Kinetic Study of the Thermal Decompositions of Biopolymers Extracted From Various Plants

A knowledge of the kinetics of decomposition of biopolymers on heating is important mainly in two domains: forest fires and the incineration of biomass for the production of electric energy. For the study by thermogravimetry of biopolymers (cellulose, holocellulose and lignin), samples of several Mediterranean plants were used.The cellulose decomposition fits well with apparent first-order kinetics. The activation energy in an air flow is about 185 kJ mol^–1. It ranges between 149 and 200 kJ mol^–1 for holocellulose (cellulose+hemicellulose) in an air flow. Under nitrogen, the values are higher. Differences in the chemical structures of the hemicelluloses (pentosan and hexosan) may explain these variations. The lignins also display various chemical structures. We observed large differences in the thermal decompositions of the various samples. The decomposition rate is increased in a nitrogen flow containing 6% oxygen. We observed a correlation between the maximum decomposition rate and the heating rate. This variation presents a particular form (linear with two slopes). Only the second part seems to be interesting.This revised version was published online in November 2005 with corrections to the Cover Date.