Development of heterogeneous cataylsis for conversion of fructose to 5-Hydroxmethlfural in aqueous consolvent systems

As global energy demands and atmospheric CO2 levels rise, sustainable green energy sources will become necessary solutions. One such energy source is cellulosic biomass, biomass is the only sustainable resource low enough in cost and of sufficient abundance for production of liquid fuels on a large scale. Sugars, derived from biomass, can be used to produce chemical feedstocks, like 5-hydroxymethylfurfural (HMF).

The highest reported yields of HMF obtained, arises from acid catalyzed dehydration of fructose in dimethyl sulfoxide (DMSO). A combination of Brønsted acids and DMSO provides effective catalytic pathways and intermediate stabilization that maximize HMF yields. However, significant contradictions exist in literature regarding the roles of DMSO, O2 and H2O in the conversion mechanism. To address these issues we utilized a 96 well plate batch reactor system to systematically exploring the influence of pH, O2, H2O, time and temperature on the fructose conversion reaction.

Primary results were: (1) DMSO is not the primary catalyst in this reaction, (2) DMSO decomposes in O2 at elevated temperatures to produce Brønsted acids that drive fructose conversion and (3) In O2 free environments H2O does not negatively influence the HMF yield. These systematic studies have allowed us to identify realistic conditions where fructose conversion to HMF can be executed with high yields, >80% at reasonable pH (~2.5) and water content.  Further we will propose an approach to exploit these insights to design heterogeneous catalysts with microenvironments that mimic optimal conditions to enable fructose conversion in flow through reactors under industrially viable conditions.