The Low Temperature Solvent-Free Aerobic Oxidation of Cyclohexene to Cyclohexane Diol over Highly Active Au/Graphite and Au/Graphene Catalysts

Rogers, Owen; Pattisson, Samuel; Macginley, Joseph; Engel, Rebecca V.; Whiston, Keith; Taylor, Stuart Hamilton; Hutchings, Graham J.

doi:10.3390/catal8080311

Cited by 14 publications

(10 citation statements)

References 36 publications

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“…However, this catalyst suffered from high selectivity to the allylic oxidation products. The same observation was made by Rogers et al for cyclohexene oxidation using oxygen. Despite the high activity of gold nanoparticles supported on carbon prepared by sol immobilization, this catalyst showed a high selectivity to the allylic products compared to epoxide, even with the addition of a co-catalyst.…”

Section: Resultssupporting

confidence: 77%

“…It was reported that adding tungsten oxide as a co-catalyst could change the selectivity toward epoxide, while MIL-101 (chromium(III) terephthalate) produced more allylic products. The same observation was made by Rogers and co-workers in the solvent-free aerobic oxidation of cyclohexene using Au catalysts supported on graphite or graphene and tungsten oxide as a co-catalyst. No product was found in the solvent- and initiator-free epoxidation of cyclooctene using air as the oxidant and supported gold catalysts by Bawaked et al , Munz et al carried out the aerobic epoxidation of olefins using platinum catalysts supported on mesoporous silica nanoparticles .…”

Section: Introductionsupporting

confidence: 74%

“…The sol immobilization method, which was used in a series of studies by the group of Hutchings for the deposition of gold nanoparticles, was found to be an effective method for the high dispersion of nanoparticles in catalysts for the solvent-free oxidation of alkenes …”

Section: Resultsmentioning

confidence: 99%

“…Thus, in addition to using oxygen as the greenest oxidant, another important way to minimize the environmental impact of an oxidation reaction is to perform it under solvent- and reductant-free conditions. However, this may result in lower yields of epoxides compared to allylic oxidation products …”

Section: Introductionmentioning

confidence: 99%

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Activated Carbon-Supported Ruthenium as a Catalyst for the Solvent- and Initiator-Free Aerobic Epoxidation of Limonene

Madadi

Kaliaguine

2021

ACS Sustainable Chem. Eng.

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The activity and selectivity of ruthenium catalysts supported on various activated carbons have been investigated in the epoxidation of limonene using molecular oxygen, the greenest oxidizing agent, under solvent/reductant- and initiator-free reaction conditions. The catalysts were prepared via different methods including impregnation, sol immobilization, and cation exchange. Supported Ru catalysts with a metal particle size ranging from 1.8 to 21 nm were obtained. The catalyst prepared by cation exchange using Darco G60, with the highest mesopore surface area and pore volume and the lowest Ru particle size (1.8 nm), was found to give the best combination of limonene conversion of 35% and higher selectivity for epoxidation products (S epox) of 57% at 80 °C and 3 bar oxygen pressure, compared to the total selectivity of 25.5% for allylic oxidation products (S allyl). Other activated carbon supports, e.g., Darco MRX, Norit RB4C, and Norit RX3, were found to yield less effective catalysts. In addition, the sol immobilization method led to the highest conversion of limonene (40.4%) but with a lower total selectivity toward epoxidation products (S epox) of 36.8% and that toward allylic oxidation products (S allyl) of 33.6%. The textural parameters of carbon-supported Ru catalysts were determined by BET, TEM, SEM, TPR, and CO chemisorption. Highly dispersed Ru particles were found to promote the formation of limonene epoxides via the reaction of limonene hydroperoxide with limonene instead of hydroperoxide decomposition to allylic radicals. Finally, the appropriate reaction conditions to maximize the selectivity of the epoxides and the reusability of the catalyst were established.

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Section: Resultssupporting

confidence: 77%

Section: Introductionsupporting

confidence: 74%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Activated Carbon-Supported Ruthenium as a Catalyst for the Solvent- and Initiator-Free Aerobic Epoxidation of Limonene

Madadi

Kaliaguine

2021

ACS Sustainable Chem. Eng.

