SU1574588A1 - Method of separating mixture of dimethylformamide and cyclohexanone - Google Patents

Abstract

The invention relates to amides of carboxylic acids, in particular to the separation of a mixture of dimethylformamide and cyclohexanone. In order to increase the purity of products and the degree of their extraction and to improve the economic indicators of production, rectification is carried out in a two-column system at pressures of 15 and 760 mm Hg. and reflux numbers 2.8 - 3.5 and 8.0 - 15.0, respectively. The method provides a simplification of the process (by replacing special types of distillation in the presence of separating agents with conventional distillation) and a high recovery rate of the target products with a high degree of purity. 1 silt, 1 tab.

Description

This invention relates to an improved process for the separation of a mixture of dimethylformamide (DMF) and cyclohexanone (PON).

The purpose of the invention — an increase in the purity of the products, the degree of their extraction, and an improvement in the economic indices of production — is achieved by performing a rectification in a two-column system at pressures of 15 and 760 mm Hg. and reflux numbers 2.8-3.5 and 8.0-15.0, respectively.

The drawing shows the scheme of implementation of the method.

The method is carried out as follows.

The initial mixture through line 1 is fed to the 12th from the cube theoretical plate (s) of the DMF regeneration column with an efficiency of 20 mt, operating at a given residual pressure of 15 mm Hg. Top temperature 46 ° С

the bottom of the liquid 53 ° C, reflux ratio of 2.8-3.5. From line 2, recovered DMF is discharged from the cube of the column, and a mixture of DMF-POC of azeotropic composition fed as feed to 15 tons of volume is discharged from distillate via line 3. from a cube to a PSC regeneration column with an efficiency of 40 t. The temperature of the top of the column is 149,), the bottom is 156.6 ° C, the set pressure is 760 mmHg. The reflux number varies in the range of 8.0-15.0. From the bottom of the column, via line 4, the recovered PSC is removed from the distillate. In the distillate, a mixture of DMF-PSC of azeotropic composition is released, which is recycled via line 5 to the DMF recovery column.

When changing the composition of the initial mixture of DMF-PSC, the sequence of columns in the circuit may vary. By reducing the pressure from 760 to 15 mm Hg. . there is a displacement of aeroheel i

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ropa by 20 mol% in the direction of enrichment of PSC. A further decrease in pressure, as studies have shown, is impractical, since then the composition of the azeotrope shifts insignificantly. In addition, a further decrease in pressure leads to an unnecessarily high metal consumption of equipment.

The following requirements were established for the quality of the target products (condition): the DMF content in the cube of the first column is not less than 99.6 mass%; the content of PSC in the cube of the second column is not less than 99.6,

The following physico-chemical characteristics were used as criteria for assessing the quality of the target products; boiling point, refractive index, content of the main substance according to chromatographic analysis (presented in the table)

A decrease in the reflux ratio (f.p.) to 2.5 results in a decrease in the DMF content in the bottom product of column 1 to 99.15 wt.%, Which is not consistent with the condition. In column II, the decrease in ph.ch. to 5 reduces the content of PSC in the bottom product to 97.3 wt.% which also does not meet the condition.

When changing the composition of the initial mixture of DMF-PSC, the sequence of columns in the scheme may change while maintaining all the parameters of their mode of operation.

The invention is illustrated by the following examples.

Example 1. 100 kg / h of the initial mixture (azeotropic composition (wt.%): DMF 48.66; PSC 51.34) is mixed with 76.07 kg / h of the recycle stream (composition wt.%: DMF 48.44, PSC 51.56) and served in the regeneration column DMF with a reflux number of 2.8 and a pressure of 15 mm Hg The bottom product in the amount of 48.7 kg / h (composition, wt.%: DMF 99.69; PSC 0.31) is taken to the accumulator. Distillate in the amount of 127.37 kg / h (composition, wt.%: DMF 29.02; PSC 70.98) is fed to the regeneration column of the PSC with a reflux ratio of 8.0 and pressure of 760 mm Hg. Bottom product in the amount of 51.3 kg / h (composition, wt.%): DMF 0.21; PSC 99.79 enters the receiver of the finished product. The distillate is recycled to the DMF recovery column for the formation of gross feed.

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EXAMPLE 2 Differs from Example 1 in the values of reflux numbers.

