Synergetic removal of elemental mercury and NO over TiCe _0.25 Sn _0.25 O _x catalysts from flue gas: Performance and mechanism study

A novel TiCe _0.25 Sn _0.25 O _x catalyst was designed and prepared by a sol-gel method for synergetic removal of NO and elemental mercury (Hg ⁰ ) from flue gas. The as-designed TiCe _0.25 Sn _0.25 O _x catalyst achieved a synergetic removal efficiency of NO (NH ₃ -SCR) and Hg ⁰ (Hg ⁰ oxidation) of 95%, 85% and 70%, 65% (after 300 ppm SO ₂ and 6 vol% H ₂ O were injected) at 200 °C under simulated flue gases conditions, respectively. Moreover, the mercury, which gathered on the surface of TiCe _0.25 Sn _0.25 O _x after adsorption and oxidation, could be released and collected by the thermal decomposition method, avoiding the secondary pollution by mercury. The mechanism underlying the synergetic removal of NO and Hg ⁰ was also investigated using various characterization techniques. The synergistic catalysis between redox and solid acid contributed to the synergetic removal of NO and Hg ⁰ over TiCe _0.25 Sn _0.25 O _x . The results of XRD and XPS revealed that the lattice oxygen was a key factor for Hg ⁰ oxidation reaction. The results of N ₂ -physisorption, NH ₃ -TPD, H ₂ -TPR and Py-IR illustrated that TiCe _0.25 Sn _0.25 O _x possessed the mesopores structure, suitable particle sizes, the excellent redox and weak acid (Lewis sites) properties, contributing to its high NO and Hg ⁰ removal efficiency. Furthermore, the removal of NO and Hg ⁰ showed a synergetic effect. The analysis of Hg-TPD and (NO + O ₂ )-TPD had confirmed that the mid-product NO ₂ of NH ₃ -SCR reaction was favorable for Hg ⁰ oxidation. In summary, the TiCe _0.25 Sn _0.25 O _x possesses not only good synergetic removal performance for NO and Hg ⁰ but also satisfactory anti-sulfur performance, which is a promising candidate for the effective and economical removal of NO and Hg ⁰ in the cement and steel industries.