FIELD: petrochemical synthesis. SUBSTANCE: dehydrogenation conducted in presence of water steam and iron oxide catalyst activated by alkali metal at elevated temperature is distinguished by that, after completion of initial period of catalyst utilization (3 to 45 days), mixed reagent stream is formed consisting of alkylaromatic hydrocarbon, steam, and alkali metal compound in amounts equivalent to 0.01 to 100 ppm of alkali metal compound based on summary weight of alkylaromatic hydrocarbon and steam; formed stream is continuously fed into reactor with amount of alkali metal sufficient to essentially maintain constant level of alkylaromatic hydrocarbon conversion and selectivity of alkenylaromatic hydrocarbon formation. EFFECT: increased lifetime of catalyst and selectivity of continuously conducted process. 61 cl, 3 dwg
