CONICET | Buscador de Institutos y Recursos Humanos

The poisoning resistance to sulfided and oxygenated compounds of some VIII Group PYGAS selective hydrogenation catalysts based on metals was assessed. Low content alumina supported Rh, Pd, Ru and Pt catalysts (0.35 wt %) were prepared from chlorided precursors. In the case of the palladium catalysts a nitrogenated precursor was also used. The catalysts were mainly assessed in the catalytic test of selective styrene hydrogenation in the presence or absence of known poisons. Model feedstocks spiked with thiophene, thiophane and tetrahydrofuran were used. The catalysts were further characterized by means of chemical analysis, XPS, TPR, and chemisorption. The results indicate that chlorided precursors yield more sulfur resistant catalysts. The effect was attributed to the formation of oxychlorinated species, refractory to reduction, that leave the metal in an electron deficient state, thus inhibiting the formation of strong poison-metal bonds. Pd based catalyts had the highest resistance to poisons of all the metals tested. This superior performance was attributed to the total occupancy of the 3d electronic levels of the Pd metal that was supposed to decrease the donation of electrons from the d-band to coordinate metal-poison bonds.