Promotional mechanism of enhanced denitration activity with Cu modification in a Ce/TiO 2 -ZrO 2 catalyst for a low temperature NH 3 -SCR system.

This study aims to investigate the enhanced low temperature denitration activity and promotional mechanism of a cerium-based catalyst through copper modification. In this paper, copper and cerium oxides were supported on TiO 2 -ZrO 2 by an impregnation method, their catalytic activity tests of selective catalytic reduction (SCR) of NO with NH 3 were carried out and their physicochemical properties were characterized. The CuCe/TiO 2 -ZrO 2 catalyst shows obviously enhanced NH 3 -SCR activity at low temperature (<300 °C), which is associated with the well dispersed active ingredients and the synergistic effect between copper and cerium species (Cu 2+ + Ce 3+ ↔ Cu + + Ce 4+ ), and the increased ratios of surface chemisorbed oxygen and Cu + /Cu 2+ lead to the enhanced low-temperature SCR activity. The denitration reaction mechanism over the CuCe/TiO 2 -ZrO 2 catalyst was investigated by in situ DRIFTS and DFT studies. Results illustrate that the NH 3 is inclined to adsorb on the Cu acidic sites (Lewis acid sites), and the NH 2 and NH 2 NO species are the key intermediates in the low-temperature NH 3 -SCR process, which can explain the promotional effect of Cu modification on denitration activity of Ce/TiO 2 -ZrO 2 at the molecular level. Finally, we have reasonably concluded a NH 3 -SCR catalytic cycle involving the Eley-Rideal mechanism and Langmuir-Hinshelwood mechanism, and the former mechanism dominates in the NH 3 -SCR reaction.