Patent GB-720655-A (GB)
Title: Improvements in the production of alkali metal (including ammonium) titanium double fluorides
IPC: C01G23/00
Filed: 1953-02-02
Abstract: Double fluorides of titanium and an alkali metal (including ammonium) are prepared by reacting a titanium sulphate with an alkaline earth compound, an alkali metal compound and a fluorine-containing salt in slight excess, separating the resulting alkaline earth metal sulphate and recovering the double fluoride.  The reaction may be effected by digestion at temperatures about 100 DEG C or by calcination at 500 to 600 DEG C the reactants being mixed dry or in paste form and the reaction product being leached with water.  The excess fluoride ions may be furnished by adding equimolecular excesses of fluorspar and sulphuric acid.  The titanium sulphate may be the normal soluble sulphate or the insoluble basic sulphate prepared for example by digesting ilmenite in concentrated sulphuric acid, adding iron to reduce the iron content to the soluble ferrous state, digesting close to boiling point thereby precipitating the basic sulphate. The reactant components may be in the form of a water soluble alkali metal salt such as the sulphate, chloride, fluoride or carbonate, and an alkaline earth metal fluoride such as fluorspar. Alternatively sodium, potassium or ammonium fluosilicates may provide the fluoride ions, in which case it is preferred that the fluorinating agent and the titanium sulphate are contacted first, followed by treatment with calcium or barium compounds. Combinations of fluorides and fluorsilicates may also be used.  If the ammonium salt is required only those reactions which take place through the medium of digestion at temperatures below 100 DEG C. are effected since calcination decomposes the ammonium titanium fluoride then formed.  According to Example (1) basic titanium sulphate is dispersed in water and sulphuric acid is added while stirring; to this acid solution is added a mixture of potassium sulphate and potassium fluoride in hot water followed by the addition of a slurry of fluorspar.  The mixture is stirred while being heated to a temperature of about 90 DEG C. and as heating continues a coarse precipitate is formed.  The clear supernatant liquid is decanted, the precipitate is washed, and the combined liquids are evaporated and crystallized; the crystals of potassium titanium fluoride are dried.  If the drying is carried out above 100 DEG C. the fluoride loses one molecule of water.  (3) Dried and powdered normal titanium sulphate is mixed with powdered potassium sulphate and fluorspar together with sufficient water to ensure complete mixing, the resulting cementitious mass is broken up and heated in a furnace to 600 DEG C. for 1 1/2 hours and the resulting sinter is ground and digested in hot water.  The end products, potassium titanium fluoride and calcium sulphate, are separated as before.  (4) Normal titanium sulphate is dissolved in water and finely divided potassium fluosilicate and potassium fluoride are added and the whole digested at 90 DEG C.; a slurry of calcium carbonate is then added and the mixture digested at 90 DEG C. for a further 1 1/2 hours and after digestion the liquid is allowed to stand when a precipitate settles out; after settling, decantation and washing the purified wash liquors and original filtrates are evaporated in order to crystallize the potassium titanium fluoride. (5) Titanium sulphates are mixed with potassium fluosilicate, potassium fluoride and calcium carbonate and the mixed powders are calcined at 600 to 700 DEG C. for 90 minutes, and the resulting sinter is ground and digested in water.  A precipitate of calcium sulphate and silica is separated in the usual manner and the combined filtrates are evaporated as before to crystallize out the double fluoride.