GB794518A - Metallic halides - Google Patents

Abstract

Halides of tantalum, lower valent halides of titanium, niobium and vanadium and tetrahalides of zirconium and hafnium are prepared by reacting at 700-1100 DEG C. in a bath of fused alkali and/or alkaline earth metal halide, a carbide or a carbide/monoxide solid solution of the desired refractory metal and fluorine, bromine, carbonyl bromide or iodine. The nature of the product with metals having more than one halide is determined by the temperature: with titanium, 700-900 DEG C. favours trivalent halides, 900-1100 DEG C. dihalides; with niobium, 700-900 DEG C. favours tetrahalides, 900-1100 DEG C. dihalides; with vanadium, 750-850 DEG C. favours trihalides, 850-1000 DEG C. dihalides; with tantalum, pentahalides are formed throughout the temperature range. These halides will generally be present in the bath combined as double or complex halides, although if an alkaline earth metal halide other than fluoride is present together with a double fluoride there is a tendency to evolve the halide (other than fluoride) of the refractory metal. The melt may be fractionally distilled to recover the various constituents or (for trihalides) cooled and then fractionally crystallized from an aqueous acid solution; dihalides are preferably used in the form of the fused salt solution. Specified fused bath components are the fluorides, chlorides, bromides and iodides of lithium, sodium, potassium, calcium, barium, strontium and magnesium and in addition refractory metal halides, e.g. alkali metal double halides, may be present before passage of the halogen into the bath. The halide present initially in the fused bath is preferably the same as that of the halide being prepared. The reaction should take place in an oxygen- and moisture-free atmosphere, e.g. of argon; the reaction vessel-e.g. of graphite-may be externally heated or the reactants may be heated by electrical elements, to a temperature 50 DEG C., preferably 100 DEG C., above the melting point of the salts. The carbide used in the reaction may be of ordinary dense form but is preferably of the less dense form described in Specification 788,296, and may be in large or small lumps or as powder. Adequate mixing is provided by bubbling in the halogenating gas. The reacted mass may be filtered under an inert atmosphere through porous graphite to remove carbon or the latter may be skimmed off. In examples: (1) 40 per cent KTiF4 is produced using titanium carbide and fluorine at 875 DEG C., and (2) 26 per cent KTiF3 is produced under the same conditions.