Physicochemical properties, pyrolysis kinetics, thermodynamic parameters of activation, and evolved volatiles of mango seed waste as a bioenergy feedstock: A potential exploration

Abstract

An investigation was conducted to elucidate the bioenergy potential of mango seed waste through pyrolysis kinetics, thermodynamics parameters of activation, and analysis of evolved volatiles. Experiments were performed in a thermogravimetric analyzer (TGA) coupled with a Fourier transform infrared (FTIR) spectrometer. The pyrolysis behavior was assumed to be the sum of four independent parallel reactions corresponding to the devolatilization of extractives, hemicellulose, cellulose, and lignin. The four applied isoconversional methods could determine the average activation energies in the ranges of 113.7 − 120.3, 150.0 − 159.9, 190.0 − 201.1, and 172.6 − 184.8 kJ mol−1 for the decomposition of these components, respectively. The pre-exponential factors obtained by Kissinger's method fell between 3.7 × 1011 and 2.6 × 1015 min−1, with A > 109 min−1, indicating that only simple chemistry reactions occurred. The master plot method assigned F-type reaction models to the devolatilization of pseudo-extractives, pseudo-hemicellulose, and pseudo-lignin. Yet, an A-type model matched well with the devolatilization of pseudo-cellulose. From the verification step of the overall kinetic expression, it was found that the simulated pyrolysis progress profiles match with an excellent agreement with the experimental data with a minimum quality of fit of 92.9%. Thermodynamic parameters of activation were determined within the range of 109.3 − 183.3 kJ mol−1 for ΔH≠, 141.7 − 191.2 kJ mol−1 for ΔG≠, and (−71.3)−3.1 J mol−1K − 1 for ΔS≠. TGA–FTIR analysis indicated that most volatile species, comprising propanoic acid, methanol, acetaldehyde, dimethyl ether, and ethanol, are released below 650 K. The results of this study are important for using mango seed waste as a low-priced material for pyrolysis, with the potential of producing bioenergy and bio-based chemicals. This approach aligns with the valorization principle of utilizing lignocellulosic residues.