Hydrogenation of pentenal over supported Pt nanoparticles: influence of Lewis-acid sites in the conversion pathway

In this study, we prepare three supported Pt NP catalysts (Pt/CeO2, Pt/Al2O3, and Pt/CeAl), which are characterized by XRD, TEM, Raman, N2-sorption, and XPS. Pt/CeAl catalysts show the best catalytic performance (52% conversion and 80% 2-pentenol selectivity) with a maximum TOF of 19,896 mmolconvert pentenol mmolPt sites-1 h-1 in the 2-pentenal hydrogenation. A distinct support effect is observed. The incorporating Al into ceria is favourable towards the formation of medium Lewis acidic sites. 2-pentenal is converted initially to 2-pentenol via the hydrogenation of C=O bond and then to pentanol, as the unsaturated Ce4+/Al3+ cations originated from Ce4+-O-Al3+ pairs, act as the acid sites and electron acceptors to polarize C=O bonds, which could facilitate 2-pentenal intramolecular nucleophilic addition toward Cδ+ site to form 2-pentenol rapidly. This study may give some hint for the further development of effective nano-Pt catalysts in the selective hydrogenation to prepare valuable chemicals.