A Multifunction Pd/Sc(OTf)<sub>3</sub>/Ionic Liquid Catalyst System for the Tandem One-Pot Conversion of Phenol to ε-Caprolactam

Shin, Ju Yeon; Jung, Da Jung; Lee, Sang Gi

doi:10.1021/cs400009w

Cited by 46 publications

(25 citation statements)

References 65 publications

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“…7 Lee and co-workers significantly improved the process by combining Sc(OTf) 3 with Pd/C, achieving full conversion at 20°C and 1 bar of H 2 . 8 The Lewis acid also favors the selectivity to the cyclohexanone by forming an adduct that is more difficult to reduce to the alcohol. Li, Luque, and collaborators achieved similar results with a fully heterogeneous system using Pd supported on the chromium-based MOF MIL-101, with the chromium centers in the MOF support proposed as Lewis acidic activators for the reaction.…”

Section: 2mentioning

confidence: 99%

Selective Hydrogenation of Phenol Catalyzed by Palladium on High-Surface-Area Ceria at Room Temperature and Ambient Pressure

et al. 2015

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Palladium supported on high-surface-area ceria effectively catalyzes the hydrogenation of phenol to cyclohexanone at atmospheric pressure and room temperature. Activation of H2 at Pd sites and phenol at surface ceria sites was investigated by probing the redox properties of the catalyst and studying the mechanism of phenol adsorption. Temperature-programmed reduction and pulsed chemisorption were used to examine the effects of prereduction temperature on catalyst dispersion and reducibility. A sharp effect of prereduction temperature on catalytic activity was observed. This dependence is rationalized as a result of interactions between palladium and ceria, which under reducing conditions enhance palladium dispersion and create different types of environments around the Pd active sites and of encapsulation of the catalyst caused by support sintering at high temperatures. Temperature-programmed diffuse reflectance infrared Fourier transform spectroscopy revealed that phenol undergoes dissociative adsorption on ceria to yield ceriumbound phenoxy and water. Reduction of the chemisorbed phenoxy species decreases the number of protonaccepting sites on the surface of ceria and prevents further dissociative adsorption. Subsequent phenol binding proceeds through physisorption, which is a less active binding mode for reduction by hydrogen. High activity can be restored upon regeneration of proton acceptor sites via reoxidation/reduction of the catalyst. ABSTRACT: Palladium supported on high-surface-area ceria effectively catalyzes the hydrogenation of phenol to cyclohexanone at atmospheric pressure and room temperature. Activation of H 2 at Pd sites and phenol at surface ceria sites was investigated by probing the redox properties of the catalyst and studying the mechanism of phenol adsorption. Temperature-programmed reduction and pulsed chemisorption were used to examine the effects of prereduction temperature on catalyst dispersion and reducibility. A sharp effect of prereduction temperature on catalytic activity was observed. This dependence is rationalized as a result of interactions between palladium and ceria, which under reducing conditions enhance palladium dispersion and create different types of environments around the Pd active sites and of encapsulation of the catalyst caused by support sintering at high temperatures. Temperature-programmed diffuse reflectance infrared Fourier transform spectroscopy revealed that phenol undergoes dissociative adsorption on ceria to yield cerium-bound phenoxy and water. Reduction of the chemisorbed phenoxy species decreases the number of proton-accepting sites on the surface of ceria and prevents further dissociative adsorption. Subsequent phenol binding proceeds through physisorption, which is a less active binding mode for reduction by hydrogen. High activity can be restored upon regeneration of proton acceptor sites via reoxidation/reduction of the catalyst.

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Section: 2mentioning

confidence: 99%

Selective Hydrogenation of Phenol Catalyzed by Palladium on High-Surface-Area Ceria at Room Temperature and Ambient Pressure

et al. 2015

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“…High yielding one-pot oximation-Beckmann rearrangement of ketones to amides using trifluoroacetic acid or FeCl 3 ·6H 2 O as a catalyst was reported by Aricò and Mahajan respectively [12,13]. More recently, Lee reported a multifunctional Pd/Sc(OTf) 3 /ionic liquid catalyst for the tandem onepot conversion of phenol to CL, in 67% overall yield, using 300 mol% 1-butyl-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]) as an additive [14]. Though very high phenol conversion and CL selectivity were achieved, this catalyst system suffered from the problems of difficult separation of the ionic liquid from the reaction mixture.…”

