Influence of intimacy for metal-mesoporous solid acids catalysts for n-alkanes hydro-conversion†
Pt on both ordered mesoporous Al-SBA-15 and commercial amorphous mesoporous silica–alumina bi-functional catalysts were prepared and studied for n-heptane hydro-isomerization and n-hexadecane hydro-cracking. We investigated the influence of the location of the Pt nanoparticles and their proximity to the acid sites; by depositing Pt in a controlled manner either in the mesopores of the solid acid or on a γ-Al2O3 binder, surrounding the solid acid particles. We demonstrate that in the case of both ordered and amorphous mesoporous acidic support, a distance between the metal and acid sites of a hundreds of nanometers gives similar results compared to the closest intimacy (below 10 nm) between these functions. Due to the medium strength Brønsted acid sites of the Al-SBA-15, Pt–Al-SBA-15 exhibits higher activity than the corresponding Pt on commercial amorphous silica–alumina. These results suggest that, in the case of mesoporous solid acids, a fine control at the nanoscale of the proximity between the active sites is less important than the number and nature of the acid sites.