JP2000247913A - Production of dichlorotoluene isomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To economically produce from a mixture of dichlorotoluene isomers each of the isomers. SOLUTION: Each of dichlorotoluene isomers is produced by separating 2,3-dichlorotoluene and 3,4-dichlorotoluene through a distillation method from a mixture of dichlorotoluene isomers and then by separating at least one of 2,6-dichlorotoluene, 2,5-dichlorotoluene and 2,4-dichlorotoluene through an adsorption and separation method from a mixture of dichlorotoluene isomers in which the concentration of 2,3-dichlorotoluene and 3,4-dichlorotoluene is low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating various isomers of DCT from a mixture of isomers of dichlorotoluene (hereinafter abbreviated as "DCT").
DCT, 3,4-DCT, 2,5-DCT, 2,4-D
CT and 2,6-DCT are important as raw materials for medicines, pesticides, dyes and the like.

[0002]

2. Description of the Related Art DCT can be produced by chlorinating toluene or monochlorotoluene.
CT is a mixture in which various isomers are present. For example, a typical composition of a DCT isomer mixture formed by chlorinating toluene is about 21% 2,6-DCT, 2,5-DCT
About 27%, 3,5-DCT 0%, 2,4-DCT about 35%, 3,4-DCT about 9%, 2,3-DCT about 8%. A typical composition of a DCT isomer mixture formed by chlorinating ortho-chlorotoluene is 2,6-
DCT about 27%, 2,5-DCT about 32%, 3,5
-DCT 0%, 2,4-DCT about 25%, 3,4-
DCT is about 2% and 2,3-DCT is about 14%.

The boiling point of each isomer of DCT is 198 ° C. for 2,6-DCT, 199 ° C. for 2,5-DCT, 3,5-DCT
T 201-202 ° C, 2,4-DCT 200 ° C,
2,3-DCT 207-208 ° C, 3,4-DCT
207-208 ° C. Since the boiling points of the isomers are close to each other, it is practically impossible to obtain a high-purity isomer by a distillation method.

For this reason, industrially, high-purity p-chlorotoluene is chlorinated to form 2,4-DCT and 3,4-D
After obtaining a chlorinated product of CT, 2,4-DCT is separated and recovered by distillation for production. However, this method cannot be said to be an economical process because it is necessary to use high-purity p-chlorotoluene as a raw material so that 2,6-DCT and 2,5-DCT are not formed as by-products.

On the other hand, a method for adsorbing and separating 2,4-DCT from a DCT isomer mixture using a zeolite adsorbent is disclosed in Japanese Patent Publication No. 2-36577 and Japanese Patent Laid-Open No. 5-70383. , 6-DCT is disclosed in Japanese Patent Publication No. 1-45457, but is inefficient as an industrial production method.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a method for efficiently separating each isomer of DCT.

[0007]

Means for Solving the Problems The present inventors have found that, among the respective isomers of DCT, the boiling points of 2,3-DCT and 3,4-DCT are both 207 to 208 ° C., and that of 2,6-DCT, ,
The boiling point of 5-DCT and 2,4-DCT is 198 to 202 ° C.
It was noted that. That is, 2,3-DCT, 3,4
-DCT is 2,6-DCT, 2,5-DCT, 2,4-
It is a boiling point difference that can be sufficiently separated by DCT and a distillation method. Thus, the DCT isomer mixture was previously distilled to 2,3-DCT,
After separating 3,4-DCT, 2,3-DCT and 3,4-D
2,3-DCT and / or 3,4-DCT are adsorbed and separated from the DCT isomer mixture consisting of CT,
2,6-DCT, 2,5-DCT, 2,4-DCT from a poor DCT isomer mixture of 3-DCT and 3,4-DCT.
The present inventors have found that adsorbing and separating at least one isomer of DCT improves the separating performance of an adsorbent and is an industrially economical method, and has reached the present invention.

