Outstanding performance of CuO/Fe–Ti spinel for Hg0 oxidation as a co-benefit of NO abatement: significant promotion of Hg0 oxidation by CuO loading

Abstract

Conversion of gaseous Hg⁰ to soluble Hg²⁺ using selective catalytic reduction (SCR) catalysts with gaseous HCl as an oxidant as a co-benefit of NO abatement is widely used for resolving Hg pollution from coal-burning power plants. Nevertheless, the performances of conventional V₂O₅–WO₃/TiO₂ for NO abatement and Hg⁰ oxidation are unsatisfactory. In this study, CuO/Fe–Ti spinel was exploited as a novel and high-activity catalyst for the simultaneous removal of NO and Hg⁰. The outstanding SCR activity and high N₂ selectivity of Fe–Ti spinel did not distinctly decrease after CuO loading; thus, CuO/Fe–Ti spinel achieved efficient NO reduction. Although Hg⁰ physical adsorption onto Fe–Ti spinel was slightly suppressed after CuO loading, the Cl* radical formation was appreciably promoted as both HCl adsorption and the conversion of adsorbed Cl⁻ to Cl* radicals were promoted. Hence, the Hg⁰ oxidation activity of Fe–Ti spinel was appreciably improved after CuO loading, and the rate of Hg⁰ oxidation for CuO/Fe–Ti spinel reached approximately 6.8–8.7 μg g⁻¹ min⁻¹, which was better than those of most other SCR catalysts. In summary, CuO/Fe–Ti spinel shows great promise as an SCR catalyst for Hg⁰ oxidation as a co-benefit of NO abatement from coal-burning flue gas (CFG).