Magnetically recyclable cellulose-derived carbonaceous solid acid catalyzed the biofuel 5-ethoxymethylfurfural synthesis from renewable carbohydrates

A series of carbonaceous solid acid catalysts were prepared by facile carbonization and sulfonation of biorenewable feedstocks (i.e., glucose, sucrose, starch and cellulose), and employed for directly converting carbohydrates in ethanol medium to synthesize 5-ethoxymethylfurfural (EMF). The carbonization temperature of cellulose and starch (500 °C) was required to be higher than that of glucose and sucrose (400 °C) to realize high –SO 3 H density and EMF yield. Based on rich exploitability of cellulose and good activity of its derived carbonaceous catalyst, magnetic cellulose-derived carbonaceous solid acid (MCC-SO 3 H) was subsequently synthesized, which possessed a porous structure with BET surface area of 35.34 m 2  g –1 , high –SO 3 H density (1.28 mmol g –1 ) and sufficient magnetism for separation (1.99 emu g –1 ). By optimizing the process variables, a maximum EMF yield of 63.2% could be achieved from fructose at 120 °C, and ethyl levulinate formation was favored at elevated temperature. The MCC-SO 3 H catalyst could be readily separated from the reaction mixture by an external magnet with recovery rate of 92.6% after six successive runs, and reused repeatedly with little deactivation. Besides, this catalyst was efficient for the one-pot transformation of fructose-based polysaccharides into EMF, affording yields of 51.3% and 32.5% from inulin and sucrose, respectively. With glucose as the substrate, instead ethyl glucoside with a high yield of 86.5% was obtained.