Hydrogenation of citral over Pt and Pt-Fe/SiO2 catalysts

Pt/SiO2 and Pt-Fe/SiO2 catalysts having a Pt loading ranging from 0.5 to 3.0 wt.% and a fixed amount of Fe in the bimetallic series, 1.0 wt.% have been prepared by the impregnation procedure, followed by calcinations and reduction in H-2 flow at 773 K. The samples were characterized by N-2 adsorption at 77 K, H-2 chemisorption at 298 K, TEM, TPR and XPS. The hydrogenation of citral at 363 K and 8.3 bar over a series of Pt/SiO2 and Pt-Fe/SiO2 catalysts was studied. Thus, the selectivity towards the unsaturated alcohol (geraniol + nerol) decreases at high loads of monometallic Pt. An effect of polarization of the C=O bond due to the presence of Fe3+ species leads to catalysts active and highly selective to the hydrogenation of the carbonyl bond. Characterization results showed that Pt is present as Pt-o and Fe mainly as Fe3+.