Bio-crude oil production using catalytic hydrothermal liquefaction (HTL) from native microalgae harvested by ozone-flotation

This work explored bio-crude oil production and the hydrocarbon distribution resulting from a catalytic HTL process with a feedstock composed by native consortium of microalgae (mostly cyanobacteria) with low lipid and high protein content. Two harvesting methods ozone-flotation and centrifugation were compared. Also, the effect of the catalysts, HZSM-5 zeolite, content (0, 5 and 7 wt% loading with respect to dry biomass) were studied. The dry biomass was liquefied in water (slurry at 4 wt%) at 350 degrees C for 120 min. Results showed that the bio-crude contained aliphatic, aromatic, cyclic, oxygenated cyclic and aliphatic compounds containing N and O, with a bio-crude yield of between 10 and 16%. The best quality of bio-crude oil was produced from microalgae harvested and pretreated by ozone-flotation at 7 wt% HZSM-5. The increase in the bio-crude quality was a result of a lower nitrogen (3.2%), oxygen (4.8%) and sulfur (0.7%) content versus centrifuged (no catalyst) microalgae 4.6%, 7.9% and 1.6% respectively.