Investigation of the Carbon-Free Chlorination Behavior and Kinetics of Titanium Compounds

Titanium tetrachloride (TiCl4), as a key intermediate linking the upstream and downstream sectors of the titanium industry, is not only the main raw material for sponge titanium production but also the core precursor for the chloride-route titanium dioxide process. Owing to the extremely limited reserves of natural rutile, the current mainstream method for TiCl4 production is the carbothermic chlorination of titanium-rich materials. However, carbothermic chlorination suffers from several challenges, including operational instability, carbon-emission burden, and difficulty in precisely controlling the carbon dosage. Therefore, this study systematically investigated the carbon-free chlorination behavior of titanium-related compounds. The results show that the carbon-free chlorination reactivity follows the order of TiC > Ti (C, N) > TiN > TiO > Ti2O3 > Ti3O5 > TiO2. With increasing oxygen content, the chlorination difficulty gradually increases. The actual mass loss of the titanium compounds is close to the theoretical mass loss. In the absence of carbon, TiO2 cannot undergo spontaneous chlorination within the temperature range of 100–750 °C. The chlorination reactions of Ti3O5, Ti2O3, and TiO are incomplete and ultimately terminate with the formation of TiO2, whereas TiC, Ti (C, N), and TiN undergo relatively complete chlorination. The chlorination processes of TiC, Ti (C, N), TiN, and TiO are all controlled by chemical reaction, with the kinetic model function expressed as G(a)=(1-a)-1-1. Their apparent activation energies are 76.71, 82.37, 105.70, and 135.91 kJ/mol, respectively. In contrast, the chlorination processes of Ti2O3 and Ti3O5 are governed by three-dimensional diffusion, with the kinetic model function expressed as G(a)=[1-(1-α)1/3]2. Their apparent activation energies are 15.04 and 19.77 kJ/mol, respectively.