Highly Dispersed Mn–Ce Binary Metal Oxides Supported on Carbon Nanofibers for Hg0 Removal from Coal-Fired Flue Gas

Abstract

Highly dispersed Mn–Ce binary metal oxides supported on carbon nanofibers (MnOx–CeO2/CNFs(OX)) were prepared for Hg0 removal from coal-fired flue gas. The loading value of the well-dispersed MnOx–CeO2 was much higher than those of many other reported supports, indicating that more active sites were loaded on the carbon nanofibers. In the present study, 30 wt % metal oxides (15 wt % MnOx and 15 wt % CeO2) were successfully deposited on the carbon nanofibers, and the sorbent yielded the highest Hg0 removal efficiency (>90%) within 120–220 °C under a N2/O2 atmosphere. An increase in the amount of highly dispersed metal oxides provided abundant active species for efficient Hg0 removal, such as active oxygen species and Mn4+ cations. Meanwhile, the carbon nanofiber framework provides the pathway for charge transfer during the heterogeneous Hg0 capture reaction processes. Under a N2+6%O2 atmosphere, a majority of Hg0 was removed via chemisorption reactions. The effects of flue gas composition were also investigated. O2 replenished the active oxygen species on the surface and thus greatly promoted the Hg0 removal efficiency. SO2 had an inhibitory effect on Hg0 removal, but NO facilitated Hg0 capture performance. Overall, carbon nanofibers seems to be a good candidate for the support and MnOx–CeO2/CNFs(OX) may be promising for Hg0 removal from coal-fired flue gas.