Hydrotreatment of two atmospheric residues from Kuwait Export and Lower Fars crude oils

Hydrodesulfurization (HDS) and the hydrodemetallization (HDM) of vanadium and nickel (HDV and HDNi) of two Kuwaiti atmospheric residues (ARs) from contrasting crudes (Kuwait Export, KEC; Lower Fars, LFC) were compared using the same commercial HDM and HDS catalysts in two stage flow reactors (HDM, first stage; HDS, second stage) under 18.5 MPa of H₂ at 370-395 C. The catalysts were stabilized by passing KEC-AR for 600 h. The kinetic parameters of HDS, HDV, and HDNi were analyzed with the removal of sulfur and metals assumed to be 1.0 and 1.2 orders of reactions, respectively, in both reactors. The calculated rate constants were fitted to Arrhenius plots with reasonable linearity. The rate constants of HDS were similar in the first stage, whereas the rate constants of KEC-AR were certainly higher than that of LFC-AR in the second stage. HDS proceeded more rapidly over the HDS catalyst of the second reactor, but the activation energy was higher. The reactive sulfur species of both ARs were removed at similar rates in the first stage, and the differing refractory sulfur species of the two ARs were removed in the second reactor. HDV and HDNi of both ARs appear to progress similarly in both reactors, but the activation energy is higher in the second reactor. Demetallization appears saturated in the second reactor at higher reaction temperatures. Similar HDV and HDNi reactivities between the ARs suggest they share a similar mechanism in which the petroporphyrins must first be liberated from the asphaltene moieties of ARs and be exposed to the catalyst surface. This mechanism indicates that the most refractory metal species require higher activation energies before they are extracted as metal sulfides. The metal accumulation on HDM catalyst suggests that HDV and HDNi share similar reactivity, which contradicts previous notions. The discrepancy may be due to this study's focus on the initial stage of the run.