Mechanism and Kinetics of Cellobiose Decomposition in Sub- and Supercritical Water

Abstract

Cellobiose decomposition kinetics and products in sub- and supercritical water were studied with a flow apparatus at temperatures from 300 to 400 °C at pressures from 25 to 40 MPa, and at short residence times (0.04−2 s). Cellobiose was found to decompose via hydrolysis of the glycosidic bond and via pyrolysis of the reducing end. Pyrolysis products were glycosylerythrose (GE) and glycosylglycolaldehyde (GG) which were confirmed by FAB-MS. Hydrolysis products were glucose, erythrose, and glycolaldehyde from cellobiose, GE, and GG, respectively, as well as glucose decomposition products. The kinetics from glucose decomposition were used to fit the experimental results and evaluate rate constants of hydrolysis (k H) and pyrolysis rate constants (k 1 and k 2). The activation energy for the hydrolysis of cellobiose and pyrolysis products GG and GE was found to be 108.6, 110.5, and 106.1 kJ/mol, respectively. In the supercritical region, there was a decrease in the pyrolysis rates k 1 and k 2 and a corresponding increase in hydrolysis selectivity from 85% to 95% as the pressure increased from 30 to 40 MPa.

Model for Random Hydrolysis and End Degradation of Linear Polysaccharides: Application to the Thermal Treatment of Mannan in Solution

“…This is in contrast to the observation of a higher degradation rate for the monomer (kgtot ) 0.45 s -1 ) 31 than for the dimer (k1 + k2 ) 0.16 s -1 ). 13 Second, the hydrolysis rate in the present model is independent of the position of the bond and of the size of the fragment. This is contrary to theoretical arguments 33 and experimental data on acid hydrolysis of xylo-oligosaccharides 14 and R-(1,4)-glucans, 15 which indicate that the glucosidic bond at the nonreducing end should be scissioned about twice as fast as the other bonds.…”

“…Optimization of model parameters indicated that mannan thermal hydrolysis has an activation energy similar to those of recently published results for cellobiose. 13 The activation energy for degradation is higher than that for hydrolysis, which may be related to the influence of the formate buffer. The present model can be applied to first-order depolymerization of other linear polymers with one link type in order to determine reaction rate constants or make predictions about molecular weight distribution on the basis of known reaction rate constants.…”

“…The high reactivity of the reducing end was observed experimentally for cellobiose. 13 Previous modeling of homogeneous hydrolysis includes, on the one hand, the development of rate equations for thermal hydrolysis of oligosaccharides 14,15 and, on the other hand, the determination of acid hydrolysis rates from modeling of experiments with a polysaccharide, dextran. 16 In addition, Monte Carlo simulation has been performed to predict glucose production from amylose.…”

Degradation Kinetics of Glucuronic Acid in Subcritical Water

“…In recent years, though studies have been published on the kinetics of the degradation and hydrolysis of mono-, di-, oligo-, and polysaccharides in subcritical water, 11,12,[15][16][17] application-oriented publications remain the majority. We too have reported several studies on the kinetics of degradation of mono-, 18) di-, [19][20][21] tri-, 22) and oligosaccharides 8) under subcritical conditions.…”

Solubility of Saturated Fatty Acids in Water at Elevated Temperatures

“…Many researchers have reported the extraction of natural substances from plant sources with subcritical water. [3][4][5][6] Kabyemela et al have investigated the epimerization and decomposition of glucose 7) and the decomposition of cellobiose 8) in sub-and supercritical water. Yoshida et al 9) have reported the production of organic acids and amino acids through the hydrolysis ofˆsh meat by subcritical water.…”