Computational studies of small neutral vanadium oxide clusters and their reactions with sulfur dioxide

Vanadium oxide is a catalytic system that plays an important role in the conversion of SO$_{2}$ to SO$_{3}$. Density functional theory at the BPW91/LANL2DZ level is employed to obtain structures of VO$_{y}$ (y=1,{\ldots},5), V$_{2}$O$_{y}$ (y=2,{\ldots},7), V$_{3}$O$_{y}$ (y=4,{\ldots},9), V$_{4}$O$_{y}$ (y=7,{\ldots},12) and their complexes with SO$_{2}$. BPW91/LANL2DZ is insufficient to describe properly relative V-O and S-O bond strengths of vanadium and sulfur oxides. Calibration of theoretical results with experimental data is necessary to compute enthalpies of reactions between V$_{x}$O$_{y}$ and SO$_{2}$. Theoretical results indicate SO$_{2}$ to SO conversion occurs for oxygen-deficient clusters and SO$_{2}$ to SO$_{3}$ conversion occurs for oxygen-rich clusters. Subsequent experimental studies confirm the presence of SO in the molecular beam as well as the presence of V$_{x}$O$_{y}$ complexes with SO$_{2}$. Some possible mechanisms for SO$_{3}$ formation and catalyst regeneration for solids are also suggested.