from first principles PP-I-1

PP-III-66Platinum-Nickel Catalyst for Hydrogenation of Edible OilsMartirena M. 1 , Simonetti S. 1,21 Universidad Tecnológica Nacional, Bahía Blanca, Argentina2 Universidad Nacional del Sur – IFISUR, CONICET, Bahía Blanca, Argentinassimonet@uns.edu.arThe oils and fats industry was among the first to use catalytic hydrogenation in order totransform liquid products in solid pastes to improve the odor and taste qualities. The mostcommon metal catalyst for hydrogenation of fatty acids is nickel, due to its high activity andselectivity, among others. However, at present bimetallic catalysts study is successful, aimingto find alternative catalysts. On the other hand, research has shown that trans fatty acids haveadverse health implications, therefore, more studies are needed to meet the new specificationsfor a greater concentration of cis isomer.In this paper we study the adsorption of cis-oleic acid on a surface Pt-Ni-Ni (111) of a catalystmodel. We designed the system and optimized by computer calculations using the method ofsuperposition and electron delocalization, analyzed 4 potential sites of adsorption on thesurface: mono-coordinated (1C), di-coordinated (2C), tri-coordinated with tetrahedralsymmetry (3CT) and tri-coordinated with octahedral symmetry (3CO).The results show generally a weak interaction between cis-oleic acid and the bimetallicsurface. The adsorption energies of cis-oleic acid on the surface Pt-Ni-Ni (111) follow thefollowing order 1C> 3CO> 3CT> 2C. At the minimum energy positions, the molecule isadsorbed through the C = C double bond at distances of 3.9 Å surface (1C), 4.2 Å (3CO),4.0 Å (3CT) and 3.9 Å (2C), respectively. Comparison of the catalytic activity between thesurfaces Ni-Pt-Ni (111) and Ni-Ni-Ni (111) showed that the stronger a molecule adsorbed theshorter distance from the surface became in the pure Ni catalyst. These results have specialsignificance in the subsequent study of the chemical bonding and the electronic structure.220