Catalytic combustion of propane over second metal-modified Ru supported on CeO2 nanosheet

Abstract

Among the CeO₂ supported noble metal catalysts, Ru/CeO₂ shows the highest activity for propane combustion. However, Ru/CeO₂ catalysts still exhibit some problems such as poor thermal stability and high temperature volatilization loss of Ru species. In this work, based on electronic structure modification and acid-base-redox property regulation, the active Ru component in Ru/CeO₂ was modified with a second element to prepare for propane (C₃H₈) combustion. Activity test and characterizations illustrated that all the selected elements reduce the C₃H₈ combustion activity due to a corresponding reduction in active Ru-O-Ce species. With the addition of Cs with strong electron-donating leads to the stabilization of Ce³⁺ within the CeO₂, consequently diminishing its redox capabilities thus exhibits suboptimal activity and stability. However, the moderately electron-donating alkaline earth metal Ba stabilizes the low-cost Ru species and improves the thermal stability. In contrast, the strongly electron-withdrawing element Nb reduces the stability of low-valence Ru species and leads to the easy loss of Ru at high temperatures. However, the prepared NbRu/CeO₂ catalyst shows better resistance to chlorine poisoning and CO₂ due to the enhancement of acidity. Finally, the reaction pathway for propane oxidation was thoroughly investigated by in-situ DRIFTS over the modified Ru/CeO₂ catalysts. The addition of Cs improves Ru′ dispersion, which in turn facilitates the oxidation of propane to propanol. With the addition of Ba, the conversion of carboxylic acid species to acid ester species is accelerated. While the addition of Nb lead to a decrease in the variety of adsorbates.