RU2144019C1 - Method of preparing pentafluoroiodoethane - Google Patents

Abstract

FIELD: organic chemistry. SUBSTANCE: method is carried out by reacting tetrafluoroethylene with mixture of iodine and iodine pentafluoride at temperature of 40-80 C in the presence of metallic antimony as catalyst and in the presence of mixture of difluoromethane with trifluoroethylene in amount of 7•10^-4÷2,6•10^-2 wt %. Process efficiency becomes higher, no inert diluent is used, process becomes cheaper and is less dangerous, and final product having high content of main agent is obtained, and additional purification thereof is thus avoided. EFFECT: more efficient preparation method.

Description

 This invention relates to the field of organic chemistry, in particular to the production of iodofluoroalkanes used in telomerization reactions for the production of low molecular weight polymers and as raw materials for the preparation of many organic compounds (including fluorinated surfactants).

 A method is described for producing pentafluorodioethane by reaction of 1,2-diiodotetrafluoroethane, iodine pentafluoride and tetrafluoroethylene in the closed reaction zone in the presence of an antimony pentafluoride catalyst or a mixture of antimony trifluoride and iodine [Pat. USA N 3283020 from 01/01/1996].

 Significant disadvantages of this method are the need for preliminary preparation of 1,2-diiodotetrafluoroethane, which leads to a complication of the process; mandatory compliance with a strictly defined ratio of reacting components, otherwise the reaction will proceed with the formation of a longer carbon chain.

 Previously published was a method of producing pentafluoroiodoethane by reacting tetrafluoroethylene with iodine monofluoride in the presence of aluminum metal as a catalyst and in the presence of an inhibitor (1,1,2-trichloro-2,2-difluoroiodoethane) [Pat. US N 3006973 dated October 31, 1961].

 The disadvantages of the method are the low yield of pentafluoroiodoethane (59% in terms of the spent tetrafluoroethylene), the mandatory use of an inhibitor, in the absence of which the main reaction products were tetrafluoromethane and carbon.

The closest in technical essence and the set of essential features is a method for producing iodofluoroalkanes by reaction of a mixture of fluoroolefins with an inert gas with a solution of iodine and antimony trioxide in iodine pentafluoride at a temperature of 40 - 80 ^o C and a contact time of 0.3 hours [Pat. Russia N 2064915, C 07 C 19/08, 17/02, 1996].

 The disadvantages of the method are low productivity; the use of an inert gas as a transporting agent in the synthesis of pentafluoroiodoethane, which does not allow to obtain the target product of high purity due to the presence of non-condensable impurities in it (inert gases). The crude obtained in this way contains not higher than 94% pentafluoroiodoethane, contains 5.2% tetrafluoroethylene, 0.6% hexafluoroethane, and 0.2% pentafluoroethane as impurities. The raw must be subjected to rectification, therefore, the process is complicated by the stage of purification.

 The use of nitrogen as an inert gas requires its additional purification from oxygen to ensure safe process control. Additional purification of nitrogen from oxygen, as well as the use of expensive helium as an inert gas, make the process more expensive.

 As a catalyst, toxic antimony trioxide is used. The presence of acidic components (iodine, iodine pentafluoride) can cause the polymerization of tetrafluoroethylene, which can lead to an uncontrolled reaction resulting in an explosion.

 The objective of the invention is to develop a method for producing pentafluoroiodoethane without the above disadvantages.

The problem is solved by the method of producing pentafluoroiodoethane by the interaction of tetrafluoroethylene with iodine and iodine pentafluoride in the presence of metallic antimony as a catalyst and in the presence of additives of a mixture of difluoromethane with trifluoroethylene in an amount of 7 • 10 ^-4 - 2.6 • 10 ^-2 wt.% As inhibitors of spontaneous polymerization of tetrafluoroethylene. With the introduction of a mixture of difluoromethane with trifluoroethylene in an amount of less than 7 • 10 ^-4 wt. % there is the formation of polytetrafluoroethylene, which complicates the process, makes it more dangerous and reduces the productivity of the process. The use of these additives in an amount exceeding 2.6 • 10 ^-2 wt.%, Leads to a deterioration in the composition of the raw material, a decrease in the content of the main substance in the resulting product.

The process is carried out at a temperature of 40 - 80 ^o C.

 The advantages of the proposed method are to increase the productivity of the process; carrying out the process without the use of an inert diluent, which reduces the cost of the process and makes it less dangerous.

 As the catalyst in the proposed method uses metallic antimony - less toxic than antimony trioxide. The presence of additives: difluoromethane and trifluoroethylene stabilizes the process, eliminating spontaneous polymerization of tetrafluoroethylene.

 The invention is illustrated by the following examples.

 Example 1

1470 g of crystalline iodine, 1230 g of iodine pentafluoride, 30 g of antimony metal were charged into a 1 L stainless steel reactor equipped with a stirrer, a jacket, a reflux condenser. The molar ratio of the starting reagents is 1: 1.25: 0.24. The reactor was heated to 60 ^° C and tetrafluoroethylene was added with the addition of 1.6 x 10 ^-2 % by weight of a mixture of difluoromethane and trifluoroethylene. The total amount of tetrafluoroethylene consumed was 1260 g. After condensation of the synthesis gases, 3096 g of a product containing 99.9% pentafluoroiodoethane and 0.1% tetrafluoroethylene were obtained. The productivity of the process is 200 g / l • h.

 Example 2

Under the conditions described in example 1, the process was carried out in the presence of 5 • 10 ^-4 wt.% A mixture of difluoromethane and trifluoroethylene. After 2 hours of the process, a polymer in the amount of 10% of the spent tetrafluoroethylene was found in the reaction mass. The process is terminated.

 Example 3

Under the conditions described in example 1, the process was carried out in the presence of 3 • 10 ^-2 wt.% A mixture of difluoromethane with trifluoroethylene. Trifluoroethylene consumption 18.8 l / h. The synthesis time is 15 hours. Received a product with a basic substance content of 93.5%. The productivity of the process is 170 g / l • h.

Claims (1)

The method of producing pentafluorodioethane by the interaction of tetrafluoroethylene with a mixture of iodine, iodine pentafluoride at a temperature of 40 - 80 ^o C, characterized in that the metal antimony is used as a catalyst and the process is conducted in the presence of 7 · 10 ^-4 - 2.6 · 10 ^-2 wt.% mixtures of difluoromethane with trifluoroethylene.