Unraveling the impact of support on bimetallic Pt-promotor interactions for selective propane dehydrogenation

Pt-Mn catalysts exhibit high performance for propane dehydrogenation (PDH), yet the influence of the support on active site formation remains debated. This study investigates Pt and bimetallic Pt-Mn species on SiO2 and θ-Al₂O₃. Combined TPR, XPS, and XRD analyses reveal accelerated MnOx reduction on SiO2, yielding 1.2-fold higher metallic Mn0 content. DFT calculations demonstrate that Pt-Mn alloying weakens propylene adsorption and increases C–C cleavage barriers without impairing C–H activation. Morphology and stability are critically support-dependent. While SiO2 facilitates selective bimetallic nanoparticles, θ-Al₂O₃ stabilizes highly undercoordinated Pt clusters that promote rapid α-coke formation and five-fold higher total carbon deposition. By optimizing the support and Mn-loading, a catalyst was developed maintaining 98% propylene selectivity over 18 days with an exceptionally low deactivation constant (k_d) of 0.0009 1/h. These insights provide a clear strategy for designing supported bimetallic catalysts with tailored selectivity for hydrocarbon conversion.