RU2280030C1 - Method for preparing perfluoroalkane sulfofluoride - Google Patents

Abstract

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to a method for synthesis of perfluoroalkane sulfofluorides used as intermediate compounds in synthesis of perfluoroalkane sulfoacids and their salts, and as a component of cleaning gas possessing the high etching rate value. Invention describes a method for synthesis of perfluoroalkane sulfofluorides that involves fluorination reaction of monohydroperfluoroalkane sulfofluorides with elemental fluorine in the presence of hydrogen fluoride chosen in the amount 8% of monohydroperfluoroalkane sulfofluoride mass wherein hydrogen fluoride is added to the flow of monohydroperfluoroalkane sulfofluoride in the presence of copper chips treated preliminary with fluorine at temperature 120-160°C. Preferable, hydrogen fluoride is used in the amount 8-30% of the latter mass. Proposed method provides the high yield of the end product up to 97.5% and intensification of the fluorination reaction with using the available raw and standard technology.

EFFECT: improved preparing method.

3 cl, 9 ex

Description

The invention relates to a method for producing perfluoroalkanesulfofluorides (PFASF) of the general formula R _f —CF ₂ —SO ₂ F, where R _f = F, CF ₃ , C ₂ F ₅ , and in particular to a method for producing trifluoromethanesulfofluoride, pentafluoroethanesulfofluoride and heptafluoropropanesulfofluoride, which are used as intermediate compounds in a number of syntheses, for example, in the synthesis of perfluoroalkanesulfonic acids and their salts (S.Benefice-Malouet, H. Blancou et al., J. of Fluorine Chemistry, 31 (1986) 319-332), as well as components of a cleaning gas, having a high etching rate.

Known electrochemical methods for producing PFASF, which are based on the electrochemical fluorination of organic raw materials (Brice, Trott, US Patent No. 2732398, publ. 1954; T. Gramstad, RN Haszeldine J. of Chem Soc. London, 1957, p. 2640-2645; HA Vogel, JCHansen, U.S. Patent No. 5,486,271, C 25 B 3/00, publ. 1994). The proposed methods have several disadvantages, namely:

- low productivity of electrolyzers;

- high energy intensity;

- decrease in the yield of target products with the growth of the hydrocarbon chain from 85 to 20%;

- the presence of a large number of degradation products;

- difficulties associated with the purification of the target products. Chemical methods for producing these perfluoroalkanesulfofluorides are described in the works (US Patent No. 3542864, 260-543, publ. 24.11.1970; RF patent No. 2237659 publ. 10.10.2004).

The known chemical method for producing pentafluoroethane and heptafluoroisopropanesulfofluorides by reacting the corresponding olefin and SO ₂ F ₂ in the presence of cesium fluoride in a solvent at 110 ° C for 60 hours has not been further developed due to the low productivity and high consumption of scarce and expensive cesium fluoride (Patent . USA No. 3542864, 260-543, publ. 24.11.1970).

A method for producing perfluoroalkanesulfofluorides using the corresponding monohydroperfluoroalkanesulfofluoride of the general formula R _f -CFH-SO ₂ F, where R _f = F, CF ₃ , C ₂ F _{5, is} fluorinated with elemental fluorine at a temperature of 0-30 ° C is also known (Russian Patent No. 2237659, publ. 10.10.2004). The method is characterized by a high yield of the target product (up to 87.5%), the use of low-waste typical technological methods and industrial commercially available raw materials. However, the need to supply fluorine at a low speed in order to prevent a simultaneous increase in temperature by more than 2 ° C makes the process lengthy and makes it difficult to use this method on an industrial scale.

