Catalytic Hydrodeoxygenation of Bio-Crude and Heavy Gas Oil Blends Using Carbon-Supported Molybdenum Catalysts

Abstract

The present study focused on decreasing the amount of oxygen present in hydrothermal liquefaction (HTL) biocrude via catalytic hydrodeoxygenation. To serve the purpose, carbon-supported molybdenum carbide catalysts were synthesized via carbothermal hydrogen reduction method using three different carbon supports, commercial activated carbon (AC), commercial multi-walled carbon nanotubes, and bioresidue (BR) obtained via solvent-extraction from a HTL product mixture. The catalysts were screened for their oxygen reduction efficiency using a blend of HTL biocrude in hydrotreated heavy gas oil. The BR-based catalyst was identified as the best-performing catalyst at the screening conditions because it exhibited a higher oxygen reduction percentage (49.2 wt %) than the catalysts synthesized using carbon nanotubes (21.5 wt %) and AC (22.4 wt %). The synthesized catalysts were characterized in order to explain their oxygen reduction percentages, and a parametric study was carried out for the best-performing catalyst to determine the effects of process parameters such as temperature, pressure, reaction time, and catalyst loading on oxygen reduction efficiency. The characterization results revealed that the BR-supported molybdenum catalyst had the highest number of strongly acidic sites, the highest concentration of β-Mo₂C on its surface, a molybdenum dispersion of 2.4 wt %, a BET surface area of 118 m²/g, and an average pore size of 9.7 nm. The oxygen reduction percentage for the BR-based catalyst improved and reached the maximum value of 59.8% for a reaction that was carried out at 325 °C and 5 MPa for 2 h with a catalyst loading of 4% w/w.