Stoichiometric redox measurements and X-ray photoelectron spectroscopy
(XPS or ESCA) studies were performed on an allyl-based Mo/SiO2 cataly
st (1.7 wt % Mo) obtained by the sublimation of Mo(eta3-C3H5)4 onto Si
O2 at 40-degrees-C. The average oxidation state estimated from stoichi
ometric measurements correlated well with those reported in the litera
ture. ESCA results indicated that reduction of the MO/SiO2 catalyst at
550-degrees-C primarily led to the formation of Mo2+. Also, the resul
ts were consistent the reported reversibility of the redox cycle. Howe
ver, the reported formation of discrete Mo4+ by oxidation of the reduc
ed catalyst at room temperature could not be substantiated.