Reaction pathways over copper and cerium oxide catalysts for direct synthesis of imines from amines under aerobic conditions

Al-Hmoud, Linda; Jones, Christopher W.

doi:10.1016/j.jcat.2013.01.027

Cited by 64 publications

(55 citation statements)

References 66 publications

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“…These observations lead us to conclude that pathway A (i.e., hydrolysis of benzyl imine and subsequent coupling of benzaldehyde and benzyl amine) is the dominant pathway for the formation of N ‐benzylidene‐1‐phenylmethanamine. We note that this conclusion is in full agreement with the recent work of Jones and co‐workers, who also observed that the addition of water both accelerated the rate of reaction and increased the maximal yield obtained during the aerobic oxidation of benzyl amine with nonpromoted CeO 2 13…”

Section: Resultssupporting

confidence: 93%

Insights into the Oxidative Dehydrogenation of Amines with Nanoparticulate Iridium Oxide

Hammond

Schümperli

Hermans

2013

Chemistry A European J

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The aerobic oxidation of amines offers a promising route towards many versatile chemical compounds. Within this contribution, we extend our previous investigations of iridium oxide-catalyzed alcohol oxidation to amine substrates. In addition to demonstrating the versatility of this catalyst, particular attention is focused on the mechanisms of the reaction. Herein, we demonstrate that although amines are oxidized slower than the corresponding alcohols, the catalyst has a preference for amine substrates, and oxidizes various amines at turnover frequencies greater than other systems found in the open literature. Furthermore, the competition between double amine dehydrogenation, to yield the corresponding nitrile, and amine-imine coupling, to yield the corresponding coupled imine, has been found to arise from a competitive reaction pathway, and stems from an effect of substrate-to-metal ratio. Finally, the mechanism responsible for the formation of N-benzylidene-1-phenylmethanamine was examined, and attributed to the coupling of free benzyl amine substrate and benzaldehyde, formed in situ through hydrolysis of the primary reaction product, benzyl imine.

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Section: Resultssupporting

confidence: 93%

Insights into the Oxidative Dehydrogenation of Amines with Nanoparticulate Iridium Oxide

Hammond

Schümperli

Hermans

2013

Chemistry A European J

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“…As shown, the reaction started smoothly without an induction period, and proceeded with high selectivity towards N ‐(benzylidene)benzylamine. At extended reaction times, the promoted formation of benzaldehyde was not observed, which is quite different from the case of well established CuO/CeO 2 catalyst It is interesting that the generation of N ‐(benzylidene) benzylamine followed the second order kinetics, that means, the reaction rate was proportional to the square of the benzylamine concentration. This found indicated that the bimolecular involved coupling step rather than the oxidation step was likely the rate determining step in the oxidative coupling of benzylamine.…”

Section: Resultscontrasting

confidence: 71%

“…In pathway A, hydrolysis of NH‐imines occurs to give the benzaldehyde due to the trace amount of water generated from the oxidation step. It is noteworthy that, as a supplement, benzaldehyde can also be generated by hydrolysis of the final product of N ‐benzylidenebenzylamine . Then the final product of N ‐benzylidenebenzylamine could be obtained by reaction of the resulting benzaldehyde and benzylamine.…”

Section: Resultsmentioning

confidence: 99%

“…Then the final product of N ‐benzylidenebenzylamine could be obtained by reaction of the resulting benzaldehyde and benzylamine. Reaction following the pathway can be enhanced by addition of water and yield considerable amount of aldehyde byproducts . In pathway B, this NH‐imines intermediate can directly react with another molecular of benzylamine to yield aminal, which then releases ammonia to give the coupled N ‐benzylidenebenzylamine.…”

Section: Resultsmentioning

confidence: 99%

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Seaweed‐like 2D‐2D Architecture of MoS₂/rGO Composites for Enhanced Selective Aerobic Oxidative Coupling of Amines

Wang

Shen

et al. 2019

ChemCatChem

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To provide a solution for pursuing high redox reactivity beyond the compromise between the numbers of sulfur vacancies and electron transfer ability, 2D‐2D architecture of MoS2/rGO composite was fabricated with 2D graphene‐like transition metal dichalcogenides and graphene. By employing this material as heterogeneous catalyst, imines, also known as Schiff base, was synthesized by direct aerobic oxidative coupling of amines. Taking advantage of few‐layered MoS2 nanosheets and graphene, catalytic performance was significantly enhanced, exhibiting both excellent conversion and remarkable selectivity. Due to the good oil‐absorbing capability of this open porous 2D‐2D architecture, the hydrolysis of NH‐imines by water was inhibited and thus aldehydes byproducts were diminished. A second order kinetic behavior was observed in the imines formation, indicating the bimolecular condensation might be the rate determining step in such coupling reaction.

