Epoxidation of propene using Au/TiO2: on the difference between H2 and CO as co-reactant
The role of the reducing gas in the direct epoxidation of propene to propene oxide (PO) using O2 over Au/TiO2 catalyst was studied by experiments and density functional theory calculations. It was found that PO can be obtained using both H2 and CO as co-reactant. The yield of PO was much lower with CO than with H2. The role of oxygen atoms of the titania support was investigated by quantum-chemical investigations, which show that the mechanism involving CO as co-reactant should proceed via surface oxygen vacancies, whereas with H2 the well accepted pathway involving OOH is favored. Steady-state isotopic transient kinetic analysis experiments demonstrate that support oxygen atoms are involved in PO formation when CO is used as the co-reactant.