Removal of Gaseous Elemental Mercury by Cylindrical Activated Coke Loaded with CoOx‑CeO2 from Simulated Coal Combustion Flue Gas

Co–Ce mixed oxides were loaded on commercial cylindrical activated coke granules (CoCe/AC) by an impregnation method to remove gaseous elemental mercury (Hg0) from simulated coal combustion flue gas at low temperature (110–230 °C). Effects of the Co/Ce molar ratio in Co–Ce mixed oxides, mixed oxides loading value, reaction temperature, and flue gas components (O2, NO, SO2, H2O) on Hg0 removal efficiency were investigated, respectively. Brunauer–Emmett–Teller analysis, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) analysis were employed to analyze the characteristics of the samples. Results showed that up to 92.5% of Hg0 removal efficiency could be obtained over Co4.5Ce6/AC at 170 °C. The remarkably high Hg0 removal ability of Co4.5Ce6/AC mainly depended on the synergetic effect between cobalt oxide and ceria. Additionally, different with the pure N2 condition, the existence of O2 and NO could increase Hg0 removal efficiency. SO2 exhibited an inhibitive effect on Hg0 removal in the absence of O2. H2O­(g) could slightly hinder Hg0 removal. The characterization results exhibited that addition of cobalt oxide led to the excellent dispersity of CeO2 on AC. TGA and XPS analysis results revealed that the captured mercury species on the used Co4.5Ce6/AC mainly existed as HgO, and both lattice oxygen and chemisorption oxygen contributed to Hg0 oxidation. Furthermore, the mechanisms involved in Hg0 removal were identified.