Acidic Zeolite L as a Highly Efficient Catalyst for Dehydration of Fructose to 5‐Hydroxymethylfurfural in Ionic Liquid

Zeolite L was synthesized by the hydrothermal method and post‐treated by NH4 exchange to adjust its acidity. The samples were systematic characterized by various techniques including XRD, X‐ray fluorescence spectroscopy, N2 adsorption–desorption, scanning electron microscopy, pyridine IR spectroscopy, and NH3 temperature‐programmed desorption. The results demonstrated that the NH4‐exchange post‐treatment increased the surface area, micropore volume, and acidity of zeolite L. The catalytic performance of the samples was tested in the dehydration of fructose to 5‐hydroxymethylfurfural (HMF) in ionic liquid (1‐butyl‐3‐methylimidazolium bromide, [bmim]Br). 99.1 % yield of HMF was obtained when the KL‐80 °C‐1 h sample (KL zeolite treated with 1 m NH4NO3 solution at 80 °C for 1 h) was used. The high efficiency could be attributed to the appropriate acid properties of the catalyst. The zeolite catalyst could be reused four times without significant decrease in activity.