Mohd Bismillah Ansari

CO2 activation and promotional effect in the oxidation of cyclic olefins over mesoporous carbon nitrides

Mesoporous carbon nitrides (MCN) were prepared by a nano-casting method using mesoporous silica as a template with different carbon and nitrogen sources like melamine only (MS-MCN), urea-formaldehyde (UF-MCN) and melamine-glyoxal (MG-MCN). These mesoporous carbon nitride materials possess nitrogen moieties which behave like a CO2-philic surface facilitating oxidation of cyclic olefins by molecular oxygen in the co-presence of CO2 below supercritical conditions. The co-presence of CO2 augmented the conversions of cyclic olefins at low pressures of CO2, depicting a promotional effect. Approaches towards quantification of promotional effects and insights into the promotional aspects have been studied.

Carbon dioxide utilization as a soft oxidant and promoter in catalysis

The utilization of CO2 as a soft oxidant and promoter is a promising concept for industrial applications that could not only contribute to the mitigation of CO2 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 CO2 has resulted in immense interest in its use as an oxidant in several reactions, such as the oxidative coupling of CH4 and the oxidative dehydrogenation of alkanes and alkyl aromatics. At present, only a few processes based on CO2 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.

Carbon dioxide augmented oxidation of aromatic alcohols over mesoporous carbon nitride as a metal free catalyst

The catalytic oxidation of primary/secondary alcohols with molecular O2 to the corresponding carbonyl compounds and acids was studied over mesoporous carbon nitride (MCN) as a metal free catalyst. The aromatic alcohols showed conversions between 34–63% with O2 whereas in the co-presence of CO2 augmented conversions (54–91%) with higher selectivities for acids were observed. The quantification of the promotional effect of the synergism in the co-presence of CO2 was found to be 18–21%. The catalyst and the gaseous mixture were analysed after the reaction with IR spectroscopy, which revealed the formation of surface carbamate and the existence of CO in the gaseous mixture. The kinetic studies revealed that the first order rate constants are higher in the co-presence of CO2 and that the kinetic ρ, obtained from the Hammett plot, indicated the development of a positive charge on the substrates during the rate determining step.