A Novel Analysis of Transient Isothermal 18O Isotopic Exchange on Commercial CexZr1-xO2-Based OSC Materials

A novel methodology for the analysis of O-18(2)-transient isothermal isotopic exchange (TIIE) response curves obtained over commercial mixed metal oxides upon the gas switch O-16(2)/Ar (30min)O-18(2)/Kr/Ar (t) at constant T in a flow CSTR micro-reactor in the absence of external and internal mass transport resistances and grain boundary effects, is presented for the first time. The specific aim of this analysis was to derive quantitative descriptors of the(16)O/O-18 exchange under pseudo-equilibrium conditions for the transfer rates of oxygen between the gas and solid phases, enabling the assessment of differences in the kinetics of bulk oxygen diffusion over a series of commercial OSC materials used in various catalytic applications (e.g. TWC), without the need of performing any mathematical and kinetic modelling of the surface/bulk oxygen diffusion processes. Based on these descriptors, commercial OSC mixed metal oxides prepared by the same chemical synthesis route but varying the value of one of the synthesis parameters, and having the same at.% composition, were proved to possess largely different transient kinetic rates and other features of the transient response curves of O-16/O-18 exchange strongly related to the bulk oxygen diffusion in the solids. This novel O-18(2)-TIIE analysis is quick and provides a reliable means for proving or disproving likely infringement of patented commercial mixed metal oxides OSC materials.