New Findings in Hydrothermal Deactivation Research on the Vanadia-Selective Catalytic Reduction Catalyst

Considering the risks of hydrothermal deterioration in vehicles, power plants, and oceangoing vessels, V2O5-WO3/TiO2 catalysts were subject to hydrothermal and thermal aging at 600, 625, 635, and 650 °C for 4–48 h. The different ratio and significant loss of active sites are main reasons for catalyst deactivation. Both Lewis and Brønsted acid sites are involved in the selective catalytic reduction reaction. Brønsted acid sites are more susceptible. High temperature plays a major role in the aging. It causes sintering, particle growth, and the anatase phase transition. Phase transformation turns out to be less important than sintering. Sintering leads to the reduction of the BET surface area, which in turn causes decrease of NH3 adsorption amount and changes of active sites. Aging time can accelerate the degree of deactivation. It also helps to change the proportion of active sites. Water vapor has no significant effect on NOX conversion rates