A multiscale modeling approach was developed to capture concentration variations in the fluid in two dimensions for catalytic flow reactors. The methodology couples continuum descriptions of the fluid phase and kinetic Monte Carlo simulations of the catalyst domain. A number of catalytic domains, placed as patches along the length of the reactor, were solved using kinetic Monte Carlo (kMC) and linked with a finite difference (FD) solver for the fluid phase. Patch dynamics concepts, such as lifting, restriction and interpolation, were employed to provide the complete set of boundary conditions to the continuum solver. A simple kinetic mechanism involving adsorption, desorption and a single-step surface reaction was used to validate the approach by comparing the solution obtained using the multiscale scheme with a model solved using a wholly implicit solution. Solutions from a mean-field model and the multiscale scheme for a system in which surface diffusion was low were then contrasted. (c) 2006 American Institute of Chemical Engineers.