JPH0478623B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a method for producing 1,2,4,5-tetramethylbenzene, which is useful as an intermediate raw material for pyromellitic acid, which is a raw material for polyimide resin, which is a thermoplastic or heat-resistant resin. When methylating xylene and/or 1,2,4-trimethylbenzene using methanol in the gas phase, proton-type crystalline aluminosilicate ZSM-5 with a primary particle size of 1 μm or less is used as a catalyst in the presence of hydrogen. 1, 2, characterized in that the reaction is carried out at
This invention relates to a method for producing 4,5-tetramethylbenzene. (Prior art) Currently, methods for producing 1,2,4,5-tetramethylbenzene include methods of direct concentration and crystallization separation from catalytic reformed oil, methods of disproportionation of trimethylbenzene, Alternatively, a method of methylating trimethylbenzene is known. Direct concentration and crystallization separation from catalytic reformed oil requires a large amount of cost and is not economical because the concentration of 1,2,4,5-tetramethylbenzene contained in the reformed oil is low. Regarding the method of disproportionating trimethylbenzene, a method using silica alumina, mordenite, or phasiasite type zeolite as a catalyst has been reported (Japanese Patent Publication No. 13778/1983). However, this method has the disadvantage that the disproportionation activity is low and the activity of the catalyst is significantly reduced. Regarding the method of methylating trimethylbenzene, a liquid phase method using a Lewis acid catalyst such as aluminum chloride is generally known, but this method has problems such as low activity and corrosion of the equipment. On the other hand, regarding the method of methylating 1,2,4-trimethylbenzene with methanol in the gas phase, a method using ZSM-5 or ZSM-5 treated with silicon tetrachloride as a catalyst has been proposed [JP-A-Show No. 59-39836, Proceedings of the 49th Spring Annual Meeting of the Chemical Society of Japan, 2Q10, 590 (1984)]. (Problems to be Solved by the Invention) The conventional method of methylating 1,2,4-trimethylbenzene with methanol in the gas phase has been greatly improved in terms of activity selectivity compared to other conventional methods. However, the catalytic activity deteriorated quickly over time and was not satisfactory as an industrial production method. (Means for solving the problem) As a result of intensive studies to solve the problem of decreased activity, the present inventors have developed a proton-type crystalline aluminosilicate ZSM-5 with a primary particle size of 1 μm or less as a catalyst. The present inventors have discovered that 1,2,4,5-tetramethylbenzene can be produced with a very small reduction in activity and a high selectivity when the reaction is carried out in the presence of hydrogen, and the present invention has been completed. That is, the present invention provides a method for producing 1,2,4,5-tetramethylbenzene by gas-phase methylation of xylene and/or 1,2,4-trimethylbenzene using methanol. The present invention relates to a method for producing 1,2,4,5-tetramethylbenzene, which is characterized by using a proton-type crystalline aluminosilicate ZSM-5 having a diameter of 1 μm or less and reacting it in the presence of hydrogen. In the present invention, a crystalline aluminosilicate is used as a catalyst, but the crystalline aluminosilicate must have an average primary particle diameter of 1 μm or less, preferably 0.5 μm or less, as observed by an electron microscope. belongs to. When the particle size is larger than 1 μm, the activity of the catalyst is greatly reduced. For example, when the reaction is carried out in a fixed bed, the activity is reduced to about half in a few hours. On the other hand, when fine particles with a particle size of 1 μm or less, especially 0.5 μm or less are used, the activity hardly decreases for several tens of hours. This fact is a surprising and hitherto unexpected finding. The reason why proton-type crystalline aluminosilicate ZSM-5 with a primary particle size of 1 μm or less exhibits less activity decline is unknown, but it is thought to be as follows. The 1,2,4,5-tetramethylbenzene used in the present invention has a large molecular diameter and is more likely to be produced at acid sites outside the pores than in the narrow pores of the crystalline aluminosilicate. When the crystals become fine particles, the ratio of acid sites outside the pores to the total acid sites increases, which is thought to extend the catalyst life. For comparison, the average particle size is
Table 1 shows the ratio of acid sites outside the pores to the total acid sites of H-ZSM-5 with a diameter of 1 μm or less and larger than that. However, the measurement is based on pyridine (total acid points) 4 at 300℃.
- Determined from the amount of irreversible adsorption of methylquinoline (acid sites outside the pores).

