CONICET | Buscador de Institutos y Recursos Humanos

The industrial process of fatty acids hydrogenation is actually carried out in gas-liquid phases, which are in contact with a Ni catalyst in a semi batch reactor. Recent studies on "good" and "bad" fats have added a new dimension to the practical and technical aspects of oil hydrogenation. Trans-isomers are thermodynamically favored during the hydrogenation and the significance of trans-fatty acids to human health was subject of debate. Several studies showed that trans fatty acids may affect plasma lipoproteins levels lowering the concentrations of high-density lipoprotein (HDL) cholesterol (good cholesterol) and increasing the concentrations of low-density lipoproteins (LDL) cholesterol (bad cholesterol). A relationship between the high ingestion of trans fatty acids and an increase in the risks of coronary diseases has been established. From these considerations arises the need to search for alternative hydrogenation catalysts that improve the catalytic process reducing the trans-isomers content in hydrogenated edible oils. In this work, the study of the cis-oleic acid adsorption, on clean and promoted (K, Mg, Co, B or Pd) PtNi(111) catalyst was performed by quantum chemical calculations. The oleic acid adsorption on PtNi(111) surface shows a weak molecule-surface interaction. No preferential site for C=C adsorption is computed and only the C=O adsorption is favored on the clean PtNi(111) surface. The adsorption properties of the PtNi(111) are improved by promoters. The stability of the system is increased and the C=C/surface distances are reduced when promoters are present. Co promoter shows the best performance in terms of system stability. The lowest C p orbital substantially interacts with Pt and Co s-p-d orbitals. The change electron density of metal centers enhance the C=C adsorption being the Pt-C interaction the more favored. After adsorption, the strength of the C=C, Pt-Pt and Pt-Co bonds decrease while a molecule-surface bond is formed.