(719b) Composition of Bio-Crude Oils from Hydrothermal Liquefaction of Algae in Batch Reactor

Due to the limitations of food, farmland, and weather, novel biofuels produced from hydrothermal liquefaction of biomass has attracted much attention. Algae-derived oils from hydrothermal liquefaction are promising because of high algae growth rates, strong CO₂-mitigation potential, and avoidance of drying requirements. In hydrothermal liquefaction, water at subcritical states (270-350°C and 80-173 bar) catalyzes depolymerization of lipids, proteins and carbohydrates in algae, leading to relatively high yields of bio-crude oil that can be valorized to transportation fuels. In this study, we investigated the influences of operating conditions (temperatures of 310-350 °C, residence times of 5-60 min, and solid algae contents of 5-10 wt.%) on the composition of bio-crude oil from hydrothermal liquefaction of Nannochloropsis salina and Galdieria sulphuraria using a variety of analytical methods. Organic molecules with molecular masses of ~150-700 Da were observed by Fourier transform ion cyclotron resonance mass spectroscopy (FT-ICR/MS) for comprehensive qualitative compositional description that employed three complimentary ionization methods. Free fatty acids in the HTL oil were quantitated by gas chromatography mass spectroscopy (GC/MS). Higher heating values and CHNS elemental content were also measured by bomb calorimeter and elemental analysis to obtain information about energy recovery relative to previous studies. Bio-crude oil characterization results will be used to optimize hydrothermal liquefaction operating conditions in a 1.8 L batch reactor and to select initial conditions for a pilot scale, continuous flow reactor.