Depolymerization of Cellulose and Cellulose Triacetate in Conventional Acetylation System

In a conventional system for the acetylation of cellulose, acetic acid, acetic anhydride and sulfuric acid act as a diluent, an acetylation reagent and a catalyst, respectively; the sulfuric acid acts as a catalyst not only for acetylation but also for depolymerization. The depolymerization behaviors of cellulose and cellulose triacetate were studied so that the degree of polymerization of the final product could be predicted. Model experiments in which the acetylation reagent was absent revealed that the depolymerization of cellulose in earlier stages of the reaction proceeds considerably faster than that of cellulose triacetate, and depolymerization of cellulose triacetate is random whereas that of cellulose is not. Simulations of the final degree of polymerization of the product were carried out using the activation energies obtained by the model experiments. The estimated degree of polymerizations showed good agreements with the experimentally obtained ones when the depolymerization rate of cellu ose was assumed to be proportional to the amount of sorbed sulfuric acid.