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Integrated Extraction and Catalytic Upgrading of Biocrude Oil from Co-hydrothermal Liquefaction of Crude Glycerol and Algae

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posted on 20.07.2021, 18:34 authored by Zheng Cui, Feng Cheng, Jacqueline M. Jarvis, Umakanta Jena, Catherine E. Brewer
Co-hydrothermal liquefaction (HTL) of wastewater algae and crude glycerol has been shown to produce higher yields at lower costs compared to wastewater algae biomass conversion alone. The biocrude oil produced from co-HTL of wastewater algae and crude glycerol does, however, have a relatively high oxygen content (10–16 wt %) and relatively low energy content (34–36 MJ/kg). To upgrade the biocrude oil to high-quality biofuel and to simplify the overall process, several organic solvents were evaluated for their ability to extract biocrude oil from the HTL products and to donate hydrogen for biocrude oil upgrading. The solvent options tested were hexane, cyclohexane, ethyl acetate, and no solvent, in combination with effective heterogeneous upgrading catalysts: H-beta zeolite, Pt/C, and Raney Ni. Biocrude oil yields varied with the polarity of solvent; as expected, solvents with high polarity led to more extraction of biocrude oil albeit with lower quality. Pt/C was the most effective catalyst for upgrading, producing a light-colored, low-viscosity liquid with lower oxygen content (0.01 wt %) and higher energy content (44 MJ/kg). The choice of solvent had relatively little effect on upgrading outcomes compared to the selection of the catalyst. The no solvent with Pt/C and the ethyl acetate with Pt/C combinations were the most promising, resulting in an upgraded oil energy content similar to gasoline and a near complete removal of oxygen. The combination of ethyl acetate and Pt/C resulted in a higher energy recovery.