RU2058283C1 - Method for purification of lower fluorochloroalkanes - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: method is carried out by treatment with chlorine followed by rectification. Mentioned above treatment is carried out in gaseous phase at 100-250 C in the layer of activated coal, presence of fluorine being preferred. Quantity of said fluorine is 0.1-1.0 mol % of chlorine amount. Degree of purification against unsaturated compounds is 80-90 %. EFFECT: increases degree of purification. 2 cl, 1 tbl

Description

 The invention relates to the chemical industry and can be used in the production of fluorochloroalkanes, in particular 1,2-difluorotrichloroethane (HFC 122A). The latter is a promising ozone-safe solvent instead of ozone-hazardous freon 113, the production of which should be discontinued in accordance with the Montreal Protocol in 1995. The technology of 1,2-difluorotrichloroethane is based on fluorination of trichlorethylene with highly valence metal fluoride of a highly oxidized state, followed by washing the raw material from acidic impurities and distillation of the target product. The presence of an admixture of fluorotrichloroethylene in 1,2-difluorotrichloroethane having a boiling point close to Freon 122A leads to a decrease in the quality of the target product and necessitates the search for effective methods for its purification from fluorotrichloroethylene.

Known purification method ftorhloralkana, namely 1,1,2-trifluorotrichloroethane (Freon 113), of unsaturated compounds e.g. diftordihloretilena by treatment with oxygen in the liquid phase at a temperature of 0-50 ^{° C} [1] The disadvantage of the method is low selectivity purification from unsaturated impurities due to the high oxidation rate of fluorochloroalkanes, in particular freons 123, 133, 122, etc.

There is another method of purification of fluorochloroalkane, namely chladone 113, from unsaturated compounds, for example, difluorodichloroethylene, which allows you to eliminate the disadvantage of the previous one and by the totality of the signs is closest to the proposed one. This method consists in treating the HFC 113 containing 1,1-diftordihloretilen chlorine in the liquid phase at a temperature of 0-60 ^{° C,} followed by isolation of the desired product rectification [2] The method is characterized by a high selectivity, and ultimately, smaller losses title product.

 The disadvantage of this method is the low cleaning efficiency due to the low rate of liquid phase chlorination.

The invention solves the problem of increasing the efficiency of the process in the purification of 1,2-difluorotrichloroethane from fluorotrichlorethylene. This is achieved in that in the method ftorhloralkana purification, in particular 1,2-diftortrihloretana, by treatment with chlorine, followed by isolation of the desired product rectification, chlorine treatment is carried out in the gas phase in a bed of activated carbon at a temperature of 100-250 ^C. In addition, the processing chlorine can be carried out in the presence of fluorine as an initiator in an amount of 0.1-1.0 mol. from chlorine taken for processing.

PRI me R. The experiments on the purification of 1,2-difluorotrichloroethane are carried out in a laboratory reactor made of nickel in the form of a pipe with a diameter of 18 mm and a length of 250 mm. The reactor is filled with activated carbon grade AR-B and is equipped with external electrical heating. The initial difluorotrichloroethane (composition is given in the table) is evaporated in a round bottom flask placed in a water bath, chlorine is also supplied from the balloon at a given speed and, in a number of experiments, fluorine. The latter is obtained in a laboratory electrolyzer from potassium dihydrotrifluoride and purified from hydrogen fluoride in a column with sodium fluoride. A mixture of vapor of difluorotrichloroethane and halogen enters a layer of activated carbon heated to a predetermined temperature, where the process of chlorination of the impurity proceeds. Upon leaving the reactor, the product is collected in a flask under reflux and analyzed. Unreacted chlorine is absorbed in a flask with a solution of sodium hydroxide (5%) and sodium thiosulfate (3%). The volume of activated carbon in the reactor is 64 cm ³ . The duration of one experiment is 3 hours. The specific conditions and results of the experiments are presented in the table (experiments 1-8). For comparison, the results of experiments on the prototype (experiments 11-12), which were carried out in a glass apparatus of a column type equipped with a reflux condenser, under continuous illumination by a fluorescent lamp, are also presented there. The duration of the experiment is 3 hours, the height of the bubble layer is 12 cm.

 The experiments show that the degree of purification of 1,2-difluorotrichloroethane from fluorotrichloroethylene by the proposed method (experiments 1-8) exceeds 80%, while fluorotrichloroethylene is quantitatively converted to fluoropentachloroethane (freon 111), which is easily separated from freon 122A by distillation.

Lowering the temperature of chlorination below 100 ^about C leads to a decrease in the degree of purification (experiment 9).

 The increase in the concentration of fluorine in chlorine over 1 mol. impractical due to a decrease in the selectivity of chlorination, as can be seen from the concentration of HFC 122A in the products of chlorination (experiment 10).

Claims (2)

1. METHOD FOR CLEANING LOWER FLORCHORALKANES from unsaturated compounds by treatment with chlorine at elevated temperature followed by distillation of the desired product, characterized in that the treatment with chlorine is carried out in the gas phase in the activated carbon layer at 100 250 ^o C.  2. The method according to p. 1, characterized in that the treatment with chlorine is carried out in the presence of fluorine in an amount of 0.1 to 1.0 mol. from chlorine taken for processing.

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