Degradation and oxidation of cellulose in acidic potassium permanganate solutions - Kinetics and product analyses

Th, heterogeneous interaction of cellulose and potassium permanganate was studied under various experimental conditions. Determinations of the reaction rate by measuring the decreasing permanganate concentrations revealed a complex reaction order in KMnO4 and a correlation of the rate with the Hammett acidity function H-0 in acidic solutions (pH < 1). The salt effect was positive, and the enthalpy of activation amounted to 63.2kJ/mol. A degradation of the cellulose was manifest by decreasing viscosities of products isolated after increasing times of reaction with permanganate. Oxidation within the same products was apparent from enhanced carbonyl and carboxyl contents. These effects could be restrained by mild reaction conditions which are still sufficient for degrading lignin. Although these results were obtained from micro crystallline cellulose, the potential of potassium permanganate to bleach pulp with minimal deterioration to cellulose seems to deserve reconsideration.