The mechanism of the catalytic oxidation of CO with O2 on an Mo catalyst supported on silica has been studied by a tracer technique using 18O2. The supported Mo catalyst was prepared by using the ready reaction between Mo(η3-C3H5)4 and the OH groups on silica. Extended X-ray absorption fine structure (EXAFS) spectroscopy showed that the Mo species attached to silica are dispersed atomically and have a dioxostructure. At steady state during oxidation with CO/O2 = 2/1, 32% of the attached Mo species were estimated to be present as Mo6+ and 68% as Mo4+. The catalytic oxidation was accompanied by oxygen isotope exchange between O2 molecules. The oxidation of the oxostructure (Mo4+) to the dioxostructure (Mo6+) by O2 molecules during the catalytic oxidation produces O atoms on the silica surface. Recombination of two migrating O atoms leads to oxygen isotope exchange between O2 molecules. The mechanism of the catalytic oxidation of CO with O2 on bulk MoO3 was re-examined with reference to that elucidated on the SiO2-supported Mo catalyst.
|Number of pages
|Journal of the Chemical Society - Faraday Transactions
|Published - 1996 Apr 7