Influence of the support composition and acidity on the catalytic properties of mesoporous SBA-15, Al-SBA-15, and Al2O3-supported Pt catalysts for cinnamaldehyde hydrogenation

Three Pt catalysts exhibiting similar metal particles size (<2 nm) were prepared on mesoporous supports differing by their chemical composition and tested in the liquid phase hydrogenation of cinnamaldehyde. The hydrogenation of the Cdouble bond; length as m-dashC bond was favored with Pt/SBA-15 and Pt/Al-SBA-15, with significantly higher reaction rates on the latter catalyst. The acidic support changes the adsorptive properties of the platinum nanoparticles, modifying their surface electron density and possibly their morphology. In contrast, Pt/Al2O3 was the most selective catalyst of the series toward cinnamyl alcohol, with Cdouble bond; length as m-dashC and Cdouble bond; length as m-dashO hydrogenations taking place at the same rate. The presence of Lewis acidic sites close to the particles is assumed to favor the adsorption of molecules via their polar Cdouble bond; length as m-dashO bond. Even if cinnamaldehyde hydrogenation does not require acidic sites to be performed, the composition and acidity of the support significantly influence the reaction rate and selectivity.