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 degrees C in a highly purified N-2 atmosphere at different heating rates of 5, 10, 20, and 40 degrees 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 Fir model. Finally, it was estimated that the pre-exponential factor was A = 2.28 x 10(13) s(-1), the kinetic exponent was n = 2.4, and the reaction model function Was f(alpha) = (1 - alpha)(2.4). The results of this Study provide useful information for designing a pyrolytic processing system using microalgae D. tertiolectar as feedstock. (C) 2009 Elsevier Ltd. All rights reserved.