Glucose Dehydration to 5-Hydroxymethylfurfural in a Biphasic System over Solid Acid Foams

A solid acid foam‐structured catalyst based on a binderless zirconium phosphate (ZrPO) coating on aluminum foam was prepared. The catalyst layer was obtained by performing a multiple washcoating procedure of ZrPO slurry on the anodized aluminum foam. The effect of the pretreatment of ZrPO, the concentration of the slurry, and the amount of coating on the properties of the foam was studied. The catalytic properties of the prepared foams have been evaluated in the dehydration of glucose to 5‐hydroxymethylfurfural (HMF) in a biphasic reactor. The catalytic behavior of ZrPO foam‐based catalysts was studied in a rotating foam reactor and compared with that of bulk ZrPO. The effect of a silylation procedure on the selectivity of the process was shown over bulk and foam catalysts. This treatment resulted in a higher selectivity due to the deactivation of unselective Lewis acid sites. Addition of methylisobutylketone leads to extraction of HMF from the aqueous phase and stabilization of the selectivity to HMF over bulk ZrPO. A more intensive contact of the foam with the aqueous and organic phases leads to an increase in the selectivity and resistance to deactivation of the foam in comparison with a bulk catalyst. Cat‐Al‐ytically coated: The preparation of a solid acid foam based on zirconium phosphate (ZrPO) coating on aluminum foam is described. The catalytic properties are evaluated in the dehydration of glucose to 5‐hydroxymethylfurfural in a biphasic rotating foam reactor (see picture). The silylation procedure leads to a higher selectivity, and a more intensive contact of the foam with aqueous and organic phases leads to an increase of selectivity and stability.