SU361559A1 - - Google Patents

Description

METHOD FOR ISOLATION OF AROMATIC HYDROCARBONS I2

This invention relates to a process for the isolation of aromatic hydrocarbons from their mixtures with non-aromatic hydrocarbons.

A known method is the separation of aromatic hydrocarbons from their mixtures with non-aromatic hydrocarbons by extractive distillation in the presence of a selective solvent with the receipt of a raffinate phase, withdrawn from the top of the extractive refining column, and an extractive phase withdrawn from the bottom of the column, followed by separation of non-aromatic hydrocarbons from the raffinate phase and aromatic hydrocarbons from the extract phase by distillation. However, mixtures of hydrocarbons, from which pure aromatic hydrocarbons are obtained by extraction distillation, contain impurities of high-boiling aromatic compounds, the boiling points of which coincide with the solvent point or lie even higher. These aromatic impurities cannot be removed from the solvent with the usual method of operating an extraction distillation unit and are slowly concentrated in the solvent, deteriorating its selective properties over time.

In addition, the extractive distillation contains a small amount of solvent in the raffinate phase emerging from the top of the column, which negatively affects the process performance.

Thus, the aim of the proposed method is to remove impurities of high-boiling aromatic compounds, which contaminate the solvent, and / or completely remove the solvent from the raffinate phase.

This goal is achieved by supplying the raffinate phase s the lower part of an additionally installed liquid extraction column, on top of which water is supplied, and in the middle part is a selective solvent separated from the solvent stream supplied at the extractive stage.

In an extraction column, the raffinate phase absorbs high-boiling aromatic hydrocarbons from the solvent, while water removes the bunches of the solvent from the raffinate.

Thus, a pure raffinate phase, a mixture of water with a solvent, is removed from the liquid extraction column, free from impurities of high-boiling aromatic hydrocarbons | Dov. As a selective solvent, predominantly α-methylpyrrolidop or dimethylformamide is used.

The drawing shows an exemplary flow diagram of an installation for carrying out the process according to the invention.

