Kinetic and thermodynamic analysis of Adenium obesum as a biofuel feedstock for pyrolysis and combustion
摘要
Rising global energy demand and the transition toward sustainable practices highlight biomass as a promising renewable resource for developing efficient and eco-friendly energy materials. However, the versatility of biomass feedstocks for thermochemical conversion necessitates evaluation of each type to enable process optimization. This study presents the first comprehensive investigation of Adenium obesum (desert rose, DR) as a renewable biofuel under both oxidative and inert conditions. Physicochemical characterization revealed low ash content with abundant fixed carbon and volatiles, yielding 17.5 MJ kg−1 of higher heating value (HHV). Thermogravimetric analysis (TGA) was performed at 5, 10, and 15 °C min−1, and kinetic parameters were evaluated by using iso-conversional model-free techniques. The average activation energies (Ea) for pyrolysis and combustion were determined as 151.9 and 71.0 kJ mol−1, respectively. The observed compensation effects validated the reliability of the TGA data, while the Criado master plot confirmed the multi-step reaction pathways, reaction-order and diffusion-controlled mechanisms during pyrolysis, and nucleation, growth, and phase-boundary models during combustion. Thermodynamic analysis showed average ΔG, ΔH, and ΔS values of 165 kJ mol−1, 146.4 kJ mol−1, and –30.1 J mol−1 K−1 for pyrolysis, and 150 kJ mol−1, 66.2 kJ mol−1, and –150 J mol−1 K−1 for combustion. Ea and ΔH have a small difference of about 5–7 kJ mol−1 which indicates facile activated complex formation. Overall, this work introduces DR as a novel, underexplored feedstock, providing critical kinetic and thermodynamic insights to optimize its valorization through pyrolysis and combustion.