Efficient synthesis of furfural from xylose over HCl catalyst in slug flow microreactors promoted by NaCl addition

Abstract

Efficient synthesis of furfural from xylose over the HCl catalyst in a water-methyl isobutyl ketone biphasic system was achieved in slug flow microreactors, using NaCl as a promotor which facilitates xylose dehydration and suppresses xylose condensation. An optimized furfural yield of 93% was obtained from 1 M xylose over 0.2 M HCl with 10 wt% NaCl at 180°C within 4 min. A comprehensive kinetic model was developed from monophasic experiments in water in microreactors, by incorporating the acidity in water and kinetic constants as a function of the chloride ion concentration. The coupling of kinetic model with furfural extraction, with consideration of phase volume change as a function of temperature and partial phase miscibility, enables to predict the results of biphasic experiments in microreactors where mass-transfer limitation was eliminated. The aqueous phase containing HCl and NaCl could be readily recycled and reused multiple times without noticeable performance loss.