Influence of Organic Liquids on the Nanostructure of Precipitated Cellulose

Organic liquids have been used in pretreatments to improve the digestibility of lignocellulosic biomass, ultimately reducing the amount of enzyme required to digest the material to its constituent sugars. To understand the influence of these solvents on cellulose nanostructure, phosphoric acid was used to solubilize cellulose (PAS cellulose) followed by washing of the PAS cellulose with organic liquids previously demonstrated to aid pretreatment. PAS cellulose washed using methanol, ethanol, and ethylene glycol had gel-like properties with disrupted nanostructures. PAS cellulose washed with acetone, 2-propanol, and water yielded an opaque white precipitate. Small-angle neutron scattering indicated the formation of loosely bundled rods of cellulose in the gel-like material. Fourier transform infrared resonance of solvent-washed, flash-dried PAS cellulose suggested an increase in interchain hydrogen bonds in the gel-like precipitates relative to the more obvious precipitates formed in other solvents. The optimal wash liquid was determined to be 40% by volume ethanol in water to induce a highly digestible, gel-like material. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 127: 2620-2627, 2013