Kinetic and thermodynamic analyses based on thermogravimetric pyrolysis of watermelon seed by isoconversional and master plots methods

Abstract

Converting watermelon seeds into biomass energy is a good environmentally friendly opportunity to meet the increasing energy demand and reduce the dependence on fossil fuels. Thermogravimetric pyrolysis of watermelon seeds was investigated under non-isothermal conditions at different heating rates under inert atmosphere. Thermogravimetric analysis of watermelon seeds revealed four pyrolysis stages, two of which are active stages. Using attained pyrolysis characteristics, activation energies were calculated applying Kissinger-Akahira-Sunose and Starink isoconversional kinetic methods. The average activation energies using Kissinger-Akahira-Sunose method were 99.9 and 161.0 kJ/mol for the second and the third stage, respectively. Similarly, the average activation energies using Starink method were 100.2 and 161.3 kJ/mol for the second and the third stage, respectively. Pre-exponential factors and reaction models were determined by the application of Criado's master plots method combined with isoconversional methods. The experimental curves matched successfully with the developed models. Thermodynamic parameters including ΔH, ΔG, and ΔS values were calculated.