2-Propanol dehydration and dehydrogenation on Pt/Al2O3 and Pt/Al2O3-CeO2 catalysts

A series of Pt-based catalysts were tested in 2-propanol dehydrogenation and dehydration reactions to produce mainly propylene and water plus acetone and hydrogen. Alumina and alumina-ceria catalytic supports (AC) were prepared by the sol-gel method. Pt catalysts were obtained by incipient-wetness impregnation (IWI), and characterized by atomic absorption spectroscopy (AAS), temperature-programmed reduction (TPR), and Fourier transform infrared spectroscopy (FTIR). It was found that the calcined catalysts (PtOx/AC) increased the dehydration capacity when compared to their respective catalytic supports, both series with no appreciable dehydrogenation products. The reduced catalysts (Pt-0/AC) showed high dehydrogenation activity in 2-propanol reactions, with high selectivity towards acetone and hydrogen at low temperatures. These catalytic systems present a change in selectivity towards propylene above 230 degrees C and the loss of activity of Pt-reduced species. This deactivation was related with the bands of asymmetric vibrations of C-H and C-O bonds in the post-reaction material characterized by FTIR, which have been attributed to either carbon deposition or oxygenated intermediates chemisorbed on the Pt surface. Moreover, the temperature range, where Pt-0 is deactivated, is progressively shifted to higher values as the amount of ceria increases. This is attributed to the fact that ceria modifies the surface interactions of Pt sites with the molecules that cause deactivation. Catalysts were completely regenerated with a mild treatment under a N-2 flow at 500 degrees C.