GB966704A - Process of dehydrogenation - Google Patents

Abstract

In the dehydrogenation of alkyl aromatic halohydrocarbons to a vinyl aromatic halohydrocarbon, the starting alkyl aromatic is passed with superheated steam through a plurality of fixed masses of a dehydrogenation catalyst and additional heat is supplied to the reactants between the catalyst masses without substantially increasing the reaction temperature. In one embodiment the whole of the superheated steam is mixed with the alkyl aromatic and the reaction mixture is heated by heat exchangers between the catalyst masses and in an alternative the steam is split into streams and a proportion added to the alkyl aromatic or reaction mixture before passing into each catalyst mass. The reaction temperature may be 600-650 DEG C. for which the steam in the first embodiment is heated to 750-825 DEG C. and in the second 725-775 DEG C. The total amount of steam may be 1.5-20 pounds per pound of alkyl aromatic and 2-5 catalyst beds may be used, arranged in a single reactor if desired. The catalyst may be Fe2O3-Cr2O3-K2CO3, Fe O-K2O, MgO-Fe O-K2CO3 or Al2O3-SiO2-Ni and the starting material ethylchlorobenzene.ALSO:In the dehydrogenation of alkyl aromatic hydrocarbons to a vinyl aromatic hydrocarbon the starting alkyl aromatic is passed with super-heated steam through a plurality of fixed masses of a dehydrogenation catalyst and additional heat is supplied to the reactants between the catalyst masses without substantially increasing the reaction temperature. In one embodiment the whole of the superheated steam is mixed with the alkyl aromatic and the reaction mixture is heated by heat exchangers between the catalyst masses and in an alternative the steam is split into streams and a proportion added to the alkyl aromatic or reaction mixture before passing into each catalyst mass. The reaction temperature may be 600-650 DEG C. for which the steam in the first embodiment is heated to 750-825 DEG C. and in the second 725-775 DEG C. The total amount of steam may be 1.5-20 pounds per pound of alkyl aromatic and 2-5 catalyst beds may be used, arranged in a single reactor if desired. The catalyst may be Fe2O3-Cr2O3-K2CO3, FeO-K2O, MgO-FeO -K2CO3 or Al2O3-SiO2-Ni and the starting material ethyl benzene, isopropylbenzene, diethylbenzene or ethylnaphthalene.