JPH03284633A - Production of 1,2,4,5-tetraethylbenzene - Google Patents

Abstract

PURPOSE:To advantageously obtain the title compound by cooling and crystallizing tegraethylbenzene fraction obtained by distilling an ethylation reaction product of benzene and/or mono- to tri-ethylbenzene under specific conditions and then subjecting the treated fraction to centrifugal filtration to carry out solid-liquid separation. CONSTITUTION:An ethylation reaction product, preferably the above-mentioned raw material of one or more kinds of benzene compounds selected from benzene and mono- to tri-ethylbenzene are ethylated with an ethylating agent in the presence of a Friedel-Crafts catalyst and then subjected to transalkylation reaction in the presence of the above-mentioned catalyst and the resultant reaction product is distilled to provide tetraethylbenzene fraction. Then the tetraethylbenzene fraction is cooled to -5 deg.C to crystallize crystal and then subjected to centrifugal filtration in >=300G centrifugal force to carry out solid- liquid separation and preferably further the liquid phase is returned to the above-mentioned ethylation process or transalkylation reaction process and then the title compound, especially useful as a raw material for pyromellitic anhydride is obtained in high purity and good yield.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] 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 anhydride.

[Conventional technology]

Tetraethylbenzene can be 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 Patent Publication No. 52-12.178, JP-A No. 61-65.827), but when an ethyl group such as ethylbenzene is It is difficult to selectively produce compounds with as many as four ethyl groups, such as tetraethylbenzene.

In addition, in order to selectively obtain L, 2,4.5-tetraalkylbenzene, there is a method of alkylating xylene with propylene or butene to produce tetraalkylbenzene (Japanese Patent Publication No. 1982-12.178, Japanese Patent Publication No. 1982-10゜). 2
No. 90, JP-A-48-72.130, JP-A-48-1
No. 9.526, JP-A-48-85.540, JP-A-4
9-35.339), a method for producing tetraalkylbenzene by alkylating pseudocumene or mesitylene with propylene (Japanese Patent Publication No. 3.369/1982)
etc. are known, but the raw materials and target objects are different from these methods.

1.2. From benzene compounds such as benzene and ethylbenzene that are easily obtained industrially and ethylating agents such as ethylene.
Although it would be advantageous if 4,5-tetraethylbenzene could be obtained in a good yield, there are problems in that a large amount of by-products are produced and isomers that are difficult to separate are produced. Furthermore, there is no known method for effectively separating isomers of tetraethylbenzene.

[Problem to be solved by the invention]

An object of the present invention is to provide an industrially advantageous method for producing 1.2.4.5-tetraethylbenzene. Other objects are to selectively produce 1.2.4.5-tetraethylbenzene in good yield and to advantageously produce tetraethylbenzene useful as a raw material for producing pyromellitic anhydride.

[Means to solve the problem]

The present invention provides a compound selected from the group consisting of benzene, ethylbenzene, diethylbenzene and triethylbenzene.
The tetraethylbenzene fraction obtained by distilling the ethylation reaction product of a species or two or more benzene compounds, -5
A method for producing 1,2.4.5-tetraethylbenzene, which comprises cooling to below °C to precipitate crystals, followed by centrifugal filtration with a centrifugal force of 300 G or more to separate a liquid phase and a solid phase. The above benzene compound is ethylated with an ethylating agent in the presence of a Friedel-Kraf catalyst, and then a rearrangement reaction is carried out in the presence of a Friedel-Kraf catalyst, and the resulting reaction product is distilled. A tetraethylbenzene fraction is obtained, this fraction is cooled and crystallized to precipitate crystals, and then centrifuged, the liquid phase is returned to the ethylation reaction or transfer reaction step, and the solid phase is the raw material for producing pyromellitic anhydride. 1 consisting of recovering as tetraethylbenzene
, 2.4.5-Tetraethylbenzene production method.

Benzene compounds include benzene, ethylbenzene,
It is diethylbenzene, triethylbenzene, or a mixture thereof. Examples of the mixture include polyethylbenzene, which is a by-product when producing ethylbenzene. Preferably, it is mainly composed of triethylbenzene or triethylbenzene and diethylbenzene.

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

Examples of the ethylating agent include ethylene, halogenated ethane, and ethanol, preferably ethylene.

The ethylation reaction may be carried out until the concentration of ethyl groups is 3.6 to 4.8 moles, preferably 4.0 to 4.4 moles, per mole of Hensen's ring. Outside this range, tetraethylbenzene is produced. The percentage decreases. The amount of Friedel-Crauch catalyst used varies depending on the type of catalyst, raw materials, etc., and in the case of aluminum chloride, it is about 5 to 25% by weight based on the polyethylbenzene. When carrying out the reaction in a continuous manner, LH5V0. It is about 1 to 20/hr.

The reaction temperature also varies depending on other conditions, and in the case of an aluminum chloride catalyst, it is about 50 to 150 °C,
In the case of a theolite catalyst, the temperature is about 150 to 300°C.

