High efficiency metal removal from hexane-extracted algae oil using super and subcritical propane

• Metal removal from algae oil was achieved by supercritical propane solvent extraction.
• Continuous metal removing process was developed.
• Required energy for metal removing was calculated.

As a renewable energy source, oil-producing algae have received much attention in recent years. Raw oil, which is normally extracted from algae using solvents such as hexane or ethyl acetate, includes trace metal compounds that rapidly deactivate the hydrogenation catalyst. In this study, metal removal from hexane-extracted algae oil with supercritical and subcritical propane extraction was examined at temperatures from 40 °C to 130 °C and at 6 MPa pressure. The results showed that the metal concentration became decreasing with temperature increasing and metals were not detectable at 114 °C. Using these results, an energy saving process was proposed. Simulation results showed that the metal removal required a mere 3–4% energy consumption compared to a lower heating value of raw oil.