Products of Cellulose Hydrolysis Made by Treatment of Feedstock with Concentrated Solutions of Sulfuric Acid
The effect of the concentration of sulfuric acid (SA) and temperature on structure and properties of cellulose had been studied. Investigations showed that that after cellulose treatment with concentrated solutions of SA the appreciable depolymerization was observed. Solubility of the initial sample at the room temperature increased gradually in the range of the acid concentration from 50 to 60 wt.% SA. When SA concentration reached 65 wt.%, then cellulose sample dissolved completely. Amorphized cellulose made by regeneration from 65 wt.% SA, was characterized by high enzymatic digestibility. At elevated temperature of hydrolysis, 45°C, content of sulfonic groups and cellulose solubility in SA increase, while yield and DP decrease. After hydrolysis of cellulose with hot 50–60 wt.% SA, the crystallinity degree of the obtained cellulose samples changed slightly, and these samples retained mainly the CI crystalline polymorph. However, when SA concentration reached 65 wt.%, then cellulose dissolved, and the regenerated cellulose had CII polymorph, reduced crystallinity and low DP. Using optimal conditions of the acidic treatment (C=57–60 wt.%, T= 45°C; t=1h) in combination with the high-power disintegration permitted obtaining the CI nanocellulose with the increased yield; this nano-product consists of crystalline cellulose particles having sizes 150–200 × 10–20 nm.