Linking isoconversional pyrolysis kinetics to compositional characteristics for multiple Sorghum bicolor genotypes

• Activation energy, Ea, determined for Sorghum bicolor via isoconversional methods.
• Observed average Ea was 226.6 ± 24.6 kJ mol−1.
• Models predicting Ea based on compositional parameters showed significant correlations.
• Predicted average Ea was 226.9 ± 57.9 kJ mol−1.
• Model robustness shown using pine (Ea in kJ mol−1 at 217.0 ± 13.1 (obs.), 210.6 ± 15.6 (pred.).

Pyrolysis activation energy, Ea, was determined using thermogravimetric analysis (TGA) for twenty Sorghum bicolor genotypes using Arrhenius-based, isoconversional kinetics formulations. Isoconversional temperatures (Tα) at various conversion levels, α from 0.05 to 1.0, were determined using TGA for separate leaf and stem tissue. Ea was then determined using Kissinger–Akahira–Sunose and Friedman formulations. Observed Ea and predictor variables including conversion level and compositional parameters (e.g. proximate, neutral detergent fiber, lignin, cellulose, and hemicellulose content and crystallinity index, were input to a stepwise regression to build an Ea prediction model. Ea calculated using Tα varied with conversion indicating more complex kinetics (multiple reactions) than a single kinetic triplet can describe although averages of observed and predicted Ea were statistically equivalent at 197 and 202 kJ mol−1, respectively. Additionally, pine wood was evaluated to assess model robustness. With no significant difference between observed and predicted Ea (217 versus 211 kJ mol−1, respectively), the model appeared robust.