A one-dimensional mathematical model was developed to simulate the performance of three reactor systems: a fixed-bed reactor, a partially selective membrane reactor, and a totally selective membrane reactor. The reaction studied was the dry reforming of methane with carbon dioxide over a 1 wt.% Rh/Al2O3 catalyst at atmospheric pressure. Experimental results were obtained with a semipermeable Vycor glass membrane and a selective silica membrane (Nanosil). The model provided good agreement between experimental and theoretical results for all three reactor configurations. Calculations also indicated that axial temperature gradients and pressure drop across the bed were negligible.