Formation of Propane in the Aqueous-Phase Processing of 1-Propanol over Platinum: A DFT Study

摘要

The reaction pathways for alkane formation from alcohols in aqueous-phase (AP) processing was studied computationally for the model system 1-propanol over flat and stepped surfaces of Pt. We examined the dehydration-hydrogenation (DH) mechanism in an acidic environment and alcohol hydrogenolysis (AH) under neutral conditions. The highest (relative) barrier of the DH mechanism was calculated at approximately 90kJmol(-1) on Pt(111), which occurs in the hydrogenation step after cleavage of the CO bond. The highest relative barrier of the AH mechanism, if the CO bond is cleaved on Pt(111), is slightly higher, 105kJmol(-1). The corresponding elementary reaction step does not start from the alcohol, but a dehydrogenated intermediate. On Pt(221), transition state geometries differ somewhat and the highest relative barriers of both mechanisms, AH and DH, are lower by 8-40kJmol(-1), than the corresponding barriers on Pt(111).