Unveiling the Active Center of the Ru3Sn7/ZnO Catalyst for Carboxylic Acid Hydrogenation: A Combined In Situ DRIFT and DFT Study

Abstract

Ru-Sn bimetallic catalysts have shown significant promise in the catalytic hydrogenation of various bioderived carboxylic acids, especially in continuous vapor-phase processes. Recently, the Ru3Sn7 intermetallic alloy has been investigated as an active site for the selective production of alcohols from carboxylic acids. However, the detailed role of the Ru3Sn7 alloy and the reaction pathway remains unclear. This study provides an experimental demonstration of the adsorption configuration of carboxylic acids on this catalyst system by in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Combined with Density Functional Theory (DFT) calculations, the research highlights the role of Ru species within the Ru3Sn7 alloy as primary adsorption sites, diverging from the widely proposed Sn-centered adsorption in prior reports. Ru3Sn7 plays a key role by providing optimal moderate acyl adsorption and an ensemble effect at the Ru-Ru dual-atom sites that promote site-sharing H and acyl intermediates, thereby lowering the conversion barrier compared to monometallic Ru and enabling selective alcohol production from carboxylic acids. These mechanistic insights are instrumental in the rational design and development of advanced catalysts with enhanced performance and selectivity for the production of value-added chemicals.