Medium effect on acid degradation of cotton and wood celluloses

Abstract

Degradation of cotton and wood celluloses treated with hydrogen chloride in different media at 65 °C for 1−120 h was studied. Results showed the use of alcohol increased the cellulosic sugar content of hydrolysate as compared to water. Additionally, the recovery of celluloses treated in alcohols was lower than that of water, particularly when using 2-propanol and 1-butanol. After degradation, the crystallinity indices of celluloses changed slightly, and increased with treatment duration. The initial degradation rates of celluloses were in the order of 1-butanol > methanol > 2-propanol > ethanol > water. However, the decreases in weight-average degree of polymerization (DPw) plateaued after approximately 72 h for cotton cellulose and 5 h for wood cellulose, and the DPw after 120 h treatment were in the range of 98–195 and 196–364 AGU (anhydrous glucose unit), respectively. This study demonstrates the acid-degradation extent of cellulose can be tailored by the selection of degradation medium. Moreover, the alcohols tend to increase the penetration of acid and consequently facilitate the degradation, especially by using alcohols with higher carbon numbers. Additionally, the vapor pressure effect of methanol at 65 °C improved the degradation of cellulose.