EPR STUDY OF KINETICS OF OXYGEN ISOTOPIC EXCHANGE INVOLVING O-ADSORBED SPECIES ON V2O5-SIO2 CATALYSTS

The kinetics of the oxygen isotopic exchange reaction involving adsorbed O- species has been investigated on partially reduced silica-supported vanadium pentoxide. The first low-field line of the EPR spectrum of adsorbed 16O- species has been taken as a measure of their concentration to monitor the following reactions: 16O- + 16O17O17O- + 16O16O, 16O- + 17O17O17O- + 16O17O. It was shown that the exchange proceeds at room temperature with a rate constant k ∼- 0.9 · 10-19 cm3 mole-1 sec-1 and that only about 70% of the adsorbed O- species participate in the process, in contrast to reactions with H2, CO, and other molecules which have been found earlier to take place even at 77 °K. © 1978.