Impacts of Pb and SO2 Poisoning on CeO2–WO3/TiO2–SiO2 SCR Catalyst

A CeO 2 –WO 3 /TiO 2 –SiO 2 catalyst was employed to investigate the poisoning mechanisms of Pb and SO 2 during selective catalytic reduction (SCR). The introduction of Pb and SO 2 suppressed the catalytic performance by decreasing the numbers of surface acid and redox sites. Specifically, Pb preferentially bonded with amorphous WO 3 species rather than with CeO 2, decreasing the numbers of both Lewis and Brønsted acid sites but exerting less influence on the reducibility. SO 2 preferentially bonded with CeO 2 as sulfate species rather than with WO 3, leading to a significant decrease in reducibility and the loss of surface active oxygen groups. Although SO 2 provided additional Brønsted acid sites via the interaction of SO 4 2– and CeO 2, it had little positive effect on catalytic activity. A synergistic deactivation effect of Pb and SO 4 2– on CeO 2 was found. Pb covered portions of the weakly bonded catalyst sites poisoned by SO 4 2–, which increased the decomposition temperature of the sulfate species on the catalyst.