Oxidation of Sulfur Dioxide over V2O5/TiO2 Catalyst with Low Vanadium Loading: A Theoretical Study

Oxidation of SO2 to SO3 is one of the major drawbacks of the commonly used vanadia-based selective catalytic reduction catalyst. Density functional theory calculations were applied to study the interaction between SO2 and the VOx/TiO2 catalyst. Two parallel calculations, one is cluster models implementing the hybrid method and the other is periodical surface model implementing the Perdew-Burke-Ernzerhof method, were made to compare them with each other. The results show that the uncovered TiO2 surface can be easily sulfated by SO2, whereas it can barely oxidize SO2 to SO3. Supported vanadia site, either vanadia monomer or vanadia dimer, is not a favorable site for SO2 adsorption. However, SO2 can be oxidized by vanadia sites through a sulfation route in which a -V(SO4)- configuration is formed. The terminal oxygen of V=O is found to bond with SO2 to produce SO3. The Bronsted acid site can enhance SO2 adsorption, whereas it will be eliminated after interacting with SO2 because the hydrogen ion of Bronsted acid will be deprived by SO2.