Pyrolysis characteristics and kinetics of the marine microalgae Dunaliella tertiolecta using thermogravimetric analyzer

A genus of unicellular green marine microalgae, Dunaliella tertiolecta, was pyrolysed in a thermogravimetric analyzer from room temperature to 900 °C in a highly purified N2 atmosphere at different heating rates of 5, 10, 20, and 40 °C/min. The results showed that three stages appeared in this thermal degradation process, with increasing temperature, initial temperature, and peak temperature of pyrolysis shifting to a higher value as the heating rate increased. The increased heating rate also resulted in increased total volatile matter. The kinetic analysis of the main pyrolysis process used a composite procedure involving the iso-conversional method and the master-plots method. The iso-conversional method indicated that the pyrolysis reaction should conform to a single reaction model with an activation energy of 145.713 kJ mol−1 using Kissinger’s method and 146.421 kJ mol−1 using Flynn–Wall–Ozawa’s method, respectively. The master-plots method suggested that the most probable reaction mechanism was described by an Fn model. Finally, it was estimated that the pre-exponential factor was A = 2.28 × 1013 s−1, the kinetic exponent was n = 2.4, and the reaction model function was f(α) = (1 − α)2.4. The results of this study provide useful information for designing a pyrolytic processing system using microalgae D. tertiolecta as feedstock.