CO hydrogenation on PdCo/NaY catalysts: Effect of ion hydration on metal phases and selectivity

Abstract Exposure of calcined PdCo/NaY catalyst precursors to water vapor, prior to reduction, strongly affects the CO hydrogenation activity and selectivity of the reduced bimetal catalysts. With samples that had been exposed to H 2 O before reduction, the formation of hydrocarbons prevails; nonhydrated reference samples of the same overall composition are mainly selective for oxygenates. After 6 h of reaction time PdCo alloy particles of 5.8 nm are detected by XRD in H 2 O-exposed catalysts, but in the reference samples the metal particles are below the limit of detection by XRD. The observed effects are attributed to the formation of mobile aequo-complexes of metal ions; after reduction they are converted to larger alloy particles, richer on Co, than in the reference samples. Results obtained with NaOH-neutralized and Co-free Pd/NaY catalysts are also discussed.