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Keywords:

  • hemicellulose hydrolysis;
  • corn stover;
  • kinetic modeling;
  • Saeman model;
  • biphasic model;
  • dilute acid pretreatment;
  • maleic acid;
  • Arrhenius equation

Abstract

Maleic acid-catalyzed hemicellulose hydrolysis reaction in corn stover was analyzed by kinetic modeling. Kinetic constants for Saeman and biphasic hydrolysis models were analyzed by an Arrhenius-type expansion which include activation energy and catalyst concentration factors. The activation energy for hemicellulose hydrolysis by maleic acid was determined to be 83.3 ± 10.3 kJ/mol, which is significantly lower than the reported Ea values for sulfuric acid catalyzed hemicellulose hydrolysis reaction. Model analysis suggest that increasing maleic acid concentrations from 0.05 to 0.2 M facilitate improvement in xylose yields from 40% to 85%, while the extent of improvement flattens to near-quantitative by increasing catalyst loading from 0.2 to 1 M. The model was confirmed for the hydrolysis of corn stover at 1 M maleic acid concentrations at 150°C, resulting in a xylose yield of 96% of theoretical. The refined Saeman model was used to evaluate the optimal condition for monomeric xylose yield in the maleic acid-catalyzed reaction: low temperature reaction conditions were suggested, however, experimental results indicated that bi-phasic behavior dominated at low temperatures, which may be due to the insufficient removal of acetyl groups. A combination of experimental data and model analysis suggests that around 80–90% xylose yields can be achieved at reaction temperatures between 100 and 150°C with 0.2 M maleic acid. Biotechnol. Bioeng. © 2008 Wiley Periodicals, Inc.