Condensed Phase Deactivation of Solid Brønsted Acids in the Dehydration of Fructose to Hydroxymethylfurfural

Catalyst deactivation resulting from the hydrothermal leaching of sulfonic acid residues and the deposition of carbonaceous residues was studied using condensed phase flow reactor experiments along with state-of-the-art solid-state NMR. Several commercially available sulfonic acid-containing heterogeneous Bronsted acids were compared by measuring the rates of sulfonic acid breakdown at hydrothermal flow conditions of 160 °C. Amberlyst 45 was found to show higher hydrothermal stability when compared to both Nafion and Amberlyst 15, with <10% loss in acidity after 48 h. The dehydration reaction of fructose to hydroxymethylfurfural (HMF) was used as a model system to compare deactivation rates from carbon deposition (fouling) to those from sulfur leaching, and deactivation from fouling was shown to be dramatically faster than that from sulfonic acid leaching alone. Fouling rates were then investigated in greater detail by comparing the influence of several factors including reactant, solvent, residence time,...