Process modeling of the batch acetylation of cotton linter pulp

Abstract

Following previous kinetic investigations of the acetylation of cotton linter pulp (Luo et al. 2013), a mathematical model was set up based on the mass and energy balances to simulate the batch acetylation process; a particular goal was to predict the temperature profile. The equations were discretized using a time-dependent finite difference method. The parameters for the model, including the kinetic parameters and heat transfer rate, were well estimated from the literature and our previous work. The model using the least-mean-square-error criterion optimizes the unknown parameters. The proposed model provides an accurate prediction of the process, including the temperature profile, peak temperature, and DS value under the peak temperature. The content of the catalyst, sulfuric acid, has a dramatic effect on the temperature profile. A slight increase in sulfuric acid content will lead to a faster dissolution process for the sulfated cellulose fibers, whereas the reaction rate of the sulfated fibers with acetic anhydride in the liquid phase is not affected. The optimized values of the activation energy are 11.0 and 7.6 kJ/mol for the dissolution processes with low and high sulfuric acid contents, respectively.