Selective Dehydration of Glucose into 5-Hydroxymethylfurfural by Ionic Liquid-ZrOCl2 in Isopropanol

Abstract

In this work, a heterogeneous catalytic system consisting of [HO2CMMIm]Cl and ZrOCl2 in isopropanol is demonstrated to be effective for 5-hydroxymethylfurfural (HMF) synthesis with glucose as the feedstock. Various reaction conditions for HMF synthesis by glucose dehydration were investigated systematically. Under optimized reaction conditions, as high as 43 mol% HMF yield could be achieved. Increasing the water content to a level below 3.17% led to the production of HMF with a higher yield, while a lower HMF yield was observed when the water content was increased above 3.17%. In addition, the data also showed that ZrOCl2 could not only effectively convert glucose into intermediate species (which were not fructose, in contrast to the literature) but also catalyze the intermediate species’ in situ dehydration into HMF. [HO2CMMIm]Cl was used to catalyze the intermediate species’ in situ conversion to HMF. The kinetics data showed that a temperature increase accelerated the intermediate species’ dehydration reaction rate. The reaction of glucose dehydration was a strong endothermal reaction.

Reaction Kinetics of Levulinic Acid Synthesis from Glucose Using Bronsted Acid Catalyst

“…At the lowest temperature used in this experiment, 140 °C, 100% conversion is not achieved until the longest reaction time. This effect of temperature on glucose conversion is in line with the experiment conducted by Ma et al [28] and Toif et al [29].…”

“…Conversely, the LA yield would be lowered as the initial glucose concentrations increased, as indicated in Figure 5(b). Too high glucose concentration promotes other reactions, such as polymerization and rehydration, resulting in by-product formation [28].…”