Fractional‐Order Kinetics Modeling of Starch Thermal Degradation

Abstract

The thermal decomposition modeling of starch granules (rice, maize, and potato) is investigated in this work. Thermogravimetric analysis (TGA) under nitrogen conditions and different heating rates is carried out. First, a model‐free analysis is carried out to determine the variability of the activation energy with the relative conversion. The results reveal that the sequence of activation energy is rice > maize > potato. In turn, the activation energy is positively correlated (ρ = 0.98) with the relative crystallinity determined by X‐ray diffraction (XRD) analysis. Then, a fractional‐order version of the Sestak–Berggren equation is used to model the starch thermal decomposition. A least‐squares approach is used to estimate the underlying parameters by fitting non‐isothermal TGA curves. The results show that the parameters depend on the heating rate, but more strongly on the XRD relative crystallinity. Overall, the results reported in this study indicate that fractional‐order kinetics models provide an accurate description of the starch thermal degradation, without the use of the traditional TGA heuristic methods used for parameter estimation.