Batch and Continuous Flow Production of 5-Hydroxymethylfurfural from a High Concentration of Fructose Using an Acidic Ion Exchange Catalyst

5-Hydroxymethylfurfural (HMF), a product of catalytic dehydration of C6 sugars, is a versatile and key renewable platform chemical. The possibility to use a high substrate concentration with high yield in a single-solvent system is one of the solutions to reduce solvent usage, energy consumption, reaction volume, and operating cost. A heterogeneous catalyst and single-solvent system were employed to develop a facile and green process for the production of HMF from fructose at high concentration under moderate conditions in batch and continuous flow modes. In the batch process, with 0.1 and 0.2 w/w ion exchange resin DR-2030 as the catalyst, 98.8% fructose conversion with 82.2% HMF yield and 99.7% fructose conversion with 85% HMF yield, respectively, were obtained from 300 g/L (30% w/w) fructose in DMSO at 110 °C. The catalyst could be reused for at least five consecutive batches. Continuous dehydration of 300 g/L fructose was carried out at 110 °C in a simple flow reactor packed with the ion exchange resin. Fructose conversion of 98% and HMF yield of 82% were obtained. HMF was purified by liquid–liquid extraction, concentration, and silica chromatography.