Remarkable effect of ordered mesoporous carbon support in tantalum oxide-catalyzed selective epoxidation of cyclooctene

Abstract

The olefin epoxidation is one of the most important reactions in chemical industry. Metal oxide supports often cause drawbacks in catalytic activity and selectivity, which has been overcome by introducing hydrophobic organic groups onto the oxide supports. The present study utilizes ordered mesoporous carbon (CMK-3 and CMK-1) as structurally defined hydrophobic catalyst support. Well-dispersed tantalum oxides supported on the ordered mesoporous carbon were prepared. Their application in catalytic epoxidation of cyclooctene demonstrates that the tantalum oxide catalysts on the ordered mesoporous carbon supports show higher performances than those of the catalysts supported on activated carbon and ordered mesoporous silica SBA-15.

Supported sub-nanometer Ta oxide clusters as model catalysts for the selective epoxidation of cyclooctene

“…Based on the number of molecules of cyclooctene converted by Ta 1 with respect to Ta n>1 (See also table S2) it is clear that the isolated atoms are more active than the tantalum clusters (about a factor four per catalytic entity). This result is consistent with previous observations in the literature 34, [39][40][41]42 and with a mechanism 43,44 in which individual tantalum centres are able to epoxidize olefins by formation of hydroperoxo, 45 peroxo and superoxo species after reaction with H 2 O 2 . 46 The conversion data allow to calculate a blank-corrected TOF of 1.72*10 5 h -1 for Ta 1 that is proof of the potential of the employed method for the preparation of the catalytically active isolated, ligand-free metal oxo moieties.…”

From single-site tantalum complexes to nanoparticles of TaxNy and TaOxNy supported on silica: elucidation of synthesis chemistry by dynamic nuclear polarization surface enhanced NMR spectroscopy and X-ray absorption spectroscopy

“…On the basis of the literature, we suggest a tentative mechanism for the cyclooctene epoxidation catalyzed by Ta x N y /TaO x N y NPs on silica, as summarized in Scheme S3. † 17 , 68 – 73 …”

Metal-supported carbon-based materials: opportunities and challenges in the synthesis of valuable products

“…dispersed tantalum oxide on an ordered mesoporous carbon (CMK-3 or CMK-1) catalyst tested in the epoxidation of cyclooctene, in the presence of aqueous H 2 O 2 , has been reported by Lin et al (Scheme 8). 37 CMK-3 and CMK-1, as carbon replicas of the mesoporous silicas SBA-15 and MCM-48, respectively, exhibited higher catalytic performance, excellent selectivity and recyclability than tantalum oxide supported on AC and also over mesoporous silica SBA-15. While all of the investigated catalysts supported on carbon showed high epoxide selectivities (around 85%), the use of the tantalum oxide supported on SBA-15 catalyst afforded the corresponding epoxide with a lower selectivity (65%).…”