Formation of propane in the aqueous-phase processing of 1-propanol over platinum: A DFT study

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 C - O bond. The highest relative barrier of the AH mechanism, if the C - O 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).