That is, the present invention relates to (1) separating 2,3-DCT and / or 3,4-DCT from a DCT isomer mixture by a distillation method,
2,6-DCT, 2,5-DCT, 2,4-D from CT and a mixture of DCT isomers poor in 3,4-DCT concentration
A method for producing a DCT isomer, comprising separating at least one DCT isomer of CT by an adsorption separation method. (2) 2,3-DCT and 3,4-DCT were separated from the DCT isomer mixture by distillation,
2,3-DCT and / or 3,4-DCT from a mixture of DCT isomers based on T and 3,4-DCT
And a method for producing a DCT isomer. (3) 2,3-DCT and / or
Alternatively, 3,4-DCT is separated by distillation, and 2,3-DCT
2,3-DCT and / or 3,4-DCT from a mixture of DCT isomers based on T and 3,4-DCT
Is separated by an adsorption separation method, while at least one of 2,6-DCT, 2,5-DCT, 2,4-DCT is obtained from a mixture of 2,3-DCT and a 3,4-DCT-poor DCT isomer mixture. A method for producing a DCT isomer, wherein the DCT isomer is separated by an adsorption separation method. It is about.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The DCT isomer mixture used in the present invention may be obtained by any method, but it is preferable to use toluene, chlorotoluene or a mixture obtained by chlorinating these mixtures. It is particularly preferable to use chlorinated toluene or o-chlorotoluene.

The distillation column used in the present invention includes, for example,
Batch rectification towers, continuous rectification towers and the like can be mentioned,
2,3-DCT, 3,4-DCT is converted to 2,6-DCT,
Any distillation column can be used as long as it can be separated from 2,5-DCT and 2,4-DCT, but a continuous rectification column is preferably used from an economic viewpoint. The operation pressure of the distillation column may be any of pressurized, normal and reduced pressure conditions. In order to improve the distillation separation efficiency, a packing material such as a Raschig ring or a lessing ring may be used.

As the zeolite that can be used in the adsorption separation method of the present invention, any zeolite can be used as long as it can adsorb DCT, and examples thereof include faujasite, beta, and MFI. Among these zeolites, faujasite is preferably used.

The faujasite-type zeolite is a crystalline aluminosilicate represented by the following general formula expressed by a molar ratio of an oxide.

[0013] _{M 2 / n O · Al 2} O 3 · xSiO 2 · yH 2 O wherein, M is a metal ion or hydrogen ion, n represents the valence of the metal ion or hydrogen ion. x is a silica / alumina ratio, and x is less than 3 when X-type zeolite;
Three or more are called Y-type zeolites. y varies depending on the degree of hydration.

The adsorption and separation performance of each isomer of DCT varies depending on the zeolite structure used. In addition, the silica / alumina ratio constituting zeolite even with the same zeolite structure,
It also changes depending on the type of exchange cation. As the adsorbent for each isomer of DCT, for example, JP-A-59-199642, JP-A-60-42340, JP-A-5-70383, JP-A-58-1983
No. 137795, Japanese Patent Laid-Open No. 3-20232, and the like. Therefore, the adsorbent may be appropriately selected according to the purpose of the present invention.

The technique for adsorptive separation of the DCT isomer by the method of the present invention may be a so-called chromatographic preparative method, or an adsorptive preparative method using a simulated moving bed in which this method is continuous. In the case of a simulated moving bed, the most adsorbed isomer is recovered in the extract stream, and the least adsorbed material is recovered in the raffinate stream.

The continuous adsorptive separation technique using a simulated moving bed is as follows:
As the basic operation, the following adsorption operation, concentration operation, desorption operation, and desorbent recovery operation are continuously circulated. As an example, an operation in the case where 2,6-DCT is separated from a mixture of DCT isomers using an adsorbent that most readily adsorbs 2,6-DCT will be described below. (1) Adsorption operation The DCT isomer mixture is brought into contact with the adsorbent and 2,6-DCT
Is selectively adsorbed as a strongly adsorbed component, and another DCT, which is a weakly adsorbed component, is recovered as a raffinate stream together with a desorbent described later. (2) Concentration operation The adsorbent selectively adsorbing 2,6-DCT, which is a strongly adsorbed component, is brought into contact with a portion of an extract described later, and the weakly adsorbed component remaining on the adsorbent is removed. It is driven off and the 2,6-DCT is concentrated. (3) Desorption operation The adsorbent containing the concentrated 2,6-DCT is brought into contact with the desorbent to expel 2,6-DCT from the adsorbent, and is recovered together with the desorbent as an extract stream. (4) Desorbent recovery operation The adsorbent substantially adsorbing only the desorbent is brought into contact with a part of the raffinate stream, and a part of the desorbent contained in the adsorbent is recovered as a desorbent recovery stream.

