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 CC 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 CC and CO 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 CO 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.

In liquid phase, the hydrogenation of the cinnamaldehyde CC bond is favored on Pt/SBA-15 and Pt/Al-SBA-15, but reaction rates are significantly higher on the latter catalyst. In contrast, on mesoporous Pt/Al2O3, CC and CO hydrogenations take place at the same rate. When metal particles are small enough (<2 nm), the composition and acidity of the support influence the particles adsorptive properties as well as the reaction rate and selectivity.Figure optionsDownload high-quality image (45 K)Download as PowerPoint slideHighlights
► Pt nanoparticles smaller than 2 nm have been prepared on three mesoporous supports.
► CO adsorption evidences changes in Pt adsorptive properties depending on the support.
► Cinnamaldehyde hydrogenation is much faster on Pt/Al-SBA-15 compared with Pt/SBA-15.
► Pt/Al2O3 is the most selective of the three catalysts in cinnamyl alcohol (>40%).
► Dramatic support effects on the particles electron density or morphology are assumed.