[Table] The proton-type crystalline aluminosilicate ZSM-5 of the present invention with a primary particle size of 1 μm or less is usually
The ratio of acid sites outside the pores to total acid sites is 0.07 or more, preferably 0.1 or more. The above crystalline aluminosilicate ZSM of the present invention
-5, for example, 100 to 120
A method of crystallization at a relatively low temperature of 0.degree. C. and under high speed stirring is used. In addition, the crystalline aluminosilicate ZSM-5 used in the present invention can be produced by known methods such as ion exchange using an acid such as nitric acid or hydrochloric acid, ammonium ion exchange using an ammonium salt solution, and then thermal decomposition into proton form. It is converted into a proton exchange type and used as a catalyst. xylene and/or 1 in the present invention,
The 2,4-trimethylbenzene/methanol molar ratio ranges from 0.01 to 100, preferably from 0.1 to 10. Furthermore, by carrying out the reaction in the present invention in the presence of hydrogen, deterioration of catalyst activity over time can be more effectively suppressed. The amount of hydrogen added is 0.01 to 0.01 to xylene and/or 1,2,4-trimethylbenzene as raw materials.
A range of 100 moles is used, preferably a range of 0.1 to 10 moles. The reaction temperature in the present invention is 200 to 500°C, preferably 250 to 400°C. The present invention is carried out under normal pressure or increased pressure, and the reaction method is preferably a flow reaction method using a fixed bed, a fluidized bed, or the like. (Effect of the invention) As is clear from the examples and comparative examples described below,
According to the present invention, 1,2,4,5-tetramethylbenzene can be produced with high selectivity with very little reduction in catalyst activity. (Example) Example 1 To 150 g of Q brand silicate aqueous solution (SiO ₂ : 29.9 wt %), 120 g of 10 wt % tetrapropylammonium hydroxide aqueous solution was added, and then aluminum sulfate [Al ₂ (SO ₄ ) _3.18H ] ₂ O] and 40 g of water were added and stirred for 10 minutes. Thereafter, 20% by weight sulfuric acid was added dropwise to the solution with strong stirring to adjust the pH to 11 to obtain a homogeneous gel. This gel was placed in an autoclave equipped with a stirrer and crystallized at 110° C. for 5 days with stirring at a rotation speed of 200 rpm. The obtained product was filtered, washed, dried at 120°C for 5 hours, then calcined in air at 500°C for 8 hours, and subjected to X-ray diffraction analysis. As a result, this product is ZSM
-5. Furthermore, this crystal was ion-exchanged with a 1N ammonium chloride aqueous solution at 60°C for 24 hours, filtered, washed, dried, and calcined at 500°C for 5 hours to form a proton form. SiO ₂ / determined by fluorescent X-ray analysis of this crystal
The Al ₂ O ₃ molar ratio was 70. In addition, the average particle diameter of primary particles observed using a scanning electron microscope is
It was 0.08 μm. Using this particulate H-ZSM-5 as a catalyst, a gas phase methylation reaction from meta-xylene and methanol was carried out under the following reaction conditions. Meta-xylene/methanol/H ₂ molar ratio = 1/
1/1.5 WHSV (meta-xylene + methanol standard) =
3.4hr ^-1 Reaction temperature: 300°C, pressure: 6Kg/cm ³ The results from 1 to 20 hours after the start of the reaction are shown in Table 2.

[Table] Not included.
Example 2 The same particulate H-ZSM used in Example 1
Using -5, a gas phase methylation reaction from 1,2,4-trimethylbenzene and methanol was carried out under the following conditions. 1,2,4-trimethylbenzene/methanol/
H ₂ = 1/2/4 WHSV (1,2,4-trimethylbenzene + methanol standard) = 3.5 hr ^-1 Reaction temperature: 280°C, pressure: 10 Kg/cm ³ Results from 1 to 20 hours after the start of the reaction It is shown in Table 3.

[Table] does not include the conversion rate.
Example 3 150 g of 10% by weight tetrapropylammonium hydroxide aqueous solution was added to 200 g of Q brand silicate aqueous solution, and aluminum sulfate [Al ₂ (SO ₄ ) ₃ .
18H ₂ O] and 50 g of water were added and stirred for 10 minutes.
Furthermore, 20% by weight sulfuric acid was added dropwise to this solution, and the pH
10.5 to obtain a homogeneous gel. This gel was placed in an autoclave equipped with a stirrer and crystallized at 120° C. for 7 days with stirring at a rotation speed of 100 rpm. The obtained product was filtered, washed, dried at 120°C for 6 hours, then calcined in air at 500°C for 8 hours, and subjected to X-ray diffraction analysis. As a result, this product is ZSM
-5. Further, this crystal was ion-exchanged with a 1N ammonium chloride aqueous solution at 60°C for 24 hours, filtered, washed, dried, and calcined at 500°C for 5 hours to form a proton form. SiO ₂ / determined by fluorescent X-ray analysis of this product
The Al ₂ O ₃ molar ratio was 35. In addition, the average particle diameter of primary particles observed using a scanning electron microscope is
It was 0.3 μm. Using this particulate H-ZSM-5 as a catalyst,
A gas phase methylation reaction from meta-xylene and methanol was carried out under the following reaction conditions. Meta-xylene/methanol/H ₂ = 1/2/2 WHSV (meta-xylene + methanol standard) = 5 hr ^-1 Reaction temperature: 330°C, pressure: 4 Kg/cm ³ Table 4 shows the results from 1 to 20 hours after the start of the reaction. Shown below.

[Table] Comparative Example The same gel as in Example 1 was placed in an autoclave equipped with a stirrer and crystallized at 180° C. for 30 hours with stirring at a rotation speed of 15 rpm. The obtained product was filtered, washed, dried at 120°C for 5 hours, then calcined in air at 500°C for 8 hours, and subjected to X-ray diffraction analysis. As a result, this product is
It was identified as ZSM-5. Furthermore, this was subjected to ion exchange in the same manner as in Example 1 to obtain a proton type. SiO ₂ / determined by fluorescent X-ray analysis of this product
The Al ₂ O ₃ molar ratio was 65. In addition, the average particle diameter of primary particles observed using a scanning electron microscope was 3μ.
It was m. Using this H-ZSM-5 as a catalyst, a gas phase methylation reaction from meta-xylene and methanol was carried out under the same conditions as in Example 1. Table 5 shows the results from 1 to 20 hours after the start of the reaction.

【table】

Claims (1)

[Claims] 1 When producing 1,2,4,5-tetramethylbenzene by gas-phase methylation of xylene and/or 1,2,4-trimethylbenzene using methanol, protons with a primary particle size of 1 μm or less are used as a catalyst. Type crystalline aluminosilicate ZSM−
5. A method for producing 1,2,4,5-tetramethylbenzene, characterized by carrying out the reaction in the presence of hydrogen.