A power plant comprises a gas turbo group with a heat transfer apparatus, for example a recuperator for the preheating of the combustion air, arranged downstream of the turbine in the smoke gas path of the gas turbo group. A smoke gas purification catalyst is arranged downstream of at least part of the heat transfer apparatus, at a point at which the smoke gas is already cooled as a result of heat exchange to an extent such that irreversible damage to the catalyst due to overheating is avoided. On the other hand, the point is selected such that a temperature necessary for maintaining the catalytic smoke gas purification is ensured. In a preferred embodiment, a temperature measurement point is arranged, at which the temperature of the catalyst or of the smoke gas flowing into the catalyst is determined, so that this temperature can be regulated by means of suitable regulating actions.