Choline chloride functionalized zeolites for the conversion of biomass derivatives to 5-hydroxymethylfurfural

Choline chloride (ChCl) functionalized zeolites (HMOR, HZSM5, HBeta, NaY, and HY) have been synthesized and tested for the conversion of biomass derivatives (cellulose, glucose, and fructose) to 5-Hydroxymethylfurfural (5-HMF). The solid-state nuclear magnetic resonance (SS-NMR) spectroscopy data reveal the existence of ionic and Lewis interactions between the ChCl and the zeolite. Ionic interactions appear to be stronger in ChCl/HZSM5 as compared to interactions in other catalysts. The thermogravimetric analyses indicate that the interaction strength decreases with silica-to-alumina ratio and varies with the type of zeolite framework and the extra-framework cation (Na+ or H+). The activity of the zeolites with moderate silica-to-alumina ratios (SAR) is found to be enhanced by the functionalization with ChCl. SS-NMR analysis attributes this enhancement in activity to better interaction of ChCl with the zeolite. However, the effect is negligible for the zeolites with either low or high SAR. The ChCl functionalized HZSM5 shows a synergistic effect in enhancing the 5-HMF yield and is stable for five cycles.