Kinetics of Glucose Epimerization and Decomposition in Subcritical and Supercritical Water

Abstract

Glucose decomposition kinetics in subcritical and supercritical water were studied for the temperatures 573, 623, and 673 K, pressures between 25 and 40 MPa, and residence times between 0.02 and 2 s. Glucose decomposition products were fructose, saccharinic acids, erythrose, glyceraldehyde, 1,6-anhydroglucose, dihydroxyacetone, pyruvaldehyde, and small amounts of 5-hydroxymethylfurfural. Fructose was also studied and found to decompose to products similar to those of glucose, except that its epimerization to glucose was negligibly low and no formation of 1,6-anhydroglucose was detected. We concluded that only the forward epimerization of glucose to fructose was important. The glucose decomposition pathway could be described in terms of a forward epimerization rate, r gf , a fructose to decomposition products rate, r f , and a glucose to decomposition products rate, r g . A kinetic model based on this pathway gave good correlation of the experimental data. In the subcritical region, r g , r f , and r gf showed only small changes with pressure at a given temperature. In the supercritical region, the rate of glucose decomposition decreased with pressure at a given temperature. The reason for this decrease was mainly due to the decrease in r gf . The pressure effect in the supercritical region shows that there is a shift among the kinetic rates, which can lead to higher selectivity for glucose when decomposing cellulosic materials.

5-Hydroxymethyl-2-Furfural (HMF) – Heat-Induced Formation, Occurrence in Food and Biotransformation - a Review

“…Glucose as an aldohexose may be involved in competing reaction pathways leading to nonfuran cyclic ethers by-products formation. The C-C bond scissions may also occur in this case [Kabyemela et al, 1997;Jing & Lu, 2008]. On the other hand some enhancement of HMF yields obtained from sucrose as a carbohydrate source was observed.…”

Targeted chemical upgrading of lignocellulosic biomass to platform molecules

“…62,63 Despite the difficulty of developing an industrial process based on these high temperatures and short residence times, the company Renmatix® has developed extensive intellectual property in this area and describes its Plantrose™ process as relying on a two-stage process similar in concept to the one ). Kinetic data was taken from Schwald and Bobleter, 199 Adschiri et al 200 Mochidzuki et al 201 Sasaki et al 61 Bobleter and Pape, 202 Amin and Reid, 203 Kabyemela et al 204 and Matsumura et al 205 (B) Predicted glucose production from cellulose in pure water. Insert is a close-up for short reaction times.…”

Kinetic analysis for the isomerization of glucose, fructose, and mannose in subcritical aqueous ethanol

“…8) Many researchers have investigated the isomerization of saccharides such as glucose, mannose, and fructose in 100% (v/v) subcritical water. [9][10][11] It was reported that aldoses isomerized easily than ketoses in 100% (v/v) subcritical water. 10) Although kinetic analysis revealed that mannose was isomerized most easily to fructose among glucose, mannose, and fructose, the yields of fructose and glucose from mannose were still low.…”