In a process for the dehydrogenation of gaseous or vaporized hydrocarbons with ironoxide containing catalysts in a fluidized bed, wherein the liberated hydrogen combines with oxygen from the catalyst to form water, between 10-100 parts by weight, preferably 20-60 parts, of the catalyst are used to each part of the hydrocarbon, the catalyst is continuously removed from the reaction vessel, reheated and reoxidized and returned to the reaction vessel. For example, n-butene, isopentane, ethyl benzene, and isopropyl benzene may be respectively converted into butadiene, isoprene, styrene or methyl styrene in the reactor at 500-700 DEG C., preferably 550-650 DEG C., in the presence of water, with the iron oxide containing catalyst, for example with up to 15% of a spinel forming additive such as aluminium oxide, chromium oxide or copper oxide, with 3 to 10% of a promoter of chromium oxide, copper oxide or silver oxide and supported on a carrier of aluminium oxide, aluminium silicate, magnesium silicate, clay or bleaching earth. The catalyst is obtained by mixing the iron oxide, the additives, promoters and the carrier and firing the mass to give a product of up to 70%, preferably 30-60% of the carrier and of a grain size of 0.3-3 mm. In an example, styrene is obtained by introducing a mixture of 1 mol. of ethyl benzene and 10 mols. of water vapour into the bottom of the dehydrogenation reactor. The reactants fluidize the catalyst, comprising 50% (wt.) ferric oxide, 40% aluminium silicate and 10% kieselguhr, of particle size between 0.3 to 2 in the proportion of 50 parts by weight to 1 part of ethyl benzene to give a 55% dehydrogenation to styrene, the length of stay of the reactants in the reaction chamber being 0.7 sec. The temperature of the reaction chamber during dehydrogenation was 625 DEG C. and of the regeneration chamber was 740 DEG C., the heated catalytic material leaving the regeneration chamber being used to heat the water vapour entering the reaction vessel.ALSO:In a process for the dehydrogenation of gaseous or vaporized hydrocarbons with ironoxide containing catalysts in a fluidized bed, wherein the liberated hydrogen combines with oxygen from the catalyst to form water, between 10-100 parts by weight, preferably 20-60 parts, of the catalyst are used to each part of the hydrocarbon, the catalyst is continuously removed from the reaction vessel, reheated and reoxidized and returned to the reaction vessel. For example, n-butene, isopentane, ethyl benzene and isopropyl benzene may be respectively converted into butadiene, isoprene, styrene or methyl styrene in the reactor at 500-700 DEG C., preferably 550-650 DEG C., in the presence of water, with the iron oxide containing catalyst, for example with up to 15% of a spinel forming additive such as aluminium oxide, chromium oxide or copper oxide, with 3-10% of a promoter of chromium oxide, copper oxide or silver oxide and supported on a carrier of aluminium oxide, aluminium silicate, magnesium silicate, clay or bleaching earth. The catalyst is obtained by mixing the oxide, the additives, promoters and the carrier and firing the mass to give a product of up to 70%, preferably 30-60% of the carrier, and of a grain size between 0.3-3 mm. In an example, styrene is obtained by introducing a mixture of 1 mol. of ethyl benzene and 10 mols. of water vapour into the bottom of the dehydrogenation reactor. The reactants fluidize the catalyst, comprising 50% (wt.) ferric oxide 40% aluminium silicate and 10% kieselguhr, of particle size between 0.3-2 in the proportion of 50 parts by weight to 1 part of ethyl benzene to give a 55% dehydrogenation to styrene, the length of stay of the reactants in the reaction chamber being 0.7 secs. The temperature of the reaction chamber during dehydrogenation was 625 DEG C. and of the regeneration chamber was 740 DEG C., the heated catalytic material leaving the regeneration chamber being used to heat the water vapour entering the reaction vessel.