Hindrance to nanofibrillation of undried pulp produced by the kraft cooking process.

Kraft pulp is the most common and economically advantageous raw material for making cellulose nanofibers (CNFs). However, when kraft pulp is subjected to mechanical fibrillation, unfibrillated pulp always remains, even though the pulp is undried. In this study, the effect of the kraft pulping process on the fibrillation of undried pulp was studied. The fibrillation ability was compared with that of undried pulp prepared using Wise method and alkaline treatment. Suspensions of undried pulps were mechanically fibrillated with a high-speed blender for different durations. The degree of fibrillation of pulps was evaluated using sedimentation, morphologies from field emission scanning electron microscopy, specific surface area, and water retention values. Every analysis showed that undried, kraft-based pulp was less fibrillated than undried, wise-based pulp. These results suggested that the kraft cooking process at high temperature hindered the fibrillation of pulp. This might be related to the aggregation occur in cellulose.

Highly efficient organosolv fractionation of cornstalk into cellulose and lignin in organic acids.

In this study, effects of fractionation solvents, catalysts, temperatures and residence time on yields, purity and chemical composition of the products were investigated at the solid/solvent ratio of 1:5 (g/g). It was revealed that mixture of acetic acid/formic acid/water at the ratio of 3:6:1 (v/v/v) resulted in crude cellulose and lignin products of relatively high purity. The use of HCl catalyst contributed to a high crude cellulose yield, while H2SO4 showed an adverse effect on cellulose yield. However, both of these acidic catalysts contributed to much lower hemicellulose contents in the resulted crude cellulose products compared with those obtained without a catalyst. Fractionation at 90°C for 180min in mixed solvents of acetic acid/formic acid/water (3:6:1, v/v/v) with or without catalyst produced crude cellulose with very low residual lignin contents (<4%).