FIG. 1 schematically shows the adsorption separation operation using the simulated moving bed. Adsorption chambers 1 to 12 filled with the adsorbent are continuously circulated and connected.

The desorbent used in these adsorption / separation methods is required not to impair the desorbing agent's separation performance in the presence of the desorbing agent, to be able to efficiently desorb the DCT adsorbed on the adsorbing agent, and to be easily used in CT. Characteristics such as being separable are required. Various alkyl-substituted and / or halogen-substituted aromatic compounds can be used as the desorbing agent satisfying such properties. Among them, trimethylbenzene,
Xylene is preferably used. The operating conditions for the adsorption separation are as follows: temperature is from room temperature to 350 ° C., preferably 50 to 250 ° C., and pressure is from atmospheric pressure to 5 MPa, preferably from atmospheric pressure to 4 MPa. The adsorption can be carried out in either the gas or liquid phase, but is preferably carried out in the liquid phase in order to lower the operating temperature and to suppress undesired side reactions of the raw material feed or the desorbent.

Embodiments for economically producing each of the DCT isomers from the DCT isomer mixture by distillation and adsorption are shown in FIGS. By a production method combining distillation separation and adsorption separation as shown in the figure, each isomer of DCT can be produced efficiently.

FIG. 2 shows that the 2,3-
FIG. 2 shows a process of distilling a DCT, 3,4-DCT mixture and then obtaining each isomer or one by adsorptive separation. This process allows 2,3-DCT
And / or 3,4-DCT and 2,3-DCT,
It is possible to obtain an isomer mixture having a low 3,4-DCT concentration.

The 2,3-DCT obtained in FIG.
Of the 3,4-DCTs, those having a low purity are preferable because both 2,3-DCTs and 3,4-DCTs can be produced by purifying and separating them by an adsorption separation method.

FIG. 3 shows that a 2,3-
DCT, 3,4-DCT An isomer mixture having a low concentration is separated by distillation, and then 2,4-DCT and / or 2,3-DCT, 3,4-DCT, 2,4-D is obtained by adsorption separation.
FIG. 4 shows a process for obtaining a DCT isomer mixture having a low CT concentration. FIG. This process allows 2,4-D
CT and / or 2,3-DCT, 3,4-DCT,
A 2,4-DCT-poor DCT isomer mixture and / or a 2,3-DCT, 3,4-DCT mixture can be obtained.

FIG. 4 shows that the mixture of 2,3-DCT, 3,4-DCT, and 2,4-DCT-poor DCT isomers obtained in the process shown in FIG.
Fig. 2 illustrates a process for obtaining 2,6-DCT and / or 2,5-DCT. By this process, the 2,3-DCT, 3,4-DCT, 2,4-DCT of FIG.
From the poorly concentrated DCT isomer mixture, 2,6-DCT
And / or 2,5-DCT can be obtained.

FIG. 5 shows a manufacturing method in which the processes of FIGS. 2 and 4 are combined.

If the DCT mixture was obtained by chlorination of o-chlorotoluene, 2,3-DCT and 3,4
The liquid rich in DCT is separated by distillation, while the 2,3-D
2,6-DCT, 2,5-DCT, 2,4-D from CT and a mixture of DCT isomers poor in 3,4-DCT concentration
Preferably, at least one DCT isomer of CT is separated by an adsorption separation method. In this case, the liquid rich in 2,3-DCT and 3,4-DCT has a purity of 2,3-DCT of 9
It is preferable to increase the number of theoretical plates in the distillation column so as to be 0% by weight or more. More preferably, the purity of 2,3-DCT is 96% by weight or more. A few obtained in this way
-DCT can be used as it is as a fine chemical product, a chemical raw material, or the like. On the other hand, 2,3-DCT
And 2,6-DCT, 2,5-DCT, 2,4-DCT from a DCT isomer mixture having a low concentration of 3,4-DCT.
At least one DCT isomer can be separated by an adsorption separation method.

