Figure shows the corresponding reaction rate profiles. It can be observed that the CO and CO2 conversion rates strongly depend on the position and, hence, on the local CO molar fraction. In particular, the CO consumption rate declines with decreasing CO availability, while the CO2 consumption rate significantly increases. At the same time the decline in the overall CH4 formation rate between the external surface and the symmetry axis is less pronounced, since the decreasing CO and increasing CO2 consumption rate are almost compensating. According to equation the formation rate of a substance Δ𝑛̇𝑖 (left hand side) in steady-state can be calculated directly from the average reaction rate (right hand side). By volume-based averaging the reaction rate profile inside the spherical catalyst pellet the reactions rates are weighed depending on the spatial position and a minor effect of the weakly pronounced spatial profiles on the effective methane formation rate determined experimentally can be concluded from the simulations.