Quantitative mass spectrometric evolved gas analysis system and its application to cellulose pyrolysis

Abstract

The theoretical and practical details of the utilisation of a quantitative mass spectrometric evolved gas analysis system are described. The pyrolysis of cellulose powder (Whatman CF11, containing ⩾ 98% α- and ⩽ 2% β- and γ-celluloses, and ⩽ 0.015% ash) in vacuo has been followed by continuously monitoring in separate experiments the yields of CO 2 and CO using both a series of isothermal studies in the temperature range 260–295°C and a rising temperature programme (100–500°C at 0.8°C min −1). In the isothermal experiments, evolution of both products appears to follow zero order kinetics over a considerable proportion of the degradation. The zero order kinetic parameters, the pre-exponential factor and the activation energy have been determined for both products. The rising temperature experiments have provided overall profiles of yields versus temperature. Deuterium labelling has been used, and subsequent pyrolysis and analysis of the evolved water ( m/z 17–20) appears to indicate that the char (empirical formula C 6H 4.3O 1.9 and yield 14%) is predominantly formed from the accessible (amorphous and surfaces of crystalline) regions of the microfibril.