Pyrolysis and co-pyrolysis of Egyptian olive pomace, sawdust, and their blends: Thermal decomposition, kinetics, synergistic effect, and thermodynamic analysis

The pyrolysis and co-pyrolysis kinetics of two Egyptian olive-pomace (Kroneiki and Shamlali), wood dust, and their blends were investigated by advanced isoconversional model-free methods (Vyazovkin and Senum-Yang) and model-fitting methods (Coats and Redfern integral method) using different integrated reaction mechanisms g(α) through TGA/DTG, and DTA techniques. Master Plot's method was applied to determine the best reaction mechanisms for the pyrolysis of the tested materials. The synergistic effect of co-pyrolysis on kinetics and the role of biomass were examined. The average values of activation energy estimated from VYA and SY kinetic methods, respectively, for KROP, SHOP, FSSD, Blend (1), and Blend (2) were 90.57 and 85.67 kJ/mol, 70.05 and 65.26 kJ/mol, 131.66 and 126.71 kJ/mol, 66.73 and 62.09 kJ/mol, and 113.12 and 108.21 kJ/mol. The co-pyrolysis of KROP, SHOP, and FSSD at a heating rate of 10 °C/min showed the best synergistic pyrolysis performance. The diffusional reaction mechanisms are the most likely reactions to describe the pyrolysis process of the first conversion stage (α = 0.1–0.5), while the reaction mechanism C8 and the reaction order model (F4) are the most likely reactions to describe the second stage (α = 0.5–0.9) pyrolysis process. The higher ΔH and ΔS values for the FSSD and Blend (2) signify that these materials consumed more energy during the pyrolysis process, while the lower ΔH and ΔS values for the KROP, SHOP, and Blend (1) showed the opposite. A blending ratio of 50% KROP, 25% SHOP, and 25% FSSD showed the best performance at a heating rate of 10 °C/min. The obtained kinetics parameters and the solution of the master plots method were validated by solving the Coats and Redfern integral method based on the reaction mechanism function g(α) that showed the best fit in the master plots method.