Regulating the MnOx structure in Ru/MnOx/γ-Al2O3 catalyst to enhance the oxidation of benzyl alcohol with molecular oxygen in liquid phase

Ru/MnO x /γ-Al 2 O 3 catalysts prepared by a facile sequential precipitation- deposition method were investigated for the aerobic oxidation of benzyl alcohol with molecular oxygen . The physicochemical properties of the synthesized catalyst were characterized by multiple analytical and characterization techniques. It was found that the highly dispersed MnO(OH) could significantly improve the catalyst activity. When a Mn loading of ca. 10 wt% was used, the catalytic activity of supported Ru catalyst was the highest. The benzyl alcohol conversion and the selectivity of benzaldehyde after 1 h reaction at 80 °C were 100 % and 99 %, respectively. Excessive Mn, however, would lead to large amount of aggregated Mn 3 O 4 , resulting in a poor activity. The Mn in the sample roasted below 300 °C was highly dispersed MnO(OH), and the corresponding catalyst showed a high activity. High-temperature aggregated MnO(OH) to Mn 3 O 4 , leading to a decreased catalyst activity. • Benzyl alcohol was oxidized to benzaldehyde over Ru/MnO x /γ-Al 2 O 3 catalyst. • The Mn content and roasting temperature affect the structure of supported MnO x . • Highly dispersed MnO(OH) on γ-Al 2 O 3 significantly enhanced the catalyst activity. • High-temperature aggregated MnO(OH) to Mn 3 O 4 , resulting in decreased catalyst activity.