JPH0437055B2 - - 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> Generally, DCT is obtained by dichlorination of toluene, but this reaction is a reaction with strong orientation, and the types of isomers obtained and the production ratio of isomers are 2,4-DCT20 ~35%, 2,5-DCT25
~55%, 2,6-DCT5~25%, 2,3-DCT8
~12%, 3,4-DCT 5~12%. Since 3,5-DCT cannot be obtained by this reaction, it is necessary to isomerize DCT if 3,5-DCT is desired. Each DCT isomer, as well as 3,5-DCT produced by isomerization, must be separated in order to be used as a simple substance. These isomers cannot be separated by distillation because their boiling points are close to each other.
For example, as shown in JP-A-60-42340, this can be achieved by an adsorption separation method or a combination of an adsorption separation method and a distillation method. It is economically extremely important to increase the concentration of the remaining DCT isomer after the target DCT isomer is separated and removed through an isomerization reaction. Then aim again
The DCT isomer is separated off and the cycle is repeated. As a method for carrying out such an isomerization reaction, JP-A-58-144330 discloses a method using mordenite-type zeolite, but the isomerization ability is not sufficient and the isomerization ability decreases with the reaction time. It was not sufficient as an industrial method. <Problems to be solved by the invention> These conventionally known isomerization catalysts do not have sufficient isomerization ability and deteriorate over time.
The present inventors solved such problems and efficiently
We conducted extensive research to establish an industrially superior method for isomerizing DCT and increasing the concentration of DCT isomers that are poorly concentrated. As a result, we found that a catalyst in which rhenium or silver is added to acid-type zeolite can improve the deterioration of isomerization ability over time, and we have already proposed this. The inventors of the present invention continued to study to improve the performance of these catalysts, and found that by adding phosphorus and/or fluorine components, the isomerization ability was increased, or side reactions were suppressed to improve the isomerization reaction. The inventors have discovered that the selectivity can be improved and have arrived at the present invention. <Means for Solving the Problems> That is, the present invention provides a DCT isomer mixture with a poor concentration of 2,6- and/or 3,5-DCT isomers, (a) an acid form of zeolite, and (b) rhenium. and (c) at least one component of phosphorus and fluorine as essential components, in the presence of hydrogen, and 2,6- and/or 3,5-DCT.
DCT characterized by increasing isomer concentration
The present invention provides an isomerization method for The acid type zeolite used in the present invention includes:
Any zeolite can be used as long as it is capable of isomerizing a DCT isomer mixture, but particularly preferred among these are mordenite-type zeolite, beta-type zeolite, pentasil-type zeolite, and the like. Particularly preferred is mordenite-type zeolite. Methods for synthesizing mordenite-type zeolites are disclosed, for example, in Japanese Patent Publication No. 47-46677 and Japanese Patent Application Laid-open No. 91032-1982. The most common way to indicate that it is a mordenite type zeolite is by
This is a line diffraction pattern. Table 1 shows the characteristic X-ray diffraction pattern of mordenite-type zeolite.

[Table] For example, how to synthesize beta-type zeolite
Disclosed in USP3308069. The most common way to indicate that it is a beta zeolite is
This is a line diffraction pattern. Table 2 shows the characteristic X-ray diffraction pattern of beta zeolite.

【table】

[Table] Typical synthetic methods for pentasil-type zeolite are shown in USP 3702886 and USP 4511547, for example. Pentasil type zeolite has a characteristic X-ray diffraction pattern shown in Table 3.

