Integrated thermal, kinetic and thermodynamic assessment of white pitch resin and α- and β-amyrin

This study investigated the thermal, kinetic, thermodynamic, and structural behavior of white pitch resin (WPR) and α- and β-amyrin (ABA) under an inert atmosphere. Thermoanalytical techniques were combined with physicochemical, spectroscopic, morphological, and X-ray diffraction analyses. Both samples presented similar higher heating values, 15.50 MJ kg−1 for WPR and 15.49 MJ kg−1 for ABA, indicating comparable energetic potential. XRD confirmed the crystalline nature of both samples, with ABA showing higher crystallinity (80.78 ± 0.5%) than WPR (68.15 ± 0.5%), consistent with its more defined composition. Spectroscopic and morphological analyses indicated greater structural heterogeneity in WPR and higher uniformity in ABA. Thermogravimetric analysis revealed distinct degradation profiles between the samples. WPR exhibited a main degradation event between 240.0 and 455.0 °C, associated with a mass loss of 89.9%, accompanied by secondary decomposition stages. Its DTG peak temperatures shifted from 311.44 to 374.68 °C as the heating rate increased. In contrast, ABA showed predominantly single-stage thermal degradation, with a mass loss of 98.62% between 200.0 and 420.0 °C and DTG peak temperatures ranging from 318.00 to 373.27 °C. TG–MS identified characteristic fragments of resinous and triterpenic compounds, linking the evolved volatiles to sample composition. Kinetic analysis using Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), Starink (STK), and Vyazovkin (VYZ) methods gave activation energies from 89.31 to 104.81 kJ mol−1. The iterative FWO and KAS procedures refined these values, yielding 96.43–101.18 kJ mol−1 for WPR and 94.39–95.48 kJ mol−1 for ABA, with R2 > 0.999. Criado’s master plot and Coats–Redfern analyses confirmed multimechanistic decomposition pathways and provided mechanism-dependent pre-exponential factors. Thermodynamic results indicated an endothermic and non-spontaneous process, with positive ΔH and ΔG values and negative entropy. Overall, kinetic modeling and thermokinetic simulation provided reliable parameters for predicting thermal behavior, optimizing pyrolysis conditions, and supporting scale-up strategies.