Pyrolysis kinetics, mechanism and thermodynamics of peanut shell based on Gaussian function deconvolution.

Abstract

As a typical biomass resource, peanut shell has the potential to produce energy and value-added products, as it is generated abundantly worldwide. Pyrolysis is increasingly utilized for the disposal of biomass wastes through thermal conversion into chemical raw materials. Assessing the pyrolysis kinetics, reaction mechanism, thermodynamic parameters for individual components of peanut shells is crucial for its valorization. In this study, conditions for pyrolysis were optimized under pure N₂ flow across temperatures ranging from 303 K to 1173 K at the temperature ramp of 10 K/min, 20 K/min, and 30 K/min. The peak-differentiating analysis using Gaussian function was employed to segregate the pyrolysis of peanut shell into several independent one-step parallel reactions, corresponding to pseudo-lignin, pseudo-cellulose, and pseudo-hemicellulose decomposition. The Coats-Redfern, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, and Vyazovkin techniques were employed to estimate kinetic parameters and reaction mechanism for each pseudo-component of peanut shell. The performed analyses revealed that the average activation energy values generally followed an order of pseudo-lignin > pseudo-hemicellulose > pseudo-cellulose, with values of 174.31 kJ/mol, 133.89 kJ/mol, and 115.44 kJ/mol by Kissinger-Akahira-Sunose, 177.79 kJ/mol, 136.53 kJ/mol, and 120.33 kJ/mol by Flynn-Wall-Ozawa, and 174.96 kJ/mol, 134.29 kJ/mol, and 116.61 kJ/mol by Vyazoykin, respectively. The Coats-Redfern method indicated that the suitable mechanism of reaction for pseudo-hemicellulose and pseudo-cellulose were random nucleation-based, while diffusional-based mechanism was identified for pseudo-lignin. The thermodynamic analysis revealed that the decomposition of peanut shell was endothermic and non-spontaneous, and it can be converted into value-added sources of energy steadily through pyrolysis process. This study offers a reliable approximation of experimental data irrespective of pyrolysis behavior and guides the resourceful utilization of peanut shell.