RU2417982C1 - Method of producing sulphonylfluorides of perfluorocarboxylic acid fluorides - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of fluorine-containing organic compounds, specifically to a method of producing sulphonylfluorides of perfluorocarboxylic acid fluorides via isomerisation of perfluoroalkane sultones using a gaseous catalyst - trimethylamine, the catalytic amount of which is optimally equal to 0.02-0.14% of the weight of perfluoroalkane sultone. The process is carried out at temperature 0-20°C.

EFFECT: method provides mild, non-emission reaction, high output of the raw isomer used in synthesis of monomers easily copolymerisable with olefins to obtain polymers for producing ion-exchange membranes for fuel cells, as well as bifunctional semi-products which can be used in several syntheses of fluorine-containing compounds.

3 cl, 3 ex

Description

The invention relates to the field of obtaining fluorine-containing organic compounds, and in particular to a method for producing sulfonyl fluorides of perfluorocarboxylic acid fluorides. Perfluorocarboxylic acid fluoride sulfonyl fluorides are intermediates that are widely used in the manufacture of monomers readily copolymerizing with olefins. In this case, polymers are formed from which ion-exchange membranes for fuel cells are produced, and bifunctional intermediates that are used in a number of syntheses of fluorine-containing compounds.

Perfluorocarboxylic acid fluoride sulfonyl fluorides are prepared according to the following scheme: perfluoroolefin (tetrafluoroethylene, hexafluoropropylene), reacting with sulfuric anhydride, forms the corresponding perfluoroalkanesultone, which in the presence of a catalyst isomerized to perfluoric acid sulfonyl fluoride perfluoride:

In the known methods for producing sulfonyl fluorides of perfluorocarboxylic acid fluorides, solid or liquid catalysts are used. So, it is known the use as a catalyst at the stage of isomerization of perfluoroalkanesultone potassium fluoride [US Pat. US 6274677, op. 2001, C07C 303/22] or sodium fluoride [WO 2007132822, op. 2007, C07C 303/22].

The method is carried out as follows: a solvent (diglyme) is added to the thoroughly dried potassium (sodium) fluoride, and perfluoroalkanesultone is gradually added dropwise. The reaction proceeds very vigorously. The presence of a solid-phase catalyst and solvent complicate the process of isolation of the target product and its purification.

Another isomerization catalyst used is a liquid catalyst, triethylamine (C ₂ H ₅ ) ₃ N. The isomerization reaction of perfluoropropane-2-β-sultone in the presence of triethylamine with a yield of the desired product of 95% is described in [JACS, 82, p. 6181, 1960; Proceedings of the USSR Academy of Sciences, chemical series, 1972 (11) C 2510-16]. No solvent is required in this process. However, the exothermic reaction of isomerization of perfluoroalkanesultones is accompanied by almost simultaneous heating of the reaction mass from 0 to 35-41 ° C, which often leads to its release. Therefore, the supply of triethylamine is carried out very slowly, while its amount should be at least 2% by weight of the sultone. These disadvantages complicate the process of producing sulfonyl fluorides of perfluorocarboxylic acid fluorides and complicate the process.

The closest (prototype) is the method described in [US Pat. US 5463005, op. 1995, C08F 228/00].

The process is carried out in a three-necked flask with a capacity of 250 ml, cooled in an ice bath and equipped with a dropping funnel, reverse and direct refrigerators, receiver, mixing device. Tetrafluoroethanesultone is placed in the flask, to which dehydrated triethylamine is slowly pinned, a violent reaction begins, after which stirring is continued for another 1 hour at room temperature. The target product is purified by distillation. The output is not shown. This method has all the disadvantages described above - the possibility of ejection of the reaction mass, a careful dosage of the catalyst, which reduces the manufacturability of the method.

The objective of the invention is to develop a simpler method for producing sulfonyl fluorides of perfluorocarboxylic acid fluorides and increase the yield of the target product.

The solution to this problem is achieved by isomerization of perfluoroalkanesultones at a temperature of 0-20 ° C using a gaseous catalyst - trimethylamine, the catalytic amount of which is optimally 0.02-0.14% by weight of perfluoroalkanesultone.

A method is proposed for producing perfluorocarboxylic acid fluoride sulfonyl fluorides by isomerization of perfluoroalkanesultones in the presence of trialkylamine, characterized in that catalytic amounts of trimethylamine are taken as trialkylamine and the process is carried out at a temperature from 0 to 20 ° C. In this case, trimethylamine is taken in an amount of 0.02% -0.14% by weight of perfluoroalkanesultone, and, in particular, C ₂ -C ₃ perfluoroalkanesultones, i.e. tetrafluoroethane-β-sultone and hexafluoropropane-2-β-sultone, are taken as isomerization This is illustrated in the examples.

