Sulfur tolerance of Pt/mordenites for benzene hydrogenation. Do Bronsted acid sites participate in hydrogenation?

The comparison of Pt electronic properties studied by in situ XANES and the kinetic study of benzene hydrogenation strongly suggests that the hydrogenation of benzene on Pt/mordenites occurs along two parallel reaction pathways. The routes proposed include (i) the monofunctional hydrogenation of benzene on the metal itself and (ii) the hydrogenation of Brønsted acid bound benzene using hydrogen dissociated on the close metal surface. In the presence of sulfur containing compounds, the activity of solely metal catalyzed route ceases, while the route involving Brønsted acid sites is more sulfur tolerant. The activity and sulfur tolerance of these catalysts for benzene hydrogenation depends upon the vicinity between metallic and Brønsted acidic sites and the concentration of the Brønsted acid sites. Increasing hydrogen partial pressure increases the rates of the reaction and the sulfur tolerance of the catalysts.