Lingkui Zhao

A review on oxidation of elemental mercury from coal-fired flue gas with selective catalytic reduction catalysts

Catalytic technologies present a more environmentally and financially sound option in the removal of elemental mercury (Hg0) from coal-fired flue gas. However, developing novel and efficient catalysts for Hg0 oxidation is still a challenge. This paper reviews the catalytic oxidation of Hg0 over a new kind of catalysts which were developed from selective catalytic reduction (SCR) catalysts of NOx. In this review, both noble metal catalysts and non-noble metal catalysts for Hg0 oxidation were summarized. An overview of mercury emissions including transformation and speciation of mercury in coal-fired flue gas was also presented. The possible mechanisms and kinetics of mercury oxidation, space velocity and the effects of flue gas components on activity and stability of the catalysts were examined. We expect that this work will serve as a theoretical underpinning for the development of Hg0 oxidation technology in flue gas.

Simultaneous removal of elemental mercury and NO from simulated flue gas using a CeO2 modified V2O5–WO3/TiO2 catalyst

To provide insight into optimizing flue gas treatment, simultaneous removal of elemental mercury (Hg0) and NO using a CeO2 modified V2O5–WO3/TiO2 catalyst was investigated. The results show that a novel V2O5–WO3/TiO2–CeO2 catalyst exhibits excellent Hg0 oxidation efficiency (88%) and NO conversion efficiency (89%) at 250 °C. Furthermore, CeO2 modified V2O5–WO3/TiO2 not only exhibits enhanced catalytic activity but also good resistance in SO2 and H2O. These catalysts were also characterized using BET, SEM, XRD, XPS, and H2-TPR. We found lower crystallinity, more reduced species and better texture properties to be presented, which were all ascribed to CeO2 doping. Also, the redox cycle (V4+ + Ce4+ ↔ V5+ + Ce3+) plays a key role in promoting Hg0 oxidation and NO conversion. In tune with the experimental results, a mechanism for the simultaneous removal of Hg0 and NO was proposed for the V2O5–WO3/TiO2–CeO2 catalysts.