Remarkable catalytic synergism of alumina, metal salt and solvent for conversion of biomass sugars to furan compounds

[Display omitted] •Metal salt, alumina, and DMSO together synergistically converted glucose to HMF.•Alumina isomerizes glucose to fructose, and CuCl2 & DMSO convert fructose to HMF.•The system can work for up to 50wt% concentrations and for different sugars.•System can tolerate water, and promises the use of industrial sugar syrups. Catalytic conversion of sugars to furan compounds has become an important field in the research area of chemicals production from biomass. Here, a remarkable synergism of transition metal salt, alumina and solvent effectively converted glucose to 5-hydroxymethylfurfural (HMF). Studies showed that the alumina participates in glucose to fructose isomerization, while metal salt and DMSO solvent promote fructose dehydration to HMF. This system can work for upto 50wt% concentration of substrate giving 52% HMF yield. This system can also convert different hexose (including disaccharides and starch) sugars to HMF and pentose sugars to furfural. In terms of HMF yield and stability, this system showed tolerance to the presence of water (upto 15wt%). Further, oxidized products of HMF showed high solubility in DMSO (45wt% for 2,5-diformylfuran and 55wt% for 2,5-furandicarboxylic acid), and they were precipitated out when water was added. These studies promise this sytem as efficient for production of HMF and its further conversions.