Study of Cellulose-Rich Materials Recovered After Dissolution of Sulphite Pulp from South African Eucalyptus Wood in [C2mim][OAc]/co-Solvent Mixtures

Abstract

Biomass processing in ionic liquids (ILs) is a promising technology but involves the simultaneous optimization of many variables in parallel. Here we investigated how dissolution of dissolving wood pulp in IL molecular co-solvents affects the structure of lignocellulosic materials. Mixtures of the IL 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) and dimethylsulfoxide (DMSO) or dimethylformamide (DMF) were used to dissolve South African eucalyptus raw (unbleached) and final (bleached) pulp and regenerated cellulose was obtained by addition of a 1:1 (v/v) water/acetone mixture. The regenerated cellulose materials were characterized by SEM, FTIR, TGA, and PXRD. The results showed that addition of co-solventsled to increased dissolution yields, presumably due to reduction of the IL viscosity facilitating faster dissolution of the wood materials. The selection of the co-solvent for the mixtures did not have a significant influence on the recovered materials, whose characteristics such as crystallinity and thermal stability depended only on the source material. Co-solvents did affect the purity of the recovered material, with DMF appearing to lead to greater contamination. Co-solvent addition is a viable approach for dissolution of dissolving wood pulp without affecting the quality of the recovered material providing removal and recovery of the spent solvents can be optimized.