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 5wt% and 20wt% 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 1031mPas 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.
Highlights
The world’s energy consumption has been projected by the US Energy Information Administration (EIA) to reach approximately 8.6 × 106 joules per annum by 2040 [1]
This study evaluates the potential for use of bio-NPs for the upgrading of heavy oil and compares the efficacy of the bio-NPs synthesised on Desulfovibrio desulfuricans with counterparts synthesised on Bacillus benzeovorans
With 5 wt% bio-produced oils after upgrading with bimetallic NPs (Pd/Pt) produced by the two bacteria, transmission electron microscopy (TEM) showed more nanoparticles (NPs) distributed within the intracellular matrix in B. benzeovorans (Fig. 2a) than in D. desulfuricans where no discrete
Summary
The world’s energy consumption has been projected by the US Energy Information Administration (EIA) to reach approximately 8.6 × 106 joules per annum by 2040 [1]. The world’s leading fuel source, supports 32% of global energy consumption, which increased by 2.3% in 2013 [2]. J.B. Omajali et al / Applied Catalysis B: Environmental 203 (2017) 807–819 ness in hetero-elements (nitrogen, sulfur and oxygen), as well as high metal contents, especially nickel and vanadium. Omajali et al / Applied Catalysis B: Environmental 203 (2017) 807–819 ness in hetero-elements (nitrogen, sulfur and oxygen), as well as high metal contents, especially nickel and vanadium These properties of heavy oil are thought to be the consequence of subsurface water flows and microbial activities within a shallow depth of low temperature environments as the oil accumulates over time [7]. Other challenges include environmental concerns such as water management, production water for steam generation, and the control of greenhouse gases and other pollutants during the extra refining required for heavy oils [8]
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