Cyclohexane oxidation using Au/MgO: an investigation of the reaction mechanism

Conte, Marco; Liu, Xi; Murphy, D. M.; Whiston, Keith; Hutchings, Graham J.

doi:10.1039/c2cp43363j

Cited by 77 publications

(72 citation statements)

References 60 publications

(60 reference statements)

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“…The cumulative effect of all these aspects shows the complexity of autoxidation reactions, along with any oxidation reaction that produces alkyl peroxides or alkyl hydroperoxide species during the process, as this will result in a parallel autoxidation pathway that can mask the actual catalytic efficiency of a system. 148,154,155 …”

Section: Characterization Of the Reaction Products In Autoxidation Prmentioning

confidence: 99%

“…202 In contrast the use of metal nanoparticle based systems like Au/MgO or Au/ZSM-5 in liquid phase, showed an enhancement of the autoxidation pathway only, thus suggesting that the metal in this case is actually a promoter. 148,154 To date one of the most complete schemes in the propagation reaction of the alkyl peroxide radical is the one obtained by Jacobs and coworkers (Scheme 9) It also considers the formation of ring opening products like formyl species 165 thus showing the variety of combinations that reactions just involving ground state triplet oxygen can achieve when compared to pure catalytic processes involving heterolytic oxygen activation. Scheme 9.…”

Section: Cyclohexane Oxidation: An Exploited Case Of Autoxidationmentioning

confidence: 99%

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Catalytic oxygen activation versus autoxidation for industrial applications: a physicochemical approach

Liu

Ryabenkova

Conte

2015

Phys. Chem. Chem. Phys.

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The activation and use of oxygen for the oxidation and functionalization of organic substrates is among the most important reactions in a chemist's toolbox. Nevertheless, despite the vast literature on catalytic oxidation, the phenomenon of autoxidation, an ever-present background reaction that occurs in virtually every oxidation process, is often neglected. In contrast, autoxidation can affect the selectivity to a desired product, to those dictated by pure freeradical chain pathways, thus affecting the activity of any catalyst used to carry out a reaction.This critical review compares catalytic oxidation routes by transition metals versus autoxidation, particularly focusing on the industrial context, where highly selective and "green" processes are needed. Furthermore, the application of useful tests to discriminate between different oxygen activation routes, especially in the area of hydrocarbon oxidation, with the aim of an enhanced catalyst design, is described and discussed. In fact, one of the major targets of selective oxidation is the use of molecular oxygen as ultimate oxidant, combined with the development of catalysts capable to perform the catalytic cycle in a real energy and cost effective manner on a large scale. To achieve this goal, insights from metallo-proteins that could find application in some areas of industrial catalysis are presented, as well as considering the physicochemical principles that are at the fundament of oxidation and autoxidation processes.3

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Section: Characterization Of the Reaction Products In Autoxidation Prmentioning

confidence: 99%

Section: Cyclohexane Oxidation: An Exploited Case Of Autoxidationmentioning

confidence: 99%

Catalytic oxygen activation versus autoxidation for industrial applications: a physicochemical approach

Liu

Ryabenkova

Conte

2015

Phys. Chem. Chem. Phys.

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“…This allowed us to propose a reaction mechanism in which CHHP is adsorbed over the catalyst surface in analogy with AlPO catalysts [55], but with molecular oxygen that reacts with C 6 H 11 • radicals in liquid phase via a diffusion limited route, rather than to be adsorbed over the catalyst surface.…”

Section: Epr Spin Trapping For the Chhp Decomposition By Fresh And Thmentioning

confidence: 99%

Insights into the Reaction Mechanism of Cyclohexane Oxidation Catalysed by Molybdenum Blue Nanorings

et al. 2015

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Molybdenum blue (MB), is a polyoxometalate with a nanoring structure comprising Mo 5+ -OMo 6+ bridges, which is active for the catalytic oxidation of cyclohexane to cyclohexanol and cyclohexanone. However, little is known about the mechanistic features responsible of this catalytic activity. In the present work, the Mo 5+ -O-Mo 6+ moieties embedded in the MB nanoring structure were characterized using diffuse reflectance-UV-Visible spectroscopy and solid state EPR spectroscopy. The amount of Mo 5+ centres was then varied by thermal treatment of the polyoxometalate in the absence of oxygen, and the resultant effect on the catalytic activity was investigated. It was observed that, an increased amount of Mo 5+ centres preserved the conversion of cyclohexane (ca. 6%) but led to a loss of selectivity to cyclohexanol giving cyclohexanone as the major product, and the simultaneous formation of adipic acid. To rationalise these results the catalysts were studied using EPR spin trapping to investigate the decomposition of cyclohexyl hydroperoxide (CHHP), a key intermediate in the oxidation process of cyclohexane. This analysis showed that CHHP has to be bound to the MB surface in order to explain its catalytic activity and product distribution.

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“…TOF (turnover frequency) of 0.2%Co/MgO was calculated to be 8.2 s −1 by TOF = ∆n -ane /(n Co × D Co ×T) (-ane denotes the cyclohexane; ∆n -ane -the converted cyclohexane (mol); n Co -the Co amount in the catalyst (moL); T-the reaction time (s)). As shown in Table 2, compared with the Co-TUD-1 [40] and Au/MgO catalysts [35], the 0.2%Co/MgO catalyst exhibits higher catalytic activity for the oxidation of cyclohexane under similar reaction conditions.…”

Section: Introductionmentioning

confidence: 96%

Catalytic Performance of MgO-Supported Co Catalyst for the Liquid Phase Oxidation of Cyclohexane with Molecular Oxygen

Wang

et al. 2017

Catalysts

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Abstract:A highly-efficient and stable MgO-supported Co (Co/MgO) catalyst was developed for the oxidation of cyclohexane with oxygen. The effects of the Co loading and support on the catalytic activity of the supported Co 3 O 4 catalyst were investigated. The results show that the Co supported on MgO presented excellent activity and stability. When the Co/MgO catalyst with the Co content of 0.2 wt % (0.2%Co/MgO) was used, 12.5% cyclohexane conversion and 74.7% selectivity to cyclohexanone and cyclohexanol (KA oil) were achieved under the reaction conditions of 0.5 MPa O 2 and 140 • C for 4 h. After being repeatedly used 10 times, its catalytic activity was hardly changed. Further research showed that the high catalytic performance of the 0.2%Co/MgO catalyst is attributed to its high oxygen-absorbing ability and the high ratio between the amount of weak and medium base sites with the help of the synergistic interaction between Co and MgO.

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Cyclohexane oxidation using Au/MgO: an investigation of the reaction mechanism

Cited by 77 publications

References 60 publications

Catalytic oxygen activation versus autoxidation for industrial applications: a physicochemical approach

Catalytic oxygen activation versus autoxidation for industrial applications: a physicochemical approach

Insights into the Reaction Mechanism of Cyclohexane Oxidation Catalysed by Molybdenum Blue Nanorings

Catalytic Performance of MgO-Supported Co Catalyst for the Liquid Phase Oxidation of Cyclohexane with Molecular Oxygen

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