The ability of a three-way catalytic converter (TWC) to treat the exhaust from a natural-gas fueled engine was evaluated by numerical simulation. A comprehensive and thermodynamically consistent surface reaction mechanism describing the surface reactions in the TWC was built by compiling elementary-step reaction kinetics involving CH4, CO, formaldehyde, NO, NH3 and N2O from literature sources. The reaction parameters are taken from literatures and fitting calculations. The mechanism was implemented in a one-dimensional PFR model describing a single channel of the catalyst. The simulation results were evaluated by comparison with field data collected from a TWC operated isothermally at steady-state. The model predicted the major trends in conversion/formation of all species in the TWC over a wide range of air to fuel ratios. Sensitivity analysis was utilized to study the key reaction steps that impact the exhaust emission mole fraction. It was found that methane, NO, CO and formaldehyde are most sensitive to the corresponding adsorption steps, while NH3 and N2O are sensitive to the reactions that relate to their formations, such as reactions involving surface hydrogen atoms for NH3 and NO for N2O. (C) 2015 Elsevier B.V. All rights reserved.