Enhancement of CeO₂ modified commercial SCR catalyst for synergistic mercury removal from coal combustion flue gas

CeO₂ modified commercial SCR (selective catalytic reduction) catalysts with different CeO₂ content were prepared and researched for synergistic mercury removal from coal combustion flue gas in this study. The characterization analyses on the catalysts indicated that the introduction of CeO₂ increased the surface area, the dispersity of the metal oxides on the TiO₂ support and the redox behavior of the catalyst, which was beneficial to the catalytic activity. The experimental results confirmed that the CeO₂ loading improved the catalytic efficiencies over the commercial SCR catalyst. The catalyst with a CeO₂ content of 4% displayed the optimal performance for NO and synergistic Hg⁰ removal, of which the NO conversion and Hg⁰ removal efficiency reached 90.5% and 78.2%, respectively, at 300 °C in simulated coal-fired flue gas. The Hg⁰ removal activity, the independence of Hg⁰ removal from HCl concentration and the effects of SO₂, NO and NH₃ on Hg⁰ removal efficiency all became positive over the modified catalyst compared to over the raw one, which was mainly due to the sufficient chemisorbed oxygen derived from the synergy of V₂O₅ and CeO₂ and the redox transformation between Ce³⁺ and Ce⁴⁺ on the catalyst surface. The CeO₂ modification generated a significant enhancement on the catalytic performance and made the commercial SCR catalyst more suitable to be employed for NO and synergistic mercury removal in a coal combustion power plant.