JPH0437053B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for isomerizing dichlorotoluene (hereinafter abbreviated as "DCT"). [Prior art] DCT is generally obtained by dichlorination of toluene, but this reaction is a highly oriented reaction, and the types of isomers obtained and the production ratio of isomers vary from 2,4-DCT20 to 35%, 2,5-DCT25
~55%, 2,6-DCT5~25%, 2,3-DCT8
~12%, 3,4-DCT 5~12%. Therefore, depending on the dichlorination of toluene, 3,5-
Since DCT cannot be obtained, it is necessary to isomerize DCT. 2,3-, 2,6-DCT isomers, as well as 3,5-DCT produced by isomerization,
To use it as a single unit, it must be separated. These isomers cannot be separated by distillation because their boiling points are close to each other.
For example, as shown in Japanese Patent Application Laid-Open No. 60-42340,
This can be achieved by an adsorption separation method or a combination of an adsorption separation method and a distillation method. The remaining DCT isomers that were separated and removed are again converted into 2,3-, 2,6-, 3,5-
It is economically extremely important to increase the concentration of at least one of the DCT isomers. Thereafter, the desired DCT isomer is separated and removed again, and this cycle is repeated. As a method for carrying out such an isomerization reaction, a method using mordenite type zeolite is disclosed in JP-A-58-144330.
The isomerization ability of 2,6-,3,5-DCT is still insufficient. Also, for example, JP-A-60-
Publication No. 42340 proposes a method for isomerizing DCT using ZSM-5;
-, 2,6-, 3,5-DCT generation does not occur. [Problems to be solved by the invention] These conventionally known isomerization reactions lack sufficient catalytic activity and require a long time for reaction, or require a large amount of catalyst, making them difficult to use as industrial isomerization methods. None of these were desirable. The present inventors solved this problem and efficiently isomerized DCT to 2,3-, 2,6-, 3,5
-As a result of intensive studies to establish an industrially superior method for increasing the concentration of at least one component of DCT, the present invention was achieved by discovering that a specific zeolite exhibits excellent catalytic performance in this reaction. [Means for solving the problems] The present invention provides 2,3-, 2,6- and 3,5-
A DCT isomer mixture having a poor concentration of at least one component of DCT is brought into contact with a catalyst consisting of an acid form of beta zeolite.
characterized by increasing the concentration of at least one component among 6- and 3,5-DCT
This provides a DCT isomerization method. For example, the synthesis method of beta-type zeolite is
Disclosed in USP3308069. The most common way to identify a beta zeolite is by its X-ray diffraction pattern. Table 1 shows the characteristic X-ray diffraction pattern of beta zeolite. Table 1 X-ray diffraction pattern lattice spacing d (Å) Intensity 11.7±0.2 M 4.18±0.08 M 3.98±0.08 VS 3.53±0.08 W 3.35±0.08 M 3.32±0.08 M 3.08±0.08 W 2.69±0.08 W Here VS = Very strong M = Intermediate strength W = Weak. Beta-type zeolite is the object of the present invention.
To use it as a catalyst for the DCT isomerization reaction, it must be converted into an acid form. Beta-type zeolite contains organic nitrogen-containing cations during the synthesis stage, so by firing, the organic nitrogen-containing cations can be decomposed into an acid form. It is also possible to further ion-exchange the alkali metal ions such as sodium present in the zeolite with protons or ammonium ions that are proton precursors, or to introduce polyvalent cations of divalent or higher valence, which may be preferable in some cases. . Ion exchange of the zeolite with the above cations can be performed by a known ion exchange method.
For example, ion exchange can be easily performed by treating zeolite with an aqueous solution containing an acid, an ammonium salt, or a water-soluble salt of a polyvalent cation. In the isomerization method of the present invention, the zeolite is usually used as a molded body. The molding method is not particularly limited, and known methods such as a rolling method, an extrusion method, and a compression method can be applied. Furthermore, if necessary during molding, a binder such as alumina sol or clay can be added.
Note that the ion exchange treatment can be performed at any stage before or after molding the zeolite. This zeolite molded body is usually activated by firing at 300 to 700°C to form a catalyst. The isomerization method of the present invention generally uses at least one of the 2,3-, 2,6-, and 3,5-DCT isomers using the acid type zeolite thus prepared as a catalyst. The concentration of the components is poor.
The DCT isomer mixture is contacted to effect isomerization. Such a reaction can be carried out according to various conventionally known isomerization operations, and may be either a gas phase reaction or a liquid phase reaction. Further, any of fixed bed, moving bed, and fluidized bed methods may be used, but fixed bed flow reaction is particularly preferred from the viewpoint of ease of operation. The reaction temperature is usually about 200 to 500℃, but especially
250-450°C is preferred. Although the reaction pressure is not particularly limited, it goes without saying that in the case of a liquid phase reaction, the reaction pressure must be set to maintain the reaction system in a liquid phase state. The weight hourly space velocity (WHSV) is 0.05 to 10 Hr ^-1 , preferably 0.1 to 5 Hr ^-1 . Furthermore, the presence of hydrogen during the isomerization reaction is often effective in extending the life of the catalyst. [Example] Hereinafter, the present invention will be explained with reference to Examples. Example 1 205.2 g of tetraethylammonium hydroxide aqueous solution (content 20%), sodium aluminate aqueous solution (Al ₂ O ₃ content 19.5%, Na ₂ O content 20.2%)
6.55g was dissolved in 150.2g of water. 65.8 g of silicic acid (SiO ₂ content 91.2%) was added to this solution and stirred to prepare an aqueous mixture slurry. Its composition expressed in molar ratio was as follows. SiO ₂ /Al ₂ O ₃ 80 RN ⁺ / (RN ⁺ + Na ⁺ ) 0.929 OH ^- /SiO ₂ 0.30 H ₂ O / OH ^- 60 This mixture slurry was charged into a 500 ml autoclave, sealed and heated to 150℃. The mixture was reacted for 9 days with stirring. Thereafter, it was cooled, filtered and washed with water five times, and dried at about 120°C overnight. As a result of measuring the obtained product by X-ray diffraction method,
The X-ray diffraction pattern shown in Table 2 was shown. The product obtained from this result was beta-type zeolite. Table 2 X-ray diffraction pattern lattice spacing d (Å) Relative intensity 11.59 16 4.16 14 3.976 100 3.528 5 3.328 14 3.033 13 2.939 3 2.688 4 Example 2 Tetraethylammonium hydroxide aqueous solution 96.2g, sodium aluminate aqueous solution 16.8g g to water It was dissolved in 254.1g. 52.6 g of silicic acid was added to this solution and stirred to prepare an aqueous mixture slurry. Its composition, expressed in molar ratio, was as follows. SiO ₂ /Al ₂ O ₃ 25 RN ⁺ / (RN ⁺ + Na ⁺ ) 0.544 OH ^- /SiO ₂ 0.30 H ₂ O / OH ^- 80 This mixture slurry was placed in a 500 ml autoclave, and the temperature was raised to 160℃ after sealing. The mixture was allowed to react for 11 days while being heated and stirred. Then cool, filter,
Washing with water was repeated 5 times and drying was carried out at approximately 120°C overnight. The obtained product was measured by an X-ray diffraction method, and the result was that the X-ray diffraction pattern was substantially the same as that of beta-type zeolite shown in Table 1. Example 3 Alumina sol was added to the beta-zeolite powder synthesized in Example 1 in an amount of 15 wt% in terms of Al ₂ O ₃ , and after kneading it was extruded into 14 to 24 meshes and calcined in air at 500° C. for 2 hours. This beta-type zeolite molded body was ion-exchanged five times at approximately 90℃ using a 10wt% ammonium chloride aqueous solution at a solid-liquid ratio of 2.0/Kg, thoroughly washed with water, dried overnight at 120℃, and then calcined at 540℃ for 2 hours. , an acid type catalyst was prepared. This catalyst will be abbreviated as catalyst "A". The isomerization reaction of DCT was carried out in the liquid phase using catalyst "A" in a fixed bed flow reactor. Reaction conditions WHSV 0.6Hr ^-1 Reaction temperature 300℃ Reaction pressure 30Kg/cm ² G Reaction time 4Hr

