CS255084B1 - A process for producing ethylbenzone alkylation of benzene by ethylene using a Friedel-Crafts catalyst - Google Patents

Abstract

A process for the preparation of ethylbenzene by alkylation of benzene with ethylene using a Friedel-Crafts catalyst based on aluminum chloride, aromatic hydrocarbons and a promoter in which an aqueous aluminum chloride solution is added as a promoter at a concentration of 0.5 to 30.0% by weight. in a ratio of 0.8 to 2.6 kg of water contained in this solution per 100 kg of total aluminum chloride used.

Description

The invention relates to a process for producing ethylbenzene by alkylation of benzene with ethylene using a Friedel-Crafts catalyst based on aluminum chloride, aromatic hydrocarbons and a promoter.

Anhydrous aluminum halides, especially aluminum chloride, are important catalysts for the so-called Friedel-Crafts and analogous reactions, such as alkylation, transalkylation, acylation, etc. The most important industrial use of aluminum chloride-based catalysts is the Friedel-Crafts alkylation of benzene with ethylene.

Aluminum chloride, a strongly acidic catalyst, does not react with benzene or ethylene on its own, but can form complexes with a number of compounds.

In the presence of promoters, i.e. substances that either themselves carry hydrogen chloride or cause the release of hydrogen chloride from aluminum chloride, aluminum chloride forms active complexes with alkylaromatic hydrocarbons. This ability is used in the preparation of liquid catalytic complexes of aluminum chloride, the use of which has eliminated a number of disadvantages associated with the use of solid aluminum chloride as an alkylation catalyst, in particular difficulties with dosing and handling, different particle sizes, coating of particles with an inactive coating, long induction time, etc.

Currently, in industrial alkylation processes, aluminum chloride-based catalysts are almost exclusively used in liquid complexes instead of solid AlCl^.

In the preparation of these liquid complexes, ethylbenzene, diethylbenzenes, polyalkylbenzenes, or a wider fraction of alkylaromatic hydrocarbons remaining during the production of ethylbenzene and other alkylaromatic compounds are used as aromatic components, depending on the type of catalyzed reaction.

As promoters for the preparation of the catalytic complex with the mentioned aromatic components, anhydrous hydrogen chloride, chlorinated hydrocarbons (e.g. ethyl chloride and water) are most often used on an industrial scale.

When using water as a promoter, when in the usual procedure liquid water is fed into a suspension of aluminum chloride in an aromatic hydrocarbon, it is not possible to ensure its sufficient homogenization even by intensive mixing and therefore, due to the high local concentration of water at the point of feed into the suspension, hydrolysis of aluminum chloride is strongly applied in this system to a greater extent than necessary. Local overheating of the reaction mixture, leakage of hydrogen chloride and losses of aluminum chloride occur, which is adversely reflected in the catalytic activity of the prepared complex and in increased consumption of AlClj in the alkylation process itself.

Some suppression of these undesirable phenomena can be achieved by a procedure in which the catalytic complex is prepared with a significant excess of the aromatic component in the aluminum chloride suspension compared to the minimum amount required for complex formation.

It has now been found that further suppression of these undesirable phenomena occurring during the preparation of the complex can be achieved by dosing the promoter in the manner of the invention.

The process for producing ethylbenzene by alkylation of benzene with ethylene using a Friedel-Crafts catalyst based on aluminum chloride, aromatic hydrocarbons and a promoter, according to the invention, consists in that an aqueous solution of aluminum chloride is fed as a promoter in a concentration of 0.5 to 30.0% by weight, preferably containing free dissolved hydrogen chloride, in a ratio of 0.8 kg to 2.6 kg of water contained in this solution per 100 kg of total aluminum chloride used. A waste aluminum chloride solution from the washing of alkylation products is preferably fed as a promoter.

For this purpose, it is advantageous to use an aqueous solution of AlCl^, which is discarded in the ethylbenzene production plant during acid washing of alkylation products with a concentration of 0.5% wt. to 3.0% wt. without circulation of washing water, or a concentrated solution with a content of up to 30% wt. AlCl^ with recirculation of washing water in this technological section.

When using a concentrated solution, unwanted hydrolysis of AlClj can be suppressed to a minimum.

An example of the basic physicochemical properties of aqueous solutions of aluminum chloride from the technological section for washing alkylation products of an ethylbenzene production plant is given in Table 1.

Table 1

with recirculation of washing water without recirculation of washing water density at 50 °C kg/m^ 1,248 1,007 content of AlClj % wt. 25.0 0.7 _H2O content 4 wt. 74.2 98.5 aromatic hydrocarbon content (mainly benzene) % wt. 0.3 0.5 HC1 content 4 wt. 0.5 0.3 Aqueous solution chloride aluminum contains in addition to dissolved A1C1 2 and dissolved chlorine

hydrogen, which, in addition to the amount of hydrogen chloride needed for complex formation and produced by hydrolysis, simultaneously activates the catalytic complex being prepared.

