Role of the Support in Controlling MnOx Oxidation State for Aerobic Oxidative Dehydrogenation of 1-phenylethanol

Manganese oxide nanocluster catalysts are known to be active in the oxidative dehydrogenation of alcohols, but their catalytic performance depends on the support. In this study, we selected three kinds of supports―Mg(OH)2, Al2O3, and SiO2―to prepare Mn oxide nanocluster catalysts. Among them, MnOx/Mg(OH)2 catalyst showed the highest yield and has higher Mn oxidation states revealed by Mn K-edge X-ray absorption near edge structure (XANES) and Mn 2p X-ray photoelectron spectroscopy (XPS) analyses. The pretreatment with CO2 before reaction significantly lowered the catalysis, suggesting that the basic sites on the support help promote the reaction. Transmission electron microscopy (TEM) analysis showed similar nanocluster sizes across all supports, indicating that activity is governed more by the oxidation state of Mn species and the basicity of the support rather than particle size. Both the Mn oxidation state and support basicity are essential for enhancing catalytic performance in alcohol oxidation.