Isolation of cellulose with ionic liquid from steam exploded rice straw

Isolation of cellulose from straw is a bottleneck for exploiting such biomass resources. In recent years, considerable concerns have arisen over new efficient and environmentally friendly way for this purpose. A novel method for cellulose isolation has been proposed by dissolving steam exploded rice straw in 1-allyl-3-methylimidazolium chloride ionic liquid (IL), following regeneration of crude cellulose by diluting the cellulose-ionic liquid solution adequately after separation of insoluble residues. The crude cellulose was then bleached by 2% hydrogen peroxide aqueous solution with low-flux ozone blowing into. No acid-insoluble lignin and only 0.85% hemicelluloses were detected in the bleached cellulose. The isolated cellulose was analyzed by SEM, FT-IR, 13C CP/MAS solid state NMR, XRD spectroscopes, and the results indicated that high quality cellulose preparation could be isolated in this manner from rice straw.

► Rice straw was pretreated with steam-explosion under optimized conditions to remove most significant hemicelluloses. ► Dissolving steam-explosion pretreated rice straw in 1-allyl-3-methylimidazolium chloride ionic liquid (IL) and filtering to remove the insoluble residues, then regenerating crude cellulose by diluting the cellulose-ionic liquid solution adequately. ► The crude cellulose was bleached with 2% hydrogen peroxide aqueous solution with low-flux ozone blowing into. ► The bleached cellulose preparation was detected to contain no acid-insoluble lignin and only 0.85% hemicelluloses.