[Table] The zeolite used in the isomerization reaction of the present invention is used in the acid form. As is well known, acid type zeolite can be obtained by converting cations in zeolite into hydrogen ions or polyvalent cations of divalent or higher valence. In particular, an acid form in which the cation is a hydrogen ion is highly active and preferred. In order to convert the cations in zeolite into hydrogen ions, the zeolite is usually ion-exchanged directly with an aqueous acid solution, or the metal cations are ion-exchanged with ammonium ions, followed by calcination. Further, when the zeolite has organic nitrogen-containing cations in advance, the organic nitrogen-containing cations can be decomposed and converted into hydrogen ions by calcination, thereby making it possible to form an acid-type zeolite. Of course, if necessary, it is also possible to ion-exchange the alkali metal ions such as sodium present in the zeolite during the zeolite production using the ion exchange method described above. One of the essential components of the catalyst used in the present invention is at least one of rhenium and silver. Rhenium is introduced into the catalyst by an impregnation method, a kneading method, or the like. Rhenium can be present in elemental form or in the form of compounds such as oxides, sulfides, and selenides; in either case, the rhenium component is approximately 0.01 of the total catalyst amount, calculated as rhenium atoms.
Excellent results are obtained when the content is from 2.0% by weight to about 2.0% by weight. Particularly preferred is about 0.05% to about 1.0% by weight. What can be used as rhenium components are:
Examples include perrhenic acid, ammonium perrhenate, and rhenium chloride. Silver is introduced by an ion exchange method, an impregnation method, a kneading method, etc.
In either case, it is preferred that the catalyst contains a silver component in terms of silver atoms of about 0.1% to about 15% by weight, particularly about 0.2% to about 10% by weight of the total catalyst amount. When silver is introduced into a zeolite component by an ion exchange method, ion exchange is generally performed with an aqueous solution, and therefore, it is essential that the silver compound that can be used be water-soluble; an example of this is silver nitrate. be able to. In the case of the impregnation method, as well as the ion exchange method, it is generally carried out in an aqueous solution, so examples of the silver compound used include water-soluble silver nitrate. However, in the case of the impregnation method, silver ions are easily ion-exchanged with zeolite, so it is considered to be substantially the same as the ion exchange method. In the case of the kneading method, the silver compound does not necessarily have to be water-soluble, and may be an insoluble compound such as silver silveride or silver carbonate. Among these methods, the ion exchange method is more preferable because it can uniformly disperse silver ions in the zeolite. Note that at least one of phosphorus and fluorine, which are essential components of the catalyst characteristically used in the present invention, is introduced by an impregnation method, a mixing method, or the like. The phosphorus or fluorine component is preferably contained in an amount of 0.05% to 1% by weight of the total amount of the catalyst as a phosphorus atom or a fluorine atom. Water-soluble phosphorus compounds are preferably used as the phosphorus component, such as phosphoric acid, ammonium phosphate,
Examples include ammonium hydrogen phosphate. What can be used as the fluorine component is preferably a water-soluble fluorine compound, such as ammonium fluoride. When such a catalyst is used in the present invention, it is usually used in the form of a molded body. The molding method is not particularly limited, and rolling methods, extrusion methods, compression methods, etc. are used. If necessary during molding, it is also possible to add a binder such as alumina sol or clay. Note that the ion exchange treatment or the application of the rhenium component is preferably carried out after molding in view of the ease of catalyst preparation. This zeolite molded body is usually activated and used as a catalyst by firing at 300 to 700°C. Another essential requirement constituting the isomerization method of the present invention is the presence of hydrogen during the isomerization reaction. The amount of hydrogen present needs to be 0.003 mol/mol or more in terms of molar ratio to the feedstock DCT, and if it is too large, it is disadvantageous in terms of economic efficiency, so the upper limit is determined by considering the economic efficiency. Usually it is 10 mol/mol or less. The isomerization method of the present invention converts a DCT isomer mixture with a poor concentration of 2,6- and/or 3,5-DCT isomers into (a) an acid form of zeolite, and (b) at least one of rhenium and silver. and (c) a catalyst containing at least one of phosphorus and fluorine as an essential component is brought into contact with the catalyst in the presence of hydrogen 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. However, a more preferred embodiment is to place the DCT in a liquid phase and to provide hydrogen gas at least partially in the liquid phase.
This is a method in which isomerization is performed while dissolved in DCT. When the high-boiling products generated on the catalyst are reacted in the liquid phase, they flow out of the system along with the liquid phase DCT, but in the case of the gas phase, they remain on the catalyst and become coke components, which are subject to catalytic activity. It can easily become a toxic substance. Furthermore, 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 . The isomers of dichlorotoluene with increased concentrations of 2,6- and/or 3,5-DCT isomers thus obtained by isomerization can be separated by adsorption separation method and/or
Or separated by distillation method. These isomers are used as intermediates for medicines and agricultural chemicals. <Example> Hereinafter, the present invention will be specifically explained with reference to Examples. Example 1 Synthetic mordenite-type zeolite (SiO ₂ /Al ₂ O ₃
(ratio 19.5 mol/mol) powder, alumina sol
Add _15wt % in terms of _Al2O3 , knead, extrude into 14-24 meshes, dry overnight at about 120℃,
C. for 2 hours in air. This mordenite molded body was ion-exchanged five times using a 10 wt % ammonium chloride aqueous solution at a solid-liquid ratio of 2.0/Kg at about 90° C. and thoroughly washed with water. Next, this ammonium ion-exchanged zeolite was dried overnight at 120°C, and 30g was collected on an absolutely dry basis. Ammonium fluoride 3.33g
The zeolite was immersed in a solution of 90 ml of distilled water and left at room temperature for 3 hours. Thereafter, the liquid was drained, and the sample was immersed in an aqueous perrhenic acid solution containing 0.06 g of rhenium as a metal, and left at room temperature for 3 hours. After that, drain the liquid again, dry it at about 120℃ overnight, and then dry it at 540℃.
℃ for 2 hours. The rhenium content contained in this catalyst was analyzed and found to be 0.09 wt%, and the fluorine content was analyzed to be 0.45 wt%. Using this catalyst, a fixed bed flow reactor is used,
The isomerization reaction of DCT was carried out in the liquid phase in the presence of hydrogen. The results are shown in Table 4. Example 2 A catalyst was prepared in the same manner as in Example 1. However, the amount of ammonium fluoride used was 1.67 g instead of 3.33 g. Results of analyzing the rhenium content contained in the catalyst
0.09wt%, and the result of analyzing the fluorine content
It was 0.29wt%. Table 4 shows the results of a reaction using this catalyst in a fixed bed flow reactor. Comparative Example 1 Synthetic mordenite zeolite (SiO ₂ /Al ₂ O ₃
(ratio 19.5 mol/mol) powder, alumina sol
Add _15wt % in terms of _Al2O3 , knead, extrude into 14-24 meshes, dry overnight at about 120℃,
C. for 2 hours in air. This mordenite molded body was ion-exchanged five times using a 10 wt % ammonium chloride aqueous solution at a solid-liquid ratio of 2.0/Kg at about 90° C. and thoroughly washed with water. The ammonium ion-exchanged zeolite was then dried at 120°C overnight, and then calcined at 540°C for 2 hours. Table 4 shows the results of a reaction using this catalyst in a fixed bed flow reactor. Comparative Example 2 Synthetic mordenite zeolite (SiO ₂ /Al ₂ O ₃
(ratio 19.5 mol/mol) powder, alumina sol
Add _15wt % in terms of _Al2O3 , knead, extrude into 14-24 meshes, dry overnight at about 120℃,
C. for 2 hours in air. This mordenite molded body was ion-exchanged five times using a 10 wt % ammonium chloride aqueous solution at a solid-liquid ratio of 2.0/Kg at about 90° C. and thoroughly washed with water. Next, this ammonium ion-exchanged zeolite was dried overnight at 120°C, and 30g was collected on an absolutely dry basis. This zeolite was immersed in an aqueous perrhenic acid solution containing 0.06 g of rhenium as a metal, and left at room temperature for 3 hours. Thereafter, the liquid was drained, dried at about 120°C overnight, and then baked at 540°C for 2 hours. As a result of analyzing the rhenium content contained in this catalyst,
It was 0.09wt%. Table 4 shows the results of a reaction using this catalyst in a fixed bed flow reactor.

