Oxidation of elemental mercury vapor over γ-Al2O3 supported CuCl2 catalyst for mercury emissions control

• CuCl2 forms multiple copper species on γ-Al2O3 surface.
• At low loadings, CuCl2 and γ-Al2O3 form inactive copper aluminate.
• At high loadings, additional CuCl2 exists in highly dispersed amorphous form.
• CuCl2/γ-Al2O3 works as a redox catalyst in O2 and HCl gases for Hg(0) oxidation.

In our previous studies, CuCl2 demonstrated excellent Hg(0) oxidation capability and holds potential for Hg(0) oxidation in coal-fired power plants. In this study, the properties and performances of CuCl2 supported onto γ-Al2O3 with high surface area were investigated. From various characterization techniques using XPS, XAFS, XRD, TPR, SEM and TGA, the existence of multiple copper species was identified. At low CuCl2 loadings, CuCl2 forms copper aluminate species with γ-Al2O3 and is inactive for Hg(0) oxidation. At high loadings, amorphous CuCl2 forms onto the γ-Al2O3 surface, working as a redox catalyst for Hg(0) oxidation by consuming Cl to be converted into CuCl and then being regenerated back into CuCl2 in the presence of O2 and HCl gases. The 10%(wt) CuCl2/γ-Al2O3 catalyst showed excellent Hg(0) oxidation performance and SO2 resistance at 140 °C under simulated flue gas conditions containing 6%(v) O2 and 10 ppmv HCl. The oxidized Hg(0) in the form of HgCl2 has a high solubility in water and can be easily captured by other air pollution control systems such as wet scrubbers in coal-fired power plants. The CuCl2/γ-Al2O3 catalyst can be used as a low temperature Hg(0) oxidation catalyst.