RU2193523C2 - Method of preparing selenium tetrafluoride - Google Patents

Abstract

FIELD: inorganic compounds technology. SUBSTANCE: selenium is fluorinated by 1: (4-5) fluorine/inert gas mixture at temperature between +5 C and -10 C and atmospheric pressure. Gas mixture is fed at velocity 20-30 l/h. Inert gas can be nitrogen, argon, or their mixture. Resulting selenium tetrafluoride is recovered via evaporation at 90-100 C and pressure up to 1.5 atm. EFFECT: simplified technology. 3 cl, 1 dwg, 1 tbl

Description

The invention relates to inorganic chemistry, to the field of production of fluorides of elements of group VI of group II of the subgroup of the Periodic system of elements, namely to the production of selenium tetrafluoride SeF ₄ .

 Selenium tetrafluoride is used, in particular, in the processes of selective fluorination in the synthesis of drugs.

Selenium tetrafluoride is a colorless liquid, characterized by a boiling point of about 105 ^o C and a melting point of about minus 9.5 ^o C.

Known [Gmelin Handbook, Se. Supplement vol. B2, Compounds. Springer-Verl. , 1984, S.9-10] various methods for producing selenium tetrafluoride. This compound is obtained by fluorination of selenium with halogen fluorides [JJ Pitts. AW Jache, Inorganic Chemistry, 7, 1968, p.1661-3], for example, ClF ₃ chlorine trifluoride [CJ Schack et al, Inorganic Chemistry, 11, 1972, p. 208-9]. Sulfur, selenium and tellurium fluorides and hexafluorides are obtained by treating the corresponding elements with chlorine fluoride [US Pat. No. 3,373,000, Cl. 23-352, claimed 11/01/66, publ. 03/12/68].

 Selenium tetrafluoride is also prepared by reacting sulfur tetrafluoride with selenium oxides or with metal selenates [US Pat. No. 3,026,179, claimed. 7.06.57, publ. 03.20.62; Chem. Abstr. V. 57, 13411].

Uranium selenides, for example, USe, USe ₂ or USe ₃ , after treatment with dissolved fluorine, form mainly selenium and uranium tetrafluorides [A.F. Clifford, AJ Morris, J. Inorganic Nucl. Chemistry, 5, 1957, p. 71-75, 73].

 However, upon receipt of selenium tetrafluoride by the methods described above, the product is substantially contaminated; in addition, some by-products are formed.

Known methods for producing selenium tetrafluoride from elements - selenium and fluorine [E.E. Aumsley, RD Peacock, PL Robinson, J. Chemical Society, 1952. p, 1231-4; C. Dagron, Comptes Rendus, 244, 1957, p. 1779-82]:
Se + 2F ₂ -> SeF ₄ .

By these known methods, selenium tetrafluoride is prepared under carefully controlled conditions; otherwise, selenium hexafluoride is formed. Before fluorination, selenium is dried in vacuum at 200 ^o C and then dispersed as a shallow layer in an empty, ice-cooled vessel made of pyrex or quartz glass.

Fluorine is dissolved in nitrogen in a ratio of 1: 1 and passed over selenium at a rate of 1 l / h with cooling at about 0 ^o C. After completion of the interaction, the liquid product is distilled and fractionated. At a temperature of about 100 ^o With or using a more concentrated fluorine flux, the main product of the interaction is selenium hexafluoride. When carrying out the process in a glass apparatus, the product contains impurities of silicon fluoride.

 The process [A. Haas, H. Wilner, Zeitschrift fur Anorganische und Allgemeine Chemie, 454, 1979, S. 17-23] can be carried out in a Teflon or quartz apparatus, while selenium vapors at high temperature interact with a mixture of fluorine gas and argon, forming a mixture of mono, selenium di and tetrafluorides, which are then deposited on a cooled surface. This necessitates the separation of fluorides.

 Closest to the proposed method is the method [J. Carre, P. Claude, J.M. Letoffe et al, J. Fluorine Chemistry, 14, 1979, p. 139-52,140].

This method is a variant of the method proposed by Aynsley et al., In which fluorination of selenium was carried out with a 1: 1 mixture of fluorine and nitrogen at a temperature of 0 ^{° C.} [E.E. Aynsley, Rd Peacock, p. 1. Robinson, Journal of the Chemical Society, 1952, 1231-4]. According to an improved method, selenium interacts with fluorine in a metal apparatus, inside of which there is a coil cooled by a refrigerant. Selenium is subjected to sublimation and applied to the surface of the coil by condensation, and then a mixture of fluorine and nitrogen is passed into the apparatus at a rate of 8 l / h. The interaction of freshly sublimated selenium with fluorine diluted with nitrogen (in a 1: 1 ratio, as in Aynsley, see above), is carried out at a temperature of minus 8 ^o C and a pressure of 200 mbar. As the reaction takes place, the resulting selenium tetrafluoride flows to the bottom of the reactor, which allows the reaction to be carried out until the initial selenium is completely consumed.

