Conversion of fructose, glucose, and cellulose to 5-hydroxymethylfurfural by alkaline earth phosphate catalysts in hot compressed water

The phosphates of alkaline earth metals (calcium and strontium) synthesized by precipitation process in acetone–water media system were used as catalysts for converting fructose, glucose, and cellulose to 5-hydroxymethylfurfural (HMF) under hot compressed water condition. It was found that the phosphates of calcium and strontium effectively catalyzed the HMF formation from fructose and glucose dehydration and cellulose hydrolysis/dehydration reaction, as compared with the non-catalytic system. The XRD analysis confirmed the CaP2O6 and α-Sr(PO3)2 crystalline phases of the catalyst samples, while acid strength of both catalysts was in a range of +3.3 ⩽ H0 ⩽ +4.8. From the study, CaP2O6 and α-Sr(PO3)2 showed similar catalytic performance toward the dehydration of sugars, providing the HMF yields of 20–21% and 34–39% from glucose and fructose, respectively; whereas the total yield of glucose and HMF from the hydrolysis/dehydration of cellulose over α-Sr(PO3)2 (34%) was higher than that over CaP2O6 (17.4%).

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► The phosphates of calcium and strontium as the hydrolysis/dehydration catalysts.
► 5-HMF from fructose, glucose, and cellulose conversion under hot compressed water.
► The CaP2O6 and α-Sr(PO3)2 have proper acid strength (3.3 ⩽ H0 ⩽ 4.8) for the reaction.
► The phosphates provided 5-HMF yields of 34–39% from fructose conversion.
► The total yield of glucose and 5-HMF (34%) from cellulose conversion over α-Sr (PO3)2.