Abstract: Oxidation of methanol catalyzed by NaOH or HNO₃ modified VO_x/Al₂O₃ was studied by solid-state nuclear magnetic resonance (NMR) spectroscopy. The acid-treated VO_x/Al₂O₃ catalyst showed stronger Bronsted acid sites compared to the unmodified VO_x/Al₂O₃ catalyst, while the base-treated VO_x/Al₂O₃ catalyst had no Bronsted acid sites. As a result, the former exhibited higher selectivity in producing dimethoxymethane from oxidation of methanol whereas the oxidation reaction catalyzed by the later yielded mainly formate. These results indicate that the Bronsted acid sites in VO_x/Al₂O₃ catalysts play a key role in the oxidation reaction converting methanol to dimethoxymethane.

Key words: solid-state NMR, catalysis, methanol oxidation, vanadium oxide