Contrasting the Pyrolysis Behavior of Selected Biomass and the Effect of Lignin

Abstract

This study was aimed at comparing the pyrolysis behavior of several selected biomass samples, namely, pine wood, poplar wood, wheat straw, and sugarcane bagasse, with a particular attention to the effect of lignin. Raw samples were first treated using Soxhlet solvent extraction with a 2:1 (v/v) mixture of toluene/ethanol to remove wax. Lignin was then removed by soaking the dewaxed samples in a 1.0 M sodium chlorite solution at 343 K till the solids became white. Fourier transform infrared (FTIR) spectroscopy analysis was applied to characterize the surface functional groups of the samples. The morphology of the samples before and after delignification treatment was analyzed using scanning electron microscope (SEM). The pyrolysis behavior of the raw and treated biomass samples was studied using a thermogravimetric analyzer (TGA) operating in nitrogen at a constant heating rate of 10 K min−1 from room temperature to the final temperature 823 K. The FTIR and SEM results indicated that lignin can be successfully removed from the raw biomass via the chemical treatment used. As expected, the pyrolysis behavior differed significantly among the various raw biomass samples. However, the pyrolysis behavior of the delignified samples showed almost identical thermal behavior although the temperature associated with the maximum rate of pyrolysis was shifted to a lower temperature regime by ca. 50 K. This suggests that the presence of lignin significantly affected the biomass pyrolysis behavior. Thus, the pyrolysis behavior of the biomass cannot be predicted simply from the individual components without considering their interactions.