Simultaneous removal of HCHO and elemental mercury from flue gas over Co-Ce oxides supported on activated coke impregnated by sulfuric acid

Abstract

To obtain a suitable catalyst for simultaneous removal of mercury and HCHO from waste flue gas, we prepared and investigated CoOx-CeO2 loaded on commercial activated coke granules treated with sulfate acid by impregnation method to remove the two toxic gases. The results revealed that the removal efficiencies of Hg0 and HCHO over Co8Ce3/ACs catalyst were 69.43% and 71.07% respectively in the presence of N2 and 6% O2 at 190 °C. And the presence of Hg0 had little impact on HCHO removal, but formaldehyde had a certain effect on Hg0 removal. In addition, the effects of individual flue gas component including O2, NO, SO2 and H2O on Hg0 and HCHO simultaneous removal performance over Co8Ce3/ACs catalyst were researched. The physicochemical properties of catalysts were characterized using BET, SEM, XRD, XPS, H2-TPR and FTIR. By analyzing these characterization results, it was found that the good removal property of the Co8Ce3/ACs catalyst was connected with good texture property, high dispersion of cobalt species and strong redox ability. Besides, the interaction between Co and Ce oxides phases could enhance the mobility of active oxygen species, which greatly improved the removal efficiencies of Hg0 and HCHO. Combined with the experiment and characterization results, end products of Hg0 and HCHO are mainly HgO, CO2 and H2O, respectively. So the mechanisms for simultaneous removal of mercury and HCHO were proposed. Of course, the Co8Ce3/ACs catalyst would be still modified to achieve the goal of practical industrial application.