A general kinetic modelling for the hydrothermal liquefaction of Spirulina platensis

Hydrothermal liquefaction (HTL) of Spirulina platensis at various temperatures (275–375 °C) and residence times (10–60 min) were studied in this work. The maximum yield reported was 41.25 wt.%, which is obtained at a process temperature of 325 °C and residence time of 30 min. A general kinetic model was developed for the hydrothermal liquefaction of Spirulina platensis to obtain the reaction rate constants of the kinetic model and then to calculate the apparent activation energy. Furthermore, the product yields from the kinetic model are obtained, which are almost in line with the experimental data with slight deviations. The pathways such as the conversion of the aqueous phase to biocrude and the biocrude to aqueous-phase conversion show higher rate constant values. The transformation of the aqueous phase and biocrude to a gaseous products has the highest value of activation energy. The low values of activation energies recorded for the biocrude production from biomass underlie the benefits of the HTL process as energetically feasible for biofuel generation from algal biomass.