This Chinese-German collaborative project addresses the computational modeling of partial hydrogenation and partial oxidation reactions over noble metal catalysts using density functional methods. The current work focuses on the model system propanol-propylene-propane on different metal surfaces. Propanol is the partial oxidation product of propylene, while the hydrogenation of the olefin yields propane. Different reaction pathways for this conversion are investigated. The two major pathways being studied are on the one hand a dehydration-hydrogenation mechanism from propane via propylene as intermediate and on the other hand the direct hydrogenation of alcohol.
The structure of the metal catalyst surface can have significant impact on the catalyzed reactions. The presence of steps or defect sites in general on the surface can change the potential energy surface and thus results in a different reaction mechanism. These effects are currently being studied by considering multiple models which use metal slabs of different low index surfaces to describe the catalyst. This work is a preparation for the investigation of more complex reaction networks e.g. in aqueous phase reforming of polyoles. Dehydration reactions of polyoles can lead to the formation of species containing hydroxy groups, C=C double bonds and also (via keto-enol tautomerism) carbonyl groups. The existence of multiple groups, which can be hydrogenated, raises the question where the hydrogenation will preferentially occur and how the preference can be controlled. The results of this computational chemistry project will help to design catalysts of high selectivity and to identify processes with fewer steps. All these insights will contribute as building blocks of “sustainable chemistry” by using environmentally available precursors.