Kinetics of oxychlorination of chromium (III) oxide
Abstract
The kinetics of oxychlorination of pure Cr2O3 with Cl2+O2 gas mixtures is studied by ThermoGravimetric Analysis (TGA) in non and isothermal conditions up to 1000°C. The reaction of Cr2O3 with Cl2+O2 chlorination gas mixtures starts at about 550°C and the reaction product is CrO2Cl2.
The oxychlorination rate of Cr2O3 is almost proportional to the chlorine partial pressure and to the fourth root of the oxygen partial pressure in the chlorinating gas mixtures. At 800°C, the maximum chlorination rate is obtained using a gas mixture having a Cl2/O2 ratio equal to 4. The apparent activation energy of the oxychlorination reaction of Cr2O3 is 87 and 46 kJ/mol at temperatures lower and higher than 650°C, respectively.
By varying the chlorine and the oxygen partial pressures of the oxychlorinating gas mixtures at temperatures higher than 550°C, it is possible to extract selectively the chromium chlorinated compounds from the chromium bearing materials.