Estudo de parâmetros cinéticos e termodinâmicos da pirólise de resíduos de madeiras e resinosos da Amazônia

Abstract

The growing demand for sustainable energy sources has driven the utilization of Amazonian residues as alternatives to fossil fuels. In this context, pyrolysis stands out as a promising thermochemical process for the conversion of different classes of biomass into biochar, biooil, and combustible gases under an inert atmosphere, contributing to waste valorization and the mitigation of environmental impacts. This work evaluated the bioenergy potential of Amazonian residues with distinct chemical natures, including lignocellulosic biomasses derived from the woods Manilkara huberi (Maçaranduba) and Dipteryx odorata (Cumaru), as well as white pitch resin and a mixture of α- and β-amyrin, through physicochemical, spectroscopic, morphological, thermogravimetric, kinetic, and thermodynamic analyses. Physicochemical characterization indicated high contents of volatile matter, fixed carbon, and total carbon, resulting in higher heating values of 15.75 MJ/kg for Maçaranduba, 15.49 MJ/kg for Cumaru, 15.50 MJ/kg for white pitch resin, and 15.49 MJ/kg for the α- and β- amyrin mixture, evidencing the energetic feasibility of the samples. Thermogravimetric analyses revealed distinct thermal behaviors, with multiple degradation stages for lignocellulosic biomasses associated with the decomposition of hemicellulose, cellulose, and lignin, and more concentrated profiles for resinous materials related to the presence of resinous and triterpenic compounds. Kinetic evaluation, conducted using the isoconversional methods of Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, Starink, and Vyazovkin, indicated activation energies ranging from 121.75 to 174.89 kJ/mol for lignocellulosic biomasses and from 89.31 to 104.81 kJ/mol for white pitch resin and the α- and β-amyrin mixture, reflecting different thermal decomposition mechanisms. Thermodynamic analysis indicated that the pyrolysis processes are endothermic and non-spontaneous, with positive values of enthalpy and Gibbs free energy and predominantly negative entropy, suggesting increased structural organization during the formation of pyrolytic products. In addition, mechanistic analysis using the Criado master plot method revealed the contribution of multiple mechanisms throughout thermal decomposition. Overall, the results demonstrate the high potential of these Amazonian residues for application in thermochemical routes for the production of biofuels and energy derivatives, contributing to the development of sustainable alternatives within the energy matrix.