Selective hydrogenation of oleic acid to fatty alcohols on Rh-Sn-B/Al2O3 catalysts. Influence of Sn content

Abstract

The influence of tin loading of Rh-Sn-B/γ-Al2O3 catalysts on the selective hydrogenation of oleic acid to fatty alcohol was studied. The catalysts were characterized by N2 sorptometry, temperature programmed reduction and X-ray photoelectron spectroscopy. Cyclohexane dehydrogenation and cyclopentane hydrogenolysis were also used to evaluate the metal function. Sn and Rh are in interaction since the conversion values of the cyclohexane, cyclopentane, and TPR profiles are modified by tin addition. Moreover, XPS analysis showed that Sn modifies the amount of Rh on the surface and its reduction state. The yield to oleyl alcohol was maximum for the Rh(1 wt%)-Sn(4 wt%)-B/γ-Al2O3 and Rh(1 wt%)-Sn(5 wt%)-B/γ-Al2O3 catalysts. This behavior could be explained considering that the Sn addition limits the Rh activity for hydrogenation of the C[dbnd]C double bond, thus increasing the formation of oleyl alcohol. At low Sn content, high selectivity to octadecane appears due to the total hydrogenation of the C[dbnd]C, C[sbnd]OH and C[dbnd]O bonds.