A modulated-TGA approach to the kinetics of lignocellulosic biomass pyrolysis/combustion

Microcrystalline cellulose, Birchwood xylan, and Organosolv lignin were selected as the representatives of the three major components in lignocellulosic biomass: cellulose, hemicelluloses and lignin, respectively. The thermal decompositions, both pyrolysis and combustion, of these biomass components as well as a natural woody biomass (Acer saccharum) were investigated using High-Resolution Modulated TGA. The activation energies of each decomposition process were determined by Modulated TGA without any assumptions and mathematical model fitting. For the combustion of microcrystalline cellulose, the char residues underwent glowing ignition due to the presence of oxygen, and its first derivative of weight loss curve showed two thermal decomposition peaks, while only a single peak was observed for pyrolysis of microcrystalline cellulose in a nitrogen atmosphere. However, the effect of air was less evident in the thermal degradation of the Birchwood xylan. With air as the sample environment in the TGA experiment, the thermal decomposition of Organosolv lignin was simplified, and the onset of the primary decomposition shifted to temperatures greater than 300 °C, the decomposition zone became narrower, and the mass of residual solids at 600 °C was negligible. Since the sum of the TGA profiles (in air) of the three major biomass components closely matched the TGA profile (in air) of an actual wood sample (A. saccharum), the potential of using TGA to predict biomass compositions was indicated.