RU2459796C1 - Method for selective production of meta-dialkylbenzenes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for selective production of meta-dialkylbenzenes (meta-diisopropylbenzene or meta-diethylbenzene) via alkylation of benzene with a lower olefin in the presence of an anhydrous aluminium chloride-based catalyst, followed by separation of the alkylate by fractionation. The method is characterised by that meta-dialkylbenzene is obtained in two steps through synthesis of mono-alkylbenzene at the first step and dialkylbenzene isomers at the second step such that, mono-alkylbenzene is obtained by reacting benzene with para-dialkylbenzene, and at the second step dialkylbenzene isomers are obtained by reacting mono-alkylbenzene with ethylene or propylene, and the mixture of dialkylbenzene isomers obtained at the second step is separated into separate isomers, from which dialkylbenzene is returned to the first step.

EFFECT: use of the present method ensures high selectivity of producing the end product through optimum combination of alkylation and transalkylation processes, and also reduces power consumption when forming recycling streams by selecting the value of conversion of the primary products.

1 cl, 2 ex, 2 dwg

Description

The present invention relates to organic synthesis, in particular to the synthesis of meta-dialkylbenzenes, in particular meta-diisopropylbenzene (m-DIPB), meta-diethylbenzene (m-DEB) and their production technologies on an industrial scale. These products can be used as starting alternative raw materials for the production of isophthalic acid (IPA) by liquid-phase oxidation, as shown in known sources [Holland patent No. 108519, 1953, GB patent No. 786930, 1957, GB patent No. 749186, 03.03.1954], where Efficient methods for producing IFC and TFA by liquid phase catalytic oxidation of the corresponding m-DIPB and p-DIPB are given.

Currently, m-xylene obtained from oil refining from the xylene fraction is mainly used as feedstock for the preparation of IFCs. It should be noted that the composition of the xylene fraction consists of xylene isomers (meta- and para-), ethylbenzene and a number of other hydrocarbons, the separation of which is a difficult and expensive task due to the proximity of the boiling points of the individual substances included in the xylene fraction. Therefore, the problem of IFC production can be solved by developing a cost-effective process for obtaining the feedstock - m-DIPB (m-DEB) by alkylation of benzene with propylene (ethylene), which could be introduced into industrial practice.

It is known [JP 3042366 B2 dated 05/31/1995; JP 3042367 B2. 05/31/1995] that the DIPB isomers are obtained during the alkylation reaction of benzene with propylene and then by transalkylation of the resulting reaction solution, which is carried out continuously in the presence of a liquid catalyst based on a complex of aluminum chloride using 2 (preferably 3) reactors. The alkylation reaction is carried out at 50-150 ° C (preferably 60-100 ° C) and a pressure of 1 to 20 atm, and the transalkylation reaction is carried out at 50-150 ° C and a pressure of 1 to 10 atm. They further describe a method for purifying and producing high-purity m-DIPB by separating p-DIPB from a crude m-DIPB containing it as an impurity and bringing the raw m-DIPB into contact with a zeolite with a pore diameter of 0.5-0.7 nm The disadvantages of these methods are that the use of zeolite for the process of separation of significant amounts of m-DIPB from the mixture is likely to be difficult in the industry, and no consideration is given to the disposal of p-DIPB obtained in these processes.

Patent [WO 2003000629 A2, 04/03/2002] describes a selective method for producing m-DIPB by contacting a feed containing meta- and ortho-diisopropylbenzenes with benzene under conversion conditions with a catalyst containing a molecular sieve. At the contacting stage, the m-DIPB output stream is enriched. The disadvantage of this method is that upon receipt of m-DIPB, only the mixture is subjected to processing, in which there is already no such component as p-DIPB, which does not allow it to be used in the process of benzene alkylation with propylene. Also, this method is difficult to implement in industrial practice due to the complexity of the operation of the catalyst with a molecular sieve.

Known [GB 2398572 A1, 11/13/2003] a method for the synthesis of p-DIPB using the starting materials only isoprbpylbenzene (IPB) and propylene. The method provides a sequence of stages:

- the supply of IPB and propylene to the alkylation zone containing an alkylation catalyst (zeolites);

- the reaction of the components of the feed to obtain the first mixture of p-DIPB and m-DIPB at a temperature of 149-204 ° C and a pressure of 4-70 atm;

- fractional distillation of the first mixture to separate p-DIPB and m-DIPB;

- isomerization of m-DIPB isolated from the 1st mixture in the presence of a transalkylation catalyst (zeolites) to obtain a second mixture of p-DIPB and m-DIPB at a temperature of 185-221 ° C;

- return of the second mixture to the stage of fractional distillation;

- extracting the obtained p-DIPB.

