Unravelling the kinetics and thermodynamics of CO₂ gasification of lignin char: an isoconversional and multi-methodological analysis

This study investigated the non-isothermal kinetics of lignin char gasification under CO₂, a topic of growing interest in the field of renewable energy. Lignin char, prepared via carbonization, was analysed using infrared spectroscopy, transmission electron microscopy, X-ray diffraction, and thermogravimetric analysis. Characterization revealed a predominantly amorphous and turbostatic structure in the lignin char. The char gasification behaviour showed a single significant mass loss, attributed to the presence of lignin. Kinetic analysis using the isoconversional model-free method was used to determine the activation energy. These data aided in identifying a suitable kinetic model via the Coats–Redfern and Malek methods. The results indicated that a chemical reaction model best describes lignin char gasification. Additionally, the calculated thermodynamic parameters (ΔH*, ΔS*, and ΔG*) confirmed the non-spontaneous and endothermic nature of the process, providing deeper insights into the energetic dynamics of lignin char gasification. This study not only contributes to the understanding of lignin char behaviour under CO₂ gasification but also aids in the advancement of sustainable energy conversion technologies.