Comparison of the Hydrothermal Decomposition Reactivities of Chitin and Cellulose

The hydrothermal decomposition of chitin and cellulose was carried out using a stainless steel tube reactor of 6-mL capacity at 300−400 °C for 30−120 s under pressures of 15−30 MPa in order to clarify the influential factors on their reactivities based on their structural analyses. Cellulose was 3 times more reactive than chitin despite their similar unit skeleton structures, probably because their functional groups at C-2 differ (OH for cellulose; NHCOCH3 for chitin). Cellulose gave a higher conversion of 100% based on methanol-insoluble (MI) yield at 350 °C for 120 s. Their structural analyses before and after the hydrothermal treatment indicate that their intra- and intermolecular structures through the hydrogen bonds may be the keys to their different hydrothermal reactivities, although solvation behaviors in hot water and reaction conditions were also influential on the hydrothermal reactivity.