Theoretical Study of Deoxygenation of Esters on Small Pt–Sn Intermetallic Clusters

Abstract: The mechanisms of reactions occurring during deoxygenation of esters on Pt and intermetallic Pt–Sn catalysts (hydrodeoxygenation (stepwise and concerted mechanisms); reactions starting with C–C, C–O, or C–H bond cleavage or simultaneous cleavage of C–O and C–H bonds; and ester pyrolysis) were studied by the density functional theory. The computations showed that on Pt and Pt–Sn intermetallics with low tin contents, the activation barriers of reactions occurring without carbon mass loss on formation of carbon oxides and methane were comparable to the activation barriers of cracking reactions leading to this loss. As the Sn content in the intermetallics increased, the activation barriers increased significantly for the cracking reactions, but insignificantly for the reactions occurring without carbon mass loss. This probably explains the observed high selectivity of Pt–Sn (1 : 5) bimetallic catalysts in the hydrodeoxygenation of esters and triglycerides.