Efficient synthesis of 5-hydroxymethylfurfural by MCM-41 modified with multiple acid sites

Abstract

As an important platform compound, HMF plays a role in renewable biomass utilization. In this study, an autoclave batch reactor was used to explore the effects of a solid acid catalyst on conversion of glucose to HMF in a biphasic reaction system. Using ordered mesoporous MCM-41 as a carrier, solid acid catalyst x%Al-MCM-41/S with Brønsted acid sites and Lewis acid sites was prepared through a simple method of sulfuric acid modification and cheap metal impregnation. BET, XRD, FTIR, SEM, TEM, EDS mapping, Py-IR and NH₃-TPD were used to characterize the porosity, crystal structure, composition, morphology, acid sites and total acid strength of the catalyst. The effects of different stirring rates, catalysts, solvents, temperatures, times, acid properties and other factors on glucose dehydration were researched. With a moderate number of acid sites, glucose can be efficiently converted into HMF at 170 °C for 1.5 h, 600 rpm, in 20 wt% NaCl aqueous solution and methyl isobutyl ketone (MIBK). The yield of HMF was 64.83% and the conversion of glucose was 99.12%. Moreover, this system could efficiently convert other carbohydrates into furfural and HMF, such as xylose, fructose, mannose, galactose, sucrose and microcrystalline cellulose. This research found that the solvent and catalyst have good recyclability and the purity of the obtained HMF was as high as 99% by easy operation of rotary evaporation.