Direct Catalytic Conversion of Cellulose to 5-Hydroxymethylfurfural (HMF)

Glucose and fructose, two abundant C6 sugar molecules from the nature, are potential feedstocks to provide sustainable supplies of basic chemical building blocks. 5-Hydroxymethylfurfural (HMF) is an important versatile sugar derivative and is a key intermediate between bio-based carbohydrate chemistry and petroleum based industrial organic chemistry. High sugar conversion to hydroxymethylfurfural (HMF) was achieved in ionic liquids with or without the addition of Bronsted acids. Catalytic amounts of metal halides in ionic liquids significantly reduced the fructose dehydration barrier, producing HMF in high yields. Most remarkably, glucose, a common sugar molecule, was selectively converted to HMF in good yield. Only negligible amount of levulinic acid was formed as a by-product. A possible mechanism is proposed for the unique catalytic function of CrCl2 in glucose conversion. Direct conversion of cellulose to HMF in a single process represents an ultimate challenge because it involves multiple elementary steps such as decrystallization and depolymerization of cellulose in high yield to glucose and the consecutive conversion of glucose to HMF. A unique catalytic system was successfully designed that led to a breakthrough toward this goal. Preliminary results will be presented and discussed.