INFLUENCE OF CHROMIUM ON THE REDUCTION BEHAVIOR OF FERRIC OXIDE BY USING CARBON MONOXIDE: TEMPERATURE PROGRAMMED REDUCTION AND KINETIC STUDIES

Abstract

© 2016, Malaysian Society of Analytical Sciences. All rights reserved.This study was undertaken to investigate the effect of chromium on the reduction behaviour of ferric oxide with carbon monoxide (10 %, v/v) in nitrogen as a reductant. Ferric oxide was impregnated with 3 % chromium to produce chromium-doped ferric oxide (Cr-Fe2O3). The reduction behaviour and the kinetic studies of Cr-Fe2O3 and Fe2O3 have been studied by temperature programmed reduction (TPR) and the phases formed of partially and completely reduced samples were characterized by X-ray diffraction spectroscopy (XRD). Meanwhile, the activation energy values were calculated from the Arrhenius equation using Wimmer’s method. TPR results indicate that the reduction of Cr-Fe2O3 proceeded in two reduction steps (Fe2O3 → Fe3O4 → Fe), while, Fe2O3 proceeded in three reduction steps (Fe2O3 → Fe3O4 → FeO → Fe) with doped ferric oxide showed a large shifted towards lower temperature. The complete reduction of ferric oxide to metallic Fe occur at 700 °C compared to the undoped ferric oxide (900°C). The XRD pattern showed that the diffraction peaks of Cr-Fe2O3 are more intense compare to Fe2O33, indicating that the improvement on the crystallinity of the characteristic peaks of Fe2O3 with no additional peak observed meaning that the chromium particles loaded on the ferric oxide were well dispersed. Furthermore, additional of 3 % chromium on ferric oxide gives larger surface area and decrease in the activation energy up to 12.39 % regarding to transition phases of Fe2O3 → Fe3O4 during the reduction process may also led to the increase in the rates of ferric oxide reduction.