JPH06199710A - Production of alkylaromatic compound - Google Patents

Abstract

PURPOSE:To produce an alkylaromatic compound in high reaction selectivity using a decreased amount of catalyst based on the produced alkylaromatic compound. CONSTITUTION:A 2-4C olefin, an aromatic compound and a Friedel-Crafts catalyst are introduced into a 1st reaction zone maintained at 90-140 deg.C to effect alkylation reaction. The molar ratio of olefin/aromatic compound is 0.2-1.0 and the amount of the catalyst is 0.0003-0.01mol based on l mol of the olefin. The reaction product containing a polyalkylaromatic compound and discharged from the 1st reaction zone is introduced together with the recycling Friedel- Crafts catalyst into a 2nd reaction zone and subjected to transalkylation reaction at 90-140 deg.C. The Friedel-Crafts catalyst is separated from the reaction product of the 2nd reaction zone and recycled to the 2nd reaction zone. The reaction product free from the catalyst is distilled to separate the aromatic compound and the polyalkylaromatic compound. The former compound is recycled through the 1st reaction zone, the latter compound is recycled through the 2nd reaction zone and the alkylaromatic compound is recovered from the reaction product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alkylaromatic compound in which an aromatic compound and a C ₂ -C ₄ olefin are reacted in the presence of a Friedel-Crafts type catalyst, and more specifically, by an alkylation method. The present invention relates to a method for producing an alkylaromatic compound, which is capable of producing an alkylaromatic compound with a high reaction selectivity by improving the amount of catalyst used per produced alkylaromatic compound.

[0002]

_2. Description of the Related Art Alkyl aromatic compounds are usually produced by contacting a C ₂ -C ₄ olefin as a raw material with an aromatic compound at a high temperature, and further produce a polyalkyl aromatic compound (dialkyl aromatic compound or more). Means a higher alkyl aromatic compound) is recovered as an alkyl aromatic compound by a transalkylation reaction with an aromatic compound. As the alkylation and transalkylation catalyst used in the above reaction, aluminum chloride is widely used because of its excellent activity and selectivity.

For example, when ethylbenzene is produced in the presence of an aluminum chloride catalyst, conventionally, the alkylation reaction and the transalkylation reaction are carried out in the same reaction zone in the range of 50 to 90.
The reaction was carried out in the temperature range of ℃, and the catalyst was separated from the reaction liquid extracted from the reactor and circulated to the reactor (Japanese Patent Publication No. Sho 49).
No. 48416). Further, JP-B-58-33206 discloses that at a reaction temperature of 140 to 200 ° C., a reaction under alkyl is carried out under a pressure sufficient to keep the reaction components and aluminum chloride as a catalyst in a single liquid phase, and then in series. Disclosed is a continuous production method of ethylbenzene by a two-step method in which a transalkylation reaction is carried out under conditions.

[0004]

However, these manufacturing methods have the following problems. When the alkylation reaction and the transalkylation reaction are carried out in the same reaction zone, the reaction rate must be increased because the temperature is relatively low, and the catalyst is circulated to increase the catalyst concentration to carry out the reaction. The rate was low.

When the alkylation reaction and the transalkylation reaction are separated and the reaction is carried out at a high temperature without recycling the catalyst, the amount of the catalyst used is less than that of the alkylation reaction, although there is no need to circulate the catalyst. However, it could not be reduced below the amount required to accelerate the transalkylation reaction, which is significantly slower. In addition, since the alkylation reaction and the transalkylation reaction are carried out at a high temperature, there are problems such as formation of by-products due to catalyst modification at a high temperature.
Under such circumstances, the object of the present invention is to improve the amount of catalyst used per alkyl aromatic compound to be produced and to make it possible to produce an alkyl aromatic compound with a high reaction selectivity. It is intended to provide a method for producing an alkyl aromatic compound.

[0006]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have conducted a detailed analysis of the alkylation reaction of benzene with ethylene and the transalkylation reaction of diethylbenzene and benzene. The reaction selectivity depends on the catalyst concentration during the alkylation reaction, and it is clear that the lower the concentration, the higher the selectivity obtained, and that the transalkylation reaction shows a high selectivity without being affected by the catalyst concentration. became. Further, it has been found that the alkylation reaction of ethylene is very fast, and a predetermined amount of reaction can be carried out at a relatively low temperature and a low catalyst concentration, and further, a decrease in the activity of the catalyst is suppressed.

On the other hand, it became clear that the transalkylation reaction has a slower reaction rate than the alkylation reaction and depends on the catalyst concentration. In addition, it was clarified that when the reaction temperature was raised, the catalyst was modified to lower the catalytic activity and form high boiling substances. From these results, it was found that the catalyst concentration in the alkylation reaction zone is low, and that in the transalkylation reaction zone, the catalyst is circulated and reused at a high concentration to allow the reaction at a relatively low temperature. The present invention has been completed based on this finding.

