While not in the focus of this study, permeation through the polymeric reactor material is possible, in principle. This may cause that Oxygen is present in the reactor, which reacts with H2 or leads to partial catalyst oxidation. To trace penetration of air into the reactor, N2 was used as indicator. Indeed, N2 was detected at a level of a few hundred ppm, as shown in Figure as function of time. Furthermore, the bed temperature for the PFA reactor is plotted, as well. Further results are available in the supporting information. The N2 level is decreasing for about 16 h until an approximately stable concentration of 350 ppm stabilizes at 180 °C. During variation I, the N2 concentration correlates with the temperature, which is also observable for PTFE (see supporting information). The increase in pressure up to 5 bar is accompanied by an increase of N2 by about 200 ppm. The change in N2 concentration during variation I can be explained by the change in permeability with temperature, but the concentration step after the increase to 5 bar has to have another reason. The profanest reason would be a permeation through the membrane of the backpressure regulator, which is controlled by nitrogen-based pilot pressure. However, this reason is unlikely, as this effect is absent for the PTFE reactor. Hence, the reactor material itself is responsible for the observation, which obviously becomes more permeable under induced stress. It has to be noted that such effect is not yet reported in literature for fluoropolymers, while for glassy fluoropolymers an opposite effect is indicated, especially under the influence of CO2 . Hence, further elaboration is needed to understand the air penetration through PFA, even though this is of limited relevance for application as reactor material on Mars. Importantly, both experimental campaigns show a high sensitivity of the catalyst toward the temperature, but a much smaller effect of pressure and composition changes. A fivefold pressure leads to a doubling of the rate; moreover, a change in feed composition has neglectable impact on the rate.