Method to heat a catalyst and/or particulate filter of an exhaust system and catalyst, in particular a nitrogen oxide storage catalyst

During the warm-up to temperature for regeneration of an automotive nitrogen oxide storage catalytic converter (5) diesel engine exhaust, a rich mixture is fed to the catalyst. Unburned hydrocarbons and carbon monoxide then react with oxygen from a storage volume, thus liberating heat energy and rapidly raising the temperature to the required regeneration level.