In-situ catalytic upgrading of heavy oil using dispersed bionanoparticles supported on gram-positive and gram-negative bacteria

Abstract

With the continuous depletion of global oil reserves, unconventional alternative oil resources like heavy oil and bitumen have become increasingly attractive. This study investigates the use of bimetallic bio-nanoparticles (bio-NPs), a potential alternative to commercial catalysts in heavy oil upgrading. The bio-NPs were made by sequential reduction of precious metal (Pd and Pt) ions with hydrogen as the electron donor at 5 wt% and 20 wt% metal loading using bacterial (Desulfovibrio desulfuricans and Bacillus benzeovorans) cells as support. The bio-NPs were characterized using transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results of the catalytic upgrading of a feed heavy oil show that the bimetallic bio-NPs produced an increment of ∼2° in API (American Petroleum Institute) gravity (i.e. ∼9.1°) better than monometallic bio-NPs (∼7.6°) on average while the API gravity using thermal upgrading was lower (6.3°). The API gravity of a commercial Ni-Mo/Al2O3 catalyst was 11.1°. However, more coking was produced using the commercial catalyst than with the bio-NPs. The extent of viscosity reduction was: 98.7% (thermal), 99.2% (bio-NPs) and 99.6% (Ni-Mo/Al2O3) below 1031 mPa s for the feed heavy oil reference (baseline). The potential advantage of using bio-NPs is that the precious metals can be sourced cheaply from waste streams, which could serve as a potential platform for the green synthesis of catalytically active materials using bacteria for in-situ catalytic upgrading of heavy oils.