DFT studies of selective oxidation of propene on the MoO3(010) surface

Abstract

Selective oxidation of propene to acrolein and acrylic acid has been applied in industry for many years. In this work, the density functional theory plus U (DFT+U) method was performed to study the hydrogen abstraction of propene on the MoO₃(010) surface. From the most stable chemisorbed propene (di-σ propene), the allyl intermediate is difficult to produce on a perfect MoO₃(010) surface because of the high barrier. In general, the barriers of the second hydrogen abstraction are much lower than those of the first one. The conclusion from our slab model calculations is consistent with the experimental results. It is found that the (3 + 2) mechanism exhibits lower barriers than the (5 + 2) mechanism. Oxygen defects facilitate the first dehydrogenation significantly, and π-allyl converts to σ-allyl favorably on defects, in agreement with a previous experimental study. The present study indicates that increasing the surface oxygen defects might be an effective way to promote the activity of MoO₃ to propene oxidation.