The mathematical modeling of the catalyst section of an atmospheric pilot-scale combustor fueled by gasified biomasses is addressed. The development of distributed three-dimensional (3D) and two-dimensional (2D) models of the single channel of the monolith catalyst; is first described. The results of models derived under different assumptions are then compared in order to identify the simplest accurate mathematical description. According to this procedure, a 2D model for circular channel geometry, which includes axial conduction in the solid walls, can be regarded as the most suitable model for parametric investigations requiring a large number of simulations. Such a model is finally applied to the analysis of the results obtained in an experimental 30 kW pilot facility. A reasonable fitting of the experimental data is achieved, and the key role of high-temperature homogeneous and catalytic kinetics in determining the combustor performances is pointed out. In particular, evidence is provided in favor of temperature self-control of the palladium catalyst because of a drop of CH4 combustion activity associated with thermal decomposition of PdO.