[0026]

Example 1 The composition of a DCT isomer mixture produced by chlorinating toluene was 2,5- / 2,4- / 2,6- / 2,3- / 3,4-DCT = 27.5 / 35.0 / 21.2 /
It was 7.7 / 8.6 (% by weight). This DCT isomer mixture was separated by distillation in a distillation column having 100 stages. as a result,
The DCT isomer composition recovered from the top of the distillation column was 2,5- / 2,4
-/ 2,6- / 2,3- / 3,4-DCT = 32.6 / 41.7 / 25.3 / 0.19 / 0.21 (% by weight). On the other hand, the DC recovered from the bottom of the distillation column
T isomer composition is 2,5- / 2,4- / 2,6- / 2,3- / 3,4-DCT = 0.84 / 0.4
3 / 0.00 / 46.6 / 51.8 (% by weight).

2,3-DCT and 3,4-DCT are 2,5
It was found that -DCT, 2,4-DCT, and 2,6-DCT can be sufficiently separated by a distillation method.

Example 2 The composition of a DCT isomer mixture produced by chlorinating o-chlorotoluene is 2,3- / 2,4- / 2,5- / 2,6-DCT = 14.5 / 18.2 / 3
6.0 / 31.2 (% by weight). This DCT isomer mixture was separated by distillation in a distillation column having 100 stages. as a result,
2,3-DCT having a purity of 96% by weight or more was obtained from the upper part of the distillation column.

It has been found that 2,3-DCT can be separated by distillation.

Example 3 Na-type X zeolite (SiO ₂ / Al ₂ O ₃ molar ratio 2.5, manufactured by Tosoh) which is a faujasite type zeolite, Na-type Y zeolite (SiO ₂ / Al ₂ O ₃ molar ratio 5.1) 130 ° C., using a molded product of Tosoh Corporation, using various metal ion exchanged adsorbents.
Table 1 shows the results of examining the adsorptive power of each isomer of DCT in the above.

[0031]

[Table 1]

From Table 1, it can be seen that the order of adsorption power of each isomer of DCT changes depending on the adsorbent and desorbent. From the comparison of the adsorption powers, the smaller the 2,3-DCT and 3,4-DCT, the more the 2,6-DCT, 2,5-DCT, 2,4-DCT.
It can be seen that the separation performance of the compound is greatly improved.

Further, a DCT isomer mixture consisting of 2,3-DCT and 3,4-DCT is adsorbed and separated by 2,3-DCT.
And / or 3,4-DCT can be separated. Further, it can be seen that 2,6-DCT can be separated as a strongly adsorbed component and 2,4-DCT can be separated as a weakly adsorbed component from the DCT isomer mixture.

Example 4 Pseudo-migration using the raw material before distillation of 2,3-DCT and 3,4-DCT shown in Example 1 and the raw material from which 2,3-DCT and 3,4-DCT were removed by distillation. The separation performance was examined on the floor.

Using Ag-Na-X as the adsorbent and ortho-xylene as the desorbent, the adsorption separation performance was evaluated in four desorption zones, three enrichment zones, three adsorption zones, and two desorbent recovery zones. 2,6-DCT production is 2,3-DCT, 3,4-
It was found that the raw material from which DCT was removed by distillation was 1.2 times higher.

Example 5 The weight ratio of 2,3-DCT and 3,4-DCT is 61.3.
/37.6 were separated on the simulated moving bed apparatus of FIG. Ag-Na-X was used as the adsorbent, and mixed xylene (o- / p- = 1.8) was used as the desorbent. From the extract, 2,3-DCT / 3,4-DCT = 99/1
(Ratio by weight) from the raffinate is 3,4-D
A component of CT / 2,3-DCT = 97/3 (weight ratio) was obtained. By removing the mixed xylene of the desorbing agent by distillation, 99 wt% of 2,3-DCT and 97 wt% of 3,4-DCT were obtained, respectively.

