JPH0639426B2 - Method for producing 1,2,4,5-tetraethylbenzene - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing 1,2,4,5-tetraethylbenzene. 1,2,4,5-Tetraethylbenzene is also useful as a raw material for producing vinylbenzenes and benzenecarboxylic acids, especially pyromellitic dianhydride.

[Conventional technology]

Tetraethylbenzene is obtained by ethylating benzene with an ethylating agent such as ethylene, but a method suitable for industrial production has not been reported.

Alkylation such as ethylation proceeds in the presence of a Friedel-Crafts catalyst (Japanese Examined Patent Publication No. 52-12,178, JP-A No. 61-65,827).
However, it is difficult to selectively produce tetraethylbenzene having four ethyl groups as compared with that having one ethyl group such as ethylbenzene.

In addition, in order to selectively obtain 1,2,4,5-tetraalkylbenzene, a method for producing tetraalkylbenzene by alkylating xylene with propylene or butene (Japanese Patent Publication No.
-12,178, Japanese Patent Publication No. 50-10,290, JP-A-48-72,130,
JP-A-48-19,526, JP-A-48-85,540, JP-A-49-35,
339), a method for producing tetraalkylbenzene by alkylating pseudocumene or mesitylene with propylene (Japanese Patent Publication No. 52-3369), and the like,
The raw material and the intended product are different from these methods.

1,2,4,5- from benzene compounds such as benzene and ethylbenzene that are easily industrially obtained and ethylating agents such as ethylene
It would be advantageous if tetraethylbenzene could be obtained in good yield, but there is a problem that a large amount of by-products are produced and isomers that are difficult to separate are produced. And the method of separating the isomer of tetraethylbenzene effectively is not known.

[Problems to be Solved by the Invention]

An object of the present invention is to provide a method for producing 1,2,4,5-tetraethylbenzene industrially advantageously. Another object is to selectively produce 1,2,4,5-tetraethylbenzene in a high yield and to advantageously produce tetraethylbenzene useful as a raw material for producing pyromellitic dianhydride.

[Means for Solving the Problems]

The present invention is selected from the group consisting of benzene, ethylbenzene, diethylbenzene and triethylbenzene.
Tetraethylbenzene fraction obtained by distilling the ethylation reaction product of one or two or more benzene compounds is -5
A method for producing 1,2,4,5-tetraethylbenzene, which comprises cooling to below ℃ to precipitate crystals and then centrifugally filtering with a centrifugal force of 300 G or more to separate a liquid phase and a solid phase, and the above-mentioned method. The benzene compound is ethylated with an ethylating agent in the presence of a Friedel-Crafts catalyst, and then this is subjected to a transfer reaction in the presence of a Friedel-Crafts catalyst, and the obtained reaction product is distilled to obtain a tetraethylbenzene fraction. Then, this fraction was cooled and crystallized to precipitate crystals, which was then centrifuged. The liquid phase was returned to the ethylation reaction or transfer reaction step, and the solid phase was recovered as tetraethylbenzene for use as a raw material for producing pyromellitic dianhydride. Is a method for producing 1,2,4,5-tetraethylbenzene.

As the benzene compound, benzene, ethylbenzene,
It is diethylbenzene, triethylbenzene or a mixture thereof, and as the mixture, there is a mixture of polyethylbenzene and the like, which is a by-product during the production of ethylbenzene. Preferably, it is mainly composed of triethylbenzene or triethylbenzene and diethylbenzene.

The ethylation reaction of a benzene compound is usually carried out in the presence of a Friedel-Crafts catalyst. As the Friedel-Crafts catalyst, there are known ones such as aluminum chloride, boron trifluoride, iron chloride, ion exchange resin, zeolite and phosphoric acid, but aluminum chloride and zeolite are preferable.

Examples of the ethylating agent include ethylene, halogenated ethane, ethanol and the like, but ethylene is preferable.

