Kinetics of chlorination and oxychlorination of chromium (III) oxide |
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Authors: | I. Gaballah N. Kanari S. Ivanaj |
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Affiliation: | (1) Present address: the Laboratoire Environnement et Minéralurgie ‘LEM’, Ecole National Supérieure de Géologie, rue du Doyen M. Roubalt, BP 40, 54501 Vandoeuvre Cedex, France;(2) the Centre National de la Recherche Scientifique, Mineral Processing and Environmental Engineering Team, Ecole National Supérieure de Géologie, rue du Doyen M. Roubalt, BP 40, 54501 Vandoeuvre Cedex, France;(3) Present address: Envo Tech, 54000 Nancy, France |
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Abstract: | Thermogravimetric analysis (TGA) is used to study the kinetics of chlorination of Cr2O3 with Cl2+N2 and Cl2+O2 gas mixtures in the temperature range of 550 °C to 1000 °C. The reactivity of Cr2O3 toward the chlorine-oxygen gas mixture is higher than that toward the chlorine-nitrogen one. Chlorination of Cr2O3 proceeds with an apparent activation energy of about 86 kJ/mol between 550 °C and 1000 °C. The apparent reaction order with respect to chlorine is about 1.23 at 800 °C. At temperatures lower than 650 °C, the shrinking sphere model is the most appropriate for describing the reaction kinetics. Oxychlorination of Cr2O3 is characterized by an apparent activation energy of about 87 and 46 kJ/mol for temperatures lower than 650 °C and higher than 700 °C, respectively. At 800 °C and using a Cl2+O2 gas mixture, the maximum reaction rate is obtained when the Cl2/O2 molar ratio is equal to 4, confirming the formation of chromium oxychloride. At this temperature, the reaction orders with respect to chlorine, oxygen, and Cl2+O2 are about 1.08, 0.23, and 1.29, respectively. Mathematical fitting of the experimental data is discussed. |
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