Heterogeneous reaction kinetics of mercury oxidation by HCl over Fe2O3 surface

Fe2O3 is one of the catalytically active compositions present in fly ash for mercury oxidation. Fe2O3 sample was prepared by a precipitation method. The textural property and surface chemical state of Fe2O3 sample were characterized by Brunauer-Emmett-Teller (BET) surface area and X-ray photoelectron spectroscopy (XPS), respectively. A series of experiments were conducted in a fixed-bed reactor to investigate the heterogeneous mercury oxidation by HCl on Fe2O3 surface. Fe2O3 can obtain a maximum mercury oxidation efficiency of 89.5% at 100 °C. Heterogeneous Hg0 oxidation by HCl over Fe2O3 surface occurs through the gas-solid reaction between gas-phase Hg0 and active surface chlorine species generated from the dissociation of HCl. Based on the experimental results, a detailed eight-step heterogeneous reaction kinetic model of mercury oxidation over Fe2O3 was proposed to predict mercury oxidation in the presence of Fe2O3 and HCl. This heterogeneous model was validated by comparison to different experimental data. The results of kinetic calculations show that model prediction is in good agreement with experimental results obtained by two research groups. Mercury oxidation process over Fe2O3 surface can be described using this heterogeneous kinetic model.