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“…The commonly used in the FTS or proposed for the SRE heterogeneous catalysts are cobalt-based ones [2][3][4][5][6][7], usually highly dispersed on inorganic oxide supports [8], which show a high activity and stability, relatively low cost and a high selectivity for the most desirable reaction products [9]. Among supports of the active phase, cerium oxide was used very often in various catalytic systems [3,10,11]. Ceria is characterized by a high oxygen transport and its storage capacity, by shifting between Ce 3+ and Ce 4+ under reductive-oxidative conditions [12,13].…”

Section: Introductionmentioning

confidence: 99%

Estimation of Average Crystallites Size of Active Phase in Ceria-Supported Cobalt-Based Catalysts by Hydrogen Chemisorption vs TEM and XRD Methods

et al. 2016

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Cobalt catalysts with CeO 2 support, unpromoted and promoted with potassium were prepared by an impregnation method. Reduced catalysts were subjected to hydrogen chemisorption at different temperatures in the range of 313-453 K. Studies have shown that calculated Co crystallites size depends on the temperature of chemisorption. The average of size crystallites of the Co active phase obtained from the total and strong chemisorption data were compared with those from measurements by other techniques, TEM and XRD. The results of comparison allowed us to indicate the most suitable chemisorption temperature, different for unpromoted (383 K) and potassium-promoted (413 K) catalysts to determine the proper Co crystallites size of active phase, compatible with the crystallites size determined by the most objective method, i.e. by TEM measurements. In the case of small metal crystallites of active phase (4-5 nm) the divergence of their average size determined by hydrogen chemisorption and TEM methods and particularly by the XRD method is definitely higher than that in the case of larger crystallites (~12 nm).can significantly influence on obtained results. More than 40 years ago Bartholomew et al. [23][24][25] show that the chemisorption of hydrogen over cobalt catalysts with various supports (SiO 2 , Al 2 O 3 , C, MgO, ZSM-5, TiO 2 ) and over unsupported cobalt is activated and highly reversible. The activation was a function of the interaction of cobalt with a support or promoter. Frequently used in catalysis, potassium promoter significantly increased the adsorption activation energy for hydrogen [26]. It is also proved that some methods for determining the hydrogen uptake, i.e. flow adsorption methods such as thermal desorption and pulse methods, measure only irreversible (strong) chemisorption [23,27]. No hydrogen desorption was detected for MgOand ZSM-5-supported and low-loaded (1-3 wt.%) aluminasupported cobalt catalysts using TPD method, even though those catalysts adsorbed hydrogen when the static technique was applied [23,24]. The special case is the Co/TiO 2 system, where due to the strong metal-support interactions the stoichiometry of hydrogen chemisorption is lower than one hydrogen atom per surface cobalt atom, even in static measurements. With exception of the cobalt systems in which the strong metal-support interactions take place, the static technique was recommended for estimation of the average size of cobalt crystallites on the basis of maximal hydrogen chemisorption uptake, usually at 373 K. A good correlation with TEM measurements was found for the Co/SiO 2 , Co/γ-Al 2 O 3 and Co/C catalysts. The paper [9] also shows that the volume of chemisorbed hydrogen (including strong and weak chemisorption) on the CoRe/γ-Al 2 O 3 catalyst varies with the temperature of chemisorption, and the use of different data leads to the determination of different average size of crystallites, even though the actual crystallites size remains unchanged. They obtained the best results when the total chemisorption...

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Reaction pathways over copper and cerium oxide catalysts for direct synthesis of imines from amines under aerobic conditions

Cited by 64 publications

References 66 publications

Insights into the Oxidative Dehydrogenation of Amines with Nanoparticulate Iridium Oxide

Insights into the Oxidative Dehydrogenation of Amines with Nanoparticulate Iridium Oxide

Seaweed‐like 2D‐2D Architecture of MoS₂/rGO Composites for Enhanced Selective Aerobic Oxidative Coupling of Amines

Estimation of Average Crystallites Size of Active Phase in Ceria-Supported Cobalt-Based Catalysts by Hydrogen Chemisorption vs TEM and XRD Methods

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Reaction pathways over copper and cerium oxide catalysts for direct synthesis of imines from amines under aerobic conditions

Cited by 64 publications

References 66 publications

Insights into the Oxidative Dehydrogenation of Amines with Nanoparticulate Iridium Oxide

Insights into the Oxidative Dehydrogenation of Amines with Nanoparticulate Iridium Oxide

Seaweed‐like 2D‐2D Architecture of MoS2/rGO Composites for Enhanced Selective Aerobic Oxidative Coupling of Amines

Estimation of Average Crystallites Size of Active Phase in Ceria-Supported Cobalt-Based Catalysts by Hydrogen Chemisorption vs TEM and XRD Methods

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Seaweed‐like 2D‐2D Architecture of MoS₂/rGO Composites for Enhanced Selective Aerobic Oxidative Coupling of Amines