That is, the present invention is summarized as follows. An aromatic compound and a C ₂ -C ₄ olefin are introduced into a first reaction zone at a relatively low temperature in the presence of a Friedel-Crafts type catalyst to carry out an alkylation reaction. The reaction product from the first reaction zone and the recovered polyalkylaromatic compound are introduced into the second reaction zone in the presence of the Friedel-Crafts type catalyst, which is reused by circulation, to carry out a transalkylation reaction. After that, the alkylaromatic compound is recovered, which is a method for producing the alkylaromatic compound.

The present invention will be described in detail below. The aromatic compound used in the present invention is a compound represented by the following formula (1), and examples thereof include benzene, toluene, ethylbenzene, isopropylbenzene, butylbenzene, phenol, chlorobenzene, and bromobenzene.

[0010]

[Chemical 1]

The olefin used in the present invention is C ₂ -C.
Up to ₄ olefins, including ethylene, propylene, butylene, isobutylene. The Friedel-Crafts type catalyst used in the present invention includes AlCl ₃ , SbC
l ₅ , FeCl ₃ , TeCl ₂ , SnCl ₄ , TiCl
₄ , TeCl ₄ , BiCl ₃ , ZnCl ₂ , BF _{3 and the} like.

The alkylation reaction of the present invention comprises 90 to 140
C ₂ -C ₄ olefin in the first reaction zone maintained at a temperature of ° C., introducing the aromatic compound and the Friedel-Crafts type catalyst. The reaction time should be at least 5 minutes, generally 10 minutes to 2 hours. Free amount of Del Crafts type catalyst C ₂ -C ₄ olefin per mole 0.0003
In the range of about 0.01 to about 0.01 mole, and the C _{2 to} C ₄ olefin / aromatic compound molar ratio to be fed should be in the range of about 0.2 to 1.0.

On the other hand, the polyalkyl aromatic compound produced in the alkylation reaction is introduced into the second reaction zone in the presence of a Friedel-Crafts type catalyst which is reused in circulation with the reaction product from the first reaction zone. After carrying out the chemical reaction, it is recovered as an alkyl aromatic compound. The transalkylation reaction temperature is preferably in the range of 90 to 140 ° C., and the molar ratio of the alkyl group to be supplied and the aromatic compound is 0.3 to 1.
2, the reaction time is at least 10 minutes, the Friedel-Crafts catalyst concentration is kept in the range of 2 to 50% by weight, and the obtained reaction product is continuously taken out from the second reaction zone. Done.

If the above reaction conditions are removed, the following problems occur, which is not preferable. If the reaction temperature is too high, the activity of the Friedel-Crafts type catalyst is reduced, which in turn leads to the formation of by-products. On the other hand, if it is too low, the desired transalkylation reaction rate will be slowed, which is not preferable.

[0015] For supplying C ₂ -C ₄ olefin / aromatic compound molar ratio, the catalyst in the alkylation reaction zone is a low concentration and the C ₂ -C ₄ olefin / aromatic compound molar ratio is high-order Alkyl aromatic compounds reduce the activity of Friedel-Crafts type catalysts. Further, if the C _{2 to} C ₄ olefin / aromatic compound molar ratio is too low, the productivity is deteriorated and neither is preferable.

The catalyst concentration in the alkylation reaction zone is C _2-
It is determined from the value that gives the desired conversion in the C ₄ olefin addition reaction. The lower the catalyst concentration in the portion where the C _{2 to} C ₄ olefin is introduced, the more the by-products can be suppressed. The catalyst concentration and residence time in the transalkylation reaction zone are determined by the amount of polyalkylaromatic compound produced in the alkylation reaction zone. If the catalyst concentration is too high, the effective use rate of the catalyst will decrease, and if it is too low, the productivity per reaction volume will decrease, which is not preferable.

The reaction product taken out from the second reaction zone is cooled, then separated from the catalyst and washed with water and caustic to remove a trace amount of the catalyst. The separated catalyst is recycled to the second reaction zone. Then, the reaction product from which the catalyst has been removed is subjected to distillation by a usual method, and the alkyl aromatic compound is separated from other higher alkylated polyalkyl aromatic compound and unreacted aromatic compound. The polyalkylaromatic compound is then recycled to the second reaction zone and converted to the desired alkylaromatic compound by a transalkylation reaction.

One of the key features of the process of the present invention is the very small amount of Friedel-Crafts type catalyst required. The effective amount of Friedel-Craft catalyst is
It is preferably about 0.0003 to about 0.01 mol, and more preferably about 0.000, per mol of C ₂ -C ₄ olefin.
The range is from 5 to about 0.006 mol. Further, another feature is that the alkyl aromatic compound can be produced with a high reaction selectivity.

The Friedel-Crafts type catalyst used is
Distillation in the alkylation reaction zone, that is, at a relatively low temperature and at a low concentration, the catalytic activity does not decrease so much, by-products are suppressed, and the alkyl aromatic compound can be produced with high selectivity. . The Friedel-Crafts catalyst can be added as it is in the form of a solid powder, or can be added as a solution in an aromatic compound.

