SU1081154A1 - Process for recovering styrene - Google Patents

Abstract

A METHOD FOR INCREASING STYRENE from a mixture of styrene and ethylbenzene by single-stage rectification in the presence of water, characterized in that, in order to reduce energy costs, water in an amount of 3.3-30% by weight is introduced into the mixture and the rectification is carried out the temperature of the top of the column is 36-70 ° C, the pressure of the top of the column is 40-200 mm Hg. and the temperature of the cube of the column 80-120 C. (L 00 SP 4 ;;

Description

The invention relates to the production of styrene, in particular, to methods for separating commercial styrene from a mixture of styrene with ethylbenzene.

At present, commercially available styrene is produced by the catalytic dehydrogenation of ethylbenzene, also by the catalytic dehydration of methylphenylcarbinol (in the process of co-production, propylene oxide and styrene). The resulting styrene raw, depending on the method and process conditions, contains 1-65 May,% ethylbenzene. According to the specification, commercial styrene should contain 0.2-0.4 wt.% Ethylbenzene

There is a known method for isolating styrene on a single vacuum column that has plates with malug hydraulic resistance tl.

However, due to the low relative volatility of the CL of the ethyl pair, ethylbenzene styrene requires a large number of plates. Usually, the hydraulic resistance of a column with such a number of plates does not allow the desired vacuum to be created in a cube. Therefore, in industrial practice, double rectification schemes are used.

There is also known a method for separating an ethylbenzene-styrene pair in the presence of effective polymerization inhibitors, which allows separation in a single column by increasing the temperature of bottom 2.

However, the energy costs of obtaining commercial styrene are not reduced.

Closest to the invention is the method of styrene separation from a mixture of styrene and ethylbenzene in the presence of water, which is carried out at atmospheric pressure, the amount of water supplied to the separable mixture is constant and is 1.44 wt.h. on 1 ma.ch. the raw material. A mixture of water and ethylbenzene is taken from the top of the column, and a water-styrene mixture is taken from below. The key pair in this case is: azeotrope (ethylbenzene water I is water. The top temperature of the column is 90-92 s, and the bottom of the column is 94-100 ° C. Z.

Although this method allows to obtain styrene in accordance with the requirements of GOST on the content of ethylbenzene, a serious drawback of it is the overhead for evaporation of large amounts of 1UDE and drying of styrene.

The aim of the invention is to reduce energy costs.

The goal is achieved by a method of separating styrene from a mixture of styrene and ethylbenzene by single-stage rectification at a temperature of the top of the column 36-TOC, pressure of the top of the tank) 40-200 mmHg

and the temperature of the bottom of the column 80-120C in the presence of water, introduced in the amount of 3.3-30 wt.% to the mixture.

The amount of water supplied is strictly dependent on the ratio of ethylbenzene and styrene in the mixture to be separated, the temperature of the top of the column is 36-70 ° C, the bottom is 80-120 ° Relative volatility of the KJ-water-styrene or azeprop (water-ethyl-benzene) -styrene separation approximately 2.5 times higher than the relative separation yields when the key pair is ethylbenzene styrene, and 2 times the key pair of azeotrope (water - ethylbenzene) - water

A change in the key pair provides a significant decrease in the reflux ratio, which leads to a reduction in the energy consumption for the separation of ethylbenzene from styrene. The energy and capital expenditures necessary for drying styrene are eliminated.

The ratio of ethylbenzene: styrene is (0.005-1.5): 1 and covers the following processes: the process of producing styrene by dehydrogenating ethylbenzene, 0.5-1.5: 1, depending on the conversion of ethylbenzene; the process of joint production of propylene oxide with styrene, 0.005-0.05: 1) processes for the separation of ethylbenzene-styrene mixtures from styrene-raw.

The drawing shows the dependence of the amount of water on the ratio of ethylbenzene and styrene in the mixture to be separated.

Example 1. Raw styrene in the amount of 6000 kg / h is fed to the distillation column. The column contains 40 practical contact stages and operates with the following parameters: column top temperature 50 ° С, bottom cubed temperature 80 С, reflux number 5, distillate selection 1000 kg / h, bottom product extraction 5000 kg / h, column top pressure 40 mmHg.

