In this study, the reaction mechanism of Hg(0) vapor oxidation over cupric chloride (CuCl2) was investigated using 10% (wt) CuCl2/alpha-Al2O3 for mercury emissions control from coal-fired power plants. The CuCl2/alpha-Al2O3 sample showed >90% Hg(0) oxidation with excellent resistance to SO2 at 140 degrees C in a simulated flue gas containing 10 ppmv HCl, 2000 ppmv SO2, and 6% O-2 gases balanced with N-2 gas. In the absence of HCl and O-2 gases, Hg(0) vapor was found to be oxidized by consuming atomic Cl of CuCl2 and reducing it to CuCl, following a Mars-Maessen mechanism. The reduced CuCl could be re-chlorinated back to CuCl2 by replenishing empty Cl atoms under 10 ppmv HCl and 6% O-2 gases readily present in coal combustion flue gases even under 2000 ppmv SO2 concentration for continuous Hg(0) oxidation. Cl-2 gas generation was not observed over CuCl2 at 140 degrees C, indicating a heterogeneous catalytic reaction. CuCl2 shows potential that can be realized in a honeycomb or plate catalyst bed. (c) 2012 Elsevier B.V. All rights reserved.