Structural response of Ni/ZrO₂ to feed modulations during CH₄ reforming reactions

Time resolved oxidation and reduction cycles of ZrO₂-supported Ni catalysts for dry reforming of CH₄ (CO₂ + CH₄ ↔ 2 CO + 2 H₂) during feed modulations have been studied. Under reaction conditions (1073 K) Ni remains fully reduced, whereas switching the feed gas to pure CO₂ results in a slow (25 sec) formation of a stable NiO phase. When switching back to reaction conditions the NiO phase is rapidly reduced (∼ 1 sec) to metallic Ni. In the context of this study, a novel capillary cell has been built, allowing the parallel treatment of 5 catalyst samples with different gas compositions and different pressures. A comparison of the capillary cell to conventional systems regarding the spectral quality and the kinetic data shows that the capillary cell can be used to obtain identical kinetic data and high quality X-ray absorption spectra. (paper)