Abstract
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•Integral model-fitting methods are more accurate for one-step reaction mechanism.•f(α)=(1-α)4·[-ln(1-α)]0.53 is the reaction model of CSW pyrolysis.•Four independent-parallel-reaction model fits well with Gaussian distributions.•Ea of pseudo-components can be reliably estimated from model-free methods.
Model-free and model-fitting methods were compared for pyrolytic conversion of the coconut shell waste. The apparent activation energy, estimated from differential and integral iso-conversional methods, increased with the progression of pyrolytic conversion. The reaction model, f(α)=(1-α)4·[-ln(1-α)]0.53, indicate that order-based nucleation and growth mechanisms control the solid-state pyrolysis of the coconut shell waste. The active pyrolysis zone was consisted of overlapping multi-component degradation peaks. Average activation energy of the pseudo-components estimated from the Kissinger’s method were 21.9kJ.mol−1, 106.4kJ.mol−1 and 108.6kJ.mol−1 for the dehydration, the degradation of pseudo-cellulose and pseudo-hemicellulose, respectively. Pseudo-lignin decomposed over a wide range of temperature with a slower conversion rate as compared to pseudo-hemicellulose and pseudo-cellulose. Average activation energy range of pseudo-lignin was estimated from the combination of model-free and model-fitting methods as 79.1–226.5kJ.mol−1.