Brönsted and Lewis acid ZSM-5 zeolites for the catalytic dehydration of glucose into 5-hydroxymethylfurfural

• Brönsted and Lewis acid ZSM-5 zeolites have been prepared and characterized.
• They are active in glucose dehydration to HMF in a H2O/MIBK system, at 195 °C.
• The addition of NaCl allows reaching a HMF yield of 42% after 30 min with H-ZSM-5.
• HMF is not rehydrated to levulinic acid.

Three different acid ZSM-5 zeolites (H-, Fe- and Cu-ZSM-5) have been prepared and tested in the catalytic dehydration of glucose into 5-hydroxymethylfurfural (HMF). A commercial NH4-ZSM-5 zeolite (MFI) was modified by thermal or ion-exchange treatments in order to create Brönsted and Lewis acid sites. The zeolitic structure is preserved, and the resulting acid zeolites have demonstrated to be active in the glucose dehydration. The influence of different experimental variables, such as reaction time and temperature, substrate:catalyst molar ratio, volume of the organic solvent and aqueous phase, as well as the density and nature of acid sites, on the catalytic behaviour was investigated. Under the optimal reaction conditions, by using a biphasic NaCl (20 wt%) aqueous solution/methyl isobutyl ketone (MIBK) system, a glucose conversion of 80% and a HMF yield of 42% were achieved at 195 °C, after only 30 min, using H-ZSM-5, which has the lowest Lewis/Brönsted molar ratio among the prepared zeolites. The reutilization of this catalyst was also examined.

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