 The complexity of the application of this method is the need for synthesis at least in two stages - preliminary sublimation and fluorination. The initial selenium is first heated to sublimation, as a result of which it is finely dispersed on the cooled surface of the coil. Thus, the interaction of the fluoroazole mixture proceeds with powdered, freshly sublimated selenium deposited on the surface in a thin layer. After applying freeze-dried selenium, it is necessary to cool the reactor volume to carry out fluorination. In addition, the resulting product collected at the bottom of the reactor may contain impurities and contaminants.

 The challenge facing the authors of the present invention is to create a simpler, more technologically advanced method for producing selenium tetrafluoride, without special preliminary treatment of the source selenium, without heating and any purification.

 This problem is solved by fluorination of the "raw" source selenium, which can be used in any form produced by industry - granular, tableted, etc., without being subjected to pre-treatment, while the resulting product should not contain impurities and impurities.

 The essence of the invention lies in the fact that selenium is poured into the apparatus for conducting fluorination with a layer of 20-25 mm in the form of any commercially available product. These can be granules or tablets, for example, produced in accordance with GOST, with a diameter of about 5 mm and a height of about 1-2.5 mm. However, the above characteristic of this product does not limit the types acceptable for use in this method. Fluorination is carried out with fluorine diluted with an inert gas, for example nitrogen, argon or helium, however, the use of nitrogen or argon is economically feasible. A mixture of inert gases, such as nitrogen and argon, in any ratio can also be used. The volume ratio of fluorine and inert gas is 1: 4-5.

The gas mixture is passed into the reactor with a feed rate of 20-80 l / h, maintaining the temperature in it from +5 ^o C to -10 ^o C. After completion of fluorination, which is determined by the temperature decrease in the reactor, cooling is stopped. The finished product, selenium tetrafluoride, is collected either at the bottom of the reactor or by evaporation. To carry out the latter, the temperature in the reactor is increased to 90-105 ^o C, replacing the refrigerant (brine) with steam and lowering the pressure to 0.3-0.5 atm. The resulting pairs of selenium tetrafluoride are removed from the reactor and collected in a collector. The product thus obtained consists of selenium tetrafluoride with a basic substance content of about 99.9%. Product analysis was performed by chromatography, by chemical interaction with potassium iodide KJ, or NMR.

 The fluorination process according to the proposed method can be carried out as described below, however, the invention is not limited to the above examples. The process can also be carried out in reactors of a different design, allowing us to implement the method developed by us.

 To carry out the method, a reactor was used in double walls and with shelves that allow the supply of cooling brine or heating steam, for example, as shown in the drawing, illustrating the process.

 The number of shelves in this reactor is not limited to the above scheme.

Initial commercial selenium, described above, is poured into the reactor 1 onto the shelves 2 with a layer of about 20-25 mm, and its mass is not limited and depends on the volume of the reactor. A cooling brine is passed into the annulus of the reactor (jacket 3) and through the coil 4, and upon reaching a temperature of +5 to -8 ^° C, a mixture of 5 fluorine and an inert gas in a ratio of 1: 4 is supplied to the reactor at a speed of about 20-80 l / h -5, respectively. A mixture of inert gases may also be used. During the fluorination process, the temperature in the reactor is maintained by supplying brine cooled to a temperature in the range from 0 to -10 ^° C. into the annulus ^. After completion of the fluorination process, which is determined by lowering the temperature in the reactor, fixed with a thermocouple, the gas supply is stopped. After that, the temperature rises to the temperature of the brine. The formed selenium tetrafluoride is either removed from the bottom of the reactor, or it is evaporated, for which instead of brine, heating steam is fed into the annulus. At a temperature of fluorination (from 90 to 105 ^o C) and a pressure of about 1.3-1.5 atm, vaporous selenium tetrafluoride evaporates and is collected in a collector equipped with a refrigerator.

Specific process parameters are given in examples 1-6, presented in the table. In the examples, the volume ratio of fluorine and nitrogen in the feed mixture is indicated. The time of the process depends on the mass of the charged source selenium, the feed rate of the gas stream containing fluorine, and the ratio of fluorine and nitrogen in it, as well as the temperature of the process. The process is conducted until the complete conversion of the source selenium. The completion of fluorination is determined by the reaction with potassium iodide of a sample taken through a test valve (not shown in the diagram). At the end of the interaction, free, unreacted fluorine appears in the selected sample, which interacts with potassium iodide, and as a result, free iodine stains the sample:
F ₂ + 2KJ -> J ₂ + 2KF.

 The developed method allows to obtain a product with a yield of at least 75% and a content of selenium tetrafluoride up to 99.9%.

 The method allows you to use the source of selenium in any form, without preliminary purification and special processing.

Claims (3)

1. The method of producing selenium tetrafluoride by fluorination of selenium by elemental fluorine supplied in a mixture with an inert gas at a reduced temperature, characterized in that the fluorination is carried out with a mixture of fluorine and inert gas in a volume ratio of 1: 4-5, at a temperature of from +5 to -10 ^o C, atmospheric pressure with a feed rate of the gaseous mixture from 20 to 80 l / h. 2. The method according to p. 1, characterized in that the obtained selenium tetrafluoride is extracted by evaporation at a temperature of 90-100 ^o C and a pressure of up to 1.5 ATM.  3. The method according to claim 1, characterized in that nitrogen or argon, or a mixture thereof in any ratio, is used as an inert gas.

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