Kinetic study of carbohydrate dissolution during tetrahydrofurfuryl alcohol/HCl pulping of rice straw

Abstract

This study investigated carbohydrate dissolution during tetrahydrofurfuryl alcohol/hydrochloric acid (THFA/HCl) pulping of rice straw, and reaction kinetics equations were derived. For both cellulose and hemicellulose fractions, dissolution during pulping could be separated into two phases. In the initial stage, or phase I, of cellulose dissolution, small amounts were solubilized. In phase II, when delignification reached a level of approximately 85%, along with increases in HCl concentration and cooking temperature, cellulose dissolution accelerated. The dissolution rate of hemicellulose also accelerated. However, the phase I dissolution rate was faster than the phase II rate. From the dissolution rates of carbohydrates (i.e., cellulose and hemicellulose), the activation energies and frequency factors were then calculated, and the reaction kinetic equations were derived. Comparing the experimental data with the predicted data, the pulp compositions, regardless of the contents of lignin, hemicellulose, or cellulose, all showed a high degree of correlation (R2 > 0.99), thus proving that the derived kinetic equations were applicable to the process rationalization of THFA/HCl pulping of rice straw and in the control of pulp chemical compositions.

Keywords

• Rice straw
• Organosolv pulping
• Tetrahydrofurfuryl alcohol pulping
• Carbohydrate dissolution
• Pulping kinetics