RU2069211C1 - Method of synthesis of 1,2-difluorotrichloroethane - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: method involves treatment of dispersed trichloroethylene with evaporated uranium hexafluoride that is diluted with inert gas at reagent ratio near to stoichiometric one. Condensed 1,2-difluorotrichloroethane or treatment products were added to reaction zone at amount 0.3-2.5 mole 1,2-difluorotrichloroethane per 1 mole uranium hexafluoride simultaneously with parental reagents. Method ensures to increase the yield of the end product up to 96.3% (by organic raw) and enhance quality without decrease content of trichloroethylene and other impurities. Method is used for freons synthesis exhibiting low ozone-destructive capability. EFFECT: improved method of synthesis. 1 tbl

Description

 The present invention relates to methods for producing chladones and may find application for the preparation of 1,2-difluorotrichloroethane (chladone-122), which relates to fluorochlorocarbons with low ozone-depleting ability.

 The problem of replacing freons that deplete the ozone layer of the Earth with freons with low ozone-depleting ability is becoming very urgent.

 One of these chladones of practical interest is 1,2-difluorotrichloroethane.

 A known method of producing uranium tetrafluoride and 1,2-difluorotrichloroethane by fluorination of trichlorethylene with uranium hexafluoride (US patent N 3382049, CL 23 353, 1968).

 The method was intended to produce uranium tetrafluoride and did not aim to obtain an organic product with high quality and yield.

 The closest in technical essence and the achieved result to the proposed one is the known method for producing 1,2-difluorotrichloroethane by treating dispersed trichloroethane at elevated temperature with evaporated uranium hexafluoride diluted with an inert gas (nitrogen, argon, etc.), with a reagent ratio close to stoichiometric (see RF patent N 2030380 on "A method for producing fluorine-containing compounds of the ethane series").

 The disadvantage of this method is the low quality and low yield of 1,2-difluorotrichloroethane: pilot tests of the method showed that the product is contaminated with impurities of organofluorine compounds, including an admixture of trifluorochloroethane. The specified impurity has a boiling point close to the boiling point of 1,2-difluorotrichloroethane and cannot be separated with sufficient completeness during rectification.

 The reason for the low quality of the target product by the known method is unacceptably high temperature in the reaction zone, causing several adverse reactions to occur.

 Trichlorethylene react with uranium hexafluoride accompanied by the release of a significant amount of heat.

The known method does not provide the ability to quickly efficiently remove the heat of reactions, as a result of which high temperatures (more than 400 ^o C) can develop at the contact points of the reacting substances.

 The proposed method eliminates the disadvantage of this method. It is based on the fact that in the known method for producing 1,2-difluorotrichloroethylene by treating dispersed trichlorethylene with evaporated uranium hexafluoride diluted with an inert gas, when the reagent ratio is close to stoichiometric, condensed recirculated 1,2-difluorotrichloroethane is simultaneously introduced into the reaction zone or processing products in an amount of 0.3 to 2.5 gram moles per gram mole of uranium hexafluoride.

 Example 1

 Evaporated uranium hexafluoride diluted with an inert gas to a concentration of 50 vol. and a mixture of liquid trichlorethylene and 1,2-difluorotrichloroethylene. The molar ratio of uranium hexafluoride: trichlorethylene: 1,2-difluorotrichloroethane is maintained at 1: 1: 2.

 The resulting uranium tetrafluoride is poured into the lower part of the reactor and accumulated there, and the organic reaction products are continuously withdrawn from the reactor, condensed and analyzed.

Analysis results, wt%
1,2-Difluorotrichloroethane 94.8
Freon-121 0.7
Freon-123 0.3
Fluorotrichloroethylene (C ₂ FCl ₃ ) 0.02
Freon-114 0.9
Freon-113 1.0
Trichlorethylene 1.6
Other impurities 0.7
The mass yield of HFC-122, calculated as the ratio of the percentage of HFC 122 to the sum of the percentages of organic products (i.e. minus unreacted trichlorethylene) is 96.3%
Example 2

 A series of experiments is carried out similar to Example 1, in which the amount of freon 122 supplied to the reaction zone is changed. In one of the experiments (op. No. 6), condensed organic products obtained in Example 1 were fed into the reaction zone.

 The results of all experiments are tabulated.

 The presented data show that the proposed method allows to obtain 1,2-difluorotrichloroethane with a minimum impurity content and high yield.

 A positive effect is ensured by feeding 0.3 to 2.5 moles of condensed 1,2-difluorotrichloroethane per mole of uranium hexafluoride into the reaction zone.

 When the consumption of 1,2-difluorotrichloroethane per 1 mol of uranium hexafluoride is less than 0.3 mol, the positive effect is noticeably reduced, and the consumption of more than 2.5 mmol per 1 mol of uranium hexafluoride does not further improve the quality and yield of 1,2-difluorotrichloroethane.

Claims (1)

 A method of producing 1,2-difluorotrichloroethane by treating dispersed trichlorethylene with evaporated uranium hexafluoride diluted with an inert gas, with a reagent ratio close to stoichiometric, characterized in that condensed 1,2-difluorotrichloroethane or treatment products are introduced into the reaction zone simultaneously with the starting reagents in an amount 0.3 2.5 moles of 1,2-difluorotrichloroethane per 1 mol of uranium hexafluoride.

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