Development of the HYD route of hydrodesulfurization of dibenzothiophenes over Pd–Pt/γ-Al2O3 catalysts

The hydrodesulfurization (HDS) of dibenzothiophene (DBT) on a series of Pd–Pt/γ-Al2O3 catalysts was studied as a function of the Pd/(Pd + Pt) molar ratio at different reaction conditions. It was determined that the catalytic performance in HDS is controlled by the Pd/(Pd + Pt) molar ratio. In particular, a synergetic effect exists rather in the development of the hydrogenation (HYD) route of HDS of dibenzothiophene than in the activity, but both can be controlled from the Pd/(Pd + Pt) molar ratio. An analysis of the relationship between the mechanism of HYD, analyzed here from a different perspective as that currently presented in the literature, and the surface properties of the bimetallic Pd–Pt alloyed particles indicated that: (i) the development of HYD is in correspondence with the capacity of Pd–Pt to hydrogenate aromatics under HDS environments; (ii) the dispersion of the active phase is not directly related to the performance in HDS. Consequently, other geometric effects are more important to the development of HYD over Pd–Pt; and (iii) Pdδ+ surface species of the Pd–Pt alloyed particles are responsible for the hydrogenation–dehydrogenation steps during HYD, whereas C–S–C bond scission mainly takes place on Pt sites.

The development of the hydrogenation route of hydrodesulfurization of dibenzothiophene over Pd–Pt/γ-Al2O3 catalysts was studied. A synergetic effect for HYD was demonstrated to exist which is in correspondence with that observed in the hydrogenation of aromatic molecules under H2S atmospheres. It is demonstrated that selectivity to HYD is a function of the Pd/(Pd + Pt) atomic ratio and that the presence of Pdδ+ surface species in the Pd–Pt system is crucial for the development of HYD.Figure optionsDownload high-quality image (130 K)Download as PowerPoint slide