Reduction of PdO/Al₂O₃ in Liquid Cyclohexane Followed <i>In Situ</i> by ATR-IR, High-Energy XRD, and XAS

Supported Pd-based catalysts used in heterogeneously catalyzed liquid phase processes often undergo an activation step through reduction of the oxide or oxidic passivation layer prior to reaction. An oxidized Pd/Al2O3 catalyst was reduced by using H2-saturated cyclohexane at 70 °C, and followed real time attenuated total reflection infrared spectroscopy (ATR-IR), high-energy X-ray diffraction (XRD), quick scanning absorption (XAS) obtain perspective from different materials properties. We show that dynamic Pd speciation changes can be monitored during phase. XRD XAS indicated isothermal PdO passes intermediate Pd0 toward formation a well-defined hydride Based on sensitivities two techniques, suggested process ends with dominant phase, while revealed equal proportion hydride. The time-resolved data occurs nucleation mechanism is rapidly converted into according contracting sphere model. identification presence mixed Pd0/PdHx appears crucial view relevance these species for instance hydrogenation reactions.