We show the potential of coupling numerical and experimental approaches in the fundamental understanding of catalytic reactors, and in particular fluidized beds. The applicability of the method was demonstrated in a lab-scale fluidized bed reactor for the platinum-based catalytic oxidation of hydrogen. An experimental campaign has been carried out for synthesizing the catalyst powders by means of atomic layer deposition in a fluidized bed reactor and characterizing them. Catalytic testing has been also run to collect data both in fixed and fluidized bed configurations. Then, after the validation of the in-house first-principles multiscale Computational Fluid Dynamic – Discrete Element Method (CFD–DEM) model, the fundamental understanding which can be achieved by means of detailed numerical approaches is reported. Thus, the developed framework, coupled with experimental information, results in an optimal design and scale-up procedure for reactor configurations promising for the energy transition.