Kinetics of the Pyrolysis of Cotton Cellulose

Abstract

The kinetics of decomposition of cellulose were studied in the temperature range of 270°-310°C with absorbent cotton and ball-milled scoured cotton, both cut in a Wiley3 mill. The decomposition of cellulose was carried out in a thermogravimetric analysis (TGA) apparatus having precise temperature control, under continuous now of helium gas. The study of the kineties was followed by the determination of the residual weight up to the limiting end point. The data furnished evidence of a complex reaction behavior up to about 40% decomposition and a first-order reaction thereafter. The major reaction of the decomposition of the cellulose molecule was considered as a two- step process: glucosidic bond scission and subsequent levoglucosan formation. The kinetics of a chain reaction mechanism have been proposed and shown to be con sistent with the experimental data. The energy of activation for the initiation reaction of the original cotton and the hall-milled cellulose was found to be 54.3 kcal/mole and 75.0 kcal mole, respectively. These large differences are believed to be due to differ ences of the fiber structure, induced in the latter case by ball mining. For the propa gation reaction, the activation energy values were 33.0 kcal mole and 37.1 kcal/mole, respectively.