This invention provides a catalytic epoxidation of styrene to styrene oxide with molecular oxygen using cobalt containing zeolite. Catalytic epoxidation of styrene-to-styrene epoxide was carried out using molecular oxygen in presence of Co.sup.2+ exchanged zeolites. Molecular oxygen from air is also useful for the epoxidation reaction at atmospheric pressure. The presence of adsorbed water molecules in the catalyst also increases the styrene conversion without affecting the styrene oxide selectivity. Various alkali and alkaline earth cationic promoters were introduced into the zeolite catalyst to increase the styrene oxide selectivity. The present invention explore the effect of adsorbed water molecules and alkali and alkaline earth metal cationic promoters in the cobalt exchanged zeolite catalyst, on the styrene conversion and styrene oxide selectivity for the catalytic epoxidation of styrene to styrene oxide with molecular oxygen.