Study on the Deactivation of V2O5–WO3/TiO2 Selective Catalytic Reduction Catalysts through Transient Kinetics

The mechanism underlying the deactivation of a commercial V2O5–WO3/TiO2 catalyst for NH3 selective catalytic reduction (SCR) of NOx through exposure to the flue gas of a coal-fired power plant was investigated by a transient kinetic analysis that focused on the distinction between the deactivation behaviors of adsorption sites and redox sites. The results showed that alkali dopants preferentially poison the active sites associated with vanadium (V5+–OH and/or V5+═O) rather than the sites associated with titania and tungsten. Obvious changes in the activation energies for NH3 desorption, oxidation, and SCR surface reaction over the used catalyst were observed. Kinetic variations showed that three other factors that are involved in the elementary surface steps are responsible for the catalyst deactivation rather than simply the decline of the NH3 adsorption capacity. Finally, the effects of these factors on the catalyst activity were analyzed at different temperatures.