[Table] From this result, 2,6-DCT, 3,5-DCT
It can be seen that the concentration of Example 4 The beta zeolite synthesized in Example 2 was used as an acid type catalyst in the same manner as in Example 3. This catalyst will be abbreviated as catalyst "B". Using a fixed bed flow reactor with catalyst “B”,
The isomerization reaction of 2,4-DCT was carried out in the liquid phase. The reaction conditions are shown below. Reaction feed material 2,4-DCT WHSV 0.6Hr ^-1 Reaction temperature 300℃ Reaction pressure 30Kg/cm ² G Reaction time 4Hr The composition of DCT after reaction is 2,5-DCT25.9%,
2,6-DCT, 2.18%3,5-DCT3.88%,2,
4-DCT61.0%, 3,4-DCT2.35%2,3-
The DCT was 4.72%. From this result, 2,3-
It can be seen that DCT, 2,6-DCT, and 3,5-DCT are generated. Example 5 Using a fixed bed flow reactor with catalyst "B",
The isomerization reaction of mixed DCT was carried out in the liquid phase. The reaction conditions are shown below. Reaction source material Mixed DCT WHSV 0.6Hr ^-1 Reaction temperature 300℃ Reaction pressure 10Kg/cm ² G Table 3 shows the composition of the reaction product liquid 24 hours after the start of the reaction.
Shown below. As shown in Table 3, 2,6-, 3,5-,
2,3-DCT each increased significantly. Comparative Example 1 Synthetic mordenite zeolite (SiO ₂ /Al ₂ O ₃
The powder (ratio: 19.5 mol/mol) was molded in the same manner as in Example 3 to obtain an acid type catalyst. This acid type mordenite type zeolite was used and mixed in the same manner as in Example 5.
The isomerization reaction of DCT was carried out. Table 3 shows the composition of the reaction product liquid 6 hours after the start of the reaction.
Shown below. It can be seen that the isomerization ability of 2,3-, 2,6-, 3,5-DCT is low.

〔Effect of the invention〕

The method of the present invention uses a catalyst consisting of an acid form of beta zeolite to isomerize a mixture of dichlorotoluene isomers.
-, 3,5-dichlorotoluene The concentration of at least one component of each isomer can be increased. 2,3-, 2,6-, and 3,5-dichlorotoluene are each separated by an adsorption separation method and/or a distillation method. These isomers are used as intermediates for medicines and agricultural chemicals.

Claims (1)

[Claims] 1 Contacting a dichlorotoluene isomer mixture with a poor concentration of at least one component among 2,3-, 2,6- and 3,5-dichlorotoluene with a catalyst consisting of an acid form of beta-type zeolite,
A method for isomerizing dichlorotoluene, the method comprising increasing the concentration of at least one of 2,3-, 2,6- and 3,5-dichlorotoluene.