The spatial distribution over the fixed bed and the axial profile of η C 4 H 10 ,MA is illustrated in Figure . Due to the temperature rise and the reduction of the reactant n-butane, the effectiveness factor decreases along the packed bed length from 0.82 to 0.65. The cooling by the tube wall yields a higher η C 4 H 10 ,MA for wall-near particles (indicated by darker colors). Nevertheless, the impact of the local packed bed structure and flow regime on the local transport phenomena and consequently on the local reactions leads to differences in the effectiveness factors of particles located on similar axial and radial positions. Moreover, η C 4 H 10 ,MA of neighboring particles can also differ significantly. Because of the increasing radial temperature gradients, the distribution of the effectiveness factor for particles with similar axial position becomes wider towards the end of the fixed bed. Reactors with longer fixed beds need to be simulated to verify if the width of this distribution declines after its maximum in the hot spot region.