Deoxy-liquefaction of three different species of macroalgae to high-quality liquid oil

• Three species of macroalgae were converted into liquid oil by deoxy-liquefaction.
• The maximum yield of liquid oil was obtained at optimum temperature.
• The liquid oils contained different compositions with different contents.
• The liquid oils had low oxygen content and high heating values.

Three species of macroalgae (Ulva lactuca, Laminaria japonica and Gelidium amansii) were converted into liquid oils via deoxy-liquefaction. The elemental analysis, FTIR and GC–MS results showed that the three liquid oils were all mainly composed of aromatics, phenols, alkanes and alkenes, other oxygen-containing compounds, and some nitrogen-containing compounds though there were some differences in terms of their types or contents due to the different constituents in the macroalgae feedstocks. The oxygen content was only 5.15–7.30% and the H/C molar ratio was up to 1.57–1.73. Accordingly, the HHV of the three oils were 42.50, 41.76 and 40.00 MJ/kg, respectively. The results suggested that U. lactuca, L. japonica and G. amansii have potential as biomass feedstock for fuel and chemicals and that deoxy-liquefaction technique may be an effective way to convert macroalgae into high-quality liquid oil.