Catalytic oxidation removal of gaseous elemental mercury in flue gas over niobium‐loaded catalyst

Nb‐Co‐Ce/Al 2 O 3 catalysts prepared by impregnation, sol‐gel method, and co‐precipitation were examined for elemental mercury (Hg 0 ) oxidation in a simulated coal combustion flue gas. The catalysts were characterized by SEM‐EDS, BET, XRD, FTIR, and XPS techniques. The performances of different niobium‐loaded catalysts on Hg 0 oxidation efficiency with regard to preparation method, assistant, reaction temperature, and typical individual flue gas were investigated. The results showed that the Hg 0 oxidation efficiency performed at the highest value for niobium‐loaded catalysts at 523 K. SO 2 was observed to have a negative effect on Hg 0 oxidation. The niobium‐loaded catalysts prepared by the sol‐gel method and co‐precipitation exhibited higher Hg 0 oxidation efficiency than that prepared by impregnation, due to higher specific surface area and more exposure of active sites. However, it also results in these catalysts being affected by SO 2 more easily. An enhancing effect of O 2 was observed and an addition of HCl would promote the Hg 0 oxidation further. Results also indicated that synergistic effects between NbO x , CoO x , and CeO x could promote the sustainable capacity of Hg 0 oxidation for Nb‐Co‐Ce/Al 2 O 3 catalysts. Hg 0 oxidation over Nb‐Co‐Ce/Al 2 O 3 catalysts is thought to follow a Mars‐Maessen mechanism in which lattice oxygen derived from NbO x would react with absorbed Hg 0 .