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 o 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.

This study compares the use of three low boiling point polar aprotic solvents, tetrahydrofuran (THF), acetone, and 1,4-dioxane, for extracting biomass sugars in ethanol biorefineries. The techno-economic analysis employs experimental data to build a chemical process model and estimate capital and operating costs of a commercial-scale biorefinery. The biomass solvent liquefaction in a 2000 metric tonne per day sugar fermentation biorefinery yields ethanol at minimum fuel-selling prices (MFSP) of $2.98 to $4.06 per gallon. THF achieves the lowest MFSP. Uncertainty analysis indicates that solvent to biomass ratio, glucose and xylose yields, feedstock price, and capital costs are the primary drivers of the ethanol MFSP. The 10% to 90% percentile for THF-based ethanol MFSP are estimated to be $2.31 and $3.21 per gallon. Life cycle analysis shows that with a lower solvent to biomass ratio as suggested by previous studies, our process could achieve GHG emissions reduction of 25% and 45% for THF and acetone cases, respectively. Further optimization of the process could lead to significant reductions in ethanol costs, commercialization risks, and GHG emissions.

This paper explores the effectiveness of several polar aprotic solvents, including 1,4‐dioxane, ethyl acetate, tetrahydrofuran (THF), methyl iso‐butyl ketone, acetone, acetonitrile, and gamma‐valerolactone (GVL), in depolymerizing cellulose into solubilized carbohydrates in the presence of acid catalyst. Whereas the yields of solubilized carbohydrates were strongly dependent on the polar solubility parameters of solvents, the use of acid catalyst substantially eliminated differences in the yields for the various solvents, which were in the range of 83–97%. The yields of levoglucosan and solubilized carbohydrates from cellulose in 1,4‐dioxane, THF, and acetone approached that of GVL, almost completely solubilizing cellulose within 1–7 min. Low initial rates of levoglucosan degradation caused these low polarity, low boiling point solvents to exhibit high stability and competitive yields of the anhydrosugar compared to high polarity and high boiling solvent such as GVL. The ease of recovery of low polarity, low‐boiling solvents makes them attractive media for production of solubilized carbohydrates, which the use of acid catalyst makes possible.