University of the Philippines - Diliman, Quezon City 1100, Philippines

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Abstract: Hydrothermal liquefaction (HTL) is a process technology suited for converting wet biomass, like microalgae, into biocrude oil. This study investigates the effects of temperature and reaction time on the mass yield and the properties of HTL biocrude oil such as higher heating value (HHV) and composition. Spirulina platensis, a microalgae species, is used as feedstock. Slurry prepared at 30% dry weight is processed in 5-mL mini-reactors. Temperatures are set at 280^oC, 320^oC, and 350^oC using a temperature-controlled sandbath. Reaction times are varied at 15 mins, 30 mins, and 45 mins. Biocrude oil is produced and separated using dichloromethane (DCM) as solvent. The mass yield of biocrude oil varies depending on temperature and reaction time ranging from 29.6% to 44.8% by mass, dry ash-free (daf) basis. Higher mass yield is observed at the lowest temperature setting of 280^oC. The HHV is measured using bomb calorimeter and calculated using Dulong's formula. The HHV ranges from 31.5 MJ/kg to 37 MJ/kg. Highest HHV is obtained for biocrude oil at 350^oC and 45 mins reaction time. The highest energy recovery is 76.8%, which is attained at 280^oC and 45 mins. Elemental analysis and GC-MS analysis are conducted to analyze the composition of biocrude oil produced. The N/C and O/C ratios of HTL biocrude oil are reduced in all experimental conditions. Nitrogen content is lowest at 350^oC and 30 mins to 45 mins reaction time.