Study of the structure and selectivity of Pt-Au catalysts supported on Al2O3, TiO2, and SiO2

A series of Pt-Au catalysts were prepared by the impregnation method on three different supports and different atomic concentrations and were characterized by conventional electron microscopy (TEM), X-ray diffraction, and as catalytic probes in the contact reaction of n-hexane. We observed changes in morphology and particle size when Au was added to Pt. A better dispersion of the metal was measured when Al2O3 and TiO2 were used as supports than with SiO2. We performed a selectivity study of the n-hexane reaction between 523 and 623 K, where the supporting materials Al2O3 and TiO2 show no catalytic activity. For the Al2O3 support we found that selectivity is oriented to hydrogenolysis products followed by isomerization and cyclic products. For the SiO2 support, we observed an increase in isomerization products and a slight increase in cyclic products, For the TiO2 support the selectivity favored hydrogenolysis products, a tendency that increased with increasing Au concentration up to a maximum at 50-50 Pt-Au. (C) 2000 Published by Elsevier Science B.V.