Efficient Selective Oxidation of Benzyl Alcohol Over Ordered Mesoporous Metal Oxides‐Supported Gold Nanoparticles

ABSTRACT Mesoporous metal oxides (CeO 2 , Co 3 O 4 , and Fe 2 O 3 ) were synthesized using a soft template method. Gold nanoparticles (Au NPs) were immobilized by deposition‐precipitation method. The as‐synthesized catalysts were characterized by powder x‐ray diffraction (p‐XRD), N 2 ‐sorption (BET), high‐resolution transmission electron microscope (HRTEM), and hydrogen temperature programmed reduction (H 2 ‐TPR). The metal oxides have mesostructured pores and surface areas, of 167.45, 35.71, and 42.91 m 2 /g for CeO 2 , Co 3 O 4 , and Fe 2 O 3 , respectively. These mesoporous oxides showed reducible characteristics at reduction temperatures above 300°C. The immobilization of the gold nanoparticles caused a shift of the reduction peaks of CeO 2 , and Fe 2 O 3 to lower temperatures. The catalytic activity of supported gold nanoparticles was evaluated on the liquid phase oxidation of benzyl alcohol with tert ‐butyl hydroperoxide (TBHP) as an oxidant. The results showed that Au/Co 3 O 4 produced higher conversions as compared to their counterparts, whereas the selectivity toward benzaldehyde was 100% when using Au/CeO 2 and Au/Fe 2 O 3 catalysts, but when Au/Co 3 O 4 was used the selectivity was 82.47%. At higher temperatures low conversions were observed, as a result of decomposition of the oxidant, TBHP. Thus, this reaction gave optimum conversions at 80°C for all supported catalysts.