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.