Carbothermal Reduction and Nitridation of Titanium Dioxide in a H₂–N₂ Gas Mixture

Abstract

This article examines carbothermal reduction/nitridation of rutile in a H2–N2 gas mixture in the temperature‐programmed and isothermal experiments in a fixed‐bed reactor. The aim of this investigation was to establish the reduction/nitridation sequence, the reaction degree, and the rate of synthesis of titanium oxycarbonitride under different experimental conditions. The off‐gas composition was monitored using an infrared sensor (CO, CO2, and CH4) and a dew point analyzer (H2O). Extents of reduction and nitridation were determined from the off‐gas composition and LECO analysis. Phase composition of reduced samples was analyzed using powder X‐ray diffraction (XRD). Rate and extent of conversion of titanium oxides to titanium oxycarbonitride increased with increasing temperature. The conversion of titania into titanium oxycarbonitride at 1150°C was completed in 180 min; the conversion time decreased to 30 min at 1300°C. Increasing temperature resulted in formation of titanium oxycarbonitride with higher TiC content. Porosity had a minor effect on the reduction/nitridation of titania with the tendency to increase the reduction rate with increasing porosity. Reduction/nitridation of titania at 1150°C followed the sequence: TiO2→Ti5O9→Ti4O7→Ti3O5→TiOxCyNz.

Phase Development in Carbothermal Reduction and Nitridation of Ilmenite Concentrates

“…Conversion of TiO 2 to titanium oxycarbonitride followed the path of conversion of rutile presented elsewhere [9,10]. Reduction of iron oxide to metallic iron and conversion of titania to titanium oxycabonitride in the H 2 -N 2 gas mixture was faster than in nitrogen.…”

“…Reduction of ilmenites started with conversion of pseudorutile into ilmenite which was further reduced to titania and metallic iron [6]. Further reduction of titania followed the same sequence as pure rutile [9,10].…”

Carbothermal Reduction and Nitridation of Ilmenite Concentrates

“…[8][9][10][11] It was shown that gas atmosphere had a significant effect on the rate of reaction. Conversion of rutile to titanium oxycarbonitride occurred at lower temperature and higher rate in comparison with production of oxycarbide.…”

“…Conversion of rutile to titanium oxycarbonitride occurred at lower temperature and higher rate in comparison with production of oxycarbide. 10,11) This stimulates a further study of synthesis of titanium oxycarbonitride from ilmenites.…”

“…No systematic study of reduction of these oxides in nitrogen-containing gas atmosphere was found in literature, although reduction of rutile in nitrogen was reported. 10,11,[18][19][20][21][22][23][24][25] This paper investigates the carbothermal reduction of ilmenites of different grades and synthetic rutile in the H2-N2 gas mixture and pure nitrogen at different temperatures. Ilmenites of different grades contain different amounts of iron and titanium oxides.…”