Improved catalytic performances of MoO3 in the oxygen-assisted dehydration of 2-butanol thanks to alpha-Sb2O4 and spillover oxygen

We clarify the mechanism of the cooperation between MoO3 and .ALPHA.-Sb2O4 in the O2-assisted dehydration of 2-butanol (220.DEG.C.). When used alone, MoO3 loses activity by over-reducing to MoO2. On the contrary, MoO3 exhibits improved conversion of 2-butanol and yield to butene when it is used in physical mixture with .ALPHA.-Sb2O4. The origin of the synergy is 2-fold: thanks to .ALPHA.-Sb2O4, 1) the reduction of MoO3 to less active MoO2 is inhibited and 2) the surface of MoO3 is dynamically stabilized to a more active and selective suboxidic state. These effects are interpreted as due to a remote control mechanism thanks to spillover oxygen formed on .ALPHA.-Sb2O4. To reach high catalytic oxidation performances, the surface of MoO3 should be stabilized during catalysis to a more active and selective suboxide. Spillover oxygen helps to do that even at high hydrocarbon concentrations. (author abst.)