Assessment of kinetic parameters, mechanisms and thermodynamics of Tithonia diversifolia pyrolysis

In the present study, Tithonia diversifolia (TD), a widely available invasive weedy plant was selected for investigating the thermo-kinetic parameters using a thermogravimetric analyzer. Isoconversional methods namely Friedman, Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sonuse (KAS), and Miura-Maki methods were applied to elucidate the kinetics of the active pyrolysis zone of TD. The kinetic parameters were also used to determine the thermodynamic parameters. Combined kinetic (CK) model was then used to determine the devolatilization model of TD. The results of Y-master plot demonstrated that the pyrolysis of TD followed initially the order-based reaction models (F4, F3, and F2), which gradually changed to diffusion model (D3) at the latter stage. The average activation energies (E-o) of biomass degradation as determined by Friedman, FWO, and KAS method were 198.13 kJ mol(-1), 195.54 kJ mol(-1), and 196.15 kJ mol(-1), respectively. The pre-exponential factor (A) determined from the Friedman, KAS, FWO, and Miura-Maki method is within the range of the order of 10(13)-10(23) min(-1). Thermodynamic outcomes also support the kinetic results. Combined kinetic model (CK model)-based one-step pyrolysis mechanisms of TD biomass was f(alpha=3.12x10(15)/beta exp(-204988/RT(1-alpha)1.1585 alpha-3.02-ln(1-alpha 0.80). Results also reveal that the single-step model explains the pyrolysis of TD to a certain extent. Characterization of the bio-oil and biochar generated during fixed-bed pyrolyser was also presented. Our results, therefore, provide valuable information regarding the bioenergy potential of TD in thermochemical conversion processes and helps in the subsequent designing of pyrolysis reactor systems.

Automated summary

In this study, the thermo-kinetic parameters of Tithonia diversifolia (TD), an invasive weedy plant, were investigated using a thermogravimetric analyzer. Different isothermal conversion methods were applied to study the kinetics of TD's pyrolysis. The results showed that TD's pyrolysis followed a one-step model, providing valuable information on its bioenergy potential and thermochemical conversion processes.