The acid-catalyzed dehydration of fructose was performed in a microbatch reactor at 90 degrees C using 1-H-3-methylimidazolium chloride, HMIM+Cl-, acting both as solvent and catalyst. A yield in 5-hydroxymethylfurfural (HMF) as high as 92% is achieved within 15-45 min. A productivity of 0.02 mmol of HMF, per min and per mmol of ionic liquid, can then be obtained. A remarkable feature, as compared with other catalytic systems, is the absence of decomposition of 5-hydroxymethylfurfural which can then be separately or continuously extracted in a simple manner with diethyl ether, thus allowing easier recycling of the ionic liquid after water removal. The absence of decomposition of 5-hydroxymethylfurfural is due to the lower free energy of activation calculated in the presence of the ionic liquid compared to other homogeneous or heterogeneous catalysts, which then makes, in a consecutive reaction network, the formation of the 5-hydroxymethylfurfural intermediate nearly quantitative. Under similar operating conditions, sucrose is nearly quantitatively transformed into HMF and unreacted glucose. (c) 2006 Elsevier B.V. All rights reserved.