A Bifunctional Mechanism for Ethene Dimerization: Catalysis by Rhodium Complexes on Zeolite HY in the Absence of Halides

Serna, Pedro; Gates, Bruce C.

doi:10.1002/ange.201008086

Cited by 12 publications

(6 citation statements)

References 35 publications

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“…In Table , we also present the structural parameters characterizing the various supports. The EXAFS results indicate that Rh(I) complexes supported on DAY zeolite have Rh–C, Rh–O, and Rh–Al coordination numbers and distances that are in good agreement with our calculated values (Table S7).…”

Section: Resultssupporting

confidence: 88%

“…We have already reported results characterizing Rh(C 2 H 4 ) 2 supported on DAY zeolite. ,− ,, The supported rhodium diethylene complex is characterized by IR bands at 3084, 3060, and 3016 cm –1 indicating the π-bonded ethylene ligands, EXAFS spectra showing the existence of two ethylene ligands per Rh atom on average, and the bonding of each Rh atom on average to two O atoms of the support. In this case, the rhodium complexes occupied all of the sites at Al cations in the zeolite, as indicated by the disappearance of the Al–OH bands at 3630 and 3565 cm –1 . ,− , …”

Section: Resultsmentioning

confidence: 93%

“…DAY zeolite-supported Rh(C 2 H 4 ) 2 complexes were synthesized similarly, by reaction of Rh(C 2 H 4 ) 2 (acac) with dealuminated Y zeolite (DAY, SiO 2 /Al 2 O 3 ratio = 30). − The rhodium loading was 1.0 wt %.…”

Section: Methodsmentioning

confidence: 99%

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Molecular Rhodium Complexes Supported on the Metal-Oxide-Like Nodes of Metal Organic Frameworks and on Zeolite HY: Catalysts for Ethylene Hydrogenation and Dimerization

Bernales

Yang

et al. 2017

ACS Appl. Mater. Interfaces

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Metal-organic frameworks (MOFs) with nodes consisting of zirconium oxide clusters (Zr) offer new opportunities as supports for catalysts with well-defined, essentially molecular, structures. We used the precursor Rh(CH)(acac) (acac is acetylacetonate) to anchor Rh(I) complexes to the nodes of the MOF UiO-67 and, for comparison, to the zeolite dealuminated HY (DAY). These were characterized experimentally by measurement of catalytic activities and selectivities for ethylene hydrogenation and dimerization in a once-through flow reactor at 298 K and 1 bar. The catalyst performance data are complemented with structural information determined by infrared and extended X-ray absorption fine structure spectroscopies and by calculations at the level of density functional theory, the latter carried out also to extend the investigation to a related MOF, NU-1000. The agreement between the experimental and calculated structural metrics is good, and the calculations have led to predictions of reaction mechanisms and associated energetics. The data demonstrate a correlation between the catalytic activity and selectivity and the electron-donor tendency of the supported rhodium (as measured by the frequencies of CO ligands bonded as probes to the Rh(I) centers), which is itself a measure of the electron-donor tendency of the support.

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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 93%

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Molecular Rhodium Complexes Supported on the Metal-Oxide-Like Nodes of Metal Organic Frameworks and on Zeolite HY: Catalysts for Ethylene Hydrogenation and Dimerization

Bernales

Yang

et al. 2017

ACS Appl. Mater. Interfaces

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“…18,19 In addition, unique reactivity of Rh(C2H4)2 complexes and few atom Rh clusters for ethane hydrogenation and dimerization have been qualitatively correlated based on x-ray absorption spectroscopy. 12 In our studies, the DRIFTS based CO chemisorption characterization approach was crucial for quantifying site type fractions and allowing proper CO:Rh normalization of total Rh site concentrations that enabled quantitative TOF calculations. In demonstrating quantitative site type-reactivity relationships, we relied on the unique frequencies and existing extinction coefficients for CO intramolecular vibrational modes on different Rh site types.…”

Section: Discussionmentioning

confidence: 99%

Isolated Metal Active Site Concentration and Stability Control Catalytic CO₂ Reduction Selectivity

2015

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CO2 reