Preparation of unsaturated organic compounds by oxidative dehydrogenation

Ethylenically unsaturated organic compounds are prepared by the oxidative dehydrogenation of an organic compound precursor containing at least two adjacent carbon atoms, each of which carbon atoms contains at least one hydrogen atom, by a process which comprises contacting a mixture comprising organic precursor, a catalyst consisting essentially of aqueous solutions of hydrogen iodide hydrate, and oxygen in the vapor phase at elevated temperatures. The organic precursor and catalyst are heated to the reaction zone threshold temperature prior to admixing with oxygen and the subsequent introduction of the reactants into the reaction zone. The reaction is characterized by an essentially iodinefree vaporized reactor effluent. Typical process include the conversion of methyl isobutyrate to methyl methacrylate and the conversion of ethyl benzene to styrene.