RU2714134C1 - Method of purifying perfluoroethyl isospropyl ketone - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: present invention relates to a method of purifying "crude" perfluoroethyl isopropyl ketone containing impurities of a dimer of hexafluoropropene, involving treatment of its "raw" with gaseous halogen with subsequent rectification of the obtained mixture. Raw is treated with gaseous chlorine in the presence of a catalyst: iron (III) chloride, supported on activated carbon, or copper (II) chloride, deposited on activated carbon.EFFECT: disclosed method enables to obtain perfluoroethylisopropyl ketone with purity of 99_95 %.1 cl, 9 ex

Description

This invention relates to organic chemistry, in particular to the preparation and purification of perfluorinated ketones including perftoretilizopropilketona (CF ₃ CF ₂ COCF (CF _{3) 2),} toxic hexenes perfluorinated - by-products formed during the synthesis of the ketone.

Perfluoroethylisopropyl ketone (hereinafter PFEIPK) is a new generation fire extinguishing agent with zero ozone depletion potential, low (120 hours) decomposition time in the atmosphere, and quick fire extinguishing. In addition, PFEIPK is an effective solvent, a medium for conducting chemical and biochemical processes, for obtaining highly pure semiconductor materials, including for growing crystals for microcircuits, it can also be used in microelectronics. However, the technological impurities contained in the hexafluoropropene dimers (hereinafter DHFP) contained in it complicate or preclude its use in chemical and biological processes, electronics, and also when used to extinguish fires in enclosed spaces. This is primarily due to the toxicity of DHFP.

The final reaction mixture formed during the synthesis of PFEIPK (“raw” PFEIPK) always contains an admixture of DHPP, its content is up to 18%, depending on the method and synthesis conditions. In most areas of application of PFEIPK, this amount is unacceptably large.

Due to the proximity of the boiling points of PFEIPK and DHFP (49.2 ° C and 48.5-51.5 ° C, respectively), the possibility of purification by rectification, including azeotropic, is excluded; purification by low-temperature crystallization or sorption is not possible. Therefore, a special place in the processes of purification of perfluorinated compounds is the chemical conversion of impurities with their subsequent separation. However, DHFP is relatively inert; its reactivity is lower than that of PFEIPK.

Various methods are known for purifying perforated liquids from dimers and trimers of hexafluoropropene.

A known method of purification from impurities DHFP [US Patent 6478979, IPC A62D 1/00, publ. 12.11.2002] by its oxidation with alkali metal permanganates in acetone or acetic acid at temperatures above room temperature and atmospheric pressure.

The disadvantages of this method are: the complex hardware design of the process, the high cost of potassium permanganate, the lack of a raw material base of this reagent in the Russian Federation, the formation of a large amount of environmentally unsafe waste requiring special, expensive disposal technology.

A known method of purification of PFEIPC from DHFP and trimer hexafluoropropene [US Patent 6774270, IPC C07C 41/00, publ. 08/10/2004] treating them with tertiary amines with preliminary isomerization of hexafluoropropene dimers, and subsequent separation of the resulting compounds by distillation or decantation.

The disadvantages of this method is the low adaptability, a large amount of toxic waste, the disposal of which is costly and time-consuming. To implement this method requires expensive, toxic and scarce reagents.

The closest technical solution is the method [RF Patent 2639148, IPC С07С 45/82, publ. 08/22/2017], which consists in treating the “raw” PFEIPK with elemental fluorine to form non-toxic perfluorinated hexanes, followed by rectification.

Thus, the hexafluoropropene dimer is removed from the “raw” PFEIPC, the removal being carried out by treatment with fluorine gas, then it is washed with an aqueous solution of sodium bicarbonate, dried with zeolite and the resulting mixture is subjected to rectification.

The disadvantage of this method is the need to use gaseous fluorine. Gaseous fluorine is expensive, inaccessible, its transportation is difficult. The high reactivity of fluorine imposes stringent requirements on the materials of the reactors (they are made from hard-to-reach and expensive nickel alloys) and on the hardware design of the processes. All these factors significantly complicate and increase the cost of the cleaning process, greatly limiting the possibility of using this method.

The objective of the invention is the creation of a more technologically advanced, safe and cheap method of purification of PFEIPK from impurities DHFP to obtain the target product of the required purity of 99.95%.

This problem is achieved by the fact that the "raw" PFEIPK is treated with gaseous chlorine. Unlike fluorine, chlorine is widely used in the national economy. Its use does not require special hard-to-reach and expensive materials for storage, transportation and use. All this simplifies and reduces the cost of cleaning technology PFEIPK.

The technical result of the invention is to simplify the technology, reduce the cost of obtaining PFEIPC purity of 99.95% and increase the safety of technology.

