Kinetic study on thermal decomposition of toluene in a micro fluidized bed reactor

This study concerned the pyrolysis behavior of toluene as the tar model compound. Pyrolysis experiments were carried out in a micro fluidized bed reactor (MFBR) under an isothermal condition. Pyrolysis kinetics for the gas components, including hydrogen, methane, ethylene and propane were calculated based on the model-free and model-fitting methods. Results showed that methane and ethylene were the major gas components at lower temperatures (650-800 °C) while propane and ethylene were the main composition of pyrolysis gas mixture at higher temperatures (800-850 °C). For the range of conversion fraction (20-80%), the apparent activation energy of propane (16.34 kJ/mol) was lower than that of ethylene (17.59 kJ/mol), then accompanied with methane (23.27 kJ/mol) and hydrogen (69.55 kJ/mol). The most probable reaction mechanism for the generation of hydrogen was three-dimensional diffusion while the evolution profiles of methane could be described by the mechanism of nucleation and growth. Chemical reaction was the most probable reaction mechanism for ethylene and propane. Results from the present study indicated that MFBR can enable a quicker reaction within the reactor than other traditional approaches. The generation of propane is easier to proceed compared to other hydrocarbons with smaller carbon numbers during pyrolysis of toluene. A comparison of kinetic models and experimental results suggested that the developed models closely predicted the thermal cracking behavior of toluene.