The utilization of CO 2 as a soft oxidant and promoter is a promising concept for industrial applications that could not only contribute to the mitigation of CO 2 levels, but also the development of economical and energy efficient syntheses of various chemicals. The abundant availability, non-toxic, economic and mild oxidizing properties of CO 2 has resulted in immense interest in its use as an oxidant in several reactions, such as the oxidative coupling of CH 4 and the oxidative dehydrogenation of alkanes and alkyl aromatics. At present, only a few processes based on CO 2 as a soft oxidant have been realised on a technical scale in spite of dedicated research. This review is intended to trace the emergence, application and understanding of such systems and shed light on the further development that may lead to industrial scale operations in the near future.
Highly ordered Metal-tetrakis(carboxyphenyl)porphyrin (Metal = Fe, Cu, Sn) bridged periodic mesoporous organosilicas (M-TCPP-PMO) with high surface area were synthesized from corresponding M-tetrakis(carboxyphenyl)porphyrin-silsesquioxanes as tetra-silanes by the solÀgel method. The BaeyerÀVilliger oxidation of ketones to the corresponding esters using molecular oxygen as an oxidant over M-TCPP-PMOs was investigated. Fe-TCPP-PMO was found to exhibit higher catalytic activity than Cu-TCPP-PMO and Sn-TCPP-PMO. The high catalytic activity is attributed to the high-valent Fe-porphyrin on the wall of mesoporous silica along with cyclohexanone, which results in successful completion of the oxygen transfer step and generation of ε-caprolactone. The obtained results demonstrate that Fe-TCPP-PMO is a promising and efficient catalyst for the BaeyerÀVilliger oxidation of ketones to esters using O 2 as the oxidant.
Mesoporous MFI zeolites (ZSM-5, TS-1, S-1) having intracrystalline mesoporosity within zeolite crystals were synthesized by microwave induced assembly through the ionic interaction between the sulfonic acid functionalized MFI zeolite nanoparticles and alkyltrimethylammonium cationic surfactants.
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