JPH0639427B2 - 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, xylene is alkylated with propylene or butene to produce tetraalkylbenzene (Japanese Patent Publication No.
52-12,178, JP-B-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 Examined Patent Publication No. 52-3369), but the raw materials and the intended products 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, no effective separation method of tetraethylbenzene isomers is 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 provides 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, under reduced pressure. Method for producing 1,2,4,5-tetraethylbenzene by precision distillation, and ethylation of the above benzene compound with an ethylating agent in the presence of a Friedel-Crafts catalyst, and then the presence of a Friedel-Crafts catalyst. under,
A transfer reaction is carried out, the resulting reaction product is distilled to obtain a tetraethylbenzene fraction, and this fraction is further subjected to precision distillation under reduced pressure to obtain a distillate containing 1,2,3,5-tetraethylbenzene. The fraction is returned to the ethylation reaction or transfer reaction step, and the fraction in which 1,2,4,5-tetraethylbenzene is concentrated is recovered as tetraethylbenzene for pyromellitic dianhydride raw material 1,2, This is a method for producing 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 performed 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 a Friedel-Crafts catalyst, and the conditions therefor may be almost the same as those for 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 by about 50 to 100 ° C. than the ethylation reaction. 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 reaches about 75 to 85% by weight.

Furthermore, during this transfer reaction or during the ethylation reaction, if the 1,2,3,5-tetraethylbenzene-enriched fraction generated in the precision distillation step described below is returned to this, isomerization also occurs simultaneously 1,2,
The yield of 4,5-tetraethylbenzene is 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
Further, precision distillation is performed under reduced pressure. Distillation is a common method for purifying substances, but the boiling point difference between tetraethylbenzene isomers is extremely small (according to literature, 1,2,4,5-tetraethylbenzene and 1,2,3,5-tetraethylbenzene). Boiling points of 246 ° C. and 247 ° C. respectively) were expected to be almost impossible to separate by distillation. However, when the present inventors tried distillation separation, 1,2,3,5-tetraethylbenzene, which is said to have a high boiling point, was distilled out first, and 1,2,4,5-tetraethylbenzene was left in the bottom of the kettle. It was found that the ethylbenzene was concentrated. Therefore, in the present invention, this tetraethylbenzene fraction is subjected to precision distillation under reduced pressure.
Concentrate 1,2,4,5-tetraethylbenzene.

The distillation is performed under reduced pressure, preferably 200 mmHg or less, more preferably 100 mmHg or less. The theoretical plate number is 50 or more, preferably 100 or more, and the reflux ratio is 20 or more, preferably 5
Precision distillation is performed with 0 or more. Distillation may be continuous or batch, and both 1,2,3,5-tetraethylbenzene-rich fractions and 1,2,4,5-tetraethylbenzene-rich fractions may be distilled. Even if it is distilled, the fraction rich in 1,2,4,5-tetraethylbenzene may be withdrawn from the bottom of the kettle.

In this precision distillation, 1,2,4,5-tetraethylbenzene is 7
The concentration may be 0% or more, preferably about 80 to 95%. The fraction enriched with 1,2,4,5-tetraethylbenzene can be directly used as a product, or may be further purified by a method such as recrystallization if necessary. Particularly preferably, when this is used as a raw material for producing pyromellitic dianhydride by vapor phase catalytic oxidation, the components contained as impurities in this fraction are completely oxidized and mixed in the product pyromellitic dianhydride. This is extremely advantageous because it is rare. In addition, it is advantageous to return the distillate containing 1,2,3,5-tetraethylbenzene to the ethylation reaction or transfer reaction step.

〔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 distillation apparatus having 190 theoretical plates, and precision distilled under the conditions of 20 mmHg and a reflux ratio of 100. When 40% of the whole was distilled, distillation was stopped, and when 1,2,4,5-tetraethylbenzene in the distillate and the residue in the kettle was analyzed, the former was 43.4% and the latter was 7%.
It was 1.2%.

Next, pyromellitic dianhydride was produced using the fraction enriched with 1,2,4,5-tetraethylbenzene as a raw material.
The conditions are such that a catalyst in which titanium oxide, vanadium pentoxide and phosphorus pentoxide are supported on an inert carrier and a reaction temperature of 380
When the reaction was carried out under the conditions of ℃, raw material / air ratio of 30 g / Nm ³ and GHSV 4,000 / hr, pyromellitic dianhydride was 43%.
It was obtained with a yield of. The purity of this pyromellitic dianhydride is 9
Although it was 5%, the purity was almost the same as pyromellitic dianhydride obtained from 99% pure 1,2,4,5-tetraethylbenzene as a raw material. The fraction enriched in 1,2,4,5-tetraethylbenzene could be returned to the transfer reaction step.

In addition, the above-mentioned tetraethylbenzene fraction was converted into 80 theoretical plates.
, And the fine distillation under the conditions of 20 mmHg and a reflux ratio of 50, and 70% of the total distillate
Analysis of 2,4,5-tetraethylbenzene showed 7
It was 7.2%. Further, when the above-mentioned tetraethylbenzene fraction was subjected to distillation calculation, the theoretical plate number was 130,
When continuously distilling under the conditions of a reflux ratio of 65 and 20 mmHg, at a charging rate of 475 kg / hr, a fraction having 1,2,4,5-tetraethylbenzene reduced to 26% from the top of the column was obtained at 222 kg / hr, It was found from the bottom of the column that a fraction of 1,2,4,5-tetraethylbenzene concentrated to 90% was obtained at 253 kg / hr.

〔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.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C07C 7/04 // C07B 61/00 300

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 further comprises precision distillation under reduced pressure. 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. The transfer reaction is carried out in the presence of a Krafts catalyst, and the obtained reaction product is distilled to obtain a tetraethylbenzene fraction. This fraction is further subjected to precision distillation under reduced pressure to obtain 1,2,
The fraction enriched with 3,5-tetraethylbenzene is returned to the ethylation reaction or transfer reaction step, and the fraction enriched with 1,2,4,5-tetraethylbenzene is converted into tetramellitic acid for producing pyromellitic dianhydride. A method for producing 1,2,4,5-tetraethylbenzene, which comprises recovering as ethylbenzene.