Over V-Sb-O/Al₂O₃ catalyst, substantially higher (~ 20 - 60% in relative) conversions of initial hydrocarbons and yields of corresponding alkenylbenzenes have been achieved under the dehydrogenation of ethylbenzene, iso- and n-propylbenzenes, 1,4-diethylbenzene and 4-ethyltoluene in the presence of carbon dioxide, compared to those in inert atmosphere, due to promotional oxidative functions of CO₂ to alleviate the dehydrogenation equilibrium as well as to maintain V-sites in active oxidation state, V⁵⁺.