A system for pre-heating a working fluid within a combustor includes a compressor for providing the working fluid to the combustor. An outer casing is disposed downstream from the compressor. The outer casing at least partially defines a high pressure plenum that at least partially surrounds the combustor. A combustion chamber is defined within the combustor downstream from the high pressure plenum. A catalytic combustor is disposed within the high pressure plenum upstream from the combustion chamber so as to provide thermal energy to the working fluid upstream from the combustion chamber.