Separation of Titanium Tetrafluoride from a Gaseous Mixture with Silicon Tetrafluoride Using Lithium Fluoride

Abstract

A new process for producing pigment grade TiO 2 from low grade ores such as ilmenite is being developed at the University of Melbourne. In this process, the titanium content of the ore is extracted by reaction with SiF 4 at about 800°C to produce a gaseous intermediate product TiF 4 . The TiF 4 leaves the reactor with SiO 2 fume and unreacted SiF 4 gas and needs to be isolated. One method of separating TiF 4 from the gas mixture is by reaction with LiF at 350-450°C to form a stable solid, Li 2 TiF 6 . Experimental work has been performed to assess the feasibility of this separation method. It is shown that, under carefully chosen conditions, the LiF reacts selectively with TiF 4 but not with SiF 4 . The reaction product, Li 2 TiF 6 , can be thermally decomposed to regenerate the LiF and TiF 4 . The pure TiF 4 generated can be further treated to produce pigment grade TiO 2 , and the LiF can be recycled. Provided SiO 2 is separated, the SiF 4 gas can be recycled and returned to the fluoridation reactor.