Conversion of Xylose to Furfural Using Lewis and Brønsted Acid Catalysts in Aqueous Media

Abstract

The role of molecular structure on pentose dehydration to furfural has been examined using HCl as a Bronsted acid catalyst in a single phase aqueous media. It is shown that xylulose dehydration results in a much higher furfural yield than xylose dehydration under similar reaction conditions. Furthermore, a cascade of reactions for the efficient conversion of xylose to furfural in a single pot reactor is presented whereby a Lewis acid, CrCl3, is used to isomerize xylose to xylulose, and a Bronsted acid, HCl, is employed to dehydrate xylulose to furfural. Using the combination of Lewis and Bronsted acids, a furfural yield of ∼39% is achieved compared to ∼29% using HCl alone, at a moderate reaction temperature (∼418 K) in a single aqueous phase, with an associated decrease in the residence time by a factor of 5. With this combined catalyst functionalities, a much higher yield (76%) to furfural can be obtained in a biphasic system at low temperatures and short times. Aside from increasing performance, our res...