Method of dehydrogenation of alkyl aromatics to alkenyl aromatics

A method for dehydrogenating an alkylbenzene compound having from 1 to 3 alkyl groups attached to a benzene nucleus of which 1 to 2 alkyl groups contain 2-3 C atoms comprising feeding said alkylbenzene compound at a temperature of 450.degree.-500.degree. C. through the inlet port of a reactor, feeding stream at a temperature of 650.degree. to about 1000.degree. C. into the interior of a fixed bed of dehydrogenation catalyst, said stream flowing in a countercurrent manner to said flow of alkylbenzenes in heat exchange relationship in said bed prior to introduction into said bed, said point of introduction being just below the point of introduction of the alkylbenzene compound into said bed, said steam being supplied in sufficient quantity to maintain the mixture, at a temperature of about 575.degree. to 675.degree. C. upon mixing the alkybenzene and steam in said catalyst bed, passing the mixture through said catalyst bed and withdrawing reacted effluent from the reactor, the total steam to hydrocarbon ratio weight to weight basis, being less than about 3 to 1, to about 0.7 to 1 each respectively.