Mesoporous Nitrogen-Doped Graphitized Carbon for Recyclable Oxidation of Cyclohexene

Abstract

Through the pyrolysis of melamine–formaldehyde resin (MF) at different temperatures, the obtained mesoporous nitrogen-doped graphitized carbon (MNC) materials are detected to have different compositions of nitrogen species. With the increase in the pyrolysis temperature, the nitrogen contents decreased significantly, especially the proportion of pyridinic N and pyrrolic N species. The graphitic N dominated in NNC-1000 °C (MNC-10) with extremely low defects and a highly graphitized degree. MNC-10 could realize selective oxidation of cyclohexene with 90.1% conversion and 92.0% selectivity on the allylic α-position and can be recycled five times without obvious decline in activity and selectivity. Although MNC obtained at 900 °C (MNC-9) has comparable activity to MNC-10, the recycle experiments of MNC-9 show a considerable decline in conversion. The obvious leaching of nitrogen contents, especially the pyridinic N species in MNC-9, resulted in more defects, which are unfavorable to catalysis. The N species in the carbon layer play a positive role in the delocalized electrons promoting cyclohexene activation and tert-butyl hydroperoxide decomposition. Thereby, peroxyl radicals are formed and trigger the subsequent propagation of the radical reaction.

Carbon-Coated MnO Quantum Dot-Decorated Three-Dimensional Graphene Aerogel Composite for High-Performance Lithium-Ion Batteries

“…Figure c displays the structural information of C@MnO QDs/GA composites. The characteristic peak located at 26° can be ascribed to the (002) plane of graphite . Additionally, the weak diffraction peaks at 35 and 40° agree well with the cubic MnO, , consistent with the HRTEM result.…”

“…The characteristic peak located at 26°can be ascribed to the (002) plane of graphite. 44 Additionally, the weak diffraction peaks at 35 and 40°agree well with the cubic MnO, 45,46 consistent with the HRTEM result. Raman spectroscopy (Figure S1) was recorded to investigate the graphitization defects in C@MnO QDs/GA composites.…”

Graphitic N-Rich Graphene for Nonradical Peroxymonosulfate Activation

“…The k value for UGNG was 14 and 52.5 times higher than those for NRG-melamine and NRG-urea, respectively (Figure S4). We speculated that both the higher graphitic N content and the surface area of UGNG contributed to its higher catalytic performance than NRG (Figure S5), as more graphitic N and larger surface area cloud provide more accessibility for the interaction of active sites with PMS to generate ROS. , A similar result was found in the UGNG samples prepared at different temperatures (Figure S6), which suggested the important role of graphitic N for PMS activation . UGNG also exhibited a higher catalytic performance than classical highly efficient metal-based catalysts.…”

“…35,36 A similar result was found in the UGNG samples prepared at different temperatures (Figure S6), which suggested the important role of graphitic N for PMS activation. 37 UGNG also exhibited a higher catalytic performance than classical highly efficient metal-based catalysts. For the highest homogeneous catalyst Fe 2+ , only about 80% of RhB could be removed within 25 min (Figure 3c), and the corresponding k value was 0.039 min −1 (Figure S7), much lower than that for UGNG.…”

Selective Oxidation of Cyclohexene over the Mesoporous H-Beta Zeolite on Copper/Nickel Bimetal Catalyst in Continuous Reactor

“…Mesoporous Ti-AlSi­(n) samples exhibited excellent activity in the oxidation of cyclohexene, achieving 100% conversion and selectivity to ketone-alcohol (KA) oil (cyclohex-2-en-1-ol and 2-cyclohexen-1-one) at low temperature and reaction time (35 °C and 30 min) . MNC-10 catalyst displayed selective oxidation of cyclohexene with 90.1% conversion and 92.0% selectivity at the allylic α-position and could be recycled five times without any noticeable decline in activity and selectivity . The catalytic epoxidation of cyclohexene with H 2 O 2 over HNb 3 O 8 samples was conducted in a batch reactor.…”