The disadvantage of this work is the use of only IPB as a feedstock, because IPB itself is a reaction product of the alkylation of benzene and propylene. It also reduces the applicability of this method for the production of predominantly p-DIPB in comparison with m-DIPB during the alkylation, because complex catalysts based on zeolites and heteroacids and a complex reactor unit for carrying out the reaction are used. In addition, in this work the problem of obtaining m-DIPB is not solved.

Closest to the claimed method for the alkylation of benzene and the production of diisopropylbenzenes is the patent [RU No. 94028723 A1. 08/01/199410], where it is proposed to obtain mono- and dialkylbenzenes (MAB, DBA). Benzene and a lower olefin are supplied to the alkylation reactor block for their interaction in the presence of a catalyst complex based on anhydrous aluminum chloride. After the reactor, the solution enters the site of separation of the catalyst complex from the alkylate. The latter is sent to the primary unit of multi-stage distillation with stages of separation of the return (unreacted) benzene, MAB, DAB and polyalkylbenzenes (PAB). Part of the raw DBA is returned to the reactor, and the other part of the crude DBA is subjected to clear rectification in the secondary unit, consisting of 3 distillation columns, before final removal from the installation (to obtain the target product). In the first column (30 theoretical plates, atmospheric pressure, the temperature below - 153 ° C, the temperature above - 190 ° C) a low-boiling fraction is separated, which is returned to the alkylation reactor. The bottom part from the 1st column enters the next (2nd) column (50 theoretical plates, atmospheric pressure, temperature below 200 ° C, temperature above 180 ° C, reflux number 10-20). In this column, low boiling products are finally removed. The distillate is returned to the reactor. The bottoms product of the 2nd column is sent to the 3rd column (30 theoretical plates, atmospheric pressure, temperature below - 193 ° C, temperature above - 183 ° C, reflux ratio - 1.5-5). As a distillation of the 3rd column is high-quality DBA (target product). Part of the bottoms product from the 3rd column is sent to the primary distillation unit, and the other part is sent to the alkylation reactor.

The disadvantage of this work can be attributed to a multi-stage scheme for the isolation and purification of the target product - DBA, as well as the fact that the task of separating and obtaining the DBA isomers themselves was not solved in this work, therefore, it is used to develop the technology for producing m-DIPB (m-DEB) limited in nature.

The aim of the proposed method is to develop a technological process for the production of lower dialkylbenzenes, namely: meta-diisopropylbenzene (m-DIPB), as well as meta-diethylbenzene (m-DEB), as a feedstock for the production of IFC, with the following requirements:

- make maximum use of the vast industrial practice of producing isopropylbenzene (IPB) by alkylating benzene with propylene in the presence of a catalyst based on anhydrous aluminum chloride;

- to achieve high selectivity for m-DIPB (m-DEB) due to the optimal combination of alkylation and transalkylation reaction processes;

- reduction of energy consumption during the organization of recycle flows by choosing the value of the conversion of the starting products.

This goal is achieved by the fact that the process of obtaining m-DIPB (m-DEB) is carried out in two reaction stages and in the stage of separation of m-DIPB (m-DEB) from alkylate. The process diagram is shown in figure 1.

At the first stage, monoalkylbenzenes - isopropylbenzene (IPB) or ethylbenzene (EB) are obtained by reacting p-DIPB or p-DEB with benzene, respectively, returned from the separation step in the presence of anhydrous aluminum chloride as a catalyst.

At the 2nd stage, the UPS / EB obtained at the 1st stage as a result of its alkylation with propylene / ethylene and in the presence of anhydrous aluminum chloride is converted into the DIPB isomers - m-DIPB and p-DIPB (the isomers of DEB - m-DEB and p DEB).

At the 3rd stage (separation) in a known manner, the reaction products are separated by distillation. At the same time, unreacted products (benzene, IPB, EB) are returned to the reaction cycle at stages 1 and 2, namely: p-DIPB (p-DEB) - to the first stage of monoalkylbenzenes production (transalkylation), IPB - to the second stage (alikylation) and the target product - m-DIPB / m-DEB is derived from the technological process as a commercial product.

The invention is illustrated in figure 2, which presents a schematic diagram of the technological process of obtaining lower dialkylbenzenes (m-DIPB, m-DEB).

