Kinetic and thermodynamic analysis of wooden crayon shavings (WCS) non-isothermal pyrolysis based on enthalpy-entropy compensation

Wooden crayon shavings (WCS) represents a novel, previously unexplored composite lignocellulosic waste material, comprising wood, waxy binders, pigments, and inorganic fillers, with promising relevance for thermochemical valorization. In this study, proximate and ultimate analyses confirmed high volatile content and carbon-rich organic matter, while SEM-EDS observations revealed a heterogeneous microstructure with distinct wood fibers, pigment-rich domains, and dispersed mineral fillers, supporting a multicomponent WCS behavior. Non-isothermal pyrolysis of WCS was investigated by TG-DTG analysis at heating rates of 5, 10, and 20 K/min, focusing strictly on intrinsic decomposition reactions. Overlapping DTG curves were successfully resolved into five pseudocomponents using Lognormal deconvolution function, achieving an excellent reconstruction accuracy (R 2 > 0.999), and enabling clear identification of extractives volatilization, hemicellulose decomposition, cellulose depolymerization, and multi-stage lignin transformation reactions. Isoconversional kinetic analysis using Friedman’s and numerical optimization methods revealed a strong dependence of activation energy on conversion, confirming chemically and kinetically heterogeneous nature of WCS pyrolysis. The obtained kinetic parameters coupled with physically meaningful reaction models (as first-order, n -th order, Avrami-Erofeev, and diffusion-controlled reaction mechanisms) were accurately reproduced experimental DTG features at all heating rates. Thermodynamic and kinetic compensation effects were validated through modified Cremer-Constable (C C) plot, activation enthalpy (ΔH # ) - activation entropy (ΔS # ) relationship, Exner and Krug criteria tests, and Compensation Quality Factor ( CQF ) analysis. The close agreement between isokinetic and compensation temperatures (∼ 733 K) with high correlation coefficients, were confirm a genuine physical-chemical origin of compensation effect, during WCS pyrolysis.