Biomass-Derived Hydrogen Donor and Equilibrated Zeolite Assisted Upgrading of Extra Heavy Bitumen: Reactor Response, Viscosity Reduction, and Compositional Shift

Nigerian bitumen sourced from Agbabu, Ondo State, is classified as an extra heavy oil, with an API gravity of 8.6° and a viscosity of 32000 mPa s at 40°C, properties that render it unsuitable for pipeline transportation or direct refinery feedstock without prior upgrading. This study evaluated hydrogen addition upgrading of the bitumen using three renewable biomass derived hydrogen donors, glycerol, sawdust, and rice husk, assessed individually and with rice husk further combined with an equilibrated zeolite catalyst, benchmarked against pyrolysis alone and catalytic upgrading without a hydrogen donor. Runs were performed in a high pressure batch reactor pressurized with 10 bar nitrogen and heated to 350°C, with pressure and temperature recorded at 10 min intervals. Upgraded liquid products were characterized for viscosity, density, and API gravity, and analyzed by Fourier transform infrared (FTIR) and gas chromatography mass spectrometry (GCMS). Viscosity decreased from 32000 mPa s in the raw feedstock to between 1900 and 2700 mPa s across the upgrading routes, a reduction of 90.6 to 94.1%, while API gravity rose from 8.6° to between 24.3° and 28.9°. The combination of rice husk and catalyst produced the most favorable outcomes, yielding the greatest viscosity reduction and highest API gravity; this ranking was consistent across all routes, with sawdust the least effective additive. Reactor pressure rise, indicative of gas evolution, was likewise greatest for the rice husk and combined runs. These findings establish rice husk as a cost effective, promising renewable hydrogen donor for bitumen upgrading, particularly with zeolite catalysis.