Hydrothermal degradation of hemicelluloses from triploid poplar in hot compressed water at 180-340 °C

Hemicelluloses isolated from triploid poplar were subjected to hydrothermal degradation at 180-340 degrees C. The detailed physicochemical characteristics of hydrothermal degradation products including monosaccharide and XOS, molecular weight, inhibitory and organic compounds were detected by HPAEC, GPC, HPLC, and GC MS, respectively. An increase in temperature led to a significant decrease in molecular weight and an increase in C-2-C-5 organic alcohols and acids. More importantly, besides two well-known routes that hemicelluloses are hydrolyzed to monosaccharide, followed by further degraded to furfural, a series of reaction routes was proposed to clarify and explain the mechanisms of the hydrothermal degradation of hemicelluloses from triploid poplar, which involved: (i) a predominant route of fragmentation; (ii) side reactions such as oxidation, dehydration, isomerization/rearrangement, and self-lactonization; (iii) larger molecular fragments from sugars by deoxydation or/and oxidation, followed by self-lactonization; and (iv) very few extensive re-polymerization including esterification and condensation among hemicelluloses and lignin fragments. (C) 2016 Elsevier Ltd. All rights reserved.