Converting bleached hardwood kraft pulp to dissolving pulp by using organic electrolyte solutions

In this laboratory study, a hardwood bleached kraft pulp (HBKP) was converted to dissolving pulp by removing hemicellulose using organic electrolyte solutions (OES), consisting of ionic liquid (1-ethyl-3-methylimidazolium acetate (EminAc)) and a polar organic solvent γ-valerolactone (GVL). The molar ratio of GVL/EmimAc, and temperature have significant effect on the swelling of HBKP fibers, thus the hemicellulose dissolution/removal process. Under the optimal conditions of GVL/EmimAc molar ratio of 4 and 60 °C, hemicellulose was effectively removed, leading to the formation of a dissolving pulp with yield of 76%, cellulose content of 91%, Fock reactivity of 56.8% and viscosity of 723 mL/g. Furthermore, the potential of using EmimAc/GVL/water ternary system to selectively remove hemicelluloses from the same HBKP was studied. The GVL/EmimAc/water ratio of 2:1:1 at 60 °C showed promising results, with yield of 76.7%, and cellulose content of 94.8%.