SU600129A1 - Method of regenerating extractive reagents - Google Patents

Description

one

This invention relates to the field of extractant recovery used to separate hydrocarbons 64 using extractive distillation, extraction or absorption.

Limes a method of purification of furfural from dimers by distilling a mixture of furfural and a polymer, followed by water washing of the distillate from furfural 1.

However, this method requires several chemical procedures for purification and is unprofitable for extractants that form azeotropes with butadiene, having a high concentration of extraheite in the azeotrope.

The known method of purification of extractants used in the separation of C4 hydrocarbons by desorption and subsequent distillation in the presence of water 2 with the output of a vapor mixture of water with hydrocarbons and carbonyl compounds as a distillate, the concentration of water in which is 30-95 wt. % with subsequent condensation and exfoliation of the mixture, the removal of the hydrocarbon layer from the system and the partial return of the aqueous layer to rectification.

However, in this method, a portion of the liquid extractant is fed to the regeneration pa after desorption, which has a relatively low concentration of diolefin dimers and carbonyl compounds. An increase in the content of these impurities in the extractant is unacceptable, since it reduces its separating ability and leads to contamination of the separation products. The content of these impurities in the extractant is maintained at a level of 1-2% by weight. On contact with water, the extractant hydrolyses and there is a loss of solvent, which is the greater, the more extractant is sent to purification and by distillation at

lack of water. The extractant contains thermopolymerization inhibitors, for example, sodium nitrite and others, as well as resins. The acids formed during the hydrolysis of the solvent interact with the inhibitors to form insoluble salts, which, like the resins, are deposited on the surface of the equipment and lead to clogging. In addition, in this method there is a large consumption of polymerization inhibitors.

In order to reduce the loss of extractants used to separate hydrocarbons. the presence of water to separate the impurities of dimers of diolefins and carbonyl compounds.

The impurity content of dimers of diolefins, water, and carbonyl compounds in the vaporous pursuit of the desorption column is 2-3 times higher than in the extractant. This makes it possible to reduce the amount of extractant removed for regeneration by a factor of 2-3 and, as a result, reduce solvent losses and reduce the cost of regenerating the extractant.

In addition, the fresh flow of the extractor did not contain thermopolymerization inhibitors, which eliminates blocking of the distillation column of the extractant in the presence of water and reducing the consumption of thermopolymerization inhibitors.

Example 1 (comparative). In the process of isolating butadiene from the dehydration fraction of n-butnlen, anhydrous dimethylformamide (DMF) was used as an extractant. The amount of butylene-divinyl fraction (BDF) fed to the separation is 40 tonnes per hour. The circulation of DMF is 310 tons per hour. For desorption of absorbed hydrocarbons from saturated DMF, a column with an efficiency of 40 practical plates is used. The rich extractant is fed to the 39th plate (score from below). The column operates at a pressure of top of 1.35 at. The temperature of the top is 78 ° C, the temperature of the cube is 160 ° C. The desorbed DMF, taken from the cube of the desorber, has the following composition, wt.%: DMF98,730

Water0.050

Sodium nitrate 0.001

Sodium formate 0.005

T amy residue0,200

Butadiene Dimers1,000

Acetone0,007

Methyl ethyl ketone 0.004

Methylvinylketone0.003

2% of the extractive distillation circulating in the system. DMF (6200 kg / h). It is supplied for regeneration from “light resins and carbonyl compounds to the rectification column in the presence of water. The column has 45 practical plates and operates at atmospheric pressure. The top temperature is 100 ° C, the cube temperature is 157 ° C. The top product of the column is condensed and exfoliated. The top layer is butadiene dimers, taken for incineration, and the bottom layer is water, with dissolved carbonyl compounds, is partially returned to the column as reflux, and partially removed from the regeneration system. The reflux amount is 2000 kg / h. Dimethylamine, a product of DMF hydrolysis, is determined in the refluxing strippers, the aqueous and dimeric layers, and nitrosodimethylamine, a highly toxic substance, is detected in the aqueous reflux. DMF containing a heavy residue, 0.1% butadiene dimers and 0.2-0.5% water is taken from the bottom of the column.

During the purification of DMF by the described method, the loss of extractant is 0.6 kg / h per 1 ton of commercial butadiene.

