Production of 5-Hydroxymethylfurfural from Fructose in Ionic Liquid Efficiently Catalyzed by Cr(III)-Al2O3 Catalyst

A series of metal-Al2O3 catalysts were prepared simply by the conventional impregnation with Al2O3 and metal chlorides, which were applied to the dehydration of fructose to 5-hydroxymethylfurfural (HMF). An agreeable HMF yield of 93.1% was achieved from fructose at mild conditions (100 degrees C and 40 min) when employing Cr(III)-Al2O3 as catalyst in 1-butyl-3-methylimidazolium chloride ([Bmim] Cl). The Cr(III)-Al2O3 catalyst was characterized via XRD, DRS and Raman spectra and the results clarified the interaction between the Cr(III) and the alumina support. Meanwhile, the reaction solvents ([Bmim] Cl) collected after 1st reaction run and 5th reaction run were analyzed by ICP-OES and LC-ITMS and the results confirmed that no Cr(III) ion was dropped off from the alumina support during the fructose dehydration. Notably, Cr(III)-Al2O3 catalyst had an excellent catalytic performance for glucose and sucrose and the HMF yields were reached to 73.7% and 84.1% at 120 degrees C for 60 min, respectively. Furthermore, the system of Cr(III)-Al2O3 and [Bmim] Cl exhibited a constant stability and activity at 100 degrees C for 40 min and a favorable HMF yield was maintained after ten recycles.