Process for dehydrogenating hydrocarbons

A process for dehydrogenating a dehydrogenatable hydrocarbon feed using a bed of steam active dehydrogenation catalyst and repetitively regenerating said catalyst with steam and oxygen-containing gas wherein the flow rate of steam through the catalyst bed is maintained constant comprising,

• passing dehydrogenatable hydrocarbon feed through the catalyst bed under dehydrogenation conditions for a predetermined period of time,
• then stopping the flow of dehydrogenatable hydrocarbon to the catalyst bed,
• then after the steam has purged at least part of the dehydrogenatable hydrocarbon from the catalyst bed passing oxygen-containing gas through the catalyst bed under regeneration conditions for a period of time,
• then stopping the flow of oxygen-containing gas to the catalyst bed,
• then after the steam has purged at least part of the oxygen from the catalyst bed passing dehydrogenatable hydrocarbon through the catalyst bed under dehydrogenation conditions wherein more than one catalyst bed is employed and wherein dehydrogenation is conducted in one catalyst bed while regeneration is conducted in another and wherein the dehydrogenated hydrocarbon that is supplied to each catalyst bed is preheated by being passed in indirect heat exchange with the effluent from a catalyst bed that is being regenerated.