(252b) Solvent and Processing Conditions for Pretreatment and Dissolution of Cellulose

Efficient utilization of biomass is hindered by the recalcitrance to dissolution of semicrystalline cellulose. [Alexandridis, P.; Ghasemi, M.; Furlani, E. P.; Tsianou, M., Solvent processing of cellulose for effective bioresource utilization. Curr. Opin. Green Sustainable Chem. 2018, 14, 40-52; DOI: 10.1016/j.cogsc.2018.05.008] Pretreatment is often used to alter the structure of cellulosic biomass in order to make cellulose more accessible to solvents and enzymes. The pretreatment involves physical and/or chemical processing which affects the degree of crystallinity and size of biomass particles. We examine here the effects of (i) solvent properties, pretreatment steps and temperature, and (ii) fiber diameter and degree of crystallinity, on the kinetics of cellulose swelling and dissolution. To this end we have combined (a) experimental results on cotton fiber swelling, change in crystallinity and dissolved amount when treated under different solvent conditions, with (b) a phenomenological model that accounts for the phenomena governing the dissolution of solid cellulose, e.g., solvent penetration, transformation from crystalline to amorphous domains, specimen swelling, and polymer chain untangling. [Ghasemi, M.; Singapati, A. Y.; Tsianou, M.; Alexandridis, P., Dissolution of semicrystalline polymer fibers: Numerical modeling and parametric analysis. AIChE Journal 2017, 63 (4), 1368-1383. DOI: 10.1002/aic.15615] [Ghasemi, M.; Alexandridis, P.; Tsianou, M. Cellulose dissolution: Insights on the contributions of solvent-induced decrystallization and chain disentanglement. Cellulose 2017, 24 (2), 571-590; DOI: 10.1007/s10570-016-1145-1] The insights obtained from this analysis would facilitate the rational selection of solvents and the design of pretreatment processes to reduce the size and degree of crystallinity of cellulosic biomass particles, leading to enhanced biomass utilization. [Ghasemi, M.; Alexandridis, P.; Tsianou, M., Dissolution of cellulosic fibers: effect of crystallinity and fiber diameter. Biomacromolecules 2018, 19 (2), 640-651; DOI: 10.1021/acs.biomac.7b01745] [Ghasemi, M.; Tsianou, M.; Alexandridis, P., Assessment of solvents for cellulose dissolution. Bioresource Technol. 2017, 228, 330-338; DOI: 10.1016/j.biortech.2016.12.049] [Ghasemi, M.; Tsianou, M.; Alexandridis, P. Population ensemble modeling of biomass dissolution. Chem. Eng. J. 2018, 350, 37-48; DOI: 10.1016/j.cej.2018.05.167]