Non-isothermal kinetic study of fodder radish seed cake pyrolysis: performance of model-free and model-fitting methods

Abstract

The scientific community has shown concern about the suitable application of different methods (model-free/model-fitting) for the determination of kinetic parameters. The application of an unsuitable method may lead to unreliable kinetic parameters. In this study, the performance of five methods for the determination of the kinetic parameters of fodder radish seed cake (FRSC) pyrolysis was evaluated. This is the first detailed study of the pyrolysis kinetics of FRSC. The characterization was performed through thermogravimetric analysis at different heating rates (5, 10, and 25 K/min) and temperatures ranged from 298 to 1073 K. Four model-free isoconversional methods (Friedman, Kissinger, Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa) were used to determine the activation energy. A model-fitting (five pseudo-components model—FPCM) method was used to obtain the kinetic parameters of fodder radish seed cake pyrolysis. A detailed evaluation of the performance of these methods to estimate the kinetic parameters of fodder radish seed cake pyrolysis was performed. The Criado method was applied to verify reaction mechanisms that governed the pyrolysis process. The activation energies (Ea) ranged from 127.70 to 991.53 kJ/mol from the four model-free methods, which presented themselves as unreliable. The FPCM presented a better performance, with higher R2 values. At low conversions, pyrolysis was controlled by diffusion mechanisms, while at higher conversions, a third-order reaction became the governing pyrolysis mechanism.