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Governing Chemistry of Cellulose Hydrolysis in Supercritical Water
Author(s) -
Cantero Danilo A.,
Bermejo M. Dolores,
Cocero M. José
Publication year - 2015
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201403385
Subject(s) - chemistry , glycolaldehyde , hydrolysis , cellulose , supercritical fluid , yield (engineering) , isomerization , dehydration reaction , dehydration , organic chemistry , reaction mechanism , fructose , inorganic chemistry , catalysis , biochemistry , materials science , metallurgy
At extremely low reaction times (0.02 s), cellulose was hydrolyzed in supercritical water ( T =400 °C and P =25 MPa) to obtain a sugar yield higher than 95 wt %, whereas the 5‐hydroxymethylfurfural (5‐HMF) yield was lower than 0.01 wt %. If the reaction time was increased to 1 s, the main product was glycolaldehyde (60 wt %). Independently of the reaction time, the yield of 5‐HMF was always lower than 0.01 wt %. To evaluate the reaction mechanism of biomass hydrolysis in pressurized water, several parameters (temperature, pressure, reaction time, and reaction medium) were studied for different biomasses (cellulose, glucose, fructose, and wheat bran). It was found that the H + and OH − ion concentration in the reaction medium as a result of water dissociation is the determining factor in the selectivity. The reaction of glucose isomerization to fructose and the further dehydration to 5‐HMF are highly dependent on the ion concentration. By an increase in the pOH/pH value, these reactions were minimized to allow control of 5‐HMF production. Under these conditions, the retroaldol condensation pathway was enhanced, instead of the isomerization/dehydration pathway.