A novel low temperature catalyst regenerated from deactivated SCR catalyst for Hg0 oxidation

In order to address the problems of treatment of deactivated SCR catalysts and explore the potential of the MnOx-based low temperature catalysts, a procedure was proposed in the present work. In the procedure, the deactivated SCR catalyst served as the catalyst support and MnOx was loaded on it. The supported catalyst was used for Hg0 oxidation in the coal-fired flue gas. Characterization of X-ray fluorescence, N2 adsorption-desorption, X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy and thermogravimetry were conducted to study the properties of the fresh and spent samples and explore the Hg0 oxidation mechanism. The synthesized catalysts showed good performance on Hg0 oxidation in a broad temperature range (150 °C-350 °C) and exhibited superior Hg0 oxidation activity at 250 °C. The results indicated that the unpoisoned V2O5 and MnOx were active for Hg0 oxidation in the presence of HCl and O2, but they played different roles at different temperature. At 150 °C and 250 °C, the MnOx was the active species for the oxidation reaction while the unpoisoned V2O5 inhibited the Hg0 oxidation process indirectly. However, at 350 °C, the V2O5 was mainly involved in Hg0 oxidation. The results also indicated that both Hg0 and HCl were adsorbed by the catalysts at different temperatures, and the adsorbed species reacted to form oxidized mercury. Therefore, the regenerated SCR catalyst might be a promising catalyst for the control of Hg0 emission from the coal-fired flue gas at low temperature.