After the ethylation reaction is completed, it is desirable to stop adding the ethylating agent and allow the rearrangement reaction to occur. That is, the reaction product immediately after ethylation is a mixture of triethylbenzene, diethylbenzene, pentaethylbenzene, etc. in addition to tetraethylbenzene, and the proportion of tetraethylbenzene is relatively small. However, when the rearrangement reaction occurs, the proportion of tetraethylbenzene increases. This seems to be because an ethyl group transfer reaction 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 rearrangement reaction is carried out in the presence of a Friedelkraff catalyst. The conditions may be almost the same as those for the ethylation reaction except that no new ethylating agent is added. Also,
During the rearrangement reaction, fresh Friedel-Kraf catalyst may be added, but it is also possible to use only the Friedel-Kraf catalyst remaining in the ethylation reaction mixture, and the conditions such as temperature and stirring may also be different from the ethyl There is no problem even if it is the same as chemical reaction. However, in order to prevent decomposition reactions, it is preferable to lower the temperature by about 50 to 100°C than the ethylation reaction. When carrying out the reaction in a continuous manner, a reactor for transfer reaction is provided,
It is preferable to pass the ethylation reaction mixture through this. When the molar ratio of ethyl groups is within the above preferred range and the rearrangement reaction is sufficiently carried out, the ratio of tetraethylbenzene is 75 to 85.
It reaches about % by weight.

Furthermore, during this rearrangement reaction or ethylation reaction, it is desirable to return the liquid phase generated in the centrifugation 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 this phase, thereby further increasing the yield of 2.4.5-tetraethylbenzene. In this case, it is desirable to carry out the reaction until the tetraethylbenzene isomer ratio reaches approximately equilibrium concentration.

After the catalyst is separated from the obtained reaction product by a conventional method, tetraethylbenzene is separated by distillation. The concentration of tetraethylbenzene is desirably 90% by weight or more, and 1.2.4% in this tetraethylbenzene fraction is
．． The ratio of 5-tetraethylbenzene to 1.2.3.5-tetraethylbenzene is approximately 6:4 near the equilibrium concentration.
It is.

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 precipitated crystals. It was expected that the crystals precipitated from the tetraethylbenzene fraction would also be paste-like, making solid-liquid separation extremely difficult. An attempt was made to lower the viscosity by adding a solvent, but even if filtration was possible, the purity was extremely low. However, if this tetraethylbenzene fraction is cooled to below 15°C to precipitate crystals and then centrifugally filtered by applying a centrifugal force of 300 G or more, the liquid phase and solid phase can be easily separated, and a product with high purity can be obtained. was found to be obtained. Therefore, in the present invention, this tetraethylbenzene fraction is heated below -5°C.
Preferably, the crystals are precipitated by cooling to -10°C to -30°C, and then heated to 300G or more, preferably 500G.
As mentioned above, centrifugal filtration is more preferably performed with a centrifugal force of 600 G or more. If the cooling temperature is too high, the recovery rate will decrease, and if it is too low, the purity will decrease. For example, when cooled to -10°C,
Although a purity of around 90% can be obtained, the purity becomes around 80% at -25°C.

Furthermore, if the centrifugal force is too small, solid-liquid separation will not be possible and purity will not improve. If the recovery rate of 1,2,4.5-tetraethylbenzene is about 50%, a purity of about 90% can be obtained.

Since the separated liquid phase is mainly composed of 1.2.3.5-tetraethylbenzene, it may be returned to the ethylation reaction or transfer reaction step. Also, the solid phase is I
Since it is mainly composed of 2.4.5-tetraethylbenzene, it can be recovered as a product, and if it is necessary to make it even more pure, it can be subjected to treatments such as recrystallization. good. In particular, if the solid phase obtained in this way, preferably a solid phase with a purity of about 80 to 92%, is used as a raw material for producing pyromellitic anhydride by gas phase catalytic oxidation, Components contained as impurities are completely oxidized and are hardly mixed into the product pyromellitic anhydride, which is extremely advantageous.

〔Example〕

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

Example 1 250 g of polyethylbenzene (diethylbenzene = 9IN, triethylbenzene: 7X, other 2X) produced as a by-product when ethylbenzene is produced by alkylating benzene with ethylene in the presence of an aluminum chloride catalyst.
and anhydrous aluminum chloride catalyst were placed in a reactor equipped with a stirrer and a reflux condenser, and an ethylation reaction was carried out by feeding an ethylating agent at a predetermined rate.

After the predetermined ethylation was completed, the supply of the ethylating agent was stopped, and the stirring was continued under the same temperature conditions to carry out the rearrangement reaction. The rearrangement reaction was carried out until the composition of the reactants became constant. After separating the catalyst from the obtained reaction product, distillation was performed to obtain a tetraethylbenzene fraction (1,2,4,5-tetraethylbenzene:/:59.2X, 1,2,3.5
Tetraethylbenzene: 39.4X, ) diethylbenzene: 0.4X, others 0.3X) were obtained.

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

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

Table 1 Next, pyromellitic anhydride was produced using the solid phase obtained in Experiment No. 3. The conditions were to use a catalyst with titanium oxide, vanadium pentoxide and phosphorus pentoxide supported on an inert carrier, reaction temperature 380°C, solid phase/air ratio 30g/Nm.
, GH3V4, 000/hr, pyromellitic anhydride was obtained in a yield of 59%. The purity of this pyromellitic anhydride was 95%, or almost as pure as that of pyromellitic anhydride obtained using 99% pure 1°2,4.5-tetraethylbenzene as a raw material.

C Effects of the Invention] 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) The tetraethylbenzene fraction obtained by distilling the ethylation reaction product of one or more benzene compounds selected from the group consisting of benzene, ethylbenzene, diethylbenzene, and triethylbenzene, at -5°C or below. A method for producing 1,2,4,5-tetraethylbenzene, which comprises cooling to precipitate crystals, followed by centrifugal filtration 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 converted into a Friedel-Crafts catalyst. A rearrangement reaction is carried out in the presence of 1, characterized in that the solid phase is returned to the ethylation reaction or rearrangement reaction step, and the solid phase is recovered as tetraethylbenzene for use as a raw material for producing pyromellitic anhydride;
Method for producing 2,4,5-tetraethylbenzene.