【table】

[Table] Example 3 Zeolite was molded in the same manner as in Example 1, and after firing, ammonium ion exchanged zeolite was heated at 120°C overnight.
30g was collected on an absolutely dry basis. Zeolite was ion-exchanged with a silver nitrate aqueous solution containing 1.5 g of silver metal at room temperature at a solid-liquid ratio of 2/Kg. After thorough washing with water, the sample was immersed in an aqueous solution containing 1.67 g of ammonium fluoride at a solid-liquid ratio of 3/Kg and left for 3 hours. Thereafter, the liquid was drained, dried at about 120°C overnight, and then baked at 540°C for 2 hours. The silver content contained in this catalyst was 4.2 wt%, and the fluorine content was 0.28 wt%. Using this catalyst, a fixed bed flow reactor is used,
The isomerization reaction of DCT was carried out in the presence of hydrogen in the liquid phase. The results are shown in Table 5. Example 4 After molding and firing in the same manner as in Example 1, ammonium ion-exchanged zeolite was dried overnight at 120° C., and 30 g on an absolutely dry basis was collected. as silver metal
Zeolite was heated at room temperature with an aqueous silver nitrate solution containing 1.5 g.
Ion exchange was performed at a solid-liquid ratio of 2/Kg. After thorough washing with water, the sample was immersed in an aqueous solution containing 0.394 g of ammonium phosphate at a solid-liquid ratio of 2/Kg, and left for 3 hours.
After that, drain the liquid, dry it at about 120℃ overnight, and then
It was baked at 540°C for 2 hours. The silver content contained in this catalyst was 4.3 wt%, and the phosphorus content was 0.08 wt%. Using this catalyst, the isomerization reaction of DCT was carried out in the liquid phase in the presence of hydrogen using a fixed bed flow reactor. The results are shown in Table 5. Comparative Example 3 A catalyst was prepared in the same manner as in Example 3. However, no treatment with ammonium fluoride was performed. Using this catalyst, a fixed bed flow reactor is used,
The isomerization reaction of DCT was carried out in the presence of hydrogen in the liquid phase. The results are shown in Table 5. Since the isomerization ability is lower than that of a catalyst treated with ammonium fluoride or ammonium phosphate, it is necessary to raise the reaction temperature by about 15°C to show the same level of isomerization ability. Example 5 A zeolite which was molded in the same manner as in Example 1 and subjected to ammonium ion exchange after firing was dried at 120° C. overnight, and 30 g on an absolutely dry basis was collected. as silver metal
Zeolite was heated at room temperature with an aqueous solution of silver nitrate containing 0.6 g.
Ion exchange was performed at a solid-liquid ratio of 2/Kg. After washing thoroughly with water, the sample was immersed in an aqueous solution containing 3.33 g of ammonium fluoride at a solid-liquid ratio of 2/Kg, and left at room temperature for 3 hours. Thereafter, the liquid was drained, and the sample was immersed in an aqueous perrhenic acid solution containing 0.06 g of rhenium as a metal, and left at room temperature for 3 hours. After that, drain the liquid again and dry it at about 120℃ overnight.
Then, it was baked at 540°C for 2 hours. Silver present in the catalyst was 1.9 wt%, rhenium was 0.9 wt%, and fluorine was 0.42 wt%. Using this catalyst, a fixed bed flow reactor is used,
The isomerization reaction of DCT was carried out in the presence of hydrogen in the liquid phase. The results are shown in Table 5.

