Understanding the behavior of chitin in Subcritical and Supercritical Water in a continuous reaction system.

Abstract

Chitin ((1,4)-β-N-acetylglucosamine) is the second most widespread bio-polymer worldwide. Its high crystallinity and low solubility limit the exploitation of its antimicrobial, non-toxic and biodegradable properties, among others. So far, batch reactors and residence times longer than 1min with sub-and supercritical water have been tested to depolymerize chitin. In this work, we investigate the influence of temperature and residence time on chitin transformation in sub- and supercritical water (25MPa, 350 °C to 385 °C), using ultrafast continuous reactors (0.3s to 12s). Within the range studied, chitin gasification above 30% was detected when operating at high temperature (T≥376 °C) and a long residence time (t≥5s). At these conditions, mean particle size of water-insoluble fraction was also reduced to ca. 280 nm. By-products such as glycolaldehyde, acetic acid and 5-HMF were identified in the water-soluble fraction, indicating the presence of side reactions.