Evaluating the Activity of Heterogeneous Tertiary Amine Catalysts for Glucose Isomerization to Fructose by Tuning Catalyst, Support, and Reaction Conditions

Glucose isomerization to fructose is a critical reaction for biomass upgrading that can be selectively catalyzed by using heterogeneous, amine-functionalized silica materials. Previous work has reported that tuning the structure of both amines and SBA-15 supports to increase activity, but it is unknown what is the combined effect of using high surface densities of aminosilanes with short linkers on a support with limited microporosity. In this work, we demonstrate that negligible micropore (NMP) SBA-15 functionalized with methyl (C1) linkers at high densities shows superior activity compared to previous aminosilica catalysts. Solid-state NMR indicated that the C1 catalyst in this highly active material exhibits reduced amine–silanol interactions compared with a propyl-bonded (C3) catalyst, a finding further corroborated by computational studies. These highly active materials are effective at high glucose concentrations, achieving a high mass yield. Overall, our results demonstrate the successful design of an active and selective material and describe combinations of tuned parameters that are suited to eventual real-world implementation.