New insights into the role of vanadia species as active sites for selective catalytic reduction of NO with ammonia over VO X /CeO 2 catalysts *

A series of VOx/CeO2 catalysts were synthesized via vanadia supported on ceria with different BET surface areas. The catalysts were employed to investigate the active sites for the selective catalytic reduction of NO with NH3 (NH3-SCR). The kinetic results show that VOx/CeO2 catalysts exhibit nearly constant apparent activation energies (Ea), indicating the same SCR reaction mechanism. The V–O–Ce bridging modes and oligomeric VOx were identified and quantified by Raman, FT-IR and H2-TPR. The amounts of the V–O–Ce bridging modes calculated by H2-TPR are correlated to the NH3-SCR intrinsic reaction rates. The turnover frequencies (TOFs) show a constant value at the same temperature, which were calculated based on the number of V–O–Ce bridging modes of VOx/CeO2 catalysts. Therefore, it can be concluded that the V–O–Ce bridging modes are the active sites of VOx/CeO2 catalysts for the NH3-SCR reaction. © 2020