(569dn) Evaluating the Activity and Scalability of Enhanced-Activity Aminosilica Catalysts for Glucose Isomerization to Fructose

Tertiary amines functionalized on mesoporous SBA-15 supports are active and selective base catalysts for isomerization of glucose to fructose. These materials can be tuned in many ways, and it has been shown that fine modifications to synthesis and structure hold great ability to vary their activity. The catalytic activity has been shown to be affected by three material properties, including the micropore volume of the support, the loading of the aminosilanes, and the structure of the aminosilanes. Separately, we have shown that activity can be increased through using materials with negligible micropore volume and increasing aminosilane surface density. These properties limit amine-silanol interactions that are hypothesized to reduce activity. We have also limited amine-silanol interactions by reducing the length of the linker connecting the amine site to the surface. A more conventionally used propyl linker is flexible and may bend inward to the surface, thus causing amine-silanol interactions, whereas higher activity is shown with a shorter methyl linker with which this effect is not as possible.

Importantly, we have recently shown that these effects can be combined. By functionalizing a methyl-linked catalyst at high loading on a support with negligible micropore volume, we have achieved significant conversion much more quickly than previously reported catalysts, with hypothesized reduction in amine-silanol interactions quantified by ¹³C cross-polarization NMR experiments. Upon establishing particularly high activity, strategies may be devised for implementing this catalyst at larger scale, including evaluation of activity and selectivity under conditions of varied initial glucose concentration. This study encompasses novelties in material synthesis, characterization, and catalytic testing, and serves to influence future material design and eventual implementation of materials currently only used on the lab scale.