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

Abstract

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 charlike 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.

Noncatalytic hydrolysis of guar gum under hydrothermal conditions

“…Presumably, the decrease in TOC values at longer reaction times results from the formation of the solid residue recovered on the glass filter. Although gaseous products were not analyzed in this study, their formation was less likely at these temperatures as has been observed for other polysaccharides under hydrothermal conditions 21,29,36 even in the presence of alkali or nickel catalyst. 37 At 180°C, the lowest temperature studied, a longer time was required to dissolve guar gum.…”

“…[16][17][18] Hydrothermal treatment leads to simple processes of low environmental impact. In fact, the hydrolytic degradation of polysaccharides such as cellulose [19][20][21][22][23][24] and hemicelluloses 25,26 under hydrothermal conditions, including supercritical conditions (above 374°C) has been extensively studied to produce mono-and oligosaccharides. Recently, we have demonstrated that naturally occurring polysaccharides, that is, pectic acid 27,28 and starch 29,30 can be converted into mono-and oligosaccharides at relatively low temperatures (around 200°C) without any catalyst under hydrothermal conditions.…”

Hydrothermal hydrolysis of starch with CO2 and detoxification of the hydrolysates with activated carbon for bio-hydrogen fermentation

“…Other studies on the hydrothermal degradation of polysaccharides (Table 1) used small batch reactors (total volume ~ 3.3-3.6 mL) heated rapidly from room temperature up to 200 °C by immersion in a molten salt bath maintained at constant temperature giving a heat-up period of about 2 min included in the reaction time for reaction completion. The reactor was quenched in cold water [19,27,33,34].…”

Hydrogen production from sewage sludge solubilized in hot-compressed water using photocatalyst under light irradiation

“…Sakaki et al intensively investigated the decomposition characteristics of plant biomass and cellulose in hot-compressed water (HCW) in order to obtain energy-rich organic compounds such as glucose [8][9][10]. Liquors thus obtained from biomass can catalytically be steam reformed into hydrogen using catalysts such as Ni=Al2O3 [11,12].…”