Ozone depolymerization of polysaccharides in different materials

The behaviour of polysaccharides contained in different cellulosic material s is studied with respect to depolymerization by ozone in an aqueous medium . The effect of concentration in the liquid phase, temperature and time upo n the depolymerization of holocellulose, bleached and unbleached pulps, mic rocrystalline and native celluloses is investigated. The viscosimetric degr ee of polymerization and the molecular weight distribution are used to moni tor the process. The results show that, at low values of temperature and pH , which inhibit the production of radicals, the depolymerization rate is mo derate 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 p hysical accessibility are the key factors to explain the observed depolymer ization profiles. Finally, the results for lignin-free materials are compar ed with those obtained with similar materials but containing residual ligni n, and this study confirms that the presence of lignin in the fibre matrix increases the depolymerization of the carbohydrates.