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 E alpha 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 Delta H and Delta G 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.