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.