Glucose and Fructose Decomposition in Subcritical and Supercritical Water:  Detailed Reaction Pathway, Mechanisms, and Kinetics

Abstract

Experiments were performed on the products of glucose decomposition at short residence times to elucidate the reaction pathways and evaluate kinetics of glucose and fructose decomposition in sub- and supercritical water. The conditions were a temperature of 300−400 °C and pressure of 25−40 MPa for extremely short residence times between 0.02 and 2 s. The products of glucose decomposition were fructose, a product of isomerization, 1,6-anhydroglucose, a product of dehydration, and erythrose and glyceraldehyde, products of C−C bond cleavage. Fructose underwent reactions similar to glucose except that it did not form 1,6-anhydroglucose and isomerization to glucose is negligible. The mechanism for the products formed from C−C bond cleavage could be explained by reverse aldol condensation and the double-bond rule of the respective enediols formed during the Lobry de Bruyn Alberda van Ekenstein transformation. The differential equations resulting from the proposed pathways were fit to experimental results to obtain the kinetic rate constants.

Properties of Hydrochar as Function of Feedstock, Reaction Conditions and Post-Treatment

“…The infra-red spectra give valuable info about the functional groups and structure of hydrochar. The use of this spectroscopy is common in thermochemical biomass conversion and well documented allowing a relatively easy assignment of the IR absorption bands [27,28]. The IR spectra of hydrochar, produced at 220 • C (Figure 9), from straw and cellulose [17], produced are very similar: strong "stretching" adsorption bands at 3400 and 2900 cm −1 for ν(O-H) and ν(C sp3 -H), a distinct ν(C=O)-band at 1700 cm −1 and a ν(C=C)-band at 1600 cm −1 .…”

Synthesis of Transportation Fuels from Biomass: Chemistry, Catalysts, and Engineering

“…Figure 18 shows the Wooten-Seeman-Hajaligol model where the first Insight into the pyrolysis mechanism can be learned from studying the chemistry for the decomposition pathways of cellulose and glucose in aqueous water, which is shown in Figure 19. [204][205][206] Glucose undergoes isomerization to form fructose, which then can undergo dehydration to form HMF. The mechanism of HMF formation is reviewed by Antal and co-workers.…”

Microwave-assisted Liquefaction of Rape Straw for the Production of Bio-oils

“…The furan derivatives that dehydrated from xylose originated from further decomposition of hemicelluloses (Dias et al 2005). The further decomposition of cellulose and hemicelluloses may also have generated organic acids, such as acetic acid (Kabyemela et al 1999;Zou et al 2011). The organic acids were esterified with methanol under acidic conditions, resulting in the increase of esters.…”