Oil can be recovered from kerogen in oil shale by pyrolysis. The devolatilization kinetics of the pyrolysis of oil shale from the Irati Formation in Brazil was studied. Kinetic parameters were determined from dynamic thermogravimetric analysis over the temperature range 323–1173 K, using different model-free methods. Evaluation and validation were performed by pyrolysis at 673 K for 3 hours. It was found that the activation energy depended on the extent of conversion. Activation energy increased over the range 215–255 kJ/mol for conversion in the range 0.15 ≤ α ≤ 0.55, where α = 1 for pyrolysis at 1173 K. When the reaction rate was high, the conversion calculated using kinetic parameters derived by the Friedman method was more accurate than those calculated from the Flynn–Wall–Ozawa and the Kissinger–Akahira–Sunose methods. The latter two methods performed better when the reaction rate was lower, i.e., at higher conversion. Isothermal kerogen pyrolysis approached an incomplete conversion limit that could be increased only by increasing the temperature; this type of behavior was predicted by the conversion dependence of activation energy. The observed activation energy is an average of the different activation energies of the individual compounds in kerogen. As conversion progresses, the compounds with lower activation energies are more readily converted, so that the average activation energy of the compounds that remain increases with increasing conversion. The work highlighted the importance of employing conversion-dependent kinetic parameters when modeling oil shale pyrolysis for process design, especially when the process is designed for high kerogen conversion.

RESUMOA matéria orgânica em xisto pirobetuminoso está estreitamente relacionada com a matéria mineral, podendo ser liberada por pirólise. O xisto possui querogênio, matéria orgânica que pode ser convertida em óleo de xisto através de pirólise. Alternativas estão sendo estudadas para o petróleo, entre as quais o xisto, que por meio do processo de pirólise possibilita produzir os mesmos derivados do petróleo. Este trabalho descreve as características da cinética de pirólise de xisto da Formação Irati, fornecido pela Unidade de Negócios da Industrialização do Xisto (SIX), da PETROBRAS, localizada na cidade de São Mateus do Sul, Paraná. Termogravimetria (TG) foi utilizada para estudar o comportamento da pirólise de xisto utilizando-se temperaturas de 100 °C a 900 °C. Os parâmetros cinéticos energia de ativação e fator pré-exponencial foram calculados usando métodos de Coats-Redfern, Friedman, Kissinger, Kissinger-Akahira-Sunose (KAS) e o método de Ozawa (FWO). Os resultados obtidos por cada modelo mostraram que a reação de pirólise é de primeira ordem, com valores de energias de ativação e fatores de frequência próximos aos da literatura. Palavras-chave: cinética, model-free, pirólise, xisto.