In situ observation of highly oxidized Ru species in Ru/CeO2 catalyst under propane oxidation

Abstract

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.