Reductive amination of phenol over Pd-based catalysts: elucidating the role of the support and metal nanoparticle size

Díaz, Maray Ortega; Gómez, Daviel; Manrique, Raydel; Reyes, Guillermo; Garcia, Julieth; Medrano, Víctor Gabriel Baldovino; Jiménez, Romel; Arteaga-Pérez, Luis E.

doi:10.1039/d2re00259k

Cited by 7 publications

(8 citation statements)

References 91 publications

(180 reference statements)

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“…The exp-6 validates the effectiveness of Rh/C for the amination of phenol preferentially into dicyclohexylamine. This result is opposite to that witnessed on Pd/C, which generates a balance between DCyA and CyPhA owing to its dehydrogenation capacity [7].…”

Section: Catalytic Experiments Primary Reaction Pathwayscontrasting

confidence: 80%

“…The proposal of a reaction scheme describing the amination of phenol for Pd/S (S = Al 2 O 3 , C, SiO 2 ) catalysts has been previously approached on the basis of preliminary evidence [7,19]. Here we discuss the results obtained for Rh/C as regard to that previously inspected for Pd/C but emphasizing on self-condensation of the primary amines (using cyclohexylamine and aniline).…”

Section: Catalytic Experiments Primary Reaction Pathwaysmentioning

confidence: 89%

“…As a result, both catalysts can be classified as mesoporous [25]. The Weisz-Prater number (ΦWP calculated for each of the reactants (Φ WPPhenol = 0.0022, Φ WPCyclohexylamine = 0.0138) [7]; allows withdrawing internal mass transfer limitations in the process (see detailed calculations in [26]). Additionally, the average particle size estimated from transmission electron microscopy (TEM) was in the same order (Figure S1).…”

Section: Surface Textural and Morphologic Properties Of Catalystsmentioning

confidence: 99%

“…Liquid-phase reactions between the phenolics and cyclohexylamine, were carried out in 4 mL reinforced glass autoclave reactors inserted in a Reacti-ThermTM system (Thermofisher, Waltham, MA, USA) equipped with an external temperature probe, magnetic stirring (900 rpm) and pressurization line according to a procedure reported elsewhere [7,24]. Refs.…”

Section: Catalytic Conversion Of Phenolsmentioning

confidence: 99%

“…These routes have technological drawbacks such as the generation of hazardous waste streams, low atomic and energy efficiencies [6]. Therefore, new, and more sustainable synthetic methods for producing secondary amines from lignocellulosicderived feedstocks, are receiving attention [7]. In this sense, phenols have been reported as a naturally-available platform for amination as they can be obtained from lignin via depolymerization processes [8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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Secondary Amines from Catalytic Amination of Bio-Derived Phenolics over Pd/C and Rh/C: Effect of Operation Parameters

et al. 2023

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The production of renewable chemicals using lignocellulosic biomass has gained significant attention in green chemistry. Among biomass-derived chemicals, secondary amines have emerged as promising intermediates for synthetic applications. Here, we report a systematic study on the reductive amination of phenolics with cyclohexylamine using Pd/C and Rh/C as catalysts. The catalytic tests were performed in batch reactors under different reaction conditions (various: amine concentration (0.1–0.4 mol/L), hydrogen pressure (0–2.5 bar), temperature (80–160 °C), and substituted phenols (phenol, o-cresol, p-cresol, and methoxyphenol)) and using tert-amyl alcohol as a solvent. The experimental observations were consistent with a multi-step mechanism, where hydrogenation of phenol to cyclohexanone is followed by condensation of the ketone with cyclohexylamine to form an imine, which is finally hydrogenated to produce secondary amines. In addition, there was evidence of parallel self-condensation of the cyclohexylamine. The study also supported a limited dehydrogenation capacity of Rh/C, unlike Pd/C, which increases this capacity at higher temperatures generating a higher yield of cyclohexylaniline (up to 15%). The study of the alkylated phenols demonstrated that the nature and propensity of hydrogenation of the phenolic controls their amination. Kinetic analysis revealed reaction orders between 0.4 and 0.7 for H2, indicating its dissociative adsorption. Meanwhile, phenol’s order (between 1–1.8) suggests a single participation of this compound in the hydrogenation step. The order of 0.4 for cyclohexylamine suggests its participation as a surface-abundant species. The apparent activation energies derived from a power law approximation were of 37 kJ/mol and 10 kJ/mol on Pd/C and Rh/C, respectively.