The essence of the invention lies in the fact that the purification of the “raw” PFEIPC containing impurities of DHFP is carried out, including their removal by treatment of the raw with gaseous halogen, followed by rectification of the resulting mixture. According to the present invention, the "raw" is treated with gaseous chlorine in the presence of catalysts. As a catalyst, iron (III) chloride supported on activated carbon or copper (II) chloride supported on activated carbon is used.

When raw PFEIPC is treated with chlorine, the impurities of DHFP (dihexafluoropropylene) contained in it add chlorine in multiple bonds, turning into saturated compounds, for example:

It is proposed to use iron (III) chlorides (FeCl ₃ ) or copper (II) (CuCl ₂ ) supported on activated carbon as catalysts. A feature of the proposed catalysts is their high selectivity. When using them, PFEIPC practically does not react with chlorine, while in the absence or use of other catalysts, destructive chlorination of PFEIPK reaches 20%, with a noticeable residual content of DHFP (comparative Examples No. 1 and No. 2). It is allowed to use a mixture of these catalysts in any ratio, but this is impractical due to the complexity of the process.

The isomers formed during chlorination - dichlorododecafluorohexane (hereinafter Dichloro DFG) are low-toxic and can be easily separated by distillation to isolate the desired product, since their boiling point is 116 ° С, while the boiling point of PFEIPK is 49 ° С.

The residual content of DHFP after rectification does not exceed 0.05% and does not affect the toxicological and other consumer properties of PFEIPK.

The method can be carried out in batch and continuous modes.

1. Periodic mode

Activated carbon is coated with a FeCl ₃ or CuCl ₂ catalyst in an amount of 20.00%. The coal is dried in vacuum at 150 ° C and a residual pressure of 130 Pa with a periodic supply of nitrogen to atmospheric pressure for 4-6 hours. Then the autoclave is cooled to 20 ° C, the “raw” PFEIPK containing impurities is loaded into it and the autoclave is filled with chlorine to an excess pressure of 0.1 MPa, after which the autoclave is heated to 160-200 ° C. The reaction is carried out for 6-8 hours. The reaction products are washed with an aqueous solution of sodium bicarbonate from acidic impurities, dried with zeolite and subjected to rectification.

2. Continuous mode

The prepared catalyst is placed in a reactor into which a “raw” PFEIPC and chlorine gas are fed. Further, the reaction products pass through a column filled with a chemical lime scavenger (hereinafter CPI) and condense. The resulting condensate is subjected to rectification.

Example No. 1 (comparative)

15.0 g of PFEIPK containing 4.80% DHPP and 95.20% PFEIPK are charged into an autoclave with a capacity of 0.12 liters. Chlorine is fed into the autoclave to an overpressure of 0.1 MPa, heated to a temperature of 250 ° C and maintained for 6 hours. After 6 hours, the contents of the autoclave are passed through a CPI column and the contents are condensed. The reaction products have the composition: unidentified low boiling compounds - 19.40%, DHFP - 2.95%, dichloro-DPH - 1.85%, PFEIPK - 75.80%. Obtaining PFEIPK given purity by distillation is not possible.

Example No. 2 (comparative)

Activated carbon in an amount of 10.0 g is loaded into an autoclave with a capacity of 0.12 liters. The coal is dried in vacuum at 150 ° C and a residual pressure of 130 Pa with a periodic supply of nitrogen to atmospheric pressure for 4-5 hours. After drying, the autoclave is cooled to 20 ° C, loaded into it 15.0 g PFEIPK containing 4.80% DHPP and 95.20% PFEIPK. Chlorine is fed into the autoclave to an overpressure of 0.1 MPa, then heated to 250 ° C and held for 6 hours. The reaction products are passed through a column of CPI and condense. The composition of the reaction products: low-boiling products - 7.80%, DHFP - 0.80%, dichloro-DFG - 6.00%, PFEIPK - 85.40%. Obtaining PFEIPK given purity by distillation is not possible.

Example No. 3

In an autoclave with a capacity of 0.12 liters, load 5.0 g of FeCl ₃ catalyst deposited on activated carbon in an amount of 20.00% in May. The catalyst is dried in vacuum at 150 ° C and a residual pressure of 130 Pa with a periodic supply of nitrogen to atmospheric pressure for 5-6 hours. After drying, the autoclave is cooled to 20 ° C, 15.0 g of PFEIPK containing 4.80% are loaded into it. DHFP and 95.20% PFEIPK. Chlorine is fed into the autoclave to an overpressure of 0.1 MPa, then heated to 160 ° C and held for 6 hours. After 6 hours, the reaction products are passed through a column of CPI and condense. The reaction products have the composition: low-boiling products - 0.08%, DHFP - 0.02%, Dichloro-DFG - 5.95%, PFEIPK - 93.95%. The resulting mixture is subjected to distillation to a content of PFEIPK 99.95%.

