International Journal of Energy Research, Vol.43, No.9, 4253-4263, 2019
Thermodynamic and experimental study on the reduction and carbonization of TiO2 through gas-solid reaction
Titanium oxycarbide (TiCxOy) has attracted much attention recently as a soluble anode used in the USTB (University of Science and Technology Beijing) or MER (Materials and Electrochemical Research) molten-salt electrolysis process to produce sponge titanium. The present study aimed to investigate the production of titanium oxycarbide from TiO2 by using CH4-H-2 gas mixture, and both thermodynamic and experimental studies were carried out. First, thermodynamic analysis in the TiO2-CH4-H-2 system was performed by the method of equilibrium calculation. The analysis indicated that TiO2 could be ultimately reduced and carbonized to TiCxOy by CH4 and H-2 gas at temperature above 1200 degrees C, and the increase of temperature was theoretically favorable to the final carbonization extent of TiCxOy. The experimental process involved the reduction of both pure TiO2 powder and TiO2 with additives using methane-hydrogen gas mixture in the temperature range from 1200 degrees C to 1450 degrees C. Experimental results showed that pure TiO2 could be reduced completely to TiCxOy at 1350 degrees C and above after 8-hour reduction. It was also found that the reduction extent of TiO2 increased with increasing time and temperature when at a low temperature range; however, a much higher temperature (above 1350 degrees C) would hinder further carbonization for the production of deposited carbon. Addition of iron oxides to TiO2 powders strongly facilitated the reduction reaction, even prompting the reaction of TiO2 to TiCxOy completely at only 1200 degrees C after 8-hour reduction. The gas-solid reaction provided a simple and quick way to produce titanium oxycarbide.