Degradation Kinetics of Dihydroxyacetone and Glyceraldehyde in Subcritical and Supercritical Water

Abstract

The degradation kinetics of dihydroxyacetone and glyceraldehyde were studied at temperature ranges of 573−673 K, pressures of 25−40 MPa, and residence times from 0.06 to 1.7 s. The reactions of glyceraldehyde gave both dihydroxyacetone and pyruvaldehyde, and yields of dihydroxyacetone were always higher than those of pyruvaldehyde. The reactions of dihydroxyacetone gave glyceraldehyde and pyruvaldehyde, while the yields of pyruvaldehyde were always higher than those of dihydroxyacetone. This pathway involves the reversible isomerization between glyceraldehyde and dihydroxyacetone and their subsequent dehydration to pyruvaldehyde. A model was formulated on the basis of this pathway, and the kinetic rate constants involved were calculated using the experimental results. As the conditions change from subcritical to supercritical, the Arrhenius relationship becomes discontinuous near the critical point of water. At a constant temperature of 673 K, the kinetics constants showed a general increase with an increase in pressure.

Online integrated fractionation-hydrolysis of lignocellulosic biomass using sub- and supercritical water

“…The continuous reactors have been employed in many applications for the valorization of sugar 83 streams allowing a precise control over the reactions [19][20][21]. These reactions can be managed 84 using pressurized water and choosing the adequate reaction conditions.…”

“…In all the runs, oligomers conversion was higher than 85%. The exception was fructose, however, the reverse reaction is almost inhibited at the same conditions [19,20].…”

“…These molecules are further isomerized into pyruvaldehyde [19], which is transformed to lactic 369 acid by an extra oxidation. Hemicellulose hydrolysis is quite similar; the first step is the …”

A Review of Hydrothermal Carbonization of Carbohydrates for Carbon Spheres Preparation

“…Glyceraldehyde was transformed from fructose, isomerization of glucose, by retro-aldol condensation [51]. Dihydroxyacetone was produced through reversible isomerization of glyceraldehydes, while both dehydrated to form pyruvaldehyde [52]. Lactic acid was formed from pyruvaldehyde by benzilic acid rearrangement [53].…”

Evaluation of Antioxidative Activity for Extracts from Defatted Rice Bran Using 5-Axe Cobweb Chart

“…Such water has a low relative dielectric constant similar to that of organic solvents, such as methanol and acetone, at ambient temperature (Ayala et al, 2001;Herrero et al, 2006). The water also has a high ion product (Kuhlmann et al, 1994), and acts as a catalyst for hydrolysis or degradation (Kabyemela et al, 1997;Lesutis et al, 1999;Haghighat Khajavi et al, 2006). In this context, we treated the defatted rice bran with subcritical water to produce extracts having antioxidative and emulsifying properties, depending on treatment temperature (Wiboonsirikul et al, 2007a;2007b;Hata et al, 2008;Murayama et al, 2009;Jeyashoke et al, 2010;Chiou et al, 2011).…”