Sunflower oil hydrogenation on Pt catalysts: Comparison between conventional process and homogeneous phase operation using supercritical propane

The hydrogenation of sunflower oil on TiO2 supported by Pt catalysts was studied. The Pt/TiO2 catalyst was modified: (a) with K and (b) by high temperature reduction treatment, in order to observe its influence on the activity and the cis-isomers selectivity. The catalysts were characterized by atomic absorption, H2 chemisorption, TPR and XRD. The hydrogenation of edible oils at conventional conditions is diffusion controlled. The addition of propane as supercritical (SC) solvent allows to perform the reaction in a homogeneous phase in contact with the solid catalyst. A significant increase in the reaction rate of the homogeneous system was observed. Regarding selectivity, the formation of trans-isomers was higher in the reaction under conventional conditions, whereas the production of saturated compound was favored in the homogeneous operation. Pt-K/TiO2 and Pt/TiO2 catalyst presented a similar TON, although the cis-isomer selectivity increased with the alkali addition. This behavior is explained in terms of a chemical modification of the noble metal.