Effects of dispersed MoS2 catalysts and reaction conditions on slurry phase hydrocracking of vacuum residue

Abstract

The slurry phase hydrocracking (HCK) of vacuum residue (VR) in the presence of dispersed MoS2 catalyst was investigated under varying temperature, pressure, and reaction time. Extended X-ray absorption fine structure (EXAFS) measurements were used to obtain structural information about the dispersed MoS2 phase during the reaction. Under a standard reaction condition of temperature 673K and pressure 10.0MPa in an autoclave batch reactor, kinetic analysis for VR HCK confirmed that the reaction occurs in a parallel manner in the production of 77% liquid oils as major products such as vacuum gas oil and distillates with the generation of gas and of 23% coke in the presence of dispersed MoS2 catalyst (0.113mmol or 360ppm Mo). Although temperatures below 653K at 9.5MPa were found beneficial in coke reduction to less than 1.0wt.% in favor of hydrogenation at 33h of reaction, higher pressures over 15MPa at 673K were more influential in accelerating the VR conversion into liquid products, reaching 90% at 4h of reaction with coke reduction down to 1.2wt.% than the cases under conditions below 10MPa. Analysis of the spent catalysts by EXAFS and TEM demonstrated that the nanosized MoS2 phase was well developed from Mo(CO)6 in the early stage of the reaction, with lower MoS and MoMo coordination verifying the small MoS2 particles having more exposed and defect sites as active phases.