According to; the hydrocarbon mixture lying down through pipeline 1 is fed into the column 2 by extractive distillation, into its middle part, to the upper part of this column, regenerated solvent is fed through pipeline 3. The top product of extraction distillation is the raffinate phase, consisting mainly of non-aromatic hydrocarbons. It is diverted via line 4 and condensation {) comfort. One part of the condensate is injected through conduit 5 into the lower part of P | rototochtapny extractor 6, the other part of it is returned to column 2 but pipeline 7. From the lower part of column 2, the extra phase phase is taken, iredsta (the mixture of solvent and aromatic hydrocarbons, and pipelines 5 and 9 are fed into the middle part of the column 10. Regenerated solvent is withdrawn from the bottom of this column, which through pipelines 11, 3 and through the heat exchanger 12 return to the extractive distillation stage. the bodies are taken into conduit 13 and solvent is introduced into the middle part of the counter-current extractor 6. In the upper part of the extractor 6, va, l, yo pipeline 14 is supplied. From the counter-current extractor 6, a mixture of water and the solvent recovered from the raffinate is removed from the countercurrent extractor 6 9 directs the processing to the column 10. From the upper part of the column 10 through conduit 16, the mixture of hydrocarbons and water obtained from the extract is sent to the phase separator 17. In it, water, as a more heavy phase, precipitates, it is sent back against a waste extractor of the pipeline 14. The pure aromatic hydrocarbons obtained as a light phase are separated using phase separator 17, and some of them are returned to the upper part of line 10 via pipeline 18. The balance of pure aromatic hydrocarbons is removed from phase separator 17 but pipe line 19. Alkyl aromatic hydrocarbons, are flowing. which lies close to or above the exact point of the solvent’s kiling point (the hydrocarbons must be co-centric in the solvent and must be redacted) are sucked out of the counter-current extractor 6 through the solution 20 line rennymi: obtained in the extraction of distillation of the raffinate. Example 1. From krekiit-gasoline nonregular get xylol fraction with so Kip. 135-160 ° С of the following composition (%): Toluene1 St-aromas80,4 Cd-aromas5,9 Syu-aromas0,1 Non-aromas 12,6 This fraction is fed by pipeline / in the amount of 500 kg / hour at a temperature of 140 ° С by 30 plate of extraction column with 60 practical plates. In the extraction column 2, pipeline 3 introduced 1,230 kg of selective solvent at a temperature of 100 ° C, consisting of 96% n-methylyrrolide (IMI) and 4% cio-arolic hydrocarbons. 130000 kcal of heat is supplied to the source of column 2. The yars collected at the top of column 2 are sucked off by conduit 4 and condensed. Kondel sat has the following composition OB%): Toluene5.1 C-aromatic hydrocarbons25.8 Non-aromatic hydrocarbons65.4 NMP1.7 93 kg of condensate is extracted by pipeline 5 to the counter-current extractor 6. The residue is fed back to pipeline 7 extracioio-distilled ( Colost 2. From the bottom of the column 2, 1696 kg of the mixture from the solvent and aromatic hydrocarbons and through the pipeline 8 are fed to the separator column 10. From the solvent flowing through pipeline 3 to the distillation column 2, a part of the current (12 kg / hour) and served by pipe 13 into the oana from the middle stages of the countercurrent extractor.The extractor is a cassation-separating column of 1/2 steps.In rrrrrrrrrrrrrrrrrrr; The extractor 5 is iodine through pipeline 14, water in an amount of 15 g, g / h. In countercurrent extractor 6, the NMP is extracted from the head product of extraction distillation. This mixture is taken from the lower part of the extractor. Odiovremeino from the part of the solvent stream supplied through pipe 13 and 13, release 4% of Xyu-aromatics and remove them from the upper part of the extractor. Pipeline 20 from extractor 6 takes 92 of the carbon mixture of the composition (in%): Toluene5.1 Cz-aromatic hydrocarbons26.1 C | o-aromatic hydrocarbons, dy0.5 Hydroaromatic hydrocarbons 68.1 From the lower part of the extractor 6 via pipeline 15 is diverted 28 , 6 kg per hour of a mixture consisting of 48% i NMP and 52% water, dy. This mixture is connected to the passage of the pipeline and pipeline 5 with product from the distillation column 2 and sent through the pipeline to the separator column 10 and the 5th / 5th plate. Column 10 is a hierogony column with 40 practical plates and operates at a pressure of 0.2 atm. 100000 kcal of heat is supplied to the evaporator of the column 10, steam from the upper part of the separator column 10 is led through conduit 16, condensed and put into phase separator 17. It separates the water phase, which flows into the extractor 6 through conduit 14 em a cocTaiBa hydrocarbon mixture (in%):

Toluene

Sz-aromatic hydrocarbons92,6

Cd aromatic

hydrocarbons7.3

Particular aromatic hydrocarbons through pipeline 19 are removed from the plant in the amount of 408 kg / hour. The remainder of the separated hydrocarbons is fed through a pipe 18 to a distillation column W. A mixture of 96% NMP and 4% Xyu-aromatic hydrocarbons in the amount of 1250 kg is removed from column 10 but the pipeline / - /. The main part of the mixture is returned to the extraction and distillation column 2, and a side stream (1%) is sent to the extractor 6.

At measure 2. Pyrolysis gasoline produced in the production of ethylene is subjected to hydrogenation. Then a benzene fraction with m.p. batch is separated from it by distillation. 70-82 ° C, containing 80% benzene. This benzene fraction is subjected to secondary hydrogenation, in which all the sulfur compounds are removed and almost all olefins are converted into saturated compounds. During this hydrogenation, high-boiling hydroxy aromatic and partially hydrogenated condensed ring systems are formed with boiling points between 150-250 ° C in an amount of 0.2% relative to the benzene fraction.

