limitations. However, the effective methanation rate even rises, due to the self-inhibiting effect of CO. Hence, the profiles developing in the 800 µm pellets compensate the effect of the CO/CO2 ratio to a certain extent, which leads to flatter profiles displayed in figure , but also cause diffusion limitations expressed by a lower effective CH4 methanation rate. This trend is even more observed at 573 K (see Figure A.2 in the appendix), where the diffusion and chemical equilibrium limitations and their impact on the reaction rate profiles are more pronounced compared to the case discussed in figure . For direct comparison of the simulation and the experiment with respect to the predicted shift in the ratio of both hydrogenation reactions, the reactant selectivity 𝑆 CO of CO is determined according to equation .