Effect of operating conditions on hydrothermal liquefaction of Spirulina over Ni/TiO₂ catalyst

In this study, the effects of reaction temperature, holding time, algae/water ratio and catalyst dosage on the yield and quality of bio-oil produced via the HTL of Spirulina were investigated. The maximum bio-oil yield (43.05 wt%) and energy recovery (ER) value (64.62%) were obtained at 260 °C for 30 min, with an algae/water ratio of 1/4 and a catalyst dosage of 5 wt%. The bio-oil samples were characterized by elemental analysis, Gas Chromatography-Mass Spectrometry (GC-MS), Fourier Transform Infrared (FI-IR), and Thermo-gravimetric analysis (TGA). Results indicated that higher heating values (HHVs) of bio-oils were in the range of 27.28-36.01 MJ/kg, and main compounds of bio-oil were amides, esters, nitriles, hydroperoxide and alkanes. Adding of the Ni/TiO₂ catalyst can decrease the contents of oxygenated and nitrogenous compounds and promote the formation of desirable components such as esters and alkanes.