The Role of Metal Species on Aldehyde Hydrogenation over Co13 and Ni13 Supported on γ‐Al2O3(110) Surfaces: A Theoretical Study

Abstract Fatty acid transformation to alkane in biomass conversion process goes through deoxygenation (DO) reaction with two possible pathways of hydrodeoxygenation (HDO) or decarbonylation (DCO) that yield different alkane products and water or CO as by‐products. The favorability of aldehyde hydrogenation step can lead to HDO route rather than DCO route. The Co/γ‐Al 2 O 3 catalyst was previously observed experimentally to promote HDO and DCO routes while mostly DCO route was promoted on Ni/γ‐Al 2 O 3 catalyst. This work, we performed density functional theory (DFT) calculations to understand the role of metal species Co and Ni supported on γ‐Al 2 O 3 on aldehyde hydrogenation which could lead to the occurrence of HDO. The structural and electronic properties of supported Co 13 and Ni 13 clusters on γ‐Al 2 O 3 were examined. The perimeter site between the metal cluster and Al atom of γ‐Al 2 O 3 support is found to be an active site on both catalysts. The calculations suggest that Co 13 /γ‐Al 2 O 3 is more kinetically and thermodynamically favorable for acetaldehyde hydrogenation than Ni 13 /γ‐Al 2 O 3 . The metal clusters also act as active sites for H 2 dissociation. The supported Co 13 cluster is oxidized at a higher degree results in higher negative charges of dissociated H 2 while those on supported Ni 13 shows heterolytic cleavage of H 2 yielding both positive and negative hydrogen charges. This behavior could facilitate lower energy barrier of hydrogenation observed on Co 13 /γ‐Al 2 O 3 catalyst.