The comparison of cellulose regeneration behavior in different solvents after sulfuric acid treatment.

In this study, a high solid/liquid ratio beyond the region normally explored in the conventional processes was applied in the sulfuric acid treatment of cellulose, and different solvents were employed in the cellulose regeneration process. The results showed that sulfuric acid in the swelling state was effective in disrupting the cellulose structure and breaking its internal hydrogen bonds. The crystal type of the cellulose samples regenerated in water was cellulose II, while samples generated in methanol and ethanol showed amorphous structures. Meanwhile, the degree of polymerization (DP), average particle size (D50), and crystallinity (CrI) values of the samples were ranked as water > methanol > ethanol in terms of the regeneration solvents. This order was correlated with the polarity and molecular size of the solvents. The stronger the polarity, the more the liquid could form hydrogen bonds with the sulfuric acid during the regeneration process, which resulted in a higher degree of cellulose agglomeration. When cellulose was regenerated in ethanol after acid treatment, its DP decreased from 210.46 ± 6.23 to 17.22 ± 4.68 and its CrI decreased from 78.90 ± 0.02 % to 15.39 ± 0.02 % which will facilitate the subsequent enzymatic hydrolysis. The results of the enzymatic hydrolysis experiments showed that the glucose productivity of the sample from ethanol was the highest among the three regeneration solvents.