The invention solves the problem of increasing the fluorination rate of monohydroperfluoroalkanesulfofluoride while increasing the yield of the target product without significantly complicating the process. The essence of the invention lies in the fact that gas-phase fluorination of monohydroperfluoroalkanesulfofluorides of the general formula R _f -CFH-SO ₂ F, where R _f = F, CF ₃ , C ₂ F ₅ (difluoromethanesulfofluoride, tetrafluoroethanesulfofluoride, hexafluoropropanesulfofluoride) is carried out by elemental fluoride in the presence of hydrogen fluoride taken in an amount of at least 8% by weight of monohydroperfluoroalkanesulfofluoride in the presence of copper chips treated with fluorine at a temperature of 120-160 ° C during preliminary passivation of the reactor unit and used to maintain a constant rate Saturn gradient across the length of the reactor. Hydrogen fluoride is added, for example, to a monohydroperfluoroalkanesulfofluoride stream. The upper limit of the content of hydrogen fluoride is not a regulatory parameter, since it does not affect the yield of the target product, but technologically and economically the most appropriate is the content of hydrogen fluoride of 8-30% by weight of monohydroperfluoroalkanesulfofluoride. The combination of these features allows you to conduct the process at a temperature of 110-160 °, the feed rate of fluorine is not regulated; the process proceeds practically without the formation of destructive fluorination products with the yield of the target product up to 97.5%.

The mixture resulting from fluorination is neutralized, dried and rectified.

All reagents used are commercially available products. Hydrogen fluoride, both formed in small amounts at the fluorination stage and introduced into the process at the fluorination stage, is removed from the target product by neutralization and washing, although it is possible to separate it by rectification or absorption by alkali metal fluorides.

The following examples illustrate the invention, but do not limit its essence.

Before conducting experimental work, the reactor assembly, consisting of an evaporator, a mixer and a reactor filled with copper chips, is passivated with elemental fluorine at a temperature of 120-160 ° C for 7-10 hours.

Example 1. In a measuring tank with a capacity of 0.25 l, made of steel 12X18H10T, a mixture is loaded containing 184 g of tetrafluoroethanesulfofluoride and 19 g of hydrogen fluoride (hydrogen fluoride content of 10.32% by weight of tetrafluoroethanesulfofluoride). The mixture with a speed of 1.2 g / min enters a tubular evaporator made of steel 12X18H10T with a length of 500 mm and a diameter of 40 mm, filled with copper chips and heated to 120 ° C. From the evaporator, the mixture in gaseous form enters a tubular nickel reactor with a length of 800 mm and a diameter of 38 mm, filled with copper shavings treated with fluorine at 150 ° C. At the same time, fluorine is supplied to the reactor at a rate of 10 l / h. This reaction takes place at a temperature of 110 ° C. The reaction products are sent to a refrigerator, cooled by water, and then into a trap with a temperature of -78 ° C. After completion of the process, the reaction products are neutralized with a 10% KOH solution at a temperature of 10–20 ° C, dried with zeolite, and collected in a container made of 12X18H10T steel. Received 209 g of crude containing 90.5% C ₂ F ₅ SO ₂ F (pentafluoroethanesulfofluoride), 2% SO ₂ F ₂ , 0.5% CF ₃ SO ₂ F (trifluoromethanesulfofluoride), 0.1% SF ₆ and 6, 9% C ₂ F ₄ HSO ₂ F (monohydroperfluoroethanesulfofluoride).

Similarly, experiments were conducted with varying the main process parameters.

Example 2. The experiment was carried out similarly to the experiment of example 1, but the ratio of hydrogen fluoride to the weight of tetrafluoroethanesulfofluoride was 8%. The obtained crude composition: 87.5% C ₂ F ₅ SO ₂ F (pentafluoroethanesulfofluoride), 3.4% SO ₂ F ₂ , 1.7% CF ₃ SO ₂ F (trifluoromethanesulfofluoride), 0.2% SF ₆ and 7, 2% C ₂ F ₄ HSO ₂ F (monohydroperfluoroethanesulfofluoride).

Example 3. The experiment was carried out similarly to the experiment of example 1, but the process temperature was 140 ° C. The obtained crude composition: 96.45% C ₂ F ₅ SO ₂ F (pentafluoroethanesulfofluoride), 3.4% SO ₂ F ₂ , 0.5% CF ₃ SO ₂ F, 0.15% SF ₆ and 0.45% C ₂ F ₄ HSO ₂ F (monohydroperfluoroethanesulfofluoride).

