Investigation of slow pyrolysis mechanism and kinetic modeling of Scenedesmus quadricauda biomass

Abstract

Bioenergy potential of microalage Scednedesmus quadricuda through pyrolysis was investigated using kinetic and thermodynamic analyses. From model-free isoconversional methods, the estimated average activation energies were 152.37 (±20.93), 174.98 (±22.38), and 153.00 (±21.23) kJ/mol, using Friedman, OFW and advance Vyazovkin methods, respectively. Avrami-Erofeev's A1/4 reaction model was the most probable single-step reaction mechanism determined from the combined kinetic analysis. The activation energy profile, however, indicated a complex degradation process in the active pyrolysis zone. Two independent parallel reactions were considered in the active pyrolysis zone. Average activation energy for low temperature conversion was 77.95 (±3.12) kJ/mol, pre-exponential coefficient 4.86E4 (±2.24E4) s−1, and n = 1.51 (±0.10), whereas for high temperature conversion, the activation energy was 73.26 (±17.93) kJ/mol, pre-exponential coefficient 1.32E3 (±2.61E3) s−1, and n = 1.21 (±0.16). Thermodynamic analysis of pyrolysis in terms of enthalpy, Gibbs free energy, and entropy indicated the feasibility of conversion.