RU2599132C1 - Method of separating mixture of solvents methanol-tetrahydrofuran-acetonitrile-water-pyridine - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemical industry. Method involves separation of a five-component mixture, which is carried out in circuits, including one or two three-column complexes of extractive distillation. Separating agents used are sulpholane and dimethylsulphoxide. In first version sulpholane is fed into first column of separation circuit and into first column of three-column complex, and dimethyl sulphoxide is fed into first column of two-column complex for processing mixture of methanol-tetrahydrofuran as obtained distillate. In second version sulpholane is fed into first column of first three-column complex, and dimethyl sulphoxide is fed into first column of second three-column complex for processing mixture of methanol-tetrahydrofuran-water as obtained distillate. Composition of initial mixture is equimolar, amount of separating agent to initial mixture ranges from 0.2:1 to 2.5:1, reflux varies within range of 0.1-3.5.

EFFECT: invention provides for extraction of all components of said five-component industrial mixture of solvents and reduced power consumption.

1 cl, 2 dwg, 2 tbl, 2 ex

Description

The invention relates to the field of basic organic synthesis, and in particular to a method for the separation of a five-component azeotropic mixture of methanol - tetrahydrofuran - acetonitrile - water - pyridine, obtained in the pharmaceutical industry.

It is known from the prior art that a mixture of methanol - tetrahydrofuran (THF) - acetonitrile (ACN) - water - pyridine can be separated by periodic extractive distillation (PER) [Hegely L. Improvement of batch distillation separation of azeotropic mixtures. PhD thesis at Institut National Politechnique de Toulouse, 2013, 197 pages]. In this work, the process is called heteroazeotropic-extractive distillation, although in this case we are talking about autoextractive distillation.

The closest analogue of the present invention, selected by the authors for the prototype, is a method for separating a mixture of methanol-tetrahydrofuran (THF) - acetonitrile (ACN) - water - pyridine by periodic extractive distillation (PER) [Lang P. et al. Solvent recovery from a multicomponent mixture by batch extractive distillation and hybrid process / Distillation Absorption, 2010, pages 295-300], according to which a separating agent (PA) is supplied to the top of the column, and the separated mixture is preloaded into the cube of the installation. As a separating agent according to the analysis of the relative volatility of the components in the specified method, it is proposed to use water or pyridine. The achieved result is the isolation of THF of a given quality.

The disadvantage of PER is the lack of regeneration of other organic solvents (methanol, ACN, pyridine). Under conditions of toughening environmental requirements, the separation process should not be limited only to the allocation of components that are in the multicomponent mixture in the maximum amount.

The technical result of the claimed invention is to reduce energy consumption and the allocation of all components of a mixture of methanol - tetrahydrofuran - acetonitrile - water - pyridine in its pure form.

The technical result is achieved by the method of separation of the specified five-component azeotropic mixture by continuous extractive distillation (ER) in schemes including one or two three-column extractive distillation complexes using sulfolane and dimethyl sulfoxide as separating agents, while the separating agent sulfolane is fed to the first column of the separation scheme and to the first a column of a three-column complex or in a first column of a first three-column complex, and a dimethyl sulfoxide separating agent is supplied either to the first column of the two-column complex for processing the methanol-tetrahydrofuran mixture as the obtained distillate, or to the first column of the second three-column complex for processing the methanol-tetrahydrofuran-water mixture as the obtained distillate.

The composition of the initial mixture is equimolar, the amount of RA to the initial mixture is from 0.2: 1 to 2.5: 1 in various schemes, phlegm varies in the range of 0.1-3.5, various fractions are selected in the distillate of the first ER column. The pressure in all columns is atmospheric. Separation schemes are proposed with the separation of all organic solvents in a complex of six columns, from two to three of which are extractive. By varying the selection of distillate in the first ER column, a reduction in capital and energy costs and an improvement in the quality of the products obtained are achieved.

The present invention is illustrated by examples 1 and 2, which differ in fractions taken in the distillate of the first ER column.

The study was conducted through a computational experiment in the Aspen Plus software package.

Example 1. In FIG. Figure 1 shows the separation scheme of a mixture of methanol - THF - ACN - water - pyridine. The first separation stage is an ER (I) column (RA - sulfolane), a methanol - THF mixture is obtained in the distillate. The bottoms product of column I is separated in column II of the ER (RA - sulfolane), water is isolated in the distillate, and in the bottom - a mixture of ACN - pyridine - sulfolane. A mixture of THF - methanol was separated in a two-column complex of ER with DMSO (columns V, VI), a mixture of ACN - pyridine - sulfolane was separated by ordinary distillation in columns III (distillation product ACN) and IV - distillation product - pyridine. The data obtained are shown in table 1.

Example 2

In FIG. Figure 2 shows the separation scheme of a mixture of methanol - THF - ACN-water - pyridine. The mixture was separated in a scheme consisting of two three-column ER complexes. The first separation stage includes an ER (I) column (RA - sulfolane), in the distillate of which a methanol-THF-water mixture is isolated, which is further separated in a three-column complex with DMSO as RA with the release of THF in an ER (IV) column, in columns V and VI - methanol and water, respectively. From the bottoms product of column I containing a mixture of ACN - pyridine - sulfolane, successive distillations of ACN (column II) and pyridine (column III) were sequentially isolated. The data obtained are shown in table 2.

Thus, for separation of a mixture of methanol - THF - ACN - water - pyridine, two basic separation schemes have been proposed, consisting of six continuous distillation columns. In the considered examples, the first stage is the separation of a five-component mixture of ER with sulfolane, and methanol - THF or methanol - THF - water fractions, respectively, are separated in the distillate.

The least energy intensive is the split circuit shown in FIG. 2 (Example 2), representing a combination of two three-column ER complexes (RA - sulfolane, DMSO). The static parameters of the operation of the columns are determined, which ensure the isolation of all products with a quality of at least 99.7 mol.%.

Claims (1)

The method of separation of a five-component azeotropic mixture of methanol - tetrahydrofuran - acetonitrile - water - pyridine by extractive distillation, characterized in that the separation is carried out in schemes comprising one or two three-column extractive distillation complexes using sulfolane and dimethyl sulfoxide as separating agents, while the separating agent sulfolane is fed to the first column of the separation scheme and to the first column of the three-column complex or to the first column of the first three-column complex, and the separating ag nt dimethyl sulfoxide is fed either to the first column of the two-column complex for processing the methanol-tetrahydrofuran mixture as the obtained distillate, or to the first column of the second three-column complex for processing the methanol-tetrahydrofuran-water mixture as the obtained distillate, while the composition of the initial mixture is equimolar, the amount of resolving agent to the initial mixture is from 0.2: 1 to 2.5: 1, phlegm varies in the range of 0.1-3.5.

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