Structural Characterizations and Phase Transition on the Reducibility of Ilmenite Ore with Different Carbon Reductants by Carbothermal Reduction Under Hydrogen Atmosphere

This research focused on investigating the properties and phase transition of ilmenite ore with various carbon reductants by performing a carbothermal reduction, followed by a hydrogen reduction (Ar:H2) at 900–1000 °C to extract rutile from the ore. To comprehend the impact of the carbon structure and characteristics on the reduction performance and incorporate a thermodynamic assessment during reduction reactions, two distinct carbon reductants: graphite (GI) and renewable carbon from palm char (PI), were selected. The phase transitions and reduced samples were examined using both qualitative and quantitative X-ray diffraction. The results revealed that ilmenite ore transformed into pseudobrookite ferrous (FeTi2O5), titanium trioxide (Ti3O5), rutile (TiO2), and iron (Fe) after carbothermal reduction at 1550 °C where brookite (TiO2) and anatase (TiO2) peaks were diminished. As the temperature rose during the secondary reduction by hydrogen, the reduction reaction sequenced as follows: FeTi2O5 → Ti3O5 → Ti2O3 → TiO2 and Fe. Due to the carbon structure and superior characteristics, the reduced PI demonstrated a greater degree of TiO2 reduction (81.8%) than the reduced GI (74.8%) at the highest reduction temperature of 1000 °C. In the early and middle stages of the reaction at high temperatures, the carbothermal reduction of ilmenite ore with solid carbon and CO participated and produced rutile, iron, and Ti3O5, whereas, in the latter stages, rutile, iron, and Ti2O3 are mostly formed when reduced by hydrogen. In conclusion, employing palm char with hydrogen atmosphere to extract pure rutile from ilmenite ore might be accomplished by using these proposed methods. Graphical Abstract: [Figure not available: see fulltext.]