Carbothermal reduction of titania in different gas atmospheres

The synthesis of titanium oxycarbide by carbothermal reduction of titania was studied in hydrogen, argon, and helium in isothermal and temperature programmed reduction experiments in a tube reactor with continuously flowing gas. In the temperature range of 1000 C to 1500 C, the reduction rate increased with increasing temperature. Formation of titaniumoxycarbide started at 1200 C in all three gases. The reduction was the fastest in hydrogen. Formation of titanium oxycarbide in hydrogen was close to completion in 120 minutes at 1300 C, 60 minutes at 1400 C, and less than 30 minutes at 1500 C. The reduction in argon and helium had similar rates and reached 90 to 95 pct after a 300-minute reduction at 1400 C to 1500 C. Faster carbothermal reduction of titania in hydrogen than in argon and helium was attributed to involvement of hydrogen in the reaction. Hydrogen reduced titania to titanium suboxides and reacted with carbon, forming methane, which reduced titaniumsuboxides to titaniumoxycarbide. Titanium oxycarbide synthesized in hydrogen for 180 minutes at 1300 C contained 13 mol pct TiO. At 1500 C, oxygen concentration decreased to a degree corresponding to 1.4 mol pct TiO. In the titanium oxycarbide produced by a 300-minute reduction at 1600 C, the TiO content was 0.6 mol pct

Carbothermal reduction of a primary ilmenite concentrate in different gas atmospheres

The carbothermal reduction of a primary ilmenite concentrate was studied in hydrogen, argon, and helium. Ilmenite and graphite were uniformly mixed and pressed into pellets. Reduction was studied in isothermal and temperature-programmed reduction experiments in a tube reactor with continuously flowing gas. CO, CO2, and CH4 contents in the off-gas were measured online using infrared sensors. The phase composition of reduced samples was characterized by X-ray diffraction (XRD). Oxygen and carbon contents in reduced samples were determined by LECO analyzers (LECO Corporation, St. Joseph, MI). The main phases in the ilmenite concentrate were ilmenite and pseudorutile. The reaction started with the reduction of pseudorutile to ilmenite and titania, followed by the reduction of ilmenite to metallic iron and titania. Titania was reduced to Ti3O5 and even more to Ti2O3, which was converted to titanium oxycarbide. Reduction was faster in hydrogen than in helium and argon, which was attributed to involvement of hydrogen in the reduction reactions. The formation of titanium oxycarbide in hydrogen started at 1000 oC and was completed in 300 minutes at 1200 oC, and 30 minutes at 1500 oC. The formation of titanium oxycarbide in argon and helium started at 1200 oC and was not completed after 300 minutes at 1300 oC