Hydrothermal decomposition of various crystalline celluloses as treated by semi-flow hot-compressed water

Various types of crystalline celluloses I, II, III_I, III_II, IV_I and IV_II that have been adjusted for their degree of polymerization were treated by semi-flow hot-compressed water (HCW) at 230–270 °C/10 MPa/15 min to study their hydrothermal decomposition. The treatments resulted in either partial or complete decomposition of the celluloses and the decomposed products were primarily recovered as hydrolyzed, dehydrated and fragmented ones as well as organic acids in the water-soluble (WS) portions. Their results of hydrothermal decomposition and its kinetics revealed that the celluloses decomposition is dependent on the types of crystalline celluloses as well as temperature of the HCW treatment. The outcome from the WS portions at 270 °C/10 MPa/15 min showed that the degree of difficulty for decomposition is lower in group II (cell II, cell III_II, cell IV_II) than group I (cell I, cell III_I, cell IV_I), indicating that group II is less resistant to decomposition by HCW treatment. Therefore, the decomposition behaviors of the cellulose are due to the inherent differences in the crystalline structures.