Oxidative reactions of cellulose under alkaline conditions

Abstract

The purpose of this investigation was to elucidate the influence of oxygen, gas pressure, and temperature on the oxidative degradation of cellulose and the formation of degradation products under alkaline conditions. In order to simplify the reaction system the experiments were carried out with the cellulose model compound cellobiose. Reaction products were determined and identified by GCFID and GC-MSD as their per(trimethylsilyl)ated derivatives. About 37 degradation products were qualitatively identified of which 33 degradation products were quantitatively evaluated. The degradation products were divided into oxidative and non-oxidative degradation products. The main degradation products were glucose as well as glycolic, lactic, glyceric, 3,4-dihydroxybutanoic, 3-deoxypentonic, and glucoisosaccharinic acids. An inhibiting character of oxygen upon cellobiose degradation was observed. At lower temperatures an increase in oxygen pressure caused the formation of non-oxidative degradation products in trace amounts. The formation of oxidative degradation products was kinetically and of non-oxidatives thermodynamically favored. The kinetic calculations revealed that at room temperature the degradation of cellobiose proceeded four times slower in air than in 1 bar nitrogen. Furthermore, the activation energy for cellobiose degradation in 1 bar nitrogen was 79 kJ/mol and rose to 122 kJ/mol in air. Based on the obtained results and made observations a new ionic reaction mechanism was postulated. Keywords: cellulose, cellobiose, alkaline oxidative degradation, degradation products, gas chromatography, mass spectrometry, kinetics, activation energy, reaction mechanism