The ethylation reaction may be carried out until the amount of the ethyl group becomes 3.6 to 4.8 mol, preferably 4.0 to 4.4 mol per 1 mol of the benzene ring. The rate decreases. The amount of Friedel-Crafts catalyst used varies depending on the type of catalyst, raw material, etc., but in the case of aluminum chloride, it is about 5 to 25% by weight with respect to the polyethylbenzene. When carrying out the reaction in a continuous system, LHSV is about 0.1 to 20 / hr. Although the reaction temperature also changes depending on other conditions, it is about 50 to 150 ° C. for the aluminum chloride catalyst and about 150 to 300 ° C. for the zeolite catalyst.

After the completion of the ethylation reaction, it is desirable to stop the addition of the ethylating agent to cause the transfer reaction. That is, the reaction product immediately after the completion of ethylation is a mixture of triethylbenzene, diethylbenzene, pentaethylbenzene, etc. in addition to tetraethylbenzene, and the ratio of tetraethylbenzene is relatively small. However, the ratio of tetraethylbenzene increases when the transfer reaction occurs. It is considered that this is because a transfer reaction of ethyl groups occurs between polyethylbenzenes having 3 or less ethyl groups and polyethylbenzenes having 5 or more ethyl groups, resulting in an increase in the proportion of tetraethylbenzene. The transfer reaction is carried out in the presence of Friedel-Crafts catalyst. The conditions may be almost the same as the ethylation reaction except that a new ethylating agent is not added. Further, during the transfer reaction, a new Friedel-Crafts catalyst may be added, but it is also possible to use only the Friedel-Crafts catalyst remaining in the ethylation reaction mixture, and the conditions such as temperature and stirring may be ethyl. It may be the same as the chemical reaction. However, in order to prevent the decomposition reaction, the temperature is preferably lower than that of the ethylation reaction by about 50 to 100 ° C. When carrying out the reaction in a continuous manner, it is advisable to provide a reactor for the rearrangement reaction and pass the ethylation reaction mixture through this. When the molar ratio of ethyl groups is within the above-mentioned preferred range and the rearrangement reaction is sufficiently performed, the ratio of tetraethylbenzene is 75%.
Reaches about 85% by weight.

Furthermore, during this transfer reaction or during the ethylation reaction, it is desirable to return the liquid phase generated in the centrifugal separation step described below. That is, since most of the liquid phase is 1,2,3,5-tetraethylbenzene, isomerization also occurs at the same time by returning the liquid phase to 1,2,4,5-tetraethylbenzene, and the yield of 1,2,4,5-tetraethylbenzene is further increased. In this case, it is desirable to carry out the reaction until the tetraethylbenzene isomer ratio becomes almost equilibrium concentration.

In the obtained reaction product, the catalyst is separated by a conventional method, and then tetraethylbenzene is separated by distillation. It is desirable that the concentration of tetraethylbenzene is 90% by weight or more, and 1,2,4,5-
The ratio of tetraethylbenzene and 1,2,3,5-tetraethylbenzene is approximately 6: 4 near the equilibrium concentration.

In the present invention, this tetraethylbenzene fraction is cooled to precipitate crystals. There are many methods for purifying substances, such as distillation and crystallization, but crystallization is often difficult depending on the nature of the crystals to be precipitated. The crystals precipitated from the tetraethylbenzene fraction were also expected to be paste-like and solid-liquid separation would be extremely difficult. A method of reducing the viscosity by adding a solvent was also tried, but the purity was extremely low even if filtration was possible. However, when the tetraethylbenzene fraction is cooled to -5 ° C or lower to precipitate crystals and then subjected to centrifugal filtration with a centrifugal force of 300 G or more, the liquid phase and the solid phase can be easily separated, and the purity is high. Was found to be obtained. Therefore, in the present invention, this tetraethylbenzene fraction is
Preferably, it is cooled to −10 ° C. to −30 ° C. to precipitate crystals, which is then centrifugally filtered with a centrifugal force of 300 G or more, preferably 500 G or more, more preferably 600 G or more. If the cooling temperature is high, the recovery rate will decrease, and if it is too low, the purity will decrease. For example, when cooled to −10 ° C., 90
% Purity can be obtained, but it is 80 at -25 ° C.
The purity is around%. On the other hand, if the centrifugal force is too small, solid-liquid separation cannot be performed and the purity cannot be improved. And if the recovery rate of 1,2,4,5-tetraethylbenzene is about 50%,
A purity of around 0% is obtained.