In reactor 2 (FIG. 2), p-DIPB (p-DEB) returned from the separation stage (column 7) is reacted with benzene, which is a mixture of fresh and isolated at the separation stage in column 5, in the presence of an anhydrous aluminum chloride catalyst - and turns into mono-alkylbenzene - IPB (EB). The site of preparation of the catalyst in the diagram is not shown. The catalyst is prepared by any method well known in the art (the catalyst itself and the method for its preparation are not the subject of this invention). The IPB (EB) obtained in reactor 2 together with the residual unreacted benzene enters reactor 1, where the return IPB (EB) is also fed from the separation stage (column 6). In reactor 1, the alkylation of IPB (EB) and benzene by propylene (ethylene) is carried out to form a mixture of isomers of m-DIPB and p-DIPB (m-DEB and p-DEB) in the ratio (2-2.5): 1. (The installation may contain one or more alkylation reactors, which may be any of the known in the art.)

The alkylate obtained in the reactor 1 enters the separation apparatus 3, where the separation of the catalyst occurs, which can repeatedly return to the reaction cycle. And the solution freed from the catalyst enters the stage of washing into the apparatus 4 from the residual catalyst with water and alkali. After separation of the aqueous layer, the organic part is fed to a separation scheme consisting of 3 distillation columns 5, 6, 7.

In the first distillation column (5), benzene is separated, which is returned to reactor 2. The bottoms product of the first column is sent to column 6, where IPB (EB) is distilled off, which is returned to reactor 1.

In the distillation column 7 enters a mixture of isomers of dialkylbenzenes. In this column, the target product m-DIPB (m-DEB) is distilled off, and p-DIPB (p-DEB) is returned for processing to reactor 2.

Depending on the required quality of IFC obtained on the basis of liquid-phase oxidation of m-DIPB (m-DEB), the latter may contain 95-99.5% of the main substance in its composition.

Figure 2: Schematic diagram of the technological process of obtaining lower dialkylbenzenes (m-DIPB, m-DEB).

The figure shows a schematic flow chart, therefore auxiliary technological equipment: boilers and refrigerators of distillation columns, pumps, intermediate tanks, automation and control equipment, etc., is not shown on it.

The following are examples of specific embodiments of the invention that illustrate but do not limit its scope.

Example 1

In the reactor 2 (figure 2) benzene is continuously fed in an amount of 251.8 g / h, p-DIPB - 137.0 g / h, the catalyst (AlCl ₃ ) - 22.6 g / h. The contents of the reactor are mixed at a temperature of 68-72 ° C and a residence time of 120 minutes. From reactor 2, the mixture continuously enters reactor 1, where IPB is also supplied in an amount of 405.9 g / h, AlCl ₃ - 11.8 g / h, propylene at a speed of 1.15 nl / min with a residence time of 60 minutes and at a temperature of 78-80 ° C. The mixture is then discharged from the reactor. First, the catalyst is separated from the reaction products (alkylate) by decantation (returned to the cycle). The resulting alkylate is washed with water and an alkali solution. After that, using rectification in a known manner, benzene is isolated in an amount of 131.9 g / h, IPB (return product) - 202.9 g / h, m-DIPB (target product) - 249 g / h and p-DIPB (returned product) in the form of a bottom residue - 137.0 g / h.

Example 2

In the reactor 2 (figure 2) benzene is continuously fed in an amount of 172.4 g / h, p-DEB - 77.6 g / h, the catalyst (AlCl ₃ ) - 14.5 g / h. The contents of the reactor are mixed at a temperature of 78-82 ° C and a residence time of 120 minutes. From reactor 2, the mixture continuously enters reactor 1, where EB is also fed in an amount of 245.4 g / h, AlCl ₃ is 7.6 g / h, ethylene is delivered at a rate of 0.79 nl / min with a residence time of 60 minutes and at a temperature of 80-83 ° C. The mixture is then discharged from the reactor. First, the catalyst is separated from the reaction products (alkylate) by decantation (returned to the cycle). The resulting alkylate is washed with water and an alkali solution. After that, using rectification in a known manner, benzene is isolated in the amount of 90.3 g / h, EB (return product) - 122.7 g / h, m-DEB (target product) - 141 g / h and p-DEB (return product ) in the form of VAT residue - 77.6 g / h.

The above examples show the possibility of achieving a new technical result, due to the purpose of this invention.

Claims (1)

A method for the selective production of meta-dialkylbenzenes (meta-diisoproblebenzene or meta-diethylbenzene) by alkylation of benzene with a lower olefin in the presence of an anhydrous aluminum chloride catalyst followed by distillation of the alkylate, characterized in that meta-dialkylbenzene is obtained in two stages by synthesis on 1- of the mono-alkylbenzene stage, and of the dialkylbenzene isomers in the 2nd stage so that mono-alkylbenzene is obtained by reacting benzene with para-dialkylbenzene, and in the 2nd stage, isomers are obtained ialkilbenzola reacting a mono-alkyl benzene with ethylene or propylene, and formed on the 2nd stage mixture dialkylbenzene isomers is separated into the individual isomers, of which dialkyl-vapor recycled to the 1st step.

Images