Hydrothermal Liquefaction of the Microalgae Phaeodactylum tricornutum: Impact of Reaction Conditions on Product and Elemental Distribution

The microalgae Phaeodactyium tricornutum was processed by hydrothermal liquefaction in order to assess the influence of reaction temperature and reaction time on the product and elemental distribution. The experiments were carried out at different reaction times (5 and 15 min) and over a wide range of temperatures (275-420 degrees C) using a batch reactor system. All fractions were quantified and analyzed in terms of specific elemental concentrations. The highest bio-oil yield (39%) was obtained at 350 degrees C when using a reaction time of 15 min. Under these conditions, 82% of the algal calorific value was recovered in the bio-oil fraction. The higher heating value of the bio-oil increased with reaction temperature and reaction time. The elemental analysis was used to map the distribution of elements in the obtained fractions with increasing temperature. Generally, most of the potassium, sodium, nitrogen, phosphorus, and sulfur were recovered in the aqueous fraction. The solid residue was found to primarily consist of a calcium phosphate compound.