Heterogeneous catalytic reaction of elemental mercury vapor over cupric chloride for mercury emissions control

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.