Thermal behavior and kinetic mechanism of microalgae and model compounds

As the third-generation biofuel, microalgae are becoming one of the most promising biomass resources. This study investigated the thermal behavior and kinetic mechanism of microalgae and its model compounds to provide reference for thermal conversion of microalgae to produce energy products. Results showed that, there was a slight mass loss during microalgae pyrolysis among 50–180 °C, which was principally due to the dehydroxylation or deamination of proteins. Microalgae mainly pyrolyzed between 180 and 500 °C, within which, protein and carbohydrate chiefly pyrolyzed below 350 °C, while lipid violently pyrolyzed above 350 °C. Besides, NH 3 released before carboxyl and CO 2 during soybean protein (PT) pyrolysis, and C = O was generated before CO 2 when sucrose (SC) pyrolyzed, while chain C-H generated at higher temperature. In addition, the average activation energy (Ea) for the decomposition of component models was in the order of OL > PT > SC. The Ea of OL reached 123.26 kJ/mol, but protein-rich Spirulina platensis (SP) had higher Ea than that of lipid-rich Nannochloropsis sp. (NS) . Besides, the kinetic mechanism of microalgae and its components PT and SC was Reaction-order model, while it was Avrami–Erofeev model for OL pyrolysis.