Dissolution of Lignin-Rich Organosolv Pulps by PEG and Urea Contents in Aqueous Alkaline Solution

In this study, we investigated the use of the contents of polyethylene glycol (PEG) and urea in sodium hydroxide (NaOH) aqueous solutions to dissolve lignin-rich organosolv pulps by evaluating dissolution yields and quality of dissolved organosolv pulp solutions towards further valorization. Unbleached pine organosolv pulp (UBOP) containing 26.8% residual lignin was prepared and then subsequently delignified with sodium chlorite to produce a delignified organosolv pulp (DOP) with 14.2% residual lignin content. It was found that lignin content of the organosolv pulps significantly impacted dissolution yield. Further, as PEG content increased in NaOH aqueous solutions, the dissolution yields of UBOP and DOP gradually decreased by an average of 18% and 20%, respectively. In contrast, the effect of urea on dissolution yield was dependent on lignin content of the feed and NaOH content in solution. The dissolution yield of UBOP increased by an average of 6% as urea, but in DOP, the dissolution yield did not change with increasing amounts of urea. In addition, residual lignin content of regenerated cellulose film fabricated from DOP dope in PEG/NaOH was higher than that found in urea/NaOH, indicating that a PEG/NaOH aqueous solution may be an effective dissolution solvent for cellulose, hemicellulose, and lignin.