Generalized two-dimensional correlation infrared spectroscopy to reveal the mechanisms of lignocellulosic biomass pyrolysis

As the initial stage of combustion, pyrolysis plays a significant role in the combustion of biomass, atypical solid fuel that contains higher volatile contents than other solid fuels. To better understand the pyrolysis mechanism, we herein employed generalized two-dimensional correlation infrared spectroscopy (2D-PCIS) to analyze the functional group evolution in bamboo chars between 250 and 600 degrees C, and by combination of the volatile release properties, the biomass pyrolysis process mechanism was speculated. We found that below 250 degrees C, the hydrogen bonding network within the biomass macromolecular structure was broken, while at 250-300 degrees C, the branched structures were broken during hydration and decarboxylation reactions, resulting in the formation of H2O, acetic acids, and CO2. The subsequent formation of various phenols between 300 and 350 degrees C mainly originated from rupture of the ether bridges in the lignin structure. In addition, molecular rearrangement of the intermediates from the decomposition of holocellulose resulted in aromatic ring formation. Interestingly, analysis by 2D-PCIS demonstrated that the aromatic rings bearing adjacent substituents easily formed double active sites following breakage of the branched structures. These structures then easily produced fused ring systems below 400 degrees C, while dehydrogenation and polycondensation at > 400 degrees C promoted the formation of fused rings from aromatic rings without adjacent substituents. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.