Pyrolysis behaviors of four lignin polymers isolated from the same pine wood

Four lignin polymers, alkali lignin (AL), klason lignin (KL), organosolv lignin (OL), and milled wood lignin (MWL), were isolated from the same pine wood. Structural characterization by FTIR and (13)C NMR indicated that the four lignins have different structural features. Their pyrolysis behaviors were analyzed by TG-FTIR and Py-GC/MS. Thermally unstable ether bonds and side branches were well-preserved in AL and MWL, but were broken in OL and KL. Pyrolysis of AL and KL produce more phenols at low temperature by the breakage of ether bonds. AL and KL show lower activation energies in the main degradation stage, quantified by a distribution activation energy model with two linearly combined Gaussian functions. The evolution behaviors of typical gaseous products, CH4, CO2, and CO, were analyzed, and insights about the correlation between chemical structure and pyrolysis behavior were obtained.