Influence of process conditions and interventions on metals content in biocrude from hydrothermal liquefaction of microalgae

We determined how different reaction conditions influence the metals contents in biocrude oil and other product fractions from hydrothermal liquefaction (HTL) of microalgae. We then assessed the effect of using different solvents for biocrude recovery and adding catalysts on the metal content in the biocrude. The Fe content was lower and the Na content higher in biocrude produced at higher temperature (400 vs 350 °C) and longer holding time (60 vs 3 min). The Fe and Na contents were reduced over 50% and 95%, respectively, by use of methyl tert-butyl ether (MTBE) rather than dichloromethane as the organic solvent for biocrude recovery and they were reduced over 98% via additional application of a supported Ni catalyst during HTL. This work demonstrates that the hydrothermal treatment conditions influence the metal content in biocrude and that judicious selection of solvent and catalyst can lead to significant reduction in the metal content in biocrude.