Since the liquid phase to be separated is mainly composed of 1,2,3,5-tetraethylbenzene, it may be returned to the ethylation reaction or transfer reaction step. Also, since the solid phase is mainly composed of 1,2,4,5-tetraethylbenzene, it can be recovered as a product, and if it is necessary to further purify it, a treatment such as recrystallization is performed. May be added. In particular, if the solid phase thus obtained, preferably having a purity of about 80 to 92%, is used as a raw material for producing pyromellitic dianhydride by vapor phase catalytic oxidation,
The components contained as impurities in this solid phase are completely oxidized and are rarely mixed in the product pyromellitic dianhydride, which is extremely advantageous.

〔Example〕

Examples of the present invention will be shown below. In addition,% represents% by weight.

Example 1 250 g of polyethylbenzene (diethylbenzene: 91%, triethylbenzene: 7%, other 2%), which is a by-product in the production of ethylbenzene by alkylating benzene with ethylene in the presence of an aluminum chloride catalyst, and an anhydrous aluminum chloride catalyst. Was charged into a reactor equipped with a stirrer and a reflux condenser, and an ethylating agent was fed at a predetermined rate to carry out an ethylation reaction.

After the predetermined ethylation was completed, the supply of the ethylating agent was stopped, and stirring was continued under the same temperature condition to carry out the transfer reaction. The transfer reaction was carried out until the composition of the reaction product became constant. After separating the catalyst from the obtained reaction product, distillation was performed, and tetraethylbenzene fraction (1,2,4,5-tetraethylbenzene: 59.2%, 1,2,3,5-tetraethylbenzene: 39.
4%, triethylbenzene: 0.4%, others 0.3%) were obtained.

This tetraethylbenzene fraction was placed in a stainless steel container and cooled to a predetermined temperature while stirring with dry ice to precipitate crystals.

The obtained slurry was charged into a centrifuge and subjected to centrifugal filtration at 670G for 2 minutes to separate into a liquid phase and a solid phase. In addition,
A 300-mesh cotton cloth was used as the filter cloth. The conditions and results are shown in Table 1.

Next, pyromellitic dianhydride was produced using the solid phase obtained in Experiment No. 3. The conditions are as follows: a catalyst having titanium oxide, vanadium pentoxide and phosphorus pentoxide supported on an inert carrier, a reaction temperature of 380 ° C., a solid phase / air ratio of 30 g / Nm ³ , G
When the reaction was carried out under the condition of HSV 4,000 / hr, pyromellitic dianhydride was obtained in a yield of 59%. Although the purity of this pyromellitic dianhydride was 95%,
The purity was almost the same as that of pyromellitic dianhydride obtained from 1,2,4,5-tetraethylbenzene as a raw material.

〔The invention's effect〕

According to the production method of the present invention, 1,2,4,5-tetraethylbenzene can be produced with high purity and high yield.

Claims (2)

[Claims] 1. A tetraethylbenzene fraction obtained by distilling an ethylation reaction product of one or more benzene compounds selected from the group consisting of benzene, ethylbenzene, diethylbenzene and triethylbenzene,
A method for producing 1,2,4,5-tetraethylbenzene, which comprises cooling to 5 ° C. or less to precipitate crystals, and then centrifugally filtering with a centrifugal force of 300 G or more to separate a liquid phase and a solid phase. . 2. One or more benzene compounds selected from the group consisting of benzene, ethylbenzene, diethylbenzene and triethylbenzene are ethylated with an ethylating agent in the presence of a Friedel-Crafts catalyst, and then this is friedel. In the presence of a Krafts catalyst, a transfer reaction is carried out, the obtained reaction product is distilled to obtain a tetraethylbenzene fraction, and this fraction is cooled and crystallized to precipitate crystals,
Then, the mixture is centrifuged, the liquid phase is returned to the ethylation reaction or transfer reaction step, and the solid phase is recovered as tetraethylbenzene for producing pyromellitic dianhydride, 1,2,4,5-tetraethylbenzene. Manufacturing method.