ChemInform Abstract: Deactivation Reaction in the Hydroxylation of Benzene with Fenton′s Reagent.

Ito, Sotaro; Mitarai, Akira; Hikino, Kenji; Hirama, Mutsumi; Sasaki, Kazuo

doi:10.1002/chin.199319135

Cited by 2 publications

(2 citation statements)

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“…Previously, the Hubbard group has noticed the surface water displacement reaction upon adsorption of quinone at the platinum oxide surface. 39,40 Meanwhile, based on the literature reports, 21−41 it has been proposed that the following electrochemical reactions also occur on the modified electrode surface: (i) the direct hydration of benzene to polyphenols and benzoquinones 42 at high oxidation potential (1.2 V) via an electro-Fenton-like reaction mechanism, 25,26 with the assistance of the iron impurity in the MWCNT 21−26 and (ii) polymerization of the benzene radical species as polyphenylene film, a graphene structural mimic, which has a rich π-electronic system. 43−46 Since the amount of adsorbed material on the MWCNT electrode surface is very small, about picogram level, and due to its composite nature, it is highly difficult to characterize the material using conventional characterization techniques like nuclear magnetic resonance, electron-spin resonance, and mass-spectroscopic techniques.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Reaction Assisted 2D π-Stacking of Benzene on a MWCNT Surface and its Unique Redox and Electrocatalytic Properties

2019

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Turning the π-structure and electronic properties of carbon nanotubes (CNTs) is a cutting-edge research topic in interdisciplinary areas of material chemistry. In general, chemical functionalization of CNT has been adopted for this purpose, which has resulted in a few monolayer thickness increment of CNT diameter size. Herein, we report an interesting observation of >10-fold increment in the apparent diameter of multiwalled carbon nanotubes (MWCNTs) brought about by a process of self-assembly of the BZ moiety on MWCNT, which is formed by electrochemical oxidation of a surface-adsorbed benzene–water cluster, {BZ-nH2O}. From physicochemical characterizations by transmission electron microscopy (TEM) and Raman and IR spectroscopic techniques and electrochemical characterizations by several radical scavenger species, it has been revealed that benzene radical moieties as a series of π-stacked layers ([BZ]-π-stack) were self-assembled on the MWCNT surface. A possible mechanism for their formation was proposed to be electrochemical oxidation of H2O from the MWCNT@{BZ-nH2O}ads layer to oxygen gas via hydroxyl radical formation and benzene cationic radical species at 1.2 V vs Ag/AgCl followed by its self-assembly into a unique MWCNT@[BZ]-π-stack network. The scanning electrochemical microscopic (SECM) technique was used to identify the in situ •OH radical formation. The electrochemical studies of a glassy-carbon-modified MWCNT@[BZ]-π-stack system showed a well-defined and highly symmetrical redox peak at an equilibrium potential E 1/2 = 0.2 V vs Ag/AgCl (pH 2 HCl/KCl), with a peak-to-peak potential separation of 0 V, highlighting the ideal-surface-confined electron-transfer nature of the redox couple. Furthermore, enhanced electrical conductivity over the unmodified MWCNT was observed when testing the surface-sensitive redox couple Fe3+/Fe2+ with the modified electrode. This new redox material showed a specific electrocatalytic reduction of hydrogen peroxide at neutral pH (pH 7 phosphate buffer solution) unlike the quinone and other organic redox mediators, which show the reduction signal only in the presence of horseradish peroxidase enzyme.

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Section: Resultsmentioning

confidence: 99%

Electrochemical Reaction Assisted 2D π-Stacking of Benzene on a MWCNT Surface and its Unique Redox and Electrocatalytic Properties

2019

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“…In addition, the inevitable leaching of iron species during heterogeneous Fenton catalysis can deactivate the catalyst and increase the iron sludge generation. 27,32,33 Thus, strategies that can overcome these issues are urgently needed to advance iron-containing heterogeneous catalysts for one-step synthesis of phenol.…”

Section: ■ Introductionmentioning

confidence: 99%

Selective Hydroxylation of Benzene to Phenol over Fe Nanoparticles Encapsulated within N-Doped Carbon Shells

Yang

et al. 2020

ACS Appl. Nano Mater.

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Iron-containing heterogeneous catalysts hold great promising for the direct hydroxylation of benzene to phenol. However, their catalytic performance is greatly hampered by the inherent drawbacks of iron-containing solids, in particular their hydrophilic surface structure and inevitable leaching of iron species during the Fenton process, which result in poor selectivity and durability toward phenol production. Herein, we demonstrate that the encapsulation of iron nanoparticles with N-doped carbon layer as core−shell nanostructures (Fe@NC) is a promising synthetic strategy to advance iron-containing solids for benzene hydroxylation. The rigid carbon shells conformably coating on iron cores not only protect iron from leaching but also facilitate the selective adsorption of benzene molecules on Fe@NC because of their excellent stability against acid etching and hydrophobic surface with the unique π-conjugated electron system. As a result, Fe@NC exhibit a robust catalytic durability and good yield with high selectivity for the direct hydroxylation of benzene to phenol. Benefiting from their unique core−shell nanostructures and strong host−guest electron interaction between metals and carbons, Fe@NC are expected to be promising also for other liquid-phase organic synthesis.

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ChemInform Abstract: Deactivation Reaction in the Hydroxylation of Benzene with Fenton′s Reagent.

Cited by 2 publications

References 1 publication

Electrochemical Reaction Assisted 2D π-Stacking of Benzene on a MWCNT Surface and its Unique Redox and Electrocatalytic Properties

Electrochemical Reaction Assisted 2D π-Stacking of Benzene on a MWCNT Surface and its Unique Redox and Electrocatalytic Properties

Selective Hydroxylation of Benzene to Phenol over Fe Nanoparticles Encapsulated within N-Doped Carbon Shells

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