Kinetic investigation of methane pyrolysis over iron-based catalyst in packed bed reactor

Methane pyrolysis emerges as a promising route to generate high-purity hydrogen and solid carbon without CO 2 emissions. This work investigates the kinetics of methane decomposition over a Fe-Al 2 O 3 catalyst with equimolar Fe/Al ratio, synthesized via fusion-decomposition method and previously identified as the best formulation for activity and carbon accumulation capacity. Experiments were carried out in a packed bed reactor under widely varying operating conditions: temperature (725–800 °C), methane concentration (2.5–95% v /v), gas hourly space velocity (1000–100,000 L(NTP) h −1 kg cat −1 ), and hydrogen co-feeding (0–80% v/v). A one-dimensional dynamic reactor model was applied to develop a predictive kinetic model able to simultaneously describe methane conversion and catalyst deactivation as functions of operating conditions, and local gas-phase and solid phase composition. Specifically, the pyrolysis rate is described with a first-order dependence on methane partial pressure, while catalyst activity is modelled as a declining function of the locally accumulated carbon, a property of the solid that varies spatially and dynamically across the reactor and the time on stream. The model combines formal simplicity with the capability to accurately reproduce methane conversion, hydrogen productivity, and carbon load and distribution under all tested conditions. Surface maps of carbon deposition and catalyst activity across the reactor length could be generated, offering predictive insights valuable for the design of experiments, including strategies for long lasting runs. The results of this study underscore the potential of Fe-based catalysts for CO 2 -free hydrogen production at the industrial scale and provide rate equations validated over an operating field of unprecedented extension, that are expected to enable the scaling up of methane pyrolysis technologies.