Hydrotalcite‐Supported Gold Catalyst for the Oxidant‐Free Dehydrogenation of Benzyl Alcohol: Studies on Support and Gold Size Effects

Abstract

Gold nanoparticles with uniform mean sizes (≈3 nm) loaded onto various supports have been prepared and studied for the oxidant‐free dehydrogenation of benzyl alcohol to benzaldehyde and hydrogen. The use of hydrotalcite (HT), which possesses both strong acidity and strong basicity, provides the best catalytic performance. Au/HT catalysts with various mean Au particle sizes (2.1–21 nm) have been successfully prepared by a deposition–precipitation method under controlled conditions. Detailed catalytic reaction studies with these catalysts demonstrate that the Au‐catalyzed dehydrogenation of benzyl alcohol is a structure‐sensitive reaction. The turnover frequency (TOF) increases with decreasing Au mean particle size (from 12 to 2.1 nm). A steep rise in TOF occurs when the mean Au particle size becomes smaller than 4 nm. Our present work suggests that the acid–base properties of the support and the size of Au nanoparticles are two key factors controlling the alcohol dehydrogenation catalysis. A reaction mechanism is proposed to rationalize these results. It is assumed that the activation of the β‐CH bond of alcohol, which requires the coordinatively unsaturated Au atoms, is the rate‐determining step.