Numerical simulations and modelling of mass transfer through random assemblies of catalyst particles: from dilute to dense reactive particulate regime

•We propose a model for the mass transfer coefficient accounting for diffusion and internal first-order chemical reaction.•We perform direct numerical simulations (DNS) of flow and transfer around particles.•A wide range of Reynolds and Schmidt numbers and Thiele modulus was explored.•We discuss the limitations of our reactive Sherwood number model.