SU475836A1 - Method of preparing hydrogen fluoride - Google Patents

Description

one

The invention relates to the technology of producing hydrogen fluoride from silicon tetrafluoride and can be used to obtain hydrogen fluoride j from waste gases from the production of phosphate processing and to increase the degree of fluoride recovery from fluorspar in the technology of production of anhydrous hydrogen fluoride | Q yes, where part fluorine is lost as silicon tetrafluoride due to the presence of silicon dioxide in the spar.

Known methods of processing tetrafluoride silicon by hydrolide, 15, with water, solutions of alkalis or solutions of various salts. The resulting solutions are processed into commodity products, for example, into concentrated (25-37%) kremneftoris-20 of hydrofluoric acid, its salts, fluorides of alkali metals and ammonium, cryolite. However, these methods do not allow hydrogen fluoride to be produced directly from silicon tetrafluoride. 25

A known method for producing hydrogen fluoride by reacting silicon tetrafluoride with water vapor in the gas phase at 700-900 ° C, according to which the initial silicon tetrafluoride 30

mixed with a small excess of water vapor against stoichiometry and a suspension of silica particles is obtained in the vapor-gas mixture of water and hydrogen fluoride. The reaction products are separated and receive hydrogen fluoride. However, this method does not allow for the complete isolation of hydrogen fluoride from silicon tetrafluoride and requires complex instrumentation associated with the protection of the equipment from corrosion.

In order to increase the yield of hydrogen fluoride to 96-98%. and to simplify the method of obtaining it, hydrolysis is proposed to carry out a 45-65% solution of sulfuric acid with a contact time of the gas phase with a solution of sulfuric acid for 10-20 minutes with a ratio of components .SOji equal to 60-120: 1, followed by separation of the resulting solution fluorosulfonic acid and heating it at 130-150 ° C.

The hydrolysis process is carried out at a temperature not exceeding 20 ° C.

Claims (1)

Hydrogen fluoride condensation is carried out after decomposition of fluorosulfonic acid at minus 15 - minus. An example. 1 m of pellets containing 5 vol.% Of silicon tetrafluoride (50 l under normal conditions) are contacted with 0.8 l of 60% sulfuric acid in a shelf absorber at 18 ° С for 10 min (ratio by volume. HjSOj, "62.5: 1). As a result of hydrolysis, 190 g of silica gel and 1240 g of solution are obtained. The degree of conversion of S i F to H F is co l. 96%. The products of hydrolysis after separation have the following composition,%: Silica gel precipitate. H ,, 5 HF 5.8} H „0 2.5 0.06. The composition of the solution HjSO 57; H, jO 28.5 $ HF 14 H2SiF; 6.05 The solution is heated to and the hydrogen fluoride is distilled off. Upon vapor condensation, liquid hydrogen fluoride of the following composition is obtained,% HF 98, Hj, SOj, 0.6, HjO 1.4, H ,, cG; The yield of fluorine with respect to fluorine in the initial silicon tetrafluoride is 94.2%. The method of obtaining hydrogen fluoride by hydrolysis of silicon tetrafluoride, characterized in that, in order to increase the yield of the product and simplify the process, the hydrolysis is carried out with a 45-65% solution of sulfuric acid at a contact time of the gas phase with a solution of sulfuric acid for 10-20 minutes with the ratio of components S i F. i 60-120 l followed by separating the resulting solution of fluorosulfonic acid and heating it at 130-150 C.