Whereas detailed kinetic models have already been implemented widely in computational fluid dynamics (CFD) simulations of gas-phase processes, CFD modeling of reactive gas-solid processes with detailed kinetics, especially in fluidized bed reactors, is a largely unexplored territory. To fill this gap, for the first time, an Euler-Euler based code, CATalytic CHemistrY FOAM (catchyFOAM) is developed to simulate gas-solid fluidized bed reactors while using microkinetic models for both the gas phase and the heterogeneous catalyst. First, the code is validated and tested by comparing with pseudohomogeneous ideal plug flow simulations, i.e., not explicitly accounting for separate gas and solid phases. Next, the capabilities of the model are illustrated by simulations of a gas-solid vortex reactor (GSVR) for the oxidative coupling of methane (OCM), with and without including pellet-scale mass transfer resistances and at both isothermal and adiabatic conditions. These simulations show that catchyFOAM is a powerful tool with numerous possibilities to design novel fluidized bed reactors and to optimize the conditions for processes involving catalytic surface chemistry, whether or not simultaneous with reactions in the gas phase (e.g., OCM, fluid catalytic cracking, catalytic partial oxidation).