CeO2-Decorated α-MnO2 Nanotubes: A Highly Efficient and Regenerable Sorbent for Elemental Mercury Removal from Natural Gas

CeO2 nanoparticle-decorated alpha-MnO2 nanotubes (NTs) were prepared and tested for elemental mercury (Hg-0) vapor removal in simulated natural gas mixtures at ambient conditions. The composition which had the largest surface area and a relative Ce/Mn atomic weight ratio of around 35% exhibited a maximum Hg-0 uptake capacity exceeding 20 mg.g(-1) (2 wt %), as determined from measurements of mercury breakthrough which corresponded to 99.5% Hg-0 removal efficiency over 96 h of exposure. This represents a significant improvement in the activity of pure metal oxides. Most importantly, the composite nanosorbent was repeatedly regenerated at 350 degrees C and retained the 0.5% Hg-0 breakthrough threshold. It was projected to be able to sustain 20 regeneration cycles, with the presence of acid gases, CO2, and H2S, not affecting its performance. This result is particularly important, considering that pure CeO2 manifests rather poor activity for Hg-0 removal at ambient conditions, and hence, a synergistic effect in the composite nanomaterial was observed. This possibly results from the addition of facile oxygen vacancy formation at alpha-MnO2 NTs and the increased amount of surface-adsorbed oxygen species.