[Table] Example 6 47.0 g of an aqueous tetraethylammonium hydroxide solution (content 20%) and 17.8 g of an aqueous sodium aluminate solution were dissolved in 332.3 g of water. 53.5 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 PN ⁺ /(RN ⁺ +Na ⁺ ) 0.305 OH ^- /SiO ₂ 0.246 H ₂ O/OH ^- 0.246 This mixture slurry was charged into a 500 ml autoclave, and after sealing, the temperature was raised to 160℃. The reaction was allowed to proceed for 7 days with stirring. Thereafter, it was cooled, filtered, washed with water 5 times, and dried overnight at about 120°C. As a result of measuring the obtained product by X-ray diffraction method,
The X-ray diffraction pattern was substantially the same as that of the mordenite zeolite shown in Table 1. Example 7 A catalyst was prepared in the same manner as in Example 1 using the mordenite zeolite synthesized in Example 6. Using this catalyst, a fixed bed flow reactor is used,
The isomerization reaction of DCT was carried out in the liquid phase in the presence of hydrogen. The results are shown in Table 6. Example 8 A catalyst was prepared using the mordenite zeolite synthesized in Example 6 as follows. Adding alumina sol to mordenite-type zeolite powder
After adding 15wt% in terms of Al ₂ O ₃ and kneading, extrusion molding into 14 to 24 meshes, drying at about 120℃ overnight,
C. for 2 hours in air. This mordenite molded body was ion-exchanged five times using a 10 wt % ammonium chloride aqueous solution at a solid-liquid ratio of 2.0/Kg at about 90° C. and thoroughly washed with water. Next, this ammonium ion-exchanged zeolite was dried overnight at 120°C, and 30g was collected on an absolutely dry basis. Ammonium phosphate 0.394
g was taken and dissolved in a perrhenic acid aqueous solution containing 0.06 g of rhenium. Soak zeolite in this mixture,
It was left at room temperature for 3 hours. Thereafter, the liquid was drained, dried at 120°C overnight, and then baked at 540°C for 2 hours. Using this catalyst, a fixed bed flow reactor is used,
The isomerization reaction of DCT was carried out in the liquid phase in the presence of hydrogen. The results are shown in Table 6.

【table】

[Table] <Effects of the Invention> According to the present invention, it is possible to provide a method for isomerizing dichlorotoluene in which the isomerization ability is increased, side reactions are suppressed, and selectivity to the isomerization reaction is improved.

Claims (1)

[Scope of Claims] 1. A mixture of dichlorotoluene isomers with a poor concentration of 2,6- and/or 3,5-dichlorotoluene isomers, (a) acid form of zeolite, (b) rhenium and silver (c) A catalyst containing at least one component of phosphorus and fluorine as essential components is brought into contact with the catalyst in the presence of hydrogen to adjust the concentration of 2,6- and/or 3,5-dichlorotoluene isomers. A method for isomerizing dichlorotoluene, which is characterized by increasing the amount of dichlorotoluene. 2. The method for isomerizing dichlorotoluene according to claim 1, wherein the zeolite is a mordenite type zeolite.