In the field of regeneration of DMF with a reflux number of 3.0 and a pressure of 15 mm Hg. Art. 100 kg / h of the initial mixture (composition, wt.%): DMF 48.66, PSC 51.34) and 71.25 kg / h of recycle stream (composition, wt.%): DMF 49.66; PSC 50.34). The withdrawal of the bottom product — DMF of 99.82% purity — is 48.6 kg / h. Distillate (composition, wt.%): DMF 28.97, PSC of 71.03) in the amount of 122.65 kg / h is fed to the reclamation column of the PSC with a reflux ratio of 10.0 and a pressure of 760 mm Hg. In the bottom product, 51.4 kg of the target PSC with a purity of 99.71% is selected. Distillate is recycled to the first column.

Example Different from the example 2 values of reflux numbers.

In the regeneration column DMF with a reflux number of 3.5 and a pressure of 15 mm Hg. 100 kg / h of the initial mixture (composition, (wt.%}: DMF 48.66; PSC 51.34) and 73.92 kg / h of the recycle stream (composition, (wt.%): DMF 49, 01; PSC 50.99). The bottom product selection - DMF with a purity of 99.92 - is 48.68 kg / h. Distillate (composition, (wt.%): DMF 28.94; PSC 71.06) in an amount of 125 , 24 kg / h is supplied to the PSC regeneration column at a reflux number of 15.0 and a pressure of 760 mm Hg. 51.32 kg / h of the desired PSC with a purity of 99.97% is taken from the bottom product.

Example 4. Different from Example 1 in composition of the starting mixture.

100 kg / h of a mixture (composition, (wt.%,) DMF 60; CO H 40) and 59.19 kg / h of recycling (composition, (wt.%): DMF 48.44; PSC 51 , 56). The selection of the bottom product DMF with a purity of 99.69% is 60.1 kg / h. Distillate selection is 99.09 kg / h. In the bottom product of the PSC regeneration column, 39.9 kg / h of the desired product are taken.

Example 5: It differs from Example 1 in the composition of the initial mixture and the sequence of columns in the circuit.

100 kg / h of the initial mixture (composition, (wt.%): DMF 25; PSC 75) is mixed with 64.49 kg / h of the recycle stream (comp. 5, (wt.%): DMF 27.72; PSC 72 , 28) and served in the regeneration column of PSC with a reflux ratio of 8.0 and a pressure of 760 mm Hg. VAT product in box 5

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The amount of 75.23 kg / h (composition, (wt0% ;: DMF 0.39; PSC 99.61) is taken to the receiver of the finished product. Distillate (composition, (wt.%): DMF 47.7; PSC 52 , 3) in the amount of 89.25 kg / h is fed to the DMF regeneration column with a reflux number of 2.8 and a pressure of 15 mm Hg. 24.77 kg / h of DMF with a purity of 99.72%, distillate are discharged from the bottom of the column. The clerplaces into the PSC regeneration column ..

The proposed method has a number of advantages in comparison with the prototype, namely:

replacing the azeotropic distillation in the presence of water eliminates the hydrolysis of DMF and provides a high recovery factor with a high degree of purity;

replacing the incineration of the PSC with its regeneration allows, on the one hand, to prevent pollution of the atmosphere, gas emissions and thereby improve the environmental performance of production-. And, on the other hand, return the expensive product to the production cycle and thus improve economic performance;

simplification of the process by replacing special types of distillation in the presence of separating agents by ordinary distillation.

Formula i-z gain

The method for separating a mixture of dimethylformamide and cyclohexanone from their

5 mixtures by rectification, characterized in that, in order to increase the purity of the products and the degree of their extraction and improve the economic performance of production,

rectification is carried out in a two-column system at pressures of 15 and 760 mm Hg. and reflux numbers 2.8-3.5 and 8-15, respectively.

Claims (1)

SUMMARY OF THE INVENTION A method for separating a mixture of dimethylformamide and cyclohexanone from a mixture thereof by distillation, which consists in the fact that, in order to increase the purity of products and the degree of their extraction and improve economic performance, 20 distillation is carried out in a two-column system at pressures of 15 and 760 mmHg. and reflux numbers 2.8-3.5 and 8-15, respectively. Substance Temperament The content of the main boiling round, ° С refraction of the substance according to chromatographic analysis, wt% DMF 152.9 PSC 155.5 1.4267 1.4505 ¹⁰ 99.8-99.9 99.8-99.9