Further, in the alkylation reaction, a halide cocatalyst is usually used together in order to obtain a high efficiency of the reaction. As a suitable halide as the cocatalyst, for example, HC is used.
1, HBr, HF, HI, for example alkyl chlorides such as ethyl chloride, propyl chloride, butyl chloride, etc., or all substances which form such halides in situ. When a cocatalyst is added, its amount is usually preferably about 0.5 to about 10 moles, more preferably about 1 to about 5 moles, per mole of Friedel-Crafts catalyst.

[0021]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

[Examples 1 to 3] A continuous alkylation reaction of benzene with ethylene was carried out in an alkylation reactor using AlCl ₃ as a Friedel-Crafts type catalyst and HCl as a cocatalyst, and then a transalkylation reactor. The continuous transalkylation reaction was carried out with recycled polyethylbenzene in the presence of recycled AlCl ₃ catalyst. The equipment used consisted of two reactors (alkylation reactor and transalkylation reactor), the alkylation reactor had an inner diameter of 7.4 cm and a length of 400 cm, and the transalkylation reactor had an inner diameter of 7.4 cm. It is made of corrosion resistant material (nickel alloy) with a length of 500 cm.

The alkylation reactor was fitted with a sparger at the bottom and the flow in the alkylation and transalkylation reactors was upward. The benzene was dehydrated and pumped to the alkylation reactor. AlCl ₃ was sent to the alkylation reactor as a solution in ethylbenzene. Benzene was mixed with the AlCl ₃ solution in ethylbenzene before the reactor. The resulting stream was then introduced into the alkylation reactor through a sparger. The cocatalyst was added via this sparger as a benzene solution of HCl with ethylene. The reaction product overflowing from the alkylation reactor was mixed with the recycled AlCl ₃ catalyst and recycled polyethylbenzene and passed through the transalkylation reactor and then cooled. Next, the reaction product separated in the catalyst separation tank was washed with water and caustic soda to remove AlCl ₃ and HCl, and then sent to the distillation column.

The AlCl ₃ catalyst separated in the catalyst separation tank is recycled to the transalkylation reactor and reused. Most of the benzene, water and non-aromatic impurities were removed in the first benzene column and this benzene stream was recycled and mixed with the fresh benzene feed to the benzene drying column. The bottoms stream from the benzene column was fed to an ethylbenzene column where the product ethylbenzene was removed overhead. The bottom stream from the ethylbenzene column was fed to a polyethylbenzene column that was operated to remove diethylbenzene and triethylbenzene. The lower stream from this column was high boiling, meaning reaction selectivity loss, which was sent to waste treatment. The results obtained by changing the ethylene / benzene (molar ratio) supplied are shown in Table 1.

[Comparative Examples 1 and 2] Experiments similar to those in Examples were conducted. However, the alkylation reaction and the transalkylation reaction are performed in the same reaction zone, and Al that is recycled is used.
Feeded with Cl ₃ catalyst and recycled polyethylbenzene and benzene. Table 2 shows the results of changing the supplied ethyl group / Bz ring (molar ratio).

[Comparative Examples 3 and 4] Experiments similar to those in Examples were conducted. However, the catalyst was not recycled and reused, but the reaction was performed at a high temperature. The reaction pressure was kept at the desired level by the addition of inert gas (N ₂ ) (partial pressure: 1.5-4 kg / cm ² ). The results are shown in Table 3.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

In the method for producing an alkylaromatic compound of the present invention, an alkylation reaction for reacting an aromatic compound with a C ₂ -C ₄ olefin in the presence of a Friedel-Crafts type catalyst is carried out at a relatively low temperature, Then, the reaction product obtained is mixed with a Friedel-Crafts type catalyst to be recycled and recycled polyethylbenzene to perform a transalkylation reaction to improve the amount of the catalyst used per alkyl aromatic compound produced. It is possible to produce an alkyl aromatic compound with a high reaction selectivity, and the industrial effect is extremely large.

Claims (1)

[Claims] 1. An aromatic compound and a C ₂ -C ₄ olefin are introduced into the first reaction zone in the presence of a Friedel-Crafts type catalyst to carry out an alkylation reaction at a reaction temperature of 90 to 140 ° C. And then introduced into the second reaction zone 90
Conducting a transalkylation reaction at a reaction temperature of ˜140 ° C. to continuously remove the reaction product from the second reaction zone, and the Friedel-Crafts type catalyst is separated from the reaction product in the second reaction zone. Then, the reaction product is circulated to the second reaction zone, and the reaction product is distilled to separate the aromatic compound and the polyalkylaromatic compound, and the recovered aromatic compound is separated into the first compound.
A method for producing an alkylaromatic compound, characterized in that the alkylaromatic compound is recovered from the reaction product while the polyalkylaromatic compound is circulated in the reaction zone and in the second reaction zone, respectively.