A mechanistic study of the oxygen insertion into MoO3 crystals as revealed by SIMS and TPSR techniques

Abstract Static secondary ion mass spectroscopy (SIMS) and temperature-programmed surface reaction (TPSR) probes were used to characterize the nature and participation of oxygen species of MoO 3 crystals in the selective oxidation of propylene. The SIMS analysis of the oxygen-l8-containing fragments of two MoO 3 crystals, possessing different exposed crystallographic planes and pretreated under the 18 O 2 + CA mixture, allowed monitoring of the directional 18 O labeling within the crystals. Moreover, the insertion level of oxygen-18 into the acrolein reaction product has been evaluated by mass spectroscopy. TPRS of chemisorbed NO has been used to evaluate the reactivity of surface oxygen ions. From these results a simple model for explaining the observed structure-sensitive partial oxidation of propylene on well-defined MoO 3 crystal structures is proposed.