Xylose hydrogenation:: kinetic and NMR studies of the reaction mechanisms

Hydrogenation of xylose over Raney nickel was studied in a batch reactor. A pseudo-homogeneous kinetic model was able to prognose the xylose and xylitol concentrations rather well. The obtained fit for the activation energies suggests that external diffusion limitations are absent in our experimental conditions. The sugar equilibria studies gave new information about the temperature dependence of the alpha-beta-pyranose equilibria. It was found that the equilibria in D2O follows an S-shaped curve, the equilibria being shifted towards the a-form at higher temperatures. (C) 1999 Elsevier Science B.V. All rights reserved.