SU1074849A1 - Process for dehydrating toluene - Google Patents

Abstract

1. METHOD FOR TOLUOLA DRYING by azeotropic distillation with water extraction - the azeotropic distillation in the upper steam stream of the column followed by separation of water from it, returning the hydrocarbon layer to the azeotropic distillation column as a reflux irrigation and removing the drained toluene layer and the composition of the layer with that, in order to increase the degree of drying, the rectification is carried out by B in the presence of isopentane supplied in the feed of the azeotropic distillation column and in the reflux irrigation, containing 50-100 wt.% of isopentane and introduced into the feeding zone or into the zone located between the feed inlet and the bottom of the azeotropic rektis S9 fixation column, the nutritional ratio: reflux irrigation .5 (L 10: (O, 3- 1). 2, The method according to claim 1, about tl and .4 a kg and with the fact that, in the composition of the upper steam flow, a triple heteroazeotrope — toluene-iso-g-pentane-water — is taken. L so t

Description

The invention relates to the petrochemical industry, in particular to methods for drying aromatic solvents, in particular, methods for drying toluene, and can be used in the processes of synthesis of organoaluminum compounds and catalysts for stereoregular polymerization of dienes.

To dehydrate various compounds. For example, alcohols, ketone esters and others, azeotropic distillation with or without a separating agent has been widely used. Cll A method of toluene drying by azeotropic distillation with water extraction in the upper steam stream of the azeotropic distillation column and sampling of dried toluene from the bottom product was used. The essence of this method is to remove water from the distillation system as solvent vapor enriched in water. Solvent vapors are condensed to form a two-phase system, water is separated, the hydrocarbon layer is returned as reflux to the top of the column — azeotropic distillation, and the dried solvent is removed from the bottom of the azeotropic distillation column. The composition of the azeotrope. For example, toluene, at 760 mm Hg. 51 mol.% Toluene and 49 mol,% water. The known method makes it possible to dry toluene to a residual water concentration of 0.0020, 005 wt.% C2.

Attempts to achieve a deeper degree of drying by increasing the reflux & h or reducing the temperature of the reflux are ineffective. At the same time, a number of technological processes, such as the synthesis of organo-organic compounds, the preparation of organolithium and organometallic polymerization catalysts require a higher degree of drying of solvents, in particular toluene. For example, the presence of small amounts of water in triisobutylaluminum promotes the formation of alumohexane polymers, drastically reducing the quality of the product.

The purpose of the invention is to increase the degree of drying of toluene.

The goal is achieved by the method of drying toluene by azeotropic distillation with selection of water in the composition of the upper steam stream of the azeotropic distillation column with subsequent separation of water from it, returning the hydrocarbon layer to the azeotropic distillation column and sampling .. 9 I Ears toluene

in the composition of the bottom product, according to which the rectification is carried out by B in the presence of isopentane supplied in the feed composition of the azeotropic distillation column and in the composition of reflux irrigation containing 50-100 wt.% of isopentane and introduced into the feed zone or in the zone located by medsdu feed and cube columns of azeotropic distillation, with a mass ratio of food: reflux irrigation 10: (0.3-1).

It is preferable to select a triple heteroazeotropic toluene-yzopentane-water as part of the upper vapor stream.

The physicochemical meaning of the effect of isopentane, based on modern concepts of the solution theory, can be explained by a change in the size of toluene – water associates, a rearrangement rearrangement due to the appearance of a much weaker isopentane – water interaction.

Using IR and NMR spectroscopy, it was found that in toluene in the region of low concentrations of water, hard-to-destroy associates of the weak interaction of the base of Bronsted (Toluene) and Bronsted acid (water) are formed.

These associates / yugts should be destroyed, and the rate of achieving a vapor-liquid equilibrium is increased several times by the introduction of a paraffinic hydrocarbon, such as isopentane.

The drawing is a diagram of the implementation of the method.

Wet toluene with a content of 0.02-0.04 wt.% Of water is fed along line 1, depending on the water content, in one of the points of the 30-50-plate column 2 above its middle part, but not above the 10-15th plate. from the top of the column. Triple toluene-isopentane-water or binary isopentane-water heteroazeotropic couples, taken from the top of the column on line 3, condense, liquid is settled, the lower water layer is removed on line 4, and the isopentane-toluene solution or isopentane is fed into the food zone or between the feed line and cubed columns as reflux irrigation on line 5.

The ratio of feed (stream 1) to reflux irrigation flow is maintained at 10: (1-0.3).

