Chlorination of Titanium Oxycarbide Produced by Carbothermal Reduction of Rutile ANDREW ADIPURI, GUANGQING ZHANG, and OLEG OSTROVSKI Titanium oxycarbide was produced by carbothermal reduction of rutile. Mixtures of titania and graphite with different carbon to titania molar ratio were pressed into pellets and heated under argon atmosphere at 1450 °C. Titanium oxycarbide was chlorinated in a horizontal tube fur- nace. Effects of furnace temperature, chlorine partial pressure, gas flow rate, and particle size on the rate and extent of chlorination were examined. The chlorination was ignited at 150 °C to 200 °C. Chlorine partial pressure and gas flow rate strongly affected the chlorination rate, while the effect of particle size was insignificant. Best chlorination results were obtained for titanium oxycarbide produced with carbon to titania molar ratio 2.5, and chlorination was close to 100 pct in 30 minutes. DOI: 10.1007/s11663-007-9117-3 Ó The Minerals, Metals & Materials Society and ASM International 2008 I. INTRODUCTION TITANIUM minerals are primarily processed into titanium dioxide white pigment, which is a valuable commodity used in paint, paper, and plastic industries because of its exceptional scattering properties, chemical stability, and lack of toxicity. [1] Usage of metallic titanium is limited because of high production cost, although titanium has superior properties such as high strength, low density, excellent corrosion resistance, extreme mechanical and thermal loading capacity, etc. Processing of titanium minerals to TiO 2 pigment or titanium metal involves chlorination process in which titanium dioxide is conventionally converted to titanium tetrachloride. Chlorination of TiO 2 occurs at high temperatures in the range 800 °C to 1100 °C, and it is a stable oxide. At these temperatures impurities are also chlorinated, which requires high-quality materials such as rutile, synthetic rutile, or TiO 2 -rich slag. Nieberlein [2] investigated the process of low-temper- ature chlorination of titanium carbide and suboxides produced by carbothermal reduction at 1500 °C. He found that a temperature of 250 °C was sufficient to ignite the reaction. The chlorination temperature was 400 °C to 500 °C. Meerson et al. [3] proposed a technol- ogy combining carburization and low-temperature chlo- rination for the production of titanium tetrachloride from titanium-iron concentrates and titanium slags. They found that carbothermal reduction at 1350 °C to 1450 °C and 150 to 200 mm Hg pressure for 30 to 120 minutes converted titania to titanium oxycarbide with 50 to 60 pct TiC and 50 to 40 pct TiO. The chlorination rate of this material at 600 °C to 700 °C was greater than that of titanium slag at 700 °C to 900 °C, but no detailed kinetic examination was reported. Zelikman and Leonova [4] investigated the chlorina- tion of titanium carbide in the form of compact briquettes at 600 °C to 900 °C. The reaction rate was controlled by the chlorine diffusion in the layer of carbon residue formed in the process of titanium chlorination. An original technology was developed for processing of calcium-containing titanium ores and slags. [5] The materials reacted with solid carbon at high temperature between the melting points of CaC 2 and TiC, and formed TiC distributed in the matrix of CaC 2 . The CaC 2 was removed by reaction with water and TiC was chlorinated at a temperature above the boiling point of TiCl 4 and below the chlorination temperature for impurities, so high-purity TiCl 4 was obtained without distillation. This technology was also applied to titanif- erous ores. [6] Brandstatter [7] developed a technology in which titanium in ilmenite ore and slag was carburized at 1700 °C to 2000 °C. The process described by Nanjo et al. [8] is similar to that suggested by Brandstatter, but used anatase as a raw material and lower carburization temperature (1200 °C to 1300 °C). Iron or iron carbide formed during the carbothermal reduction were sepa- rated from titanium carbide by crushing and magnetic separation. [7,8] The chlorination temperatures were approximately 300 °C [8] and 200 °C to 500 °C. [7] In the low-temperature chlorination, impurities do not chlorinate or chlorinate very slowly. [9–11] This permits selective chlorination of titanium carbide, decreases the chlorine consumption and waste genera- tion, and makes the entire technology of ilmenite processing more efficient and environmentally friendly. No detailed investigation of kinetics and mechanisms of chlorination of titanium oxycarbide under different operational conditions was reported in literature. This article presents results of a systematic experimental study of chlorination of titanium oxycarbide obtained ANDREW ADIPURI, PhD Student, GUANGQING ZHANG, Lecturer, and OLEG OSTROVSKI, Professor, are with the School of Materials Science and Engineering, University of New South Wales, UNSW Sydney, NSW 2052, Australia. Contact e-mail: G.Zhang@ unsw.edu.au Manuscript submitted December 10, 2006. Article published online January 8, 2008. METALLURGICAL AND MATERIALS TRANSACTIONS B VOLUME 39B, FEBRUARY 2008—23