Catalytic oxidation of sulfur dioxide over a-Fe_2O_3/SiO_2 catalyst promoted with Co and Ce oxides

摘要

Hematite (alpha-Fe2O3) is a promising alternative to the catalysts currently used due to its low cost, fairly good activity and environmentally friendly properties. In this study, alpha-Fe2O3/SiO2 nanocatalysts promoted with cobalt and cerium (Co3O4-CeO2-alpha-Fe2O3/SiO2) were prepared via wet co-impregnation method, and the effects of promoters on catalytic performances for SO2 oxidation at different temperatures, SO2 concentrations, cycle numbers, catalytic stability as well as catalyst charging were investigated. The results indicated that SO2 conversion rose with the increasing of catalyst charging and SO2 concentration. Also, the as-prepared catalyst had the maximum SO2 conversion at the reaction temperature of 500 degrees C, excellent catalytic recyclability and activity stability. Its physicochemical and redox properties were characterized by XRD, BET, SEM, FT-IR and XPS. The results of XRD and FT-IR spectra confirmed that the formation of Ce2FeO4 network in the Co-Ce co-doped catalysts proved the promoting effect of cerium on higher valence state of the active ingredient. The N-2 adsorption/desorption results evidenced that cerium could increase the proportion of mesoporous, and the XPS spectra indicated that cobalt and cerium in the catalysts could increase the available oxygen (O-beta/O-alpha) for the redox reaction. Due to its excellent low onset temperature, fairly good activity and environmentally friendly properties, the as-prepared catalyst of Co3O4-CeO2-alpha-Fe2O3/SiO2 appeared to be more efficient for the SO2 conversion in a large concentration range.