next, a mixture containing these BT, 2.6-OCT, and DBT was introduced into a distillation column and subjected to rectification treatment. As each fraction, 83'C/20Torr: 47.7g (BT: 88
．． 27%, 0.284 moj2, DCT: 11.73
%, 0.034 moff), 86°C/20 To
rr: 197.7g (2,6-DCT: 99.49
%, 1.222 moff), 121”C/20To
rr: 464.4g (DBT: 98.80%, 2.2
49 mof) was obtained.

The distillation yields of 2.6-OCT and DBT were 94.6% and 98.1%, respectively. The obtained DBT was returned to the chlorination step I. In addition, the fraction containing BT and DCT was used for charging BT in the disproportionation reaction step (2).

The present invention consists of a chlorination process, a transalkylation process, a disproportionation process and an alkylation process from DBT.
In the method for producing OCT, by performing the disproportionation reaction and the alkylation reaction in the presence of 2.6-OCT,
It has the following advantages.

The catalyst used in the transalkylation can be used as it is in the disproportionation reaction and the alkylation reaction without being separated from the reaction solution. Further, by suppressing the disproportionation reaction rate in the disproportionation step to 60% or less, the reaction time can be shortened, and the loss of t-butyl groups and the amount of high-boiling substances produced can be reduced.

Furthermore, by alkylating BT in the presence of 2.6-OCT, the ratio of coexisting BT to 2.6-OCT can be reduced, making it easier to separate 2.6-DCT.

As a result, operations such as distillation, disproportionation reaction, and catalyst removal become easier, and the distillation equipment becomes smaller and energy costs are reduced.

Claims (2)

[Claims] (1) Chlorinating 3,5-di-t-butyltoluene to 3
, chlorination step to obtain 5-di-t-butyl-2,6-dichlorotoluene, converting 3,5-di-t-butyl-2,6-dichlorotoluene and toluene into transalkyl transalkylation step to obtain 2,6-dichlorotoluene and t-butyltoluene; t-butyltoluene is disproportionated in the presence of the same catalyst as the transalkylation catalyst to obtain 3,5-di-t-butyltoluene; - In a method for producing 2,6-dichlorotoluene consisting of a disproportionation step and an alkylation step to obtain butyltoluene, 2,6-dichlorotoluene is separated after the disproportionation reaction and alkylation reaction of t-butyltoluene. A method for producing 2,6-dichlorotoluene, characterized in that: (2) The disproportionation reaction rate for obtaining 3,5-di-t-butyltoluene from t-butyltoluene in the disproportionation step is 10 to 60%. A method for producing 2,6-dichlorotoluene.