One of the challenges of full-scale computer simulation of a catalytic reactor is to consider the different scales involved in the problem in a practical fashion. In a monolith catalytic converter, these scales range from the molecular scale for the reactions, through the pore scale, washcoat scale, channel scale, and finally the full converter scale. This paper describes the implementation of a model reduction methodology using look-up tables to perform a consistent comparison of six different catalytic converters used for the catalytic combustion of methane. A detailed mechanistic model for methane combustion is used. Diffusion in the non-uniform washcoat is considered. The converters have different cell densities and wall thicknesses. Steady state and transient light-off simulations are performed. Efficient computational speed is achieved by successive model reduction, which allows the preservation of detailed small-scale information. The results obtained show that there is a non-intuitive relationship between the various operating parameters, which can only be deduced from a comprehensive model.