TG-FTIR Study on the Pyrolysis Properties of Lignin from Different Kinds of Woody Biomass

Abstract

Pyrolysis properties of lignin separated from four different kinds of wood (fir, larch, poplar, and eucalyptus) compared with commercial lignin were investigated using a thermogravimetric analyzer coupled to a Fouriertransform infrared spectrometer(TG-FTIR). Kinetic parameters of lignin thermal cracking reaction, such as activation energy and pre-exponential factor, were calculated using a three-dimensional diffusion model. The carbon residue rate and activation energy of softwood lignin were higher than those of hardwood lignin, showing that the decomposition of the former is relatively more difficult than that of the latter during pyrolysis. The distinct characteristic peaks of small-molecule gases and oxygenated chemicals such as ethers, phenols, acids, aldehydes, and alcohols were observed near the maximum weight loss rate by analyzing the 3D IR spectrum of the gas phase products. The formation routes of the main gaseous products were discussed, and the following order of releasing amounts was noted: CO₂>CH₄>H₂O>CO. It is believed that these results will provide valuable information for the thermo-chemical conversion process of lignin from the point of view of feedstock.