Conversion of glucose to 5-hydroxymethyl furfural in water-acetonitrile-dimethyl sulfoxide solvent with aluminum on activated carbon and maleic acid

The development of sustainable, efficient routes for conversion of glucose in biomass to 5-hydroxymethylfurfural (HMF), an important green intermediate in the production of value-added chemicals and fuels, has emerged due to the need to replace depletion of non-renewable fossil sources and climate change caused by their use. In this study, we describe a highly efficient reaction system for the production of HMF with a combination of homogeneous catalyst and heterogeneous catalyst in a polar cosolvent. The catalyst system consists of activated carbon (AC) supported aluminum (AC-Al) and maleic acid (MA) dissolved in a mixture of water, acetonitrile (ACN) and dimethyl sulfoxide (DMSO). Kinetic analysis of HMF production from glucose shows that carbon supported aluminum catalyst in combination with homogeneous maleic acid favored fructose dehydration to HMF instead of the formation of insoluble humins when compared to dissolved aluminum chloride and maleic acid in the same solvent. In addition, the rate constant of HMF hydrolysis to levulinic and formic acid was lower for AC-Al compared to dissolved Al. Response surface methodology (RSM), with central composite rotatable design (CCRD), identified the optimum conditions for glucose conversion to HMF as 168 degrees C for 11 min with a predicted molar yield of 50.3 mol%, which compared well to the experimentally verified yield of 45.8 mol% for these reaction conditions. To test the influence of glucose concentration on HMF yield, a range of initial glucose concentrations were examined. Results showed that the HMF yield increased with the decrease of weight percentage of glucose, suggesting that second order reactions result in humins formation.

Automated summary

In this study, a highly efficient reaction system for the production of HMF using a combination of AC-Al and MA in a polar cosolvent was successfully established. The optimized conditions for glucose conversion to HMF were determined using response surface methodology, with a predicted molar yield of 50.3 mol% matching well with the experimentally verified yield of 45.8 mol%. Additionally, it was found that HMF yield increased with decreasing glucose concentration, suggesting that second order reactions result in the formation of humins.