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The influence of wood components and cellulose crystallinity on the kinetic degradation of different wood species has been investigated using thermogravimetry. Four wood species were studied: Pinus elliottii (PIE), Eucalyptus grandis (EUG), Mezilaurus itauba (ITA) and Dipteryx odorata (DIP). Thermogravimetric results showed that higher extractive contents in the wood accelerate the degradation process and promote an increase in the conversion values at low temperatures. Alternatively, the results indicated that the cellulose crystallinity inhibits wood degradation; organized cellulose regions slow the degradation process because the well-packed cellulose chains impede heat diffusion, which improves the wood’s thermal stability. The wood degradation mechanism occurs by diffusion processes when the conversion values are below 0.4. When the conversion values are above 0.5, the degradation is a result of random nucleation with one nucleus in each particle. [ABSTRACT FROM AUTHOR]

This work deals with pyrolysis decomposition of wood chips and the main components of wood by thermogravimetric analysis (TGA). Experiments were carried out in the inert atmosphere of nitrogen. The pyrolysis temperature range was varied linearly from 20 °C to 900 °C with the heating rate equal to 5 K min1 to detect all the changes without overlapping. Samples of cellulose, hemicellulose and lignin were used as main components of wood. Thermogravimetric (TG) and differential thermogravimetric (DTG) curves were obtained from experimental data. These records were compared with those obtained by mathematical modeling. The distribution activation energy model (DAEM) was used for mathematical description of experimental data and the prediction of kinetic parameters. According to the DAEM approach, every possible decomposition reaction with various values of activation energies is in progress at each time and temperature. Preexponential factors, mean activation energy and variance were obtained as kinetic parameters. This model is able to describe the integral decomposition curve of biomass, however, a problem occurs when describing the differential curve of biomass thermal decomposition. In general, this model does not accurately describe the decomposition of materials, which are a mixture of several compounds. [ABSTRACT FROM AUTHOR]