In situ synchrotron diffraction of the electrochemical reduction pathway of TiO2

Despite over ten years of work into the low-cost electrowinning of Ti direct from the oxide, the reduction sequence of TiO2 pellets in molten CaCl2 has been the subject of debate, particularly as the reduction pathway has been inferred from ex situ studies. Here, for the first time white beam synchrotron X-ray diffraction is used to characterize the phases that form in situ during reduction and with ∼100 μm resolution. It is found that TiO2 becomes sub-stoichiometric very early in reduction, facilitating the ionic conduction of O ions, that CaTiO3 persists to nearly the end of the process and that, finally, CaO forms just before completion of the process. The method is quite generally applicable to the in situ study of industrial chemical processes. Implications for the industrial scale-up of this method for the low-cost production of Ti are drawn.