Thermodynamic Assessment of Thermochemical Extraction Routes for Titanium Group Metals
DOI:
https://doi.org/10.30544/MMD88Abstract
The thermochemical extraction of titanium group metals (Ti, Zr, Hf) is limited by the extreme thermodynamic stability of their oxides. This study presents a thermodynamic assessment of carbothermic, metallothermic, and halide-based processes using HSC Chemistry 10 software. Ellingham and predominance area diagrams (Ti-C-O, Zr-C-O, Hf-C-O) show that direct carbothermic reduction is inhibited by stable carbide formation, requiring temperatures above 1700 °C for Ti and above 2000 °C for Zr and Hf under high vacuum. Calcium is the only metal considered here that is thermodynamically capable of direct oxide reduction; however, kinetic barriers and product-layer formation limit its practical use. In contrast, carbochlorination lowers the thermodynamic barrier by converting stable oxides into volatile chlorides, which can subsequently be reduced by Mg or Na. This work provides a unified thermodynamic comparison that explains the industrial preference for the Kroll and Hunter processes and identifies favorable operating ranges for titanium group metal extraction.
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