Example 4. The experiment was carried out similarly to the experiment of example 3, but the amount of hydrogen fluoride by weight of tetrafluoroethanesulfofluoride was 12%. The obtained crude composition: 96.25% C ₂ F ₅ SO ₂ F (pentafluoroethanesulfofluoride), 3.5% SO ₂ F ₂ , 0.55% CF ₃ SO ₂ F (trifluoromethanesulfofluoride), 0.15% SF ₆ and 0, 5% C ₂ F ₄ HSO ₂ F (monohydroperfluoroethanesulfofluoride).

Example 5. The experiment was carried out as in example 3, but the amount of hydrogen fluoride by weight of tetrafluoroethanesulfofluoride was 30%. The crude composition obtained was 94.88% C ₂ F ₅ SO ₂ F (pentafluoroethanesulfofluoride), 2.1% SO ₂ F ₂ , 0.1% CF ₃ SO ₂ F, 0.11% SF ₆ , 4.81% C ₂ F ₄ HSO ₂ F (monohydroperfluoroethanesulfofluoride).

Example 6. The experiment was carried out similarly to the experiment of example 3, but the process temperature was 160 ° C. Raw composition obtained: 90.4% C ₂ F ₅ SO ₂ F (pentafluoroethanesulfofluoride), 6.5% SO ₂ F ₂ , 1.6% CF ₃ SO ₂ F), 1.0% SF ₆ and 0.5% C ₂ F ₄ HSO ₂ F.

Example 7. The experiment was carried out as in example 1, but the amount of hydrogen fluoride by weight of tetrafluoroethanesulfofluoride was 60%. The crude composition was obtained: 93.3% C ₂ F ₅ SO ₂ F (pentafluoroethanesulfofluoride), 4.5% SO ₂ F ₂ , 0.7% CF ₃ SO ₂ F (trifluoromethanesulfofluoride), 0.3% SF ₆ and 1, 2% C ₂ F ₄ HSO ₂ F (monohydroperfluoroethanesulfofluoride).

Example 8. The experiment was carried out as in example 1, but the fluorination was subjected to difluoromethanesulfofluoride in an amount of 134 g. Received 145 g of the target trifluoromethanesulfofluoride. The yield was 95.4%.

Example 9. The experiment was carried out as in example 1, but hexafluoropropanesulfofluoride, taken in an amount of 252 g, was fluorinated. 235 g of the target heptafluoropropanesulfofluoride were obtained. The yield was 93.2%.

As can be seen from the above examples, the method of producing perfluoroalkanesulfofluorides provides a high yield of the target product using typical technological methods, available raw materials at a sufficiently high feed rate of elemental fluorine.

Claims (3)

1. The method of producing perfluoroalkanesulfofluorides of the general formula R _f -CF ₂ -SO ₂ F, where R _f = F, CF ₃ , C ₂ F ₅ , by fluorination of monohydroperfluoroalkanesulfofluorides of the general formula R _f -CFH-SO ₂ F, where R _f -F, CF ₃ , C ₂ F ₅ , elemental fluorine, characterized in that the fluorination is carried out in the presence of hydrogen fluoride taken in an amount of not less than 8% by weight of the starting monohydroperfluoroalkanesulfofluoride, and hydrogen fluoride is introduced into the stream of monohydroperfluoroalkanesulfofluoride in the presence of copper chips pretreated with fluorine at a temperature of 120 -160 ° C. 2. The method according to claim 1, characterized in that the fluorination of monohydroperfluoroalkanesulfofluorides is carried out at a temperature of 110-160 ° C. 3. The method according to claim 1, characterized in that the hydrogen fluoride is introduced into the reaction zone in a mixture with monohydroperfluoroalkanesulfofluoride in an amount of 8-30% by weight of the latter.