Oxidation of gaseous elemental mercury by hydrochloric acid over CuCl2/TiO2-based catalysts in SCR process

Abstract

CuCl2/TiO2-based catalysts were examined to investigate the role of copper chloride for the oxidation of gaseous elemental mercury in selective catalytic reduction (SCR) process. CuCl2 on CuCl2/TiO2 catalyst was decomposed releasing Cl by calcination at high temperatures and restored to its original form by being exposed to gas phase HCl, reversibly. The activity for mercury oxidation was significantly increased with the increase of CuCl2 loading and HCl concentration. CuCl2/TiO2 catalysts revealed high activity for mercury oxidation even in the absence of HCl. This suggests that mercury oxidation could occur via a Mars–Maessen mechanism by which adsorbed or weakly bound Hg0 would react with Cl in CuCl2 that is replenished from gas phase HCl. However, the activity of CuCl2-loaded catalysts for NO removal considerably decreased with the increase of temperature above 300–350°C, which may be due to the ability of CuCl2 for NH3 oxidation in SCR reaction.