Shuchang Wu

Active Sites and Mechanisms for Direct Oxidation of Benzene to Phenol over Carbon Catalysts

The direct oxidation of benzene to phenol with H2 O2 as the oxidizer, which is regarded as an environmentally friendly process, can be efficiently catalyzed by carbon catalysts. However, the detailed roles of carbon catalysts, especially what is the active site, are still a topic of debate controversy. Herein, we present a fundamental consideration of possible mechanisms for this oxidation reaction by using small molecular model catalysts, Raman spectra, static secondary ion mass spectroscopy (SIMS), DFT calculations, quasi in situ ATR-IR and UV spectra. Our study indicates that the defects, being favorable for the formation of active oxygen species, are the active sites for this oxidation reaction. Furthermore, one type of active defect, namely the armchair configuration defect was successfully identified.

Model Molecules with Oxygenated Groups Catalyze the Reduction of Nitrobenzene: Insight into Carbocatalysis

The role of different oxygen functional groups on a carbon catalyst was studied in the reduction of nitrobenzene by using a series of model molecules. The carbonyl and hydroxyl groups played important roles, which may be ascribed to their ability to activate hydrazine. In comparison, the ester, ether, and lactone groups seemed to be inactive, whereas the carboxylic group had a negative effect. The reaction occurred most likely through a direct route, during which nitrosobenzene may be converted directly into aniline.

Reduction of nitrobenzene catalyzed by carbon materials

Abstract The reduction of nitrobenzene catalyzed by different carbon materials (mainly carbon nanotubes) was studied. TGA, TPD, TEM, N2 adsorption-desorption, and Raman spectroscopy were used to show that it was oxygenated groups that gave catalytic activity, while the surface area, pore structure, morphology, structural defects and Fe impurities in the catalysts did not have a significant influence on the activity. The carbonyl group played an important role, but the carboxylic group and anhydride adversely affected the reaction. The conjugated π system, which was necessary for electron transfer and nitrobenzene adsorption, was another critical factor. The reaction proceeded through the direct route in which the intermediate nitrosobenzene was converted directly to aniline quickly.

Nitrobenzene reduction catalyzed by carbon: does the reaction really belong to carbocatalysis?

The reduction of nitrobenzene could proceed in the presence of carbon. The activity mainly originated from carbonyl groups on the carbon surface instead of metal impurities which were embedded in the carbon.

Noncovalent functionalization of multi-walled carbon nanotubes as metal-free catalysts for the reduction of nitrobenzene

Multi-walled carbon nanotubes were functionalized with small organic molecules containing specific ketonic carbonyl groups through noncovalent van der Waals and π–π interactions. The comparison of intrinsic activities for a series of catalysts indicates that the carbonyl groups are active sites in the reduction of nitrobenzene, and the catalysts functionalized with phenanthraquinone exhibit relatively high activity and selectivity.