Characterization of active sites of Pd/Al2O3 model catalysts with low Pd content by luminescence, EPR and ethane hydrogenolysis

Spectroscopic (laser-induced luminescence (LIL) and EPR) and catalytic (ethane hydrogenolysis) techniques were used for characterization of the active sites of Pd/Al2O3 catalysts. These techniques have high sensitivity and make it possible to study the catalysts with Pd concentrations as low as 0.02–0.03 wt.%. It was found by EPR using spin probes that the electron donor sites of the support are modified by the deposited palladium. It was found by LIL that the Pd deposition has a substantial effect on the state of hydroxyls on the Al2O3 surface. The obtained results indicate that at Pd concentrations 0.5 wt.% or lower supported Pd does not form PdO phase. Instead, it is stabilized in the form of atomically dispersed ion clusters. The possible role of the Al2O3 donor sites in stabilization of such clusters is discussed.

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► Pd/Al2O3 catalysts in the Pd concentration range of 0.02–1.0 wt.% are studied.
► Laser-induced luminescence is used for investigation of the catalysts
► Spin probes for characterization of Pd/Al2O3 active sites are suggested.
► The activity in ethane hydrogenolysis and CO oxidation is studied.
► Surface donor sites are shown to be important for Pd stabilization.