Example 2 (comparative). The desorption of hydrocarbons from saturated DMF is carried out under conditions similar to Example 1. The extractant is regenerated for regeneration in the vapor phase from the 15th plate of the desorption column at 120 ° C. The amount of side extraction is 2575 kg / h. Vaporous side sampling, having the following composition, wt.%:

DMFA95,440

Acetylene compounds 0.010

Butadiene0,060

Water0,820

Butadiene dimers2,330

Acetone0,067

Methyl ethyl ketone 0,400

Methylvinylketone0,270

subjected to pre-condensation to distance € 4 from hydrocarbons (butadiene and acetylene compounds). The condensate composition, wt.%:

DMFA95,500

Butadiene0.001

Water0,820

Butadiene dimers2,330

Acetone0,670

Methyl ethyl ketone 0,400

Methylvinylketone0,270

in the amount of 2573.2 kg / h, it was sent to a DMF distillation column from butadiene dimers and carbonyl compounds in the presence of water. The mode of operation of the column is similar to that of the regeneration DMF colol from the "light tar" given in Example 1. The amount of reflux is 830 kg / h. During the purification of DMF by the proposed method, the loss of the extractant is 0.26 kg / h per ton of commercial butadiene.

; EXAMPLE 3. In the process of isolating butadiene from the n-butylenes dehydrogenation fraction, dimethylacetamide (DMAA) containing 5% water is used as an extractant. The amount of BDF supplied to the separation, 40 t / h The circulating DMAA is 400 ton / h. For desorption of absorbed hydrocarbons from saturated DMAA, a column with an efficiency of 40 practical plates is used. Saturated extractant served on the 39th plate. The column is operated at a pressure of 1.1 at. The top temperature is 80 ° C, the bottom temperature is 140 ° C. The extractant is taken out for regeneration in the vapor phase from the 8th plate of the desorption column at 13 ° C. The amount of side selection is 2847 kg / h. Vaporous side selection of the composition, wt.%:

DMAA86,945

Acetylene compounds 0,005

Butadiene0,020

Water8,720

Butadiene dimers2,810

Acetone 0.750

Methyl ethyl ketone 0,450

Methylvinylketone0,300

subjected to preliminary rectification with

the purpose of removing C4 hydrocarbons on a column having 5 practical plates and a reflux ratio of 0.5. The bottom product of the preliminary distillation column, containing not more than 0.001% of € 4 hydrocarbons, in the amount of 2846.3 kg / h is fed to the DMAA distillation column from dimers and carbonyl compounds in the presence of water. Coloina has 45 practical plates and operates at atmospheric pressure. The top temperature is 100 ° C, the cube temperature is 169 ° C. The top product of the column is condensed and exfoliated. The top layer is butadiene dimers, taken for incineration, and the bottom layer is water with dissolved carbonyl compounds, partially returned to the column as reflux, and partly removed from the regeneration system. The reflux amount is 920 kg / h. DMAA containing a heavy residue, 0.1% butadiene dimers and 0.2-0.5% water is taken from the bottom of the column.

Example 4. In the process of isolating butadiene from the dehydrogenation and -buthenes fraction, N-MCtilnirrolidone (MP) containing 5% water is used as the extractant. The amount of BDF supplied to the separation, 40 t / h Pyrculation MP is 360 t / h. To desorb absorbed hydrocarbons from the saturated extractant, a column with an efficiency of 30 practical plates is used. Saturated extractant served on the 29th plate. The column operates at a pressure of 1.1 atm. The top temperature is 80 ° C, the cube temperature is 145 ° C. The extractant is taken out for regeneration in the vapor phase from the 23rd plate at 100 ° C. The amount of side selection is 3547 kg / h.

Vaporous side selection of the composition, wt.%:

MP87,281

Acetylene compounds 0,009

Butadiene0,041

Water9,430

Acetone0,610

Methyl ethyl ketone 0.360

Methylvinylketone0,240

precondensed for

separation from hydrocarbons C. Condensate composition, wt.%:

MP87,319

Butadiene0.001

Water9,440

Butadiene dimers2,030

And cetone 0,610

Methplatylketon0,360

Methyl Vinyl keto 0.240

in the amount of 3543.3 kg / h, it was sent to the MP distillation column from dimers and carbonyl compounds in the presence of water. The column has 45 practical plates and operates at a pressure of 0.3 at. The temperature of the top is 70 ° С, the temperature of the cube is 160 ° С. The top layer is butadiene dimers, taken for incineration, and the bottom layer is water with dissolved carbonyl compounds, partially returned to the column as reflux, and partly removed from the regeneration system. The reflux amount is 1144 kg / h. MP containing the heavy residue, 0.1% bztadiene dimers and 0.2-0.5% water is taken from the bottom of the column.

Formula and 3 about b and e and

A method for regenerating extractants used to separate hydrocarbons is € 4,

including desorption of the extractant followed by separation of impurities of dimers of carbonic compounds and carbonyl compounds from a part of the desorbent extractant by rectification in the presence of water, which is separated from C4 hydrocarbons by rectification or condensation and fed to the stage

rectification in the presence of water. Sources of information taken into account in the examination 1. US Patent No. 3432597, cl. 260-680, published. 1969.

2. For number 2001682/04, cl. From 07C 7/06, 1974, according to which a decision was made to issue an author's certificate.