Pyrolytic carbon as support matrix for heterogeneous oxidation catalysts: The influence of pyrolytic process on catalytic behavior

Mn(II)-Based Catalysts Supported on Nanocarbon-Coated Silica Nanoparticles for Alkene Epoxidation

“…The data in Figure show that all Mn-SiO 2 @nC catalysts achieve very fast catalytic kinetics. Among them, the kinetically faster reaction occurs in the presence of Mn II L­[SiO 2 @nC 3 ] and is completed in 1 h. This result is comparable to the currently fastest reaction time reported for bulk carbon materials Mn II -L@PCox and Mn II -L@PC 2 ox by our group …”

“…The present data show that the carbon coating affects the reaction kinetics by decreasing the reaction time as follows: Mn II L­[SiO 2 @nC 1 ] (2.5 h) > Mn II L­[SiO 2 @nC 2 ] (1.5 h) > Mn II L­[SiO 2 @nC 3 ] (1 h). The beneficial role of carbon as the support for the same Mn-catalyst has also been reported by bulk carbons. ,− In our recent works, we suggested that the hydrophobic character of the carbonaceous support may be of key importance by repelling the water molecules that are produced during catalysis . The present work shows that only a carbon nanocoating of SiO 2 is adequate to obtain the important benefit of fast kinetics in heterogeneous epoxidation catalysis.…”

“…The findings of the present work demonstrate for the first time that carbon-based supports are not necessary, and only a carbon coating is required to obtain the important benefit of fast kinetics in heterogeneous epoxidation catalysis. These reaction times (up to 1 h) and high TOF numbers (>700) are comparable to catalysts that have been supported on pure nanocarbon and bulk carbon materials in the past. , …”

“…As analyzed by detailed electron paramagnetic resonance studies, during the oxidative catalytic operation, the fast performing Mn-catalysts operate under a high concentration of the high-redox Mn states, that is, Mn IV O, which are transiently formed by the catalytic cycle . These highly reactive Mn-intermediates are necessary for the alkene epoxidation, but a side-effect is the self-deactivation of the catalyst. , Thus, the data in Figure show that a trade-off between TOFs and reusability can be achieved by considering the case of the Mn II L­[SiO 2 @nC 1 ] nanocatalyst. Flame-spray-pyrolysis allows controlled engineering of the nanocarbons toward an optimizable performance/reusability strategy.…”

“…Our research group systematically explored the development of functional catalysts based on SBA-15, MCM-41, and colloidal silica surface. , A significant finding is that carbon can be an excellent support for the development of hybrids, that is, the immobilization on Mn-catalysts on carbon materials. − Studies revealed a common basis for several carbon supports such as activated carbon, graphene oxide, , carbon nanotubes, , graphitic carbon nitride, pyrolytic carbon from recycled-tire char, mesoporous CMK-3, and 3D macroporous carbon (3DOM) . Importantly, all carbon-based hybrids significantly enhance the kinetics of the heterogeneous catalysts. ,− A review of the overall catalytic results for a given Mn-catalyst indicates that in the presence of carbon-based supports, there is a distinctive decrease in catalytic reaction time, which causes high TOF numbers. , For comparison, the same Mn-catalyst grafted on SiO 2 shows typically 500% slower kinetics (see Supporting Information Figure S1). All of these findings show that a leap forward can be a scale-up, that is, industrial-scale production of hybrid nanocarbon-based supports and their Mn-catalyst hybrids and a fundamental understanding and control of the required key properties of the nanocarbon support, which is related to the catalytic performance.…”