Abstract
A series of MnOx/CeO2 (Mn/Ce), MnOx/ZrO2 (Mn/Zr), and MnOx/Ce0.75Zr0.25O2 (Mn/CZ) catalysts prepared by an impregnation method were tested for their ability to catalyse the oxidation of Hg-0 at relatively low temperature (423 K). Various characterization techniques, namely, Brunauer-Emmett-Teller (BET) surface area analysis, X-ray diffraction (XRD), Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), and H-2-temperature programmed reduction (H-2-TPR) were employed to understand the structural, surface, and redox properties of the prepared catalysts. Specific aspects of the catalysis of Hg-0 oxidation that were investigated included the influence of MnOx loading (5, 15, and 25%) and the influence of HCl and O-2. Among the catalysts tested, the 15Mn/CZ catalyst achieved the best Hg-0 oxidation performance (similar to 83% conversion of Hg-0 to Hg2+) in the presence of HCl and O-2. The higher activity of the 15Mn/CZ catalyst was most likely due to the presence of more oxygen vacancies, enhanced Mn4+/Mn4+ + Mn3+ + Mn2+ ratio and more surface adsorbed oxygen, which were proved by XRD, BET, Raman, and XPS. H-2-TPR results also show that the strong interaction between the Ce0.75Zr0.25O2 support and MnOx improved the redox properties significantly as compared to pure CeO2 and ZrO2 supported MnOx catalysts.