Pyrolytic thermal degradation kinetics of pigeon pea stalk (Cajanus Cajan): Determination of kinetic and thermodynamic parameters

Abstract

This article highlights the pyrolytic thermal degradation behavior of pigeon pea stalk (PPS) at different heating rates (β) ranging from 10 to 40 °C/min in inert nitrogenous atmosphere using the thermogravimetric analysis (TGA). Three isoconversional methods: Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Starink method were used to evaluate the kinetic parameters, including activation energy (Ea) and pre-exponential factor for range of conversion degree (α) 0.1 to 0.9. The highest average value of activation energy for PPS was found 126.24kJmol−1 for FWO method followed by Starink and KAS method as 122.59kJmol −1 and 116.23kJmol −1 respectively. Pre exponential factor (A) and thermodynamic parameters such as change in Gibbs free energy (G), enthalpy (ΔH) and entropy (ΔS) were computed and critically discussed. The average value of ΔH was found as 117.36, 110.95 and 120.97kJmol −1 for FWO, KAS and Starink method, respectively. Whereas, ΔG values were noticed very close to each other (ranges from 302 to 315kJmol −1) and average values of ΔS were − 181, −192 and −185Jmol−1K−1 for OFW, KAS and Starink method, respectively. The difference between average activation energy and value of ΔH was noticed imperceptible (∼5kJmol −1), which is a positive confirmation about the generation of green product from PPS requiring low energy potential. As summary PPS was found to have significant potential to be used as a feedstock for bioenergy production.