Mechanistic Insight into the Catalytic Oxidation of Cyclohexane over Carbon Nanotubes: Kinetic and In Situ Spectroscopic Evidence

Abstract

As some of the most interesting metal-free catalysts, carbon nanotubes (CNTs) and other carbon-based nanomaterials show great promise for some important chemical reactions, such as the selective oxidation of cyclohexane (C6H12). Due to the lack of fundamental understanding of carbon catalysis in liquid-phase reactions, we have sought to unravel the role of CNTs in the catalytic oxidation of C6H12 through a combination of kinetic analysis, in situ spectroscopy, and density functional theory. The catalytic effect of CNTs originates from a weak interaction between radicals and their graphene skeletons, which confines the radicals around their surfaces. This, in turn, enhances the electron-transfer catalysis of peroxides to yield the corresponding alcohol and ketone.

Covalent and noncovalent functionalization of pristine and defective graphene by cyclohexane and dehydrogenated derivatives

“…The physisorption energies that we report in this work for both species are comparable to adsorption of benzene on pure or processed graphene [54] and consequently their adsorption on graphene can be considered a functioning capture and elimination mechanism. Furthermore, interaction of C 6 H 12 with carbon-based materials has taken center-stage in other important applications including exfoliation of graphene in solution [55], metal-free selective oxidation of saturated hydrocarbons [27,31] and the characterization of multi-walled carbon nanotubes using hydrocarbons [28]. As regards geometries that exhibit covalent bonding, we report a charge transfer from the molecule to the graphene network.…”

“…C 6 H 12 was found to bind slightly more strongly than benzene even though all molecule-CNT interactions were of dispersive nature. DFT was also applied by Yang et al [31] to study the mechanism of CNT-catalyzed oxidation of C 6 H 12 by molecular oxygen.…”

Transformation of worst weed into N-, S-, and P-tridoped carbon nanorings as metal-free electrocatalysts for the oxygen reduction reaction

“…40 The remarkably better stability makes our catalyst as a potent candidate for ORR, especially for methanol alkaline fuel cells.…”

Doped Nanostructured Carbon Materials as Catalysts

“…176 Cheap metal-free catalysts have emerged as promising candidates for this transformation, with oxidative reactions over heteroatom-doped carbons receiving increasing attention, since they are able to activate oxygen molecules without the assistance of any metals. [177][178][179][180][181] Oxidative dehydrogenation (ODH) of light alkanes offers a potentially attractive route to alkenes, since the reaction is exothermic and avoids the thermodynamic constraints of non-oxidative routes by forming water as a byproduct. In addition, carbon deposition (coke formation) during ODH is eliminated, leading to stable catalytic activity.…”