Kinetic investigation of dilute acid hydrolysis of hardwood pulp for microcrystalline cellulose production

Abstract

This work presents a kinetic investigation of dilute sulfuric acid hydrolysis of bleached hardwood kraft pulp. The temperature-time dependence shows fast xylose extraction during the initial period of the process, while the glucose content increases slowly and permanently over the period. A conversion of xylose into furfural and furfural-derived chromophores is observed. It is established that only a low-brightness microcrystalline cellulose when a degree of polymerization below 300 can be obtained from hardwood pulp. The study of the acid hydrolysis kinetics, with respect to the degree of polymerization of microcrystalline cellulose, shows that the modified Prout-Tompkins equation describes most adequately the process. According to that kinetic model, the hydrolysis rate depends on a combination of chemical interaction and diffusion processes. It is evident that the activation energy does not change in the course of the process, i.e. the cellulose active centers do not change their activity.

Keywords: Acid hydrolysis; Kinetics; Microcrystalline cellulose; Prout-Tompkins equation.