Benzene fraction after

Hydrogenation has the following composition (%)

Benzene 80.0

Non-aromatic hydrocarbons

And lil aromatic

hydrocarbons0,2

The raw materials are introduced through a pipeline / in an amount of 1000 kg / hour and a temperature of 80 ° C to the 30th plate of the extraction and distillation column .2 with 60 practical plates. The pipeline 3 in the column 2 serves 2672 kg of selective solvent at a temperature of 90 ° C, which consists of 92.6% of dimethylformamide (DMF) and 7.4% of alkyl aromatic hydrocarbons. Into the evaporator of the extraction and distillation column 2, 300,000 kcal of heat are added. Collecting 2 columns in the head of the column are withdrawn through line 4 and condense. One part of this condensate in the amount of 238 kg, consisting of 16.8% benzene and 83.2% non-aromatic hydrocarbons, is withdrawn from the column via line 5. The remaining condensed vapors are fed as return through line 7 to column 2.

 3432 kg of solvent and aromatic hydrocarbons are removed from distillation column 2 by duct 8.

A portion of the flow (27 kg / h) of the solvent flowing through conduit 3 to the distillation column 2 is fed through conduit 13 to one of the middle stages of the extractor 6. The extractor is a column with 12 steps. Into the lower part of the extractor 6 a head product is fed from the irregular column 2, to the upper part of the extractor 6, but the pipeline 14 is fed 35 kg of water per hour. In the extractor 6, 7.4% of alklaromatic hydrocarbons are extracted from the partial flow of solvent supplied through the pipeline 13. This solution is withdrawn from the top stage of the extractor. In this way, an extract of 6 92 kg of a hydrocarbon mixture of the composition (in%) is taken:

Benzene 16,7

Alkylaromatic

hydrocarbons0,8

ieomatic hydrocarbons82,5

From the bottom of the counter-current extractor 6, a mixture of ns 42% DMF and 58% water is taken through a pipeline of 15–60 kg / h. This mixture is displaced with the product of distillation distillation supplied to the pipe 8, rotode 8, and 1 to T1 pipe hell 9 is fed to the sanitary column 10 on the 15th plate. The centrifugal column 10 is represented by a distillation column with 40 practical plates and operates under a pressure of 0.4 atm. The column evaporator 10 is supplied with 200000 kca, 1 heat.

The vapors collected in the upper part of the separator column 10 are led through conduit 16, are condensed and put into phase separator 17. In it, the aqueous phase is separated, which through conduit 14 is drawn into extractor 6. The upper phase is pure benzene, from which 760 kg / h is taken by pipeline 19. The remainder of pure benzene is fed as a return through a trubon.a, from 18 to a separator column / (9. A mixture of 82.6% of DMF and 7.4% of alklaromatic hydrocarbons in an amount of 2,700 kg is taken from the bottom parts of coloins 10 by pipeline 11. The main part ozvraschayut but do truboprovo 3 to column 2, nobochiy flux (1%) is fed into the extractor 13 through line 6.

Subject and 3 about ip ete and n

Claims (2)

1. The method of separation of aromatic hydrocarbons nz mixtures of them with non-aromatic hydrocarbons by extractive irregularly and in the presence of a selective solvent to obtain a raffinate phase, withdrawn from the top of the extractive baffle column, and an extract phase withdrawn from the bottom of the column, followed by separation of aromatic hydrocarbons from the extract phase distillation, characterized in that, in order to remove highly sensitive aromatic compounds contaminating the solvent and / or completely removing (solvent of raffinate phase containing nonaromatic hydrocarbons raffinate phase fed into the bottom of additionally installed liquid extraction column, on top of which water is supplied, and a middle portion IB - selective solvent is extracted from the supplied stream to an extractive distillation step of the solvent. 2. A method according to claim 1, characterized in that m-methylproprrolide or dimethylformamide is used as a selective solvent. /five Tj J V 20 / " ff / J / ./ ten