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.

Figure optionsDownload high-quality image (195 K)Download as PowerPoint slide