Role of catalyst defect sites towards product selectivity in the upgrading of vacuum residue

Abstract

Slurry hydrocracking is an upcoming technology which effectively upgrade residues and produces more valuable distillate products. Catalyst used in this process enhances hydrogenation and reduces coke formation. Nanoflower molybdenum sulfide (MoS2 NanoF) is synthesized by a simple hydrothermal treatment of ammonium heptamolybdate and sulfur powder. The morphology is determined by scanning electron microscopy (SEM) showing that curved nanoplates of MoS2 grow like petals of a flower. High-resolution transmission electron microscopy (HR-TEM) images reveals the arc-like and angular shape of nanorods of MoS2 fringes, proving the interlayer growth of MoS2 nanoplates. These curved plates create defects in the MoS2 sites that are highly active for a hydrogenation reaction. X-ray photoelectron spectroscopy (XPS) results suggest the presence of Mo+4 and S-2 in the synthesized catalyst. Raman analysis also supports the formation of a few layers of MoS2 phases. The activity of the synthesized catalyst is evaluated for slurry phase hydrocracking of a vacuum residue (VR) at high-temperature and high-pressure conditions. MoS2 NanoF catalyst exhibits higher hydrocracking and hydrotreating activities. It is mainly due to the presence of highly active defect structure of MoS2. Higher activities indicate the presence of higher hydrogenation sites in the synthesized MoS2 NanoF catalyst. Moreover, this hydrogenation activity substantially reduces coke formation during hydroprocessing of the residue.