In situ observation of highly oxidized Ru species in Ru/CeO2 catalyst under propane oxidation†
In this work, we prepared a promising catalyst for propane oxidation composed of ruthenium supported on polycrystalline hollow CeO2 nanospheres. It was found that the Ru loading on the CeO2 support strongly improves its catalytic activity, decreasing the T50 by about 200 °C (from 500 to about 300 °C). By utilizing several ex situ techniques (XRD, HR-STEM, Raman spectroscopy, ICP analysis) and in situ NAP-XPS, we investigated the effect of different pre-treatments (calcination, reduction, and C3H8 oxidation reaction) on the morphology, structure, and chemical state of the Ru/CeO2 catalyst. The correlations between the chemical state of ruthenium in the Ru/CeO2 catalyst and its activity in C3H8 oxidation received particular attention. Here, it is shown for the first time that the Ru/CeO2 interaction with an oxygen-rich atmosphere (C3H8 + O2 (1 : 10)) at ≥300 °C results in ruthenium oxidation to volatile RuO4, leading to Ru evaporation/desorption from the outer surface and homogeneous high dispersion inside the powder catalyst.