Integrated multi-model kinetic and thermodynamic analysis of petroleum pitch gasification in oxygen atmosphere: Mechanistic insights using TGA and SEM–EDS techniques

Waste-to-energy and the maximum utilization of refinery by-products have become strong scientific interests, with gasification emerging as a sustainable pathway for effective conversion. In this context, detailed insight into petroleum pitch gasification is crucial for enabling its efficient and sustainable use as a viable feedstock in industrial gasification. The present study conducted TGA experiments at heating rates of 1.5, 2.25, 2.6, and 3.5°C/min. Multi-model isoconversional kinetic methods, including the Friedman, Flynn – Wall – Ozawa (FWO), Kissinger – Akahira – Sunose (KAS), and Starink, were employed to evaluate the activation energy over a wide range of conversions. In addition, the model-fitting Coats – Redfern and Criado’s methods were applied to elucidate the reaction model further and capture the gasification’s complexity. The mean activation energies were 158.5, 160.3, 164.0, and 160.6 kJ/mol at the Friedman, KAS, FWO, and Starink methods. The gasification process exhibited the contracting sphere model. Thermodynamic parameters (ΔHα, ΔGα, ΔSα), estimated using the Eyring equation, indicated gasification’s endothermic and non-spontaneous nature. SEM analysis of the intermediate residual chars revealed intermediate coke structures, pore development, and crack formation, which acted as active reaction sites during gasification. This multi-dimensional approach provides a comprehensive framework for understanding, modeling, and optimizing petroleum pitch gasification systems by integrating kinetics and thermodynamics.