Activity and SO2 resistance of amorphous CeaTiOx catalysts for the selective catalytic reduction of NO with NH3: in situ DRIFT studies

Abstract

A series of Ce_aTiO_x catalysts with different Ce/Ti molar ratios was prepared by a sol–gel method and used for selective catalytic reaction (SCR) of NO with NH₃. The NO conversion values confirmed that the Ce_0.3TiO_x catalyst showed a much higher activity at low temperature, and the catalyst exhibited 100% NO conversion in the broad temperature range of 200–350 °C and nearly 100% N₂ selectivity. The catalysts were characterized by the BET surface area, XRD, XPS, NH₃-TPD and H₂-TPR. These results demonstrated that the excellent catalytic performance of the complete amorphous Ce_0.3TiO_x catalyst was associated with the strong interactions between Ce and Ti, the higher BET surface area, abundant acid sites, and greater presence of Ce³⁺ and chemisorbed oxygen. In situ DRIFTS was used for studies of the reaction mechanism and SO₂ resistance. The results indicate that the L–H reaction pathway can be hindered in the presence of SO₂ at low temperature (<200 °C), however the reaction mainly via the E–R reaction pathway at high temperature (>200 °C) led to a satisfactory SO₂ resistance.