67. Kumar, Sandeep; Gupta, Ram B.. Hydrolysis of Microcrystalline Cellulose in Subcritical and Supercritical Water in a Continuous Flow Reactor. Industrial & Engineering Chemistry Research (2008), 47(23), 9321-9329.
For cellulosic ethanol prodn., efficient hydrolysis of cryst. cellulose to easily fermentable sugars is important. The focus of this study is to maximize the yield of cellulose hydrolysis in subcrit. and supercrit. water at practically achievable reaction times. Microcryst. cellulose is treated with subcrit. and supercrit. water in a temp. range of 302-405 C, at a pressure of 27.6 MPa, and residence times of 2.5-8.1 s. Cellulose-water slurry of 2.7 wt % after mixing with preheated water is rapidly heated to the reaction temp. and then the reaction product is rapidly cooled in a continuous reactor. Cellulose partially dissolves in subcrit. water at 302 C and completely dissolves at 330 C. About 65% of cellulose converts to the oligomers and monomers at 335 C in 4.8 s and also at 354 C in 3.5 s. Upon increase in the reaction time or temp. to supercrit. region, oligomers and monomers partially degrade to glycoaldehyde dimer, D-fructose, 1,3-dihydroxyacetone dimer, anhydroglucose, 5-HMF, and furfural. The effect of temp., pressure, and reaction time on formation of various products is studied. In addn., the effect of a base catalyst, K2CO3, was examd. The catalyst increased cellulose gasification in the 302-333 temp. range.