Effects of reaction parameter on catalytic hydrothermal liquefaction of microalgae into hydrocarbon rich bio-oil

Abstract

Hydrothermal liquefaction (HTL) of Spirulina microalgae was studied over different metal supported (Co, Ni and Fe) on carbon nanotube (CNT) in the presence of different solvents (water, ethanol and methanol) for 30 min Reaction time. Maximum bio-oil yield (43.6 wt%). was found with Co/CNT catalyst at 290 °C under ethanol solvent. The catalytic HTL up-gradation decreased the bio-char yield significantly. However the bio-oil quality significantly improved with using the Co/CNT and Ni/CNT catalyst. Also, improved performance with higher amount of bio-oil and lower amounts of bio-char and gas were achieved, which is due the several reactions are happening during the HTL process. Catalytic HTL also revealed that introducing catalysts accelerates the microalgae macromolecules degradation. Being impregnated by metal, catalysts with improved acid sites and thereby, advanced deoxygenation and hydrogenation activities were achieved. Moreover higher percentage of hydrocarbon was obtained with the catalytic liquefaction of microalgae under ethanol solvent. Elemental analysis showed that during the liquefaction reaction promotes the hydrogenation/hydrodeoxygenation and produced less oxygenates bio-oils.