Ozone depolymerization of polysaccharides in different materials

The behaviour of polysaccharides contained in different cellulosic materials is studied with respect to depolymerization by ozone in an aqueous medium. The effect of concentration in the liquid phase, temperature and time upon the depolymerization of holocellulose, bleached and unbleached pulps, microcrystalline and native celluloses is investigated. The viscosimetric degree of polymerization and the molecular weight distribution are used to monitor the process. The results show that, at low values of temperature and pH, which inhibit the production of radicals, the depolymerization rate is moderate for lignin-free materials. However; this rate and its maximum extend increase markedly with temperature. Moreover, the experiments suggest that the reactivity of ozone and the amount of radicals in the system and its physical accessibility are the key factors to explain the observed depolymerization profiles. Finally, the results for lignin-free materials are compared with those obtained with similar materials but containing residual lignin, and this study confirms that the presence of lignin in the fibre matrix increases the depolymerization of the carbohydrates.