Platinum-nickel catalyst for hydrogenation of edible oils

M. MARTIRENA; S. SIMONETTI

Conferencia; IX International Conference Mechanisms of Catalytic Reactions; 2012

The oils and fats industry was among the first to use catalytic hydrogenation in order to transform liquid products in solid pastes to improve the odor and taste qualities. The most common metal catalyst for hydrogenation of fatty acids is nickel, due to its high activity and selectivity, among others. However, at present bimetallic catalysts study is successful, aiming to find alternative catalysts. On the other hand, research has shown that trans fatty acids have adverse health implications, therefore, more studies are needed to meet the new specifications for 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 catalyst model. We designed the system and optimized by computer calculations using the method of superposition and electron delocalization Atomic. Analyze 4 potential sites of adsorption on the surface: mono-coordinated (1C), di-coordinated (2C), tri-coordinated with tetrahedral symmetry (3CT) and tri-coordinated with octahedral symmetry (3CO). The results show generally a weak interaction between cis-oleic acid and the bimetallic surface. The adsorption energies of cis-oleic acid on the surface Pt-Ni-Ni (111) follow the following order 1C> 3CO> 3CT> 2C. At the minimum energy positions, the molecule is adsorbed 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 the surfaces Ni-Pt-Ni (111) and Ni-Ni-Ni (111), it appears that the more strongly adsorbed molecule and a shorter distance from the surface occur in the pure nickel catalyst. These results have special significance in the subsequent study of the chemical bonding and the electronic structure.