SU423789A1 - METHOD OF OBTAINING 1,1-DIFLETORETHANE AND VINYL FLUORIDE - Google Patents

Description

one

The invention relates to a process for the preparation of 1,1-difluoroethane and vinyl fluoride used as fluorine-containing monomers with valuable properties.

A known method for the preparation of vinyl fluoride and 1,1-Dinfluoroethane by fluorination of hydrogen chloride with hydrogen fluoride at a temperature of 280-320 ° C in the presence of a catalyst CrR3, CoC1H2O3. The outputs of the target products are 1,1-Dpfluoroethal 45.8%, fluorine vinyl 46.2%.

However, upon receipt of these products by a known method, the service life of the catalyst is very short, which has a sufficient effect on reducing the yield of the target products. Thus, during the operation of the catalyst for 17 hours, the target products are formed in maximum amounts (59.3% 1,1-difluoroethane and 29.9% vinyl fluoride); such yields of the target products are preserved if the catalyst is operated for up to 130 hours, then the yields begin to decrease after 170 hours of operation, the yields of the target products are reduced by 45-50% of the maximum; Up to 7% of acetylene, ethylene, and ethane are present in the reaction products — compounds that adversely affect the purification and subsequent use of influenyl fluoride and 1,1-difluoroethane.

In order to obtain higher and more stable yields, it is recommended to use aluminum fluoride supplemented with chromium oxide as a catalyst. Optimum yields are achieved when a P1 catalyst is used containing 96 wt. % aluminum fluoride and 4 wt. % chromium oxide.

The proposed catalyst does not lose activity during 250 hours. Thus, by passing a mixture of vinyl chloride and hydrogen fluoride in molar ratios of 1: 3 and a temperature of 385 ° C through a flow reactor filled with the proposed catalyst, a steady yield of reaction products is established for 15–20 minutes. The reaction product has the following composition: Vlnilfluoride 16.8%, 1,1-difluoroethane 53.1%, vnnchloride 30.1%; after 50 hours, the content of vinyl fluoride is 17.3%, 1,1-Dnipro-fluoro-a, 56.1%, and vinyl chloride, 26.6%; after 150 hours, the content of vinyl fluoride is 16.8%, 1,1-difluoroethane 55.5%, and vinpl chloride 27.7%; after 200 hours, the content of vinyl fluoride is 16.5%, 1,1-difluoroethane 55.0%, vinyl chloride 28.5%; after 250 hours, the content of vinyl fluoride is 14.7%, 1,1-difluoroethane 53.9%, the amount of chlorofluoride is 28.37o, ethylene is 3.1%, etc.

For preparation of the catalyst, chemically pure aluminum fluoride and chromium nitrate are taken and mixed together to form a homogeneous mass. Then from

This mixture is compressed into tablets under a pressure of 200 atm, which are calcined at 500 ° C to convert chromium nitrate to chromium oxide.

The catalytic fluorination of viyl chloride with hydrogen fluoride is carried out in the vapor phase in a flow reactor with a diameter of 27 mm and a length of 1000 kg. The temperature in the reactor is measured with a chromel-alumel thermocouple with an accuracy of ± HS. The flow rate of anhydrous gaseous hydrogen fluoride is measured with a special rheometer made from a copper tube with a teflon membrane, and the flow rate of vinyl chloride is measured using a glass rheometer. Before the reaction, the catalyst is dried in the reactor in a stream of dry gas at a temperature of 300 ° C for 3-4 hours.

For the study of fluoride of vinyl chloride fluoride, catalysts containing Cr2O3 are taken. The reaction temperature is 250-400 ° C, and the molar ratio of the vinyl chloride: hydrogen fluoride componeites is 1: 1 -1: 10. The reaction products, after washing off unreacted hydrogen fluoride hydrogen with a solution of potassium hydroxide and drying over calcium chloride, are examined on a gas-liquid-chromatograph of the Chromium-1 type. The highest co-versions of vinyl chloride in 1,1-di | fluoroethane and viyl fluoride are observed using a catalyst consisting of 96% aluminum fluoride and 4% chromium oxide.

The proposed catalyst does not lose its activity for 250 hours of continuous operation.

Example. In a steel reactor with a diameter of 27 mm and a length of 1000 mm, 60 g of a catalyst consisting of 96% A1P3 and 4% C0250 is loaded and dried at 300 ° C for 3 hours in a stream of dry nitrogen; then the temperature is raised to 385 ° C and 100 g (1.6 moles of thoroughly cleaned in dried vinyl chlord, with a speed of

94.5 hours and 97 g (4.8 moles) of anhydrous hydrogen fluoride at a rate of 283.5 (the molar ratio of vinyl chloride: hydrogen fluoride is 1: 3).

Reaction product. After washing from non-reacted hydrogen fluoride

A 20% -. Solution of potassium hydroxide and drying over calcium chloride is condensed in a special receiver at a temperature of dry ice (-78 ° €). According to gas chromatographic data, the resulting product consists of

56.1% 1,1-dvfluoroethane, 17.3% vinyl fluoride

and 26.6% unreacted vinyl chloride.

The reaction products are separated by low-temperature distillation on a Podtilnik-type column with a length of 1300 mm and a diameter of 8 liters, filled with a nozzle of six twisted in spirals, with a diameter of 1.2 mm each, made of 0.2 mm nickel wire;

total nozzle length 1150 mm. The selection is carried out in the gas phase with a reflux ratio of at least 10. As a result of distillation, 12.8 g of vinyl fluoride, 59.8 g, 1.1-d) of 1-fluoroethane and 24.9 g of vinyl chloride are obtained.

Subject invention

Claims (2)

1. A method for producing bifluoro-ethane and vinyl fluoride by fluorinating vinyl chloride with hydrogen fluoride at elevated temperature in the presence of a catalyst followed by separation of the target product by known methods, characterized in that, in order to intensify the process, aluminum fluoride with chromium oxide is used as a catalyst . 2. A method according to claim 1, characterized in that a catalyst is used comprising 96 weight. % aluminum fluoride and 4 wt. % oxide homo.