Boosting C₃H₈ Oxidation at Low Temperature Over a Highly Dispersed Ir/TiO₂ Catalyst

Abstract

Iridium (Ir) nanoparticles with loadings of 0.6, 1.2, 1.8, and 3 wt % were supported on TiO2 in the anatase phase by the deposition–precipitation with urea (DPU) method and were evaluated as catalysts for the thorough oxidation of propane (C3H8). Ir/TiO2 was active in the total oxidation of C3H8 at low temperatures (150–300 °C). The C3H8 oxidation reaction rate and turnover frequency values were improved with increasing iridium loadings until 1.8 wt %, featuring the following order: 1.8Ir/TiO2 > 3Ir/TiO2 > 1.2Ir/TiO2 > 0.6Ir/TiO2 > TiO2. HAADF–STEM exhibited that iridium was spread over the TiO2 anatase surface, displaying average particle sizes ranging from 1.6 to 1.9 nm. XPS analysis revealed a mixture of Ir0/Ir2+ species deposited on the TiO2 surface, and their ratio was dependent on the treatment gas (air or hydrogen). Pyridine thermo‐desorption revealed high Lewis acidity, which increased with higher iridium loadings, showing different behavior patterns in the thoroughly oxidized C3H8. Characterization of the Ir/TiO2 catalysts conducted by in situ DRIFTS tests unveiled the presence of acetone and aldehyde species as the main reaction intermediates when the samples were treated under hydrogen conditions. Additional ex situ characterizations such as H2‐TPR, BET, and XRD were also carried out and discussed.