Gaseous trimethylamine (CH ₃ ) N, boiling at a temperature of + 2 ° C, serves either in parts or continuously. At the same time, the temperature of the reaction mass is controlled, not allowing it to rise above 20 ° C. The temperature at this level is maintained by cooling the reactor. The initial temperature of perfluoroalkanesultone, at which the isomerization process begins, is from 0 to + 2 ° C. After the reaction, the mass is maintained at a temperature of + 45 ° C to complete the isomerization of perfluoroalkanesultone.

Carrying out the reaction above 20 ° C leads to the formation of by-products. At lower temperatures, as with less catalyst, the reaction slows down. The method with a higher amount of catalyst is not economically feasible.

Studying the chemistry of the process of isomerization of perfluoroalkanesultones, the authors studied various compounds as possible isomerization catalysts, including, in addition to trimethylamine, BF ₃ , PF ₅ , NF ₃ , NH ₃ . It was found that NF ₃ , NH ₃ have catalytic activity, the reaction proceeds without significant simultaneous heat release, but with a low yield of 50-80%. The isomerization process in the presence of trimethylamine gently passes, but the yield reaches 99%.

The process of isomerization of perfluoroalkanesultones using triethylamine is highly exothermic and is accompanied by instant heating of the reaction mass, which leads to the release of the target product.

Although trimethylamine, like triethylamine, belongs to lower alkyl amines, the reaction of isomerization of perfluoroalkanesultone in its presence proceeds at the phase boundary, other than in the presence of triethylamine, with no significant heating of the reaction mass.

Trimethylamine is a gaseous product; previous researchers have not previously used it for isomerization of perfluoroalkanesultones.

The use of trimethylamine under the indicated conditions leads to the following process improvements:

the reaction proceeds gently, without emissions;

due to the fact that a gaseous catalyst is used, in addition to a small amount, it is not necessary to carry out a separation stage of the reaction mass; the yield of the crude isomer is increased to 99%.

The examples given illustrate the implementation of the method as proposed by this invention.

Example 1

In a 200 ml stainless steel reactor equipped with a magnetic stirrer, a Goffer crane, pressure gauge and thermocouple, 56 g of tetrafluoroethane-β-sultone (perfluoroalkanesulton C ₂ ) are charged. The reactor is cooled in ice water to a temperature of 0 to + 2 ° C and 0.012 g (20 ml) of gaseous trimethylamine is fed with stirring, maintaining the temperature not higher than 6 ° C. After cooling to the initial temperature, a second portion of trimethylamine is fed, maintaining the temperature to 20 ° С, after cooling to 3 ° С, the next portion is fed, and if the temperature does not rise, the reaction mass is heated to 45 ° С to complete the reaction. The whole cycle takes about 6 hours. Received 55.55 g of perfluoroacetic acid fluoride sulfonyl fluoride, which corresponds to a yield of 98.5%, after distillation, the purity of the product is 99.2%.

Example 2

In the reactor of Example 1, 69 g of hexafluoropropane-2-β-sultone (perfluoroalkanesultone C ₃ ) obtained by the reaction of sulfur trioxide and hexafluoropropylene are charged, cooled to + 2 ° C, and 0.097 g of trimethylamine are added in portions, preventing heating above 15 ° C. After termination of the temperature rise, the reaction mass was kept at a temperature of 45-50 ° C for 2 hours. The yield was 68.3 g (99%) of 3-fluorosulfonyl perfluoropropionic acid fluoride. After distillation, the product has a purity of 99.2%.

Example 3

2.5 kg of tetrafluoroethane-β-sultone (perfluoroalkanesultones C ₂ ) are charged into a 2.5 liter steel reactor equipped with a Goffer crane, pressure gauge, stirrer and thermocouple and, after cooling the reactor to + 2 ° C, 2 , 0 g of trimethylamine with a speed at which there is no increase in the temperature of the reaction mass above 15 ° C. After feeding trimethylamine, the reactor is heated to 45 ° C and the reaction mass is maintained at this temperature for 3 hours, after which 2.47 kg of perfluoroacetic acid fluoride sulfide (98.8%) are distilled from the reactor with a purity of 99.3%.

The use of trimethylamine under the indicated conditions leads to the following process improvements:

the reaction proceeds gently, without emissions;

due to the small amount of gaseous catalyst, separation of the reaction mass is not required;

the yield of the crude isomer is increased to 99%.

Thus, the present invention allows to simplify the method of producing sulfonyl fluorides of perfluorocarboxylic acid fluorides and increase the yield of target products.

Claims (3)

1. The method of producing sulfonyl fluorides of perfluorocarboxylic acid fluorides by isomerization of perfluoroalkanesultones, characterized in that catalytic amounts of trimethylamine are taken as trialkylamine and the process is carried out at a temperature of from 0 to 20 ° C. 2. The method according to claim 1, characterized in that trimethylamine is taken in an amount of 0.02-0.14% by weight of perfluoroalkanesultone. 3. The method according to claim 1, characterized in that C ₂ -C ₃ perfluoroalkanesultones are isomerized.