Decomposition of Cellulose in Near-Critical Water and Fermentability of the Products

The noncatalytic decomposition characteristics of cellulose in near-critical water were examined by heating a sealed reactor in which the cellulose and water were charged in a salt bath kept at 305, 355, or 405 °C. Cellulose was rapidly decomposed to water solubles (WS), and the WS was further decomposed after the WS yield reached nearly 80%. The heating time giving the maximum WS yield was shortened to under 15 s by increasing the treatment temperature to over 355 °C. In the WS formation process, hydrolysis preferentially occurred, and the glucose yield reached 40% by the treatment for 15 s in the bath kept at 355 °C. On entering the second decomposition process, the WS was converted to gaseous products and methanol-soluble products, and char-like solid products were formed from the liquid phase. The hydrolysate of cellulose obtained in the WS formation process was subjected to a fermentation test, and the formed glucose was confirmed to be converted to ethanol.