This study aims to produce renewable diesel and
biopriviliged chemicals from microalgae that can thrive in wastewater
environment. <i>Spirulina</i> (SP) was
converted into biocrude oil at 300ºC for a 30-minute reaction time via hydrothermal
liquefaction (HTL). Next, fractional distillation was used to
separate SP-derived biocrude oil into different distillates. It was found that 62%
of the viscous SP-derived biocrude oil can be separated into liquids at about 270ºC
(steam temperature of the distillation). Physicochemical characterizations, including
density, viscosity, acidity, elemental compositions, higher heating values and chemical
compositions, were carried out with the distillates separated from SP-derived
biocrude oil. These analyses showed that 15% distillates could be used as
renewable diesel because they have similar heating values (43-46 MJ/kg) and
carbon numbers (ranging from C8 to C18) to petroleum diesel. The Van Krevelan
diagram of the distillates suggests that deoxygenation was effectively achieved
by fractional distillation. In addition, GC-MS analysis indicates that some
distillates contain biopriviliged chemicals like aromatics, phenols and fatty
nitriles that can be used as commodity chemicals. An algal biorefinery roadmap
was proposed based on the analyses of different distillates from the SP-derived
biocrude oil. Finally, the fuel specification analysis was conducted with the
drop-in renewable diesel, which was prepared with 10 vol.% (HTL10) distillates
and 90 vol.% petroleum diesel. According to the fuel specification analysis,
HTL10 exhibited a qualified lubricity (<520 µm), acidity (<0.3 mg KOH/g)
and oxidation stability (>6 hr), as well as a comparable net heat of
combustion (1% lower), ash content (29% lower) and viscosity (17% lower) to
those of petroleum diesel. Ultimately, it is expected that this study can provide
insights for potential application of algal biocrude oil converted via HTL.
