GB729845A - Improved preparation of double alkali metal-titanium fluorides - Google Patents

Abstract

A double fluoride of an alkali metal (as herein defined) and titanium is produced from a ferric iron-containing titanium ore by reducing the ferric iron content to the ferrous state, forming a reaction mixture of the thus reduced ore with an alkali metal fluoride, or with an alkali metal fluosilicate together with 2-4 molar per cent. of alkali metal fluoride, reacting the mixture in an aqueous medium in the presence of sulphuric acid, and recovering the resultant double fluoride. The term "alkali metal" refers to these metals and ammonium except where otherwise noted. The reduction of the iron in the ore (suitably concen trated beach sand is preferred) may be performed at 1,000-1,200 DEG C., using, e.g. hydrogen or ammonia but preferably carbon monoxide or carbon, the latter, e.g. as petroleum coke being usually used in quantities not exceeding 10 parts by weight per 100 parts of ilmenite. Reoxidation is avoided by quenching in water or discharging into a container from which air is excluded. It is desirable to add to the reaction mixture a small quantity, e.g. 2-3 molar per cent. in relation to the H2SO4, of chloride ion, as catalyst an this may be supplied as alkali metal or hydrogen chloride. When an alkali metal fluoride is employed, the reagents are used in proportions slightly (e.g. 2-4 molar per cent.) in excess of that required for equations such as FeO.TiO2+6NaF+2H2O--> Na2TiF6+2Na2SO4+Fe(OH)2+H2O in which a part of the sodium fluoride may be replaced by that of another alkali metal, or if desired by an alkaline earth metal. The above-mentioned excess may alternatively be supplied by hydrogen fluoride. In general, when using fluorides the reduced ilmenite is finely powdered and slurried with water: the finely powdered fluorides are added, with the chloride catalyst. 50 per cent. sulphuric acid is then added dropwise with stirring, the temperature being kept below 100 DEG C. The mixture is diluted with water, digested filtered and the filtrate crystallized in a manner depending upon the solubility of the components present; ferrous hydroxide may be recovered from the residue. When using alkali metal silicofluorides, as indicated by the reaction FeO.TiO2+ K2SiF6+H2SO4-->K2TiF6+ FeSO4+SiO2H2O, only one-third of the normal amount of sulphuric acid need be used. This reaction may be carried out by similar processes to that described above, or the solid reactants (which in this method need not include chlorides and should not include ammonium salts) are mixed and calcined at 600-800 DEG C. in a reducing atmosphere for a short period of time and then comminuted and reacted with sulphuric acid as before. Examples are given.