Improve titanate reduction by electro-deoxidation of Ca₃Ti₂O₇ precursor in molten CaCl₂

Abstract

The low O²⁻ diffusion rate in the electro-deoxidation of titanium containing compounds by either the OS process or the FFC process leads to a low reaction speed and a low current efficiency. In this study, Ca₃Ti₂O₇ was used as a precursor to improve the reduction speed of titanium. Because of the greater number of “diffusion channels” created in cathode as Ca²⁺ liberates from Ca₃Ti₂O₇ precursor in the electro-deoxidation process, the O²⁻ diffusion rate was improved significantly by using Ca₃Ti₂O₇ instead of CaTiO₃ as precursor. Parallel constant voltage electrolysis (3.2 V) confirms that Ca₃Ti₂O₇ and CaTiO₃ are reduced simultaneously because of their similar crystal structures. However, the reduction area of Ca₃Ti₂O₇ spreads much faster than that of CaTiO₃, indicating a difference in the O²⁻ diffusion rate. Constant voltage cyclic voltammetry (CV) and theoretical analysis of the crystal structure were also conducted to compare the differences between Ca₃Ti₂O₇ and CaTiO₃. The results indicate that using a precursor with a greater number of soluble cations, titanium reduction speed can be greatly improved in the electro-deoxidation process. Finally, a new electrolysis method for converting and recycling excess CaO from the Ca₃Ti₂O₇ precursor was proposed.

Keywords

calcium titanate / Ca₃Ti₂O₇ / molten calcium chloride / solid-state reaction / reaction speed

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