[0037]

According to the method of the present invention, a high purity DCT isomer can be obtained efficiently by separating the DCT isomer.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an adsorption / separation operation using a simulated moving bed which is one embodiment of the adsorption / separation method of the present invention.

FIG. 2 is a schematic diagram of an example of a production flow for economically producing each isomer of DCT by combining distillation and adsorption separation.

FIG. 3 is a schematic diagram of an example of a production flow for economically producing each isomer of DCT by combining distillation and adsorption separation.

FIG. 4 is a schematic diagram of an example of a production flow for economically producing each isomer of DCT by combining distillation and adsorption separation.

FIG. 5 is a schematic diagram of an example of a production flow for economically producing each isomer of DCT by combining distillation and adsorption separation.

[Explanation of symbols]

 1 to 12: adsorption chamber 13: desorbent supply line 14: extract extraction line 15: isomer mixture supply line 16: raffinate extraction line 17: desorbent recovery line 18: valve

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Tetsuji Kitagawa 1 Toray Co., Ltd. Nagoya Office, 9-9 Oe-cho, Minato-ku, Nagoya-shi, Aichi

Claims (7)

[Claims] (1) a dichlorotoluene isomer mixture,
3-Dichlorotoluene and / or 3,4-dichlorotoluene are separated by distillation, and 2,6-dichlorotoluene,
A process for producing dichlorotoluene isomers, comprising separating at least one dichlorotoluene isomer of 2,5-dichlorotoluene and 2,4-dichlorotoluene by an adsorption separation method. 2. A process according to claim 2, wherein the mixture of isomers of dichlorotoluene is 2,3.
-Dichlorotoluene and 3,4-dichlorotoluene are separated by distillation, then 2,3-dichlorotoluene and / or Alternatively, a method for producing a dichlorotoluene isomer, comprising separating 3,4-dichlorotoluene by an adsorption separation method. 3. A process according to claim 1, wherein the mixture of isomers of dichlorotoluene is 2,3.
-Dichlorotoluene and / or 3,4-dichlorotoluene are separated by distillation, and 2,3-dichlorotoluene and 2,3-dichlorotoluene And / or 3,4-dichlorotoluene is separated by adsorption separation, while 2,3-dichlorotoluene and 3,4
Separating at least one dichlorotoluene isomer of 2,6-dichlorotoluene, 2,5-dichlorotoluene, 2,4-dichlorotoluene from a dichlorotoluene isomer mixture having a low dichlorotoluene concentration by an adsorption separation method; A process for producing a characteristic dichlorotoluene isomer. 4. The process for producing a dichlorotoluene isomer according to claim 1, wherein the adsorbent used in the adsorption separation method is a faujasite type zeolite. 5. The method according to claim 1, wherein the dichlorotoluene isomer mixture is a dichlorotoluene isomer mixture obtained by chlorination of toluene and / or o-chlorotoluene. A method for producing a dichlorotoluene isomer. 6. A 2,3-dichlorotoluene having a purity of 96% by weight or more is separated from a dichlorotoluene isomer mixture obtained by chlorination of o-chlorotoluene by a distillation method.
At least one dichlorotoluene isomer of 2,6-dichlorotoluene, 2,5-dichlorotoluene, and 2,4-dichlorotoluene is obtained from a dichlorotoluene isomer mixture having a low concentration of 2,3-dichlorotoluene and 3,4-dichlorotoluene. The process for producing a dichlorotoluene isomer according to any one of claims 1 to 4, wherein the isomers are separated by an adsorption separation method. 7. A process for preparing a mixture of isomers of dichlorotoluene,
-Dichlorotoluene and 3,4-dichlorotoluene are separated by distillation, and then 2,3-dichlorotoluene or 3,3-dichlorotoluene or 3 4. The method according to claim 2, wherein after purifying and separating any one of 4,4-dichlorotoluene by an adsorption separation method, the remaining dichlorotoluene isomer purified and separated is separated by an adsorption separation method. 4. The method for producing a dichlorotoluene isomer according to claim 1.