Insights into the Inhibition of Acidic Hydrolysis of Cellulose by Its Solation

Cellulose hydrolysis in dilute mineral acids was investigated, and a plateau in cellulose conversion was observed such that an extended reaction time did not result in further conversion of cellulose, which severely reduced the hydrolysis efficiency of cellulose. The characterization results indicated that the crystallinity indexes of cellulose and the deposition of humins were not the key factors inhibiting the reaction but rather the solation of cellulose in the presence of water, protons, and anions was the key. The hydrolysis reaction proceeded after the solated state of cellulose was disrupted by means of filtration, increased temperature, or the addition of organic solvents and inorganic salts. However, a new plateau in cellulose conversion eventually formed and inhibited the hydrolysis reaction again. Therefore, continuous disruption of the solated system of cellulose is the key strategy to achieve high cellulose conversion under even mild reaction conditions.