A new method for preparing a catalytic aluminum chloride complex using an aqueous solution of AlCl as a promoter is based on suppressing the adverse effects associated with the dosing of water as a promoter, simultaneous activation of the prepared complex with dissolved hydrogen chloride, and saving aluminum chloride during its preparation.

A new method for producing a catalytic complex of aluminum chloride for catalysis in organic syntheses, in particular for the alkylation of benzene with low molecular weight olefins, based on a suspension of aluminum chloride in aromatic hydrocarbons, consists, according to the invention, in that the preparation of the complex is carried out at a temperature of 10 to 90 °C, preferably 20 to 75 °C, while an aqueous solution of aluminum chloride with a concentration of 0.5 wt. % to 30 wt. % is gradually dosed as a promoter, while the suspension is constantly stirred. In an amount of 1.5 to 2.5 kg per 100 kg of suspended AlCl^.

As aromatic hydrocarbons for the preparation of the catalytic complex, some of the following hydrocarbons can be used alone or in a mixture, or in a mixture with benzene:

ethylbenzene, alkylbenzenes, polyethylbenzenes, fractions of polyalkylaromatic hydrocarbons remaining during the production of ethylbenzene with a boiling point above 136 °C.

The production of the catalytic complex according to the invention can be carried out as follows:

An aromatic hydrocarbon is placed in a vessel equipped with a stirrer and protected against corrosion by chlorides and hydrochloric acid, the stirrer is started and the required amount of aluminum chloride is poured into the vessel with constant stirring. The vessel is closed and the required amount of aqueous aluminum chloride solution is gradually added to the resulting suspension of AlClg in the aromatic component with constant stirring. After the addition of the aqueous solution of AlClj, the contents of the vessel are stirred until all the aluminum chloride is converted into the complex.

The above procedure can produce both a catalytic complex prepared with an excess of the aromatic component and a homogeneous catalytic complex prepared with the minimum amount of the aromatic component required for the formation of the complex.

The catalytic complex prepared by the supported process is a suitable catalyst for the alkylation of benzene with ethylene. The new process achieves higher catalytic activity of the complex, reduction of losses of AlClj and HC1 promoter due to unwanted hydrolysis, which is positively reflected in the reduction of the Specific consumption of AlCl ₃ per unit amount of ethylbenzene produced in the actual technological alkylation process. At the same time, savings of AlCl ₃ per unit amount of the prepared complex are achieved by using AlCl ₃ dissolved in the waste aqueous solution of aluminum chloride from the washing of alkylation products of the ethylbenzene production plant.

The method of producing the catalytic complex and its use in the technological process of alkylation of benzene with ethylene are illustrated by the following examples. (For comparison, an example of the usual method of preparing the catalytic complex with liquid H^O as a promoter is given):

Example 1

200 kg of diethylbenzene fraction from the production of ethylbenzene are introduced into a steel enamelled vessel equipped with a stirrer. After the stirrer is started, 100 kg of AlCl^ is poured into the vessel, the vessel is closed and 2.7 kg of H^O are gradually added to the AlCl^ suspension with continuous stirring over 1 hour. After the end of the dosing, the contents of the vessel are stirred for another 4 hours.

After separation of the excess aromatic layer (70 kg), 232.2 kg of catalytic complex (designated Kl) was obtained as a clear reddish-brown liquid with the following basic properties: AlCl content, g/kg 430.47 o 3 density at 30 C kg/m 1,090 viscosity at 30 °C mm ² /s 6.2

+) activity (mol C^H^/60 min) 3.81.10 ^-2

+) Initial activity of the complex expressed in moles of reacted ethylene during alkylation under the catalytic effect of the complex per unit time.

Example 2 ř

200 kg of diethylbenzene fraction from the production of ethylbenzene are introduced into a steel enamelled vessel equipped with a stirrer. After the stirrer is switched on, 100 kg of AlCl3 is poured into the vessel, the vessel is closed and 1.6 kg of an aqueous solution of aluminium chloride containing 1.17% by weight of _AlCl3 , 0.22% by weight of free _HCl and 0.5% by weight of aromatic hydrocarbons is gradually added to the suspension of AlCl3 over a period of 1 hour, with continuous stirring. After the addition is complete, the contents of the vessel are stirred for another 4 hours.

