Kinetic analysis of Botryococcus braunii pyrolysis using model-free and model fitting methods

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 Šesták 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(α) = (1 − α)n·αm 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 58.3–60.5kJ·mol-1, 49.5–109kJ·mol-1 and 79.1–88.5kJ·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.