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Section: Catalytic Experiments Primary Reaction Pathwayscontrasting

confidence: 80%

Section: Catalytic Experiments Primary Reaction Pathwaysmentioning

confidence: 89%

Section: Surface Textural and Morphologic Properties Of Catalystsmentioning

confidence: 99%

Section: Catalytic Conversion Of Phenolsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Secondary Amines from Catalytic Amination of Bio-Derived Phenolics over Pd/C and Rh/C: Effect of Operation Parameters

et al. 2023

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Selective Amination of Phenol to Cyclohexylamine over Metal‐Acid Bifunctional Catalysts Derived from Nickel Phyllosilicates

Wang

Qiu

et al. 2023

ChemCatChem

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Phenol amination to various valuable amines has attracted considerable attention in heterogeneous catalysis, but limited studies have focused on non-noble metal catalysts. This study reports a bifunctional catalyst (Ni/SiO 2 -AE) containing nickel nanoparticles and Lewis acid sites derived from nickel phyllosilicates for efficient amination of phenol to cyclohexylamine. The Ni/SiO 2 -AE catalyst resulted in 89.4% phenol conversion and 86.0% selectivity to cyclohexylamine at 160 °C for 2 h, which outperforms the catalysts by conventional deposition-precipitation (Ni/SiO 2 -DP) and wetness-impregnation (Ni/SiO 2 -WI). The turnover frequencies based on the actual exposed metal surface area for Ni/SiO 2 -AE, Ni/SiO 2 -DP, and Ni/SiO 2 -WI are calculated as 71.7, 49.0, and 8.7 h À 1 , respectively. Results demonstrate that the Ni nanoparticles exsoluted from nickel phyllosilicates participate in the activation of dihydrogen molecules, and the Lewis acid sites stemmed from coordination unsaturated Ni 2 + sites on the catalyst serve to adsorb and activate phenol. The synergistic effect of the dual-functions intensifies the phenol amination.

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Exploring the Mechanisms and Kinetic Modeling of Phenol Amination Using Pd and Rh‐Based Catalysts

Ortega,

Garrido,

Gómez

et al. 2024

ChemCatChem

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Producing biomass‐derived chemicals to replace their petrochemical counterparts has long been an aspiration of the green chemistry research community. However, synthesizing secondary amines from biomass precursors presents several challenges related to catalyst nature and the mechanistic understanding of reaction systems. Here, we unravel the mechanistic and kinetic implications of the reductive amination of phenol with cyclohexylamine over Pd/C and Rh/C. A competitive Langmuir‐Hinshelwood reaction model well interpreted the kinetic data, suggesting that support‐metal interfaces serve as active sites for H2, –NH2 and =NH activation. The apparent activation energies for imine hydrogenation were 87.6 kJ mol‐1 (Pd/C) and 34.5 kJ mol‐1 (Rh/C), while ΔHads and ΔSads values confirmed the physicochemical consistency of the model. Moreover, the catalysts demonstrated their high stability to operate for several catalytic cycles, with minor activity losses due to metal leaching and partial sintering of Pd nanoparticles. Despite phenol reductive amination follows similar mechanisms on Rh/C and Pd/C, they show differences in selectivity because the hydrogenation of imine is more efficient on Rh0 than on Pd0. This is the first mechanism‐oriented kinetic study for phenol reductive amination; thus, it provides valuable information for process design and scale‐up.

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Reductive amination of phenol over Pd-based catalysts: elucidating the role of the support and metal nanoparticle size

Abstract: The heterogeneously catalyzed reductive amination of phenolics from lignin is considered an attractive sustainable route for the synthesis of primary or high-order aromatic and aliphatic amines. Here, the reductive amination...

Cited by 7 publications

References 91 publications

Secondary Amines from Catalytic Amination of Bio-Derived Phenolics over Pd/C and Rh/C: Effect of Operation Parameters

Secondary Amines from Catalytic Amination of Bio-Derived Phenolics over Pd/C and Rh/C: Effect of Operation Parameters

Selective Amination of Phenol to Cyclohexylamine over Metal‐Acid Bifunctional Catalysts Derived from Nickel Phyllosilicates

Exploring the Mechanisms and Kinetic Modeling of Phenol Amination Using Pd and Rh‐Based Catalysts

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