Highly active Ga promoted Co-HMS-X catalyst towards styrene epoxidation reaction using molecular O2

•Co-HMS-X catalyst showed catalytic activity for direct styrene epoxidation reaction.•Al, Ga and Tl (0.25 mol%) are used as promoters in Co-HMS-X catalyst.•The highly active Ga-Co-HMS-X (Co/Ga = 4) had large number of acidic sites.•The catalyst is stable up to three cycles.•It could epoxide cyclooctene with reasonably good conversion.

Atom efficient synthesis of various value added products has been focused as an intense research area after Kyoto protocol. Styrene epoxidation is a challenging reaction as styrene epoxide is an important monomer for large number of polymers. It has been found that surface acidity and redox property of the catalyst has a major contribution to the catalytic activity for oxidation reaction. In this study Co-HMS-X catalyst was prepared and characterized by BET surface area and porosity measurement, SAXS, SANS, FESEM, HRTEM, UV–vis spectra, FTIR, 29Si NMR, H2-TPR and NH3-TPD techniques. It is observed that 5 mol% Co-HMS-X showed highest catalytic activity for styrene epoxidation reaction using molecular O2 as an oxidant. Interestingly it is found that among three different dopant (Al, Ga, Tl), the Ga promoted Co-HMS-X catalyst (Si:Co:Ga = 100:5:1.25) showed highest catalytic activity in terms of styrene conversion (100%) and styrene epoxide selectivity (68%). The unusual trend of Al, Ga and Tl towards the activity of Co-HMS-X (5 mol%) catalyst has been discussed from the results obtained in the H2-TPR and NH3-TPD study.

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