Cistus shells used as a sustainable matrix for bioenergy production through slow pyrolysis process: Kinetic and thermodynamic study

Cistus shells have attracted considerable attention as a potential feedstock for second-generation biofuels, specifically through fixed-bed pyrolysis. Analyzing the composition of cistus shells exhibits a high proportion of volatile products (74.82%), carbon (69.02%), oxygen (26.48%), and notably, a high calorific value (23290 kJ kg−1). Characterizing the bio-oil derived from cistus shells contains various compounds like fatty acids and alcohols that can be converted into fuels. The Eα values, determined using the FWO and KAS methods, were 179.773 kJ mol−1 and 177.92 kJ mol−1, respectively. The kinetics were described by the D3, D2, F3, and P2/3 models, with corresponding energies of 87 kJ mol−1, 78 kJ mol−1, 56 kJ mol−1, and 53 kJ mol−1, respectively. Increasing the conversion rate from 35% to 55% results in an increase in ΔH and ΔG values for the FWO method from 148.11 kJ mol−1 to 190.5 kJ mol−1 and from 168 kJ mol−1 to 202 kJ mol−1, respectively. For the KAS method, the values increase from 146 kJ mol−1 to 188 kJ mol−1 and from 44.44 kJ mol−1 to 85 kJ mol−1. Notably, the entropy variation decreased as the conversion rates increased, indicating a stronger tendency to approach thermodynamic equilibrium during the pyrolysis process.