Thermal Decomposition and Kinetics Analysis of Microwave Pyrolysis of Dunaliella salina Using Composite Additives

Abstract

The thermal characteristics and kinetics of the microalgae Dunaliella salina were evaluated through microwave catalytic pyrolysis under composite additives (blends of graphite (GP) and Na2CO3 (NC)). GP was blended with NC of 0%, 30%, 50%, 70%, and 100%, which were named as NC, 3GP7NC, 5GP5NC, 7GP3NC, and GP. Then different amounts (5%, 10%, and 15%) of NC and 5GP5NC were also studied. The pyrolysis characteristic parameters, characteristic index (D) and activation energy (E), and thermodynamic parameters, including enthalpy (∆H) and Gibbs free energy (∆G), were studied in this paper. In all the groups with the amount of 5%, the initial decomposition temperature (Ti) decreased with the NC proportion of the composite additive increased. The 5GP5NC group obtained the largest values of maximum weight loss rate (Rmax), average weight loss rate (Rmean), and D, which were 3.78%/min, 1.67%/min, and 12.35 × 10−7, respectively. However, the NC group achieved a small value of E (66.28 kJ/mol), ∆H (60.46 kJ/mol), and ∆G (175.97 kJ/mol). When changing the amounts of 5GP5NC, the suitable amount was 15%, based on its largest D (13.76 × 10−7), smallest E (52.49 kJ/mol), excellent weight loss, and thermodynamic characteristic. For NC, the maximum Rmax was obtained at 15%, while the greatest D and minimum E were achieved at 5%.