In modern industrial practice, a variety of highly exothermic reactions are promoted by contacting of the reaction mixture in the gaseous or vapor phase with a heterogeneous catalyst. A need exists for improved catalytic structures employing integral heat exchange which will substantially widen the window or range of operating conditions under which such catalytic structures can be employed in highly exothermic processes like catalytic combustion or partial combustion. The highly exothermic process characteristics of catalytic reactors are investigated with integral heat exchange structures. Ethane mole fraction and gas-phase reaction rate profiles in catalytic reactors are presented, and ethane mole fraction, flow velocity, gas-phase reaction rate, and temperature contour plots are illustrated for catalytically supported thermal combustion systems. The present study aims to provide an improved reaction system and process for combustion of a fuel wherein catalytic combustion using a catalyst structure employing integral heat exchange affords a partially-combusted, gaseous product which is passed to a homogeneous combustion zone where complete combustion is promoted by means of a flame holder. Particular emphasis is placed upon the catalytic reactor configuration that allows the oxidation catalyst to be backside cooled by any fluid passing through the cooling conduits. The results indicate that the percentage of reaction completed in the exothermic catalytic reaction channel depends both upon the flow rate of the fuel-oxidant mixture through the exothermic catalytic reaction channel and upon the physical characteristics of the catalytic reactor. The tortuosity of the catalytic channels is increased by changing their cross-sectional area at a multiplicity of points along their longitudinal axes. The gas flow velocity entering the exothermic catalytic reaction channel should exceed the minimum required to prevent flashback into the fuel-oxidant stream upstream of the reactor if the fuel-oxidant mixture entering the exothermic catalytic reaction channel is within the limits of flammability. Catalytically-supported thermal combustion in the catalytic reactor is achieved by contacting at least a portion of the carbonaceous fuel intimately admixed with air with a solid oxidation catalyst having an operating temperature substantially above the instantaneous auto-ignition temperature of the fuel-air admixture. The film heat transfer coefficient provides useful means of characterizing the different flow geometries provided by the various flow channel configurations which distinguish the catalyst-coated channels from the catalyst-free channels of the catalyst structure. The total residence time in the combustion system should be sufficient to provide essentially complete combustion of the fuel, but not so long as to result in the formation of oxides of nitrogen.