Pyrolytic kinetics of steam exploded lignin by TG/DTG analysis
Steam exploded lignin (SEL) thermal decomposition was investigated by thermogravimetric technique (TG/DTG) within the temperature range from room temperature to 920°C under different heating rates (10, 20, 30, 40, and 50°C. min-1). Little differences in the mass losses with heating rates were observed from TG analysis. It was established that SEL pyrolysis consisted of three main stages: water evaporation (< 200°C); devolatilization of organic volatiles (200-600°C); and char formation (> 600°C). The kinetic processing of non-isothermal TG/DTG data was performed by model-free methods proposed by Flynn-Wall-Ozawa (FWO) and Kissing-Akahira-Sunose (KAS). The average activation energies calculated from FWO and KAS methods are 74.2 kJ. mol-1 and 173.2 kJ. mol-1, respectively. Experimental results showed that values of kinetic parameters from both methods were analogous and could be successfully applied to understand the complex degradation mechanism of SEL. It is also helpful to achieve a better understanding of the devolatilization process of different type of biomass.