Water gas shift and partial oxidation of CH4 over CeO2–ZrO2(–La2O3) and Pt/CeO2–ZrO2(–La2O3): Performance under transient conditions

• Ce–Zr(–La) oxides with or without supported Pt were studied in transient conditions of WGS and POM.
• Bulk oxygen mobility and lattice OSC determines CO2 evolution during start-up regimes.
• Lattice modification by La reduces sintering of Pt clusters.
• Rate constants of the surface steps and lattice oxygen diffusion were estimated.

Nanocrystalline ceria-zirconia(-lanthana) based fluorite-like oxide solid solutions prepared via polymerized complex precursor route, with or without supported Pt, have been used for detailed transient kinetic studies of water gas shift (WGS) and partial oxidation of methane (POM) at 650 °C and short (∼10−2 s) contact times. It was shown that high bulk oxygen mobility and storage capacity characterizing nanocrystalline structure of ceria–zirconia and regulated by the partial substitution of Ce for La are responsible for vigorous CO2 evolution during start-up regimes. At the same time, it favors preferential methane and CO oxidation on Pt particles, thus revealing a crucial importance of Pt cluster structure.