Abstract
The kinetics of Botryococcus braunii pyrolysis was studied using commonly used model-free and model-fitting methods. Differential and integral versions of iso-conversional model-free methods provide effective apparent activation energy as a function of conversion. Reaction-order and Sestak and Berggren (SB) models were considered for the estimation of global single reaction mechanism. It was shown that SB model with an empirical function f(alpha)=(1-alpha)(n).alpha(m) was the most probable reaction mechanism. The constituents namely carbohydrate, protein and lipid were found to decompose simultaneously. Average activation energy of these components were obtained from Friedman and Kissinger-Akahira-Sunose (KAS) methods. Depending on the iso-conversional method, the activation energy ranges of pseudo-carbohydrate, pseudo-protein and pseudo-lipid were found as 58.3-60.5 kJ.mol(-1), 49.5-109 kJ.mol(-1) and 79.1-88.5 kJ.mol(-1), respectively. Model-free methods when applied on biomass as whole or on separate component yielded matching results. Decomposition of pseudo-carbohydrate was 2-3 times faster than other two components. Pseudo-lipid was shown to impede the progress of pyrolytic conversion.