Example No. 4

The experiment is carried out in the conditions of Example No. 3, using a catalyst of 5.0 g CuCl ₂ - 20.00% on activated carbon. The experiment is carried out at 175 ° C. The reaction products have the composition: low-boiling products - 0.08%, DHFP - 0.04%, dichloro-DHFP - 5.95%, PFEIPK - 93.93%. The resulting mixture is subjected to distillation to a content of PFEIPK 99.95%.

Example No. 5

To the evaporator is a tube with a diameter of 18.0 mm and a length of 230.0 mm, filled with a catalyst - FeCl ₃ on activated carbon (20%), heated to 300 ° С, raw PFEIPK containing 4.80% DHFP and 95.20% is fed PFEIPK at a rate of 0.8 g / min. At the same time, chlorine gas is supplied to the evaporator at a rate of 10.0 ml / min. From the evaporator, a gaseous mixture of raw PFEIPK and chlorine enters the reactor tube, with a diameter of 18.0 mm and a length of 550.0 mm, filled with a catalyst — FeCl ₃ supported on activated carbon (20%) and heated to 300 ° C. The reaction products pass through a tube 400.0 mm long and 18.0 mm in diameter, filled with KhPI and condense. After 20 minutes, the flow of components is stopped. Content (15.5 g) was analyzed. Composition: low-boiling products - 0.10%, DHFP - 0.03%, dichloro-DFG - 5.96%, PFEIPK - 94.0%. The resulting mixture is subjected to distillation to a content of PFEIPK 99.95%.

Example No. 6

The experiment is carried out under the conditions of Example No. 5, but instead of a FeCl ₃ catalyst, a CuCl ₂ catalyst supported on activated carbon is used. The experiment is conducted for 20 minutes. The reaction products (15.6 g) has the following composition: low-boiling products - 0.14%, DHFP - 0.04%, dichloro-DPH - 5.56%, PFEIPK - 94.26%. The resulting mixture is subjected to rectification to a PFEIPK content of 99.95 %

Example No. 7

The experiment is conducted under the conditions of Example No. 6, however, the chlorine feed rate is reduced to 3.5 ml / minute. The contents of 15.8 g are analyzed. Composition: low-boiling products - 0.14%, DHFP - 0.04%, dichloro-DFG - 5.63%, PFEIPK - 94.19%. The resulting mixture is subjected to distillation to a content of PFEIPK 99.95%.

Example No. 8

The experiment is carried out in the conditions of Example No. 6, but the duration of the experiment is 240 minutes. The reaction products (190.6 g) have the composition: low-boiling products - 0.13%, DHFP - 0.04%, dichloro-DPH - 5.70%, PFEIPK - 94.13%. The resulting mixture is subjected to distillation to the content of PFEIPK 99.95%

Example No. 9

In the evaporator - a tube with a diameter of 100.0 mm and a length of 1200.0 mm, filled with a catalyst - CuCl ₂ on activated carbon (prepared according to Example No. 3) heated to a temperature of 300 ° C, PFEIPK raw is fed from a metering unit at a speed of 3.4 kg / hour. (4.80% - DHFP, 95.20% - PFEIPK). Chlorine is supplied there at a rate of 18 l / h. A gaseous mixture of chlorine and “raw” PFEIPK enters the reactor — a pipe with a diameter of 120 mm and a length of 1800 mm, filled with a catalyst — CuCl ₂ deposited on activated carbon. The reaction products pass through a direct refrigerator cooled to a temperature of plus 10 ° C and enter a collector cooled to minus 30 ° C. The reaction products, condensed after 20 hours of operation, are heated to plus 20 ° C and analyzed. Composition: low-boiling products - 0.12%, DHFP - 0.04%, dichloro-DPP - 5.50%, PFEIPK - 94.34%. Next, the resulting mixture is fed into a cube distillation column. The volume of the cube is 60 l, the diameter of the column is 100 mm, the height is 7200 mm. The column is filled with a regular nozzle. The rectified product is filtered through a column of CaA zeolite and has the composition: low-boiling products - 0.01%, DHFP - 0.04%, PFEIPK - 99.95%.

Thus, it can be seen from the above examples that the problem has been solved and the technical result has been achieved: a more technologically advanced, safe and cheaper way to obtain PFEIPK of a given purity of 99.95% is developed.

Claims (1)

The method of purification of the “raw” perfluoroethyl isopropyl ketone containing impurities of the hexafluoropropene dimer, comprising treating its “raw” with gaseous halogen followed by distillation of the resulting mixture, characterized in that the “raw” is treated with gaseous chlorine in the presence of a catalyst: iron (III) chloride supported on activated carbon or copper (II) chloride supported on activated carbon.