In tab. Figure 1 shows the composition of the streams of raw materials and separation products: Option I - separation is carried out without the addition of water; Option II - 200 kg / h of water is supplied to the column.

Example 2. This example differs from Example 1 only in the composition of the streams of raw materials and excretion products shown in Table 2. Option I - separation is carried out without adding water, Option II - 200 kg / h of water are supplied to the column.

Example 3. An organic mixture (ethylbenzene and styrene in the ratio 1.5: 1) in the amount of 400 g / h and water 120 g / h (30% by weight to the mixture to be separated) is fed to a column with 35 theoretical steps — touch . Parameters of solonna operation: i-temperature of the top 36 ° С, pressure of the top 60 mm Hg, temperature of the cube 98 С, reflux number 0.5, top product 361.6 g / h, selection of the bottom product 158.4 g / h .

Example 4. A mixture of ethylben, ash and wash in a ratio of 0.67: 1 in the amount of 400 g / h and water of 90 g / h (22 wt.%) Are fed to a column with 35 theoretical contact stages. The operating parameters of the column: top temperature 70 ° C, pressure 200 mm Hg; the temperature of the cube is 120 ° C, the reflux number is 0.72, the selection of the top product is 252.3 g / h, the selection of the bottom product is 237.7 g / h.

Example 5. Ethylene benzene and styrene in a ratio of 0.046: 1 in the amount of 400 g / h and water of 30 g / h (7.8 wt.% With respect to the mixture to be separated) are fed to a column with 35 theoretical contact stages. The operating parameters of the column: top temperature 60 ° C, top pressure 125 mm Hg, the temperature of the cube

110 ° С, reflux number 3, the selection of the top product of it 51.2 g / h, the selection of the food product - 378.8 g / h.

The compositions of the streams in examples 3-5 are presented in table. 3. in table. Figure 4 shows the comparative data for the separation of a mixture of ethylbenzene and styrene in various ways: without adding water, according to known and proposed methods.

0 (In all cases, the number of theoretical plates is 35, the reflux number is 0.6).

As follows from the data table. 4, the effect is achieved as a result of the separation process under conditions where the key is water-styrene or azeotrope (water ethylbenzene) - styrene, the relative volatility of which is higher than

0 by a known method. This achieves a better separation of ethylbenzene, reduces the energy consumption for separation and eliminates the stage of styrene drying.

Table 1

table 2

Water

Ethylbenzene240,060.0

Styrene1,06,040,0

Total: 400.0100.0

Water

Ethylbenzene 160.0. 40.0

Styrene240,060,0

Total: 400.0100.0

18.04.5

382.0 95.5 400.0 100.0

Table 3,

For example 3

71.15 55.0 39.29

28.85 85.0 60.71

100.0 140.0 100.0

For example 4

51.11 45.0 25.71 48.89 130.0 74.29 100.0 175.0 100.0

For example 5

9,917,02,42

90.09 282.0 97.58 100.0 289.0 Software, 0

297.0 59.40 128.3 54.81 168.7 63.45

113.0 22.60 93.0 39.73

ol

90.0 18.00 12.85.46

500.0 100.0 234.1 100.0

Continued table. 3

Table 4

Continued table. four.

20.0 7.52

77.2 29.03

265.9 100.0

 the temperature of the top of the column is 64 ° C; the cube is 100 ° C;

temperature of the top is 90 ° С, cubes are 100 ° С, pressure of the top is 760 g.1 m Hg; water ratio; divided mixture: 1.44: 1 wt.h.

"" "The temperature of the top, the cube is 101 ° C, the pressure of the top is 60 mm Hg, the ratio of water; divided mixture Oh, 297-L May. h

Continued table. four

Claims (1)

METHOD FOR ISOLATING STYROL from a mixture of styrene and ethylbenzene by a single-stage distillation in the presence of water, characterized in that, in order to reduce energy costs, water is introduced into the initial mixture in an amount of 3.3-30 wt.% Per mixture and distillation is carried out at the top temperature columns 36-70 ° C, pressure! the top of the column 40-200 mm RT.article and the temperature of the cube of the column 80-120 ° C. separation of the products of dehydrogenation of ethylbenaol. Abstract of Cand. Diss, M., 1975 (prototype). 30. Water