In situ Methanation on Mars: A Process Concept Study on the Impact of H2/CO2 and Recycle Ratio

For planning return missions from Mars, considerations about the supply of rocket fuel are crucial. Since transportation of propellant from Earth and storage at Mars is costly and energy intensive, in situ resource utilization (ISRU) for methane production on Mars presents a promising solution. The major challenge is to identify a simple and robust production process, which provides the required purity of the propellant. In this study, we compare two different process concepts, with and without recycle, under realistic operating conditions using thermodynamic modelling and simulation. The H2/CO2 feed ratio is crucial to achieve sufficiently high methane selectivity and thereby reduce the effort in product gas cleaning and the overall process complexity. At the same time, recycling unreacted reactants reduces resource consumption, which is preferable for ISRU scenarios. Hence, our study provides a basis for more detailed process design using kinetic information on the involved process steps.