Section: Introductionmentioning

confidence: 99%

Direct catalytic synthesis of ε-caprolactam from cyclohexanol using [n-C16H33N (CH3)3]H2PW12O40 as a catalyst

Wang

Yang

et al. 2015

Catalysis Communications

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“…Such a problem had also been encountered by Shin et al, where Pd/ Sc(OTf) 3 /ionic liquid system was employed as the catalyst for the tandem synthesis of CPL from phenol. [16] To account for such "quenched" activity, we perform ICP-MS (Table S3) analysis of the used catalyst and find that 40 % of Pd leaches from the MOF support after the first round of tandem catalysis, which could be induced by the strong acidic condition and chloride ions which facilitate the dissolving of Pd by coordination. [27] Currently, more endeavors are ongoing to resolve the Pd leaching issue.…”

Section: Resultsmentioning

confidence: 99%

“…The core problem of the tandem reaction starting from phenol is that the required reaction environment for oximation-Beckmann rearrangement is quite harsh, which is under strong acidic and high-temperature conditions. [16,28] Pd nanoparticles cannot survive in these conditions, most likely due etching by the acid and poisoning by the solvent such as CH 3 CN, resulting in the lost activity of Pd in recycled catalysts for phenol hydrogenation.…”

Section: Resultsmentioning

confidence: 99%

Tandem Synthesis of ϵ‐Caprolactam from Cyclohexanone by an Acidified Metal‐organic Framework

Zhang

Chen

et al. 2021

ChemCatChem

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Tandem synthesis of ɛ-caprolactam, one of the largest scaled commercial chemicals, is highly desired from the viewpoint of cost, energy, and environment. However, relevant studies have remained largely underexplored. By using a one-pot strategy, we encapsulated phosphotungstic acid (PTA) into a chromium terephthalate metal-organic framework (MOF), MIL-101, for the efficient tandem conversion of cyclohexanone to ɛ-caprolactam.The highly dispersed PTA in the MOF matrix showed a high yield of ɛ-caprolactam through a tandem oximation-Beckmann rearrangement reaction at 100°C for 12 h. Moreover, MIL-101-PTA was recycled three times, with only a slight loss in their catalytic performance. To the best of our knowledge, this represents the first report using acidified MOF for a tandem oximation-Beckmann rearrangement reaction.

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A Multifunction Pd/Sc(OTf)₃/Ionic Liquid Catalyst System for the Tandem One-Pot Conversion of Phenol to ε-Caprolactam

Cited by 46 publications

References 65 publications

Selective Hydrogenation of Phenol Catalyzed by Palladium on High-Surface-Area Ceria at Room Temperature and Ambient Pressure

Selective Hydrogenation of Phenol Catalyzed by Palladium on High-Surface-Area Ceria at Room Temperature and Ambient Pressure

Direct catalytic synthesis of ε-caprolactam from cyclohexanol using [n-C16H33N (CH3)3]H2PW12O40 as a catalyst

Tandem Synthesis of ϵ‐Caprolactam from Cyclohexanone by an Acidified Metal‐organic Framework

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A Multifunction Pd/Sc(OTf)3/Ionic Liquid Catalyst System for the Tandem One-Pot Conversion of Phenol to ε-Caprolactam

Cited by 46 publications

References 65 publications

Selective Hydrogenation of Phenol Catalyzed by Palladium on High-Surface-Area Ceria at Room Temperature and Ambient Pressure

Selective Hydrogenation of Phenol Catalyzed by Palladium on High-Surface-Area Ceria at Room Temperature and Ambient Pressure

Direct catalytic synthesis of ε-caprolactam from cyclohexanol using [n-C16H33N (CH3)3]H2PW12O40 as a catalyst

Tandem Synthesis of ϵ‐Caprolactam from Cyclohexanone by an Acidified Metal‐organic Framework

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A Multifunction Pd/Sc(OTf)₃/Ionic Liquid Catalyst System for the Tandem One-Pot Conversion of Phenol to ε-Caprolactam