After separation of the excess aromatic layer (70 kg), 231.3 kg of catalytic complex (designated K-2) was obtained as a clear reddish-brown liquid with the following basic properties:

A1C1 content ₃ g/kg 432.42 density at 30 °C kg/m ² 1,092 viscosity at 30 °C mm ² /s 6.3

+) activity (mol C2H4/6O min) 4.12.10 ²

Example 3

200 kg of diethylbenzene fraction from the production of ethylbenzene are introduced into a steel enamelled vessel equipped with a stirrer. After starting the stirrer, 100 kg of AlClj is poured into the vessel, the vessel is closed and 1.94 kg of an aqueous solution of AlClj containing 25% by weight of AlClj, 0.5% by weight of free HCl and 0.3% by weight of aromatic hydrocarbons is gradually added to the suspension of aluminium chloride over a period of 10 minutes with continuous stirring. After the end of the dosing, the contents of the vessel are stirred for another 5 hours. After separation of the excess aromatic layer (70 kg), 231.9 kg of catalytic complex (designated K/3) was obtained as a clear reddish-brown liquid with the following basic properties:

AlCl^ content g/kg 433.31 density at 30 °C kg/m ³ 1,092 viscosity at 30 °C mm ² /s 6.3

+) activity (mol C ₂ H ₄ /60 min) 8.4.10 ^-1

Example 4

100 kg of diethylbenzene fraction from the production of ethylbenzene is placed in a steel enamelled vessel equipped with a stirrer. After the stirrer is started, 100 kg of AlCl ₃ is poured into the vessel, the vessel is closed and 2.17 kg of an aqueous solution of AlCl ₃ containing 25% by weight AlClg, 0.5% by weight free HC1 and 0.3% by weight aromatic hydrocarbons is gradually added to the A1C1 ₃ suspension over a period of 10 min with continuous stirring. After the dosing is complete, the contents of the vessel are stirred for another 5 hours. A homogeneous catalytic complex (designation K-4) is obtained as a reddish-brown clear liquid without an excess of a separable aromatic layer with the following basic properties:

AlClj content g/kg 497.31 density at 30 °C kg/m ³ 1,230 viscosity at 30 °C mm ² /s 13.1

+) activity (mol C ₂ H ₄ /60 min) 8.4.10 ^-2

Example 5

200 kg of diethylbenzene fraction from the production of ethylbenzene are introduced into a steel enamelled vessel equipped with a stirrer. After starting the stirrer, 100 kg of A1C1 ₃ is poured into the vessel, the vessel is closed and 2.05 kg of an aqueous solution of A1C1 ₃ containing 29.27% by weight of A1C1 ₃ , 0.48% by weight of free HCl and 0.3% by weight of aromatic hydrocarbons is gradually added to the suspension of aluminium chloride over a period of 10 min with constant stirring. After the end of the dosing, the contents of the vessel are stirred for another 5 hours. After separation of the excess aromatic layer (70 kg), 232 kg of catalytic complex (designation K-5) was obtained as a clear reddish-brown liquid with the following basic properties:

AlCl content density at 30 °C viscosity at 30 °C +) activity (mol C ₂ H ₄ /60

Example 6 g/kg kg/m ³ 2 , mm /s min)

433.62 1,092

6.3

8.4.10'

100 kg of diethylbenzene fraction from the production of ethylbenzene is introduced into a steel enamelled vessel equipped with a stirrer. After starting the stirrer, JUO kg of AlClj is poured into the vessel, the vessel is closed and 2.3 kg of an aqueous solution of aluminium chloride containing 29.27% by weight of AlClj, 0.48% by weight of free HCl and 0.3% by weight of aromatic hydrocarbons is gradually added to the AlClj suspension over a period of 10 minutes with continuous stirring. After the end of the dosing, the contents of the vessel are stirred for another 5 hours. A homogeneous catalytic complex (designation K-6) is obtained as a reddish-brown clear liquid without an excess of a separable aromatic layer with the following basic properties:

content A1C1 ₃ density at 30 °C viscosity at 30 °C +) activity (mol C ₂ H ₄ /60

Example 7 g/kg 497.64 kg/m ³ 1 230 mm ² /s 13.1 min) 8.4.10

In an experimental continuous alkylation unit, the alkylation of benzene with ethylene was carried out at a molar ratio of benzene:ethylene of 2.5:1 and a temperature of 98 °C in the presence of a continuously dosed catalytic complex prepared according to example 1-6, and the specific consumption was monitored.

AlClj per unit amount of ethylbenzene produced depending on the method of catalyst preparation. The results are given in the table:

Catal. complex (designation) K-1 K-2 K-3 K-4 K-5 K-6 specific consumption of AlClg (kg/t of ethylbenzene produced) 12.8 11.6 9.8 9.9 9.9 9.8

Claims (2)

OBJECT OF THE INVENTION Process for the production of ethylbenzene by alkylation of benzene with ethylene using a Friedel-Craffs catalyst based on aluminum chloride, aromatic hydrocarbons and a promoter, characterized in that an aqueous solution of aluminum chloride in a concentration of 0.5 to 30.0% by weight is supplied as the promoter. preferably containing free dissolved hydrogen chloride, in a ratio of 0.8 kg to 2.6 kg of water contained in this solution per 100 kg of aluminum chloride used. 2. A process according to claim 1, wherein the promoter is a waste solution of aluminum chloride from the scrubbing of the alkylation products.