Effects of H2O and CO2 on the catalytic oxidation property of V/W/Ti catalysts for SO3 generation.

Graphical abstract Highlights • H 2 O and CO 2 have a nonlinear effect on the generation of SO 3. • High concentration of H 2 O decreases SO 3 generation by inhibiting SO 2 adsorption. • High concentration of CO 2 decreases of SO 3 generation by decreasing Oα proportion on catalyst. Abstract The understanding of the generation mechanism of SO 3 on V/W/Ti catalysts provides needed information for the achievement of ultra-low emission of pollutants and effective control of SO 3 generation. This study predominantly investigates the catalytic oxidation mechanism of V/W/Ti catalysts for SO 3 generation under H 2 O and CO 2 conditions. Ion Chromatography (IC), X-ray Fluorescence (XRF), Brunauer–Emmett–Teller (BET) specific surface area, Scanning Electron Microscopy image (SEM), Energy Dispersive X-ray (EDX), SO 2 Temperature-Programmed Desorption (SO 2 -TPD), X-ray Photoelectron Spectroscopy (XPS) experiments, and Fourier Transform Infrared spectroscopy (FT-IR) were used to characterize catalyst properties and the catalytic oxidation generation mechanism of SO 3. Results show that Catalyst V content was more influential than physical property on the generation of SO 3. In this study, when H 2 O or CO 2 was added into the reaction atmosphere, the generation amount of SO 3 would increase firstly, and then gradually decrease with the further increase of H 2 O or CO 2 concentration. Through further mechanistic analysis, it was found that the influence mechanism of H 2 O and CO 2 on the generation of SO 3 was different. Various kinds of intermediate species such as [OH] and HOSO 2 were introduced by the addition of H 2 O, resulting in the increase of lattice oxygen (Oα) proportion and SO 3 generation path. However, the inhibition effects of high concentration of H 2 O on SO 2 adsorption and sulfur oxides migration were the main reason for the decrease of SO 3 generation under high H 2 O containing conditions. Conversely, although the adsorption SO 2 was promoted by CO 2 , high CO 2 addition leads to the apparently reduction of Oα proportion on catalyst resulting in the decrease of SO 3 generation. [ABSTRACT FROM AUTHOR]