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“…Recent studies have shown the effectiveness of a tungsten oxide co-catalyst to direct the hydroperoxide intermediate towards the epoxide, however, this is also limited due to the equimolar formation of the allylic alcohol [13]. The formation of cyclohexane diol is also restricted by the lack of water to facilitate hydrolysis of the epoxide [14].…”

Section: Introductionmentioning

confidence: 99%

Low temperature solvent-free allylic oxidation of cyclohexene using graphitic oxide catalysts

et al. 2020

Self Cite

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A range of graphitic oxides have been utilised as metal free carbocatalysts for the low temperature oxidation of cyclohexene. The activity of the catalysts was correlated with the amount of surface oxygen on the graphitic oxide. In the case of cyclohexene oxidation, major selectivity is observed to allylic oxidation products. This is in contrast to the epoxide being the major product in linear alkene oxidation. This selectivity was maintained over long reaction times and at a conversion of above 50 %. Only small amounts of epoxide were observed, which eventually decreases at higher conversion due to hydrolysis to cyclohexane diol. The similarity between the non-catalysed and the catalysed product distribution suggests that these catalysts act as a solid initiator, and the role of the graphitic oxide is to decrease the lengthy induction period observed in the blank non-catalysed reaction.

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Liquid‐Phase Cyclohexene Oxidation with O₂ over Spray‐Flame‐Synthesized La_1−xSr_xCoO₃ Perovskite Nanoparticles

Büker

Alkan

Chabbra

et al. 2021

Chemistry A European J

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La1−xSrxCoO3 (x=0, 0.1, 0.2, 0.3, 0.4) nanoparticles were prepared by spray‐flame synthesis and applied in the liquid‐phase oxidation of cyclohexene with molecular O2 as oxidant under mild conditions. The catalysts were systematically characterized by state‐of‐the‐art techniques. With increasing Sr content, the concentration of surface oxygen vacancy defects increases, which is beneficial for cyclohexene oxidation, but the surface concentration of less active Co2+ was also increased. However, Co2+ cations have a superior activity towards peroxide decomposition, which also plays an important role in cyclohexene oxidation. A Sr doping of 20 at. % was found to be the optimum in terms of activity and product selectivity. The catalyst also showed excellent reusability over three catalytic runs; this can be attributed to its highly stable particle size and morphology. Kinetic investigations revealed first‐order reaction kinetics for temperatures between 60 and 100 °C and an apparent activation energy of 68 kJ mol−1 for cyclohexene oxidation. Moreover, the reaction was not affected by the applied O2 pressure in the range from 10 to 20 bar. In situ attenuated total reflection infrared spectroscopy was used to monitor the conversion of cyclohexene and the formation of reaction products including the key intermediate cyclohex‐2‐ene‐1‐hydroperoxide; spin trap electron paramagnetic resonance spectroscopy provided strong evidence for a radical reaction pathway by identifying the cyclohexenyl alkoxyl radical.

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The Low Temperature Solvent-Free Aerobic Oxidation of Cyclohexene to Cyclohexane Diol over Highly Active Au/Graphite and Au/Graphene Catalysts

Cited by 14 publications

References 36 publications

Activated Carbon-Supported Ruthenium as a Catalyst for the Solvent- and Initiator-Free Aerobic Epoxidation of Limonene

Activated Carbon-Supported Ruthenium as a Catalyst for the Solvent- and Initiator-Free Aerobic Epoxidation of Limonene

Low temperature solvent-free allylic oxidation of cyclohexene using graphitic oxide catalysts

Liquid‐Phase Cyclohexene Oxidation with O₂ over Spray‐Flame‐Synthesized La_1−xSr_xCoO₃ Perovskite Nanoparticles

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The Low Temperature Solvent-Free Aerobic Oxidation of Cyclohexene to Cyclohexane Diol over Highly Active Au/Graphite and Au/Graphene Catalysts

Cited by 14 publications

References 36 publications

Activated Carbon-Supported Ruthenium as a Catalyst for the Solvent- and Initiator-Free Aerobic Epoxidation of Limonene

Activated Carbon-Supported Ruthenium as a Catalyst for the Solvent- and Initiator-Free Aerobic Epoxidation of Limonene

Low temperature solvent-free allylic oxidation of cyclohexene using graphitic oxide catalysts

Liquid‐Phase Cyclohexene Oxidation with O2 over Spray‐Flame‐Synthesized La1−xSrxCoO3 Perovskite Nanoparticles

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Product

Resources

About

Liquid‐Phase Cyclohexene Oxidation with O₂ over Spray‐Flame‐Synthesized La_1−xSr_xCoO₃ Perovskite Nanoparticles