Bifunctionality of a MoS2-Amorphous Silica-Alumina-Dispersed Catalyst for Slurry-Phase Hydroconversion: Effect of Acid and Hydrogenating Site Ratios

To achieve maximum yield from bifunctional catalysts in slurry-phase hydrocracking of heavy oil, an appropriate balance between the acidic and hydrogenating functions of the catalyst is required. In this study, the bifunctional behavior of MoS2-amorphous silica-alumina (ASA) catalysts was investigated by varying the number of Bronsted acid sites (eta H+) and MoS2 edge sites (eta Mo) associated with ASA and MoS2, respectively. Using a model feed consisting of phenanthrene and decalin, we report evidence of bifunctional catalysis for MoS2-ASA catalysts with eta H+/eta Mo ratios between 3.1 and 15.5. Deviations from bifunctional behavior were also observed: at a low eta H+/eta Mo ratio (0.39), phenanthrene hydrogenation was preferred, whereas at the highest eta H+/eta Mo ratio (30.9), acid-catalyzed reactions dominated and promoted coke formation that resulted in catalyst deactivation. Considering that the in situ formation of MoS2 blocked some acid sites on the ASA, we introduced a new parameter that quantified the number of Bronsted acid sites available in the reactor system (eta H-c(+)). We show that the total product yield correlated with eta H-c(+) and that the maximum yield occurred for the catalyst with the highest eta H-c(+).