Abstract: Self-regenerative catalysts for dehydrogenating an alkylaromatic hydrocarbon to the corresponding alkenylaromatic hydrocarbon are continuously activated by steaming successive small portions of the catalyst bed during normal operation. Each small portion of the catalyst bed is steamed for about 7-30 minutes at least once every 24 hours by a separate small steam inlet which during the activation period admits a flow of steam sufficient to exclude hydrocarbon feed from that portion of the bed. The process is applicable to both heated case reactors and to adiabatic reactors using packed or radial beds. Reactors adapted for use of the process are described.