Acid‐Catalyzed Dehydration of Fructose into 5‐Hydroxymethylfurfural by Cellulose‐Derived Amorphous Carbon

Carbonaceous solid (CS) catalysts with SO 3 H, COOH, and phenolic OH groups were prepared by incomplete hydrothermal carbonization of cellulose followed by either sulfonation with H 2 SO 4 to give carbonaceous sulfonated solid (CSS) material or by both chemical activation with KOH and sulfonation to give activated carbonaceous sulfonated solid (a ‐ CSS) material. The obtained carbon products (CS, CSS, and a ‐ CSS) were amorphous; the CSS material had a small surface area (<0.5 m 2  g −1 ) and a high SO 3 H group concentration (0.953 mmol g −1 ), whereas the a ‐ CSS material had a large surface area (514 m 2  g −1 ) and a low SO 3 H group concentration (0.172 mmol g −1 ). The prepared materials were evaluated as catalysts for the dehydration of fructose to 5‐hydroxymethylfurfural (5‐HMF) in the ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([BMIM][Cl]). Remarkably high 5‐HMF yields (83 %) could be obtained efficiently (80 °C and 10 min reaction time). CSS and a ‐ CSS catalysts had similar catalytic activities and efficiencies for the conversion of fructose to 5‐HMF in [BMIM][Cl]; this could be explained by the trade‐off between SO 3 H group concentration (high for CSS) and surface area (high for a ‐ CSS). The cellulose‐derived catalysts and ionic liquid exhibited constant activity for five successive recycles, and thus, the methods developed provide a renewable strategy for biomass conversion.