Four Logistic Distribution Activation Energy Model on Catalytic Pyrolysis Kinetics of Biomass Wastes by Loading Potassium and Iron

The pyrolysis kinetics of herb residues with potassium and iron addition were investigated using thermogravimetric analysis (TGA) and a four-logistic distribution activation energy model (4LG-DAEM). The model included hemicellulose, cellulose, lignin, and a pseudo-component for coke. Kinetic compensation effects and n -order mechanism functions were incorporated to better fit the catalytic pyrolysis process. Compared with conventional models, the 4LG-DAEM captured the TG curve characteristics more accurately, with R 2 values above 0.995. Fitted parameter analysis showed that potassium addition significantly reduced the activation energies of cellulose, hemicellulose, lignin, and biochar reactions, but narrowed the reaction temperature ranges. Iron addition had a smaller effect on activation energies but widened the reaction temperature range. The combination of potassium and iron had a synergistic effect, enhancing the secondary reactions of hemicellulose, cellulose, and coke more effectively than single catalysts. Potassium–iron composite catalysts notably increased the proportion of biochar secondary reactions in the total process. Additionally, the 4LG-DAEM model demonstrated strong predictive ability for the kinetics of potassium–iron catalyzed pyrolysis of various biomasses.