Production of solubilized carbohydrate from cellulose using non-catalytic, supercritical depolymerization in polar aprotic solvents†
We report yields of solubilized and depolymerized carbohydrate from solvent processing of cellulose as high as 94% without use of catalysts. Cellulose was converted using a variety of polar aprotic solvents at supercritical conditions, including 1,4-dioxane, ethyl acetate, tetrahydrofuran, methyl iso-butyl ketone, acetone, acetonitrile, and gamma-valerolactone. Maximum yield of solubilized products from cellulose, defined as both depolymerized carbohydrate and products of carbohydrate dehydration, was 72 to 98% at 350 °C for reaction times of 8–16 min. In all cases solvents were recovered with high efficiency. Levoglucosan was the most prevalent solubilized carbohydrate product with yields reaching 41% and 34% in acetonitrile and gamma-valerolactone, respectively. Levoglucosan yields increased with increasing polar solubility parameter, corresponding to decreasing activation energy for cellulose depolymerization.