The Key Role of Textural Properties of Aluminosilicates in the Acid-Catalysed Dehydration of Glucose into 5-Hydroxymethylfurfural

Three protonated zeolites (H-ZSM-5, H-Y and H-Beta) were prepared and tested in the catalytic dehydration of glucose into 5-hydroxymethylfurfural (HMF). The catalytic results are compared with those obtained with a mesoporous MCM-41-type aluminosilicate, in order to assess the influence of textural and acid properties on the catalytic performance. The dehydration process was carried out in a biphasic water/methyl-isobutyl ketone (MIBK) system, and the positive effect of NaCl addition (20 wt. %) on both HMF selectivity and yield was observed. Using the H-Beta zeolite in a NaCl aqueous solution/MIBK, at 195 degrees C, the best catalytic results were obtained, with a HMF yield of 56%, close to that obtained with 10Al-MCM-41 (63%), after only 30 min of reaction time; whereas HMF yields rose only up to 42% using H-ZSM-5 and H-Y. This fact demonstrates the positive effect of mesoporosity to favour the dehydration of glucose to HMF. The reutilisation of these catalysts was also examined.