Influence of the synthesis route on Au-Ir/Al2O3 catalysts performing the total propane oxidation reaction at low temperature

• Au-Ir/Al2O3 catalysts were prepared by three different synthesis routes. • The synthesis route significantly influences the overall performance of C 3 H 8 oxidation. • Distinct particle size distributions of Au and Ir were obtained through different synthesis routes. • The sequential deposition displayed the lowest T for C 3 H 8 oxidation and high stability. • Intermediate species in the total C 3 H 8 oxidation were elucidated by in situ DRIFTS. The current study highlights synthesis as a key parameter for obtaining Au-Ir/Al 2 O 3 bimetallic catalysts using the deposition-precipitation with urea (DPU) method. Both co-deposition and sequential deposition (first by adding Au and then Ir and vice versa) were employed. These approaches were compared with the sol-gel and impregnation methods, revealing notable differences in the catalytic oxidation of C 3 H 8 at low temperatures. The Au-Ir/Al 2 O 3 catalysts prepared via co-deposition and sequential deposition demonstrated outstanding results, producing nanoparticles as small as 1 nm when thermally reduced in hydrogen at 400 °C; also, these catalysts exhibited greater capacity for oxidizing C 3 H 8 below 280°C than the Ir/Al 2 O 3 and Au/Al 2 O 3 -based catalysts. Characterization of the catalysts was conducted by employing various techniques, including in-situ DRIFTS, UV-Vis, BET, H 2 -TPR, HAADF-STEM-EDS, XPS and surface acidity determinations by pyridine thermo-desorption. This last technique showed differences in total acidity (Brönsted and Lewis) provoked by the Au-Ir interaction in the different catalysts, which significantly influenced their ability to oxidize C 3 H 8 towards CO 2 . The results emphasize the effectiveness of the co-deposition and sequential deposition methods using the DPU approach compared to the sol-gel and impregnation methods.