Oxygen isotope equilibration and exchange as probes for differing dioxygen interactions with pure and rhodia-promoted CeO2 and Al2O3

Comparisons are made between the catalytic activities of CeO2, Al2O3 and Rh2O3 when pure, or in the case of CeO2 and Al2O3 when promoted by rhodia dispersed thereon, in respect of: (a) activity at 290 K for homomolecular oxygen isotope equilibration of an equimolar (18O2 + 16O2) probe gas, the so-called R0 process, (b) activity under T-ramp for heterophase oxygen isotope exchange between surface lattice \(^{16} O_s^{2 - }\) and O2 highly enriched in 18O, which is shown to occur predominantly by single-stay exchange of both oxygen atoms of dioxygen (the so-called R2 process).