Unraveling the Pyrolysis mechanisms of Syagrus palm waste fibers through Gaussian deconvolution and kinetic modeling

Abstract

The thermal decomposition kinetics and thermodynamics of Syagrus romanzoffiana waste rachis fibers (SrWRFs) were investigated through thermogravimetric analysis in a nitrogen atmosphere at heating rates (β) of 30, 40, and 50°C/min. The Coats–Redfern method was employed to determine kinetic parameters, including activation energy (Ea), pre-exponential factor (A), and reaction mechanisms. In contrast, thermodynamic properties such as enthalpy change (ΔH), Gibbs free energy (ΔG), and entropy change (ΔS) have been derived to evaluate the energy requirements and spontaneity of the pyrolysis process. A three-parallel Gaussian reaction model was employed to deconvolute the degradation profiles of hemicellulose, cellulose, and lignin, revealing distinct temperature intervals for each component: hemicellulose (200–345°C), cellulose (305–398°C), and lignin (220–650°C), with high fitting accuracy (R2 ≥ 0.99537). The kinetic analysis identified sigmoidal rate (SR) models (SR6, SR7, and SR8) as the most suitable, yielding Ea values ranging from 97.31 to 262.11 kJ/mol, which increased with higher heating rates. Thermodynamic results indicate that SrWRF pyrolysis is endothermic (ΔH > 0) and nonspontaneous (ΔG > 0), with negative entropy changes (ΔS) suggesting an increase in molecular order among the degradation products. The kinetic compensation effect was confirmed, demonstrating a linear relationship between lnA and Eₐ.