It is recommended that isopentane concentration in reflux irrigation should be maintained at least 50100 Mat;.%. In this case, toluene is taken from the bottom of the column along line b, in which the water content does not exceed 0.0005% by weight. When the concentration of isopentane in the reflux stream is less than. 50% deteriorates with purification, since such a quantity of isopuetane is not enough to destroy the toluene – water associates. Increasing the amount of isopentane is not economical and requires a large number of plates in the o-section. This also explains the choice of the mass ratio of feed flow and reflux irrigation. When organizing the process according to the proposed method, irrigation also serves as food. In the azeotropic rectification, the feed always performs the function of reflux, since reflux is supplied in a small amount (yr of may.% Of the feed). The top under the conditions of the proposed method works as a separation. This is necessary for deep drying, as very often the power, and especially phlegm, does not contain water in the dissolved state, but in the emulsified state, the presence of which knocks down the mode of operation of the column. Example .1 (by the well-known method). . In the azeotropic drying column with the number of theoretical plates 30, 1000 kg / h of toluene and 0.3 kg / h of diluted water are fed to the 10th plate from the top. The process indicators are as follows: Toluene vapor recovery with water, kg / h593.9 including water, kg / h93.99 Return of toluene with water to the column, kg / h, to the 5th plate from the top 599.73 including water, kg / h93.63 Withdrawal of water from the system, - kg / h0.26 Withdrawal of toluene with water from the bottom part, kg / h 1000.04 including water, kg / h Water concentration in dried toluene, wt.% Temperature in the bottom parts of the column, ° C Temperature in the upper part of the column, ° C Pressure in the bottom of the column, ata Pressure in the upper part of the column, ata Toluene refers to liquids that are prone to the formation of an emulsion with Doi. The disadvantage of this method is that, as a result of the formation of an emulsion, a hydrocarbon containing more water than the limit of its solubility in a given hydrocarbon is supplied to the reflux. As a result, the reinforcing part of the column is bridged, which dramatically reduces the drying efficiency. The above example 1 describes just such a case of the column. But during the operation of the column. When the water is not in the emulsified state, the degree of drying of the toluene is also low — the moisture content according to the prototype is 0.00130, 002% by weight. Example 2. In the azeotropic drying column (30 theoretical plates) on the 15th plate from the top serves 1000 kg / h of toluene, 10 kg / h of isopentane, 0.3 kg / h of dissolved water (line 1). The content of isopentane in reflux irrigation 50 wt.%. The mass ratio of nutrition and reflux irrigation is 10: 1. Process indicators are as follows:. Vapor collection, kg / h of toluene50,510 water .0,305 isopentane50,515 Reflux of the organic layer of condensate on the 30th plate from the top, kg / h of toluene50,510water .0.005 isopentane50,515 Output from the system, kg / h 0.3 Output from the system of bottom liquid, kg / h toluene of isopentane water Content of water on dried toluene Temperature in the bottom of the column, ° С Pressure in the bottom of the column, ata Temperature in the upper part of the column, ° С Pressure in the upper part of the column, at 1 Example 3 To the azeotropic drying column (50 theoretical plates) to the 15th plate from the top.

1000 kg / h of toluene, 10 kg / h of isopentane and 0.3 kg / h of dissolved water (line 1) are fed. The content of isopentane in reflux irrigation 100 wt.%. The mass ratio of nutrition in reflux irrigation is 10; 0.3. Process indicators follow; Vapor extraction, kg / h

isopentane water

Reflux irrigation return the organic layer of condensate to the 15th plate from the top kg / h

isopentane water

Output from the water system, kg / h

Conclusion from the system of liquid cubes, 25E /

toluene

water

isopentane

water concentration on dried toluene,

wt ..%

TejvffiepaTypa in the bottom of the column, ° C

Pressure in the bottom column, ata

The temperature at the top of the column, ° C

Pressure at the top of the column, ata

The resulting bottoms product is directly used in the preparation of polymerization catalysts, since isopentane is also used in this process.

and careful separation of this mixture

not required.

If it is necessary to use individual toluene, the release of isopentane from the cube is easy.

can be carried out by rectification.

From the results of the examples it can be seen that the degree of drying of toluene is increased in comparison with the known method. The concentration of water in dried toluene decreases from 0.004 to 0.0002% by weight.

At the same time, when sampling a distilled ternary heteroazeotrope of toluene-isopentane-water, the degree of

be elevated to contain traces of water.

Claims (2)

1. METHOD OF DRYING TOLUENE by azeotropic distillation with water withdrawal - as part of the upper steam stream of the azeotropic distillation column, followed by separation of water from it, returning the hydrocarbon layer to the azeotropic distillation column as reflux irrigation and selecting dried toluene as a part of the bottoms product, characterized in that, in order to increase the degree of drying, distillation is carried out in the presence of isopentane supplied in the feed composition of the azeotropic distillation column and in the composition of reflux irrigation ., - comprising 50-100 wt% of isopentane and introduced into the feed zone or in a zone located between the feed inlet and the bottom of the column by azeotropic distillation, a weight ratio of St. § 'power: 10 reflux irrigation f 0,3-1). 2. The method according to π. 1, with the fact that, in the composition - ^{1 of the} upper steam stream, a triple heteroazeotropic - toluene-isopentane-water is selected. SU 10748