(482c) Characterization of Cupric Chloride-Impregnated Sorbents for Elemental Mercury Capture From Coal Combustion Flue Gas

Carbon sorbent injection is one of the most promising mercury control technologies from coal-fired power plants.  CuCl₂-impregnated activated carbon sorbent has demonstrated excellent mercury oxidation and adsorption performance in our previous studies.  In addition, when CuCl₂ is impregnated onto noncarbonaceous substrates, the material has shown excellent elemental mercury oxidation, but not adsorption capability.  Our previous study using XAFS shows that mercuric chloride (HgCl₂) is a major resultant oxidized mercury compound generated over the CuCl₂-impregnated activated carbon sorbent.  This study focused on investigating the structure and electronic state of CuCl₂-impregnated sorbent supported on activated carbon and alumina.

CuCl₂-impregnated activated carbon and alumina sorbents were extensively characterized using TGA-MS, XRD, XPS, XAFS and SEM/EDS techniques. XAFS results suggested that CuCl₂ supported on AC be reduced to Cu+ species during impregnation, probably by the reduction sites on the support surface.  Copper was still coordinated with Cl^- ions on carbon surface at relative high copper loading sorbent, whereas it might be mainly connected to oxygen functional group on carbon surface at low copper loading sorbent (i.e. 1% CuCl₂-AC), but Cu-C bonding was not observed on the sorbent.  High Cl concentration on the sorbent enhanced the elemental mercury oxidation and organic polar solvent (isopropyl alcohol) could impregnate higher Cl loading on the carbon surface than water.  The valence change of copper between Cu²⁺ and Cu⁺ was probably responsible for the mercury oxidation reaction.  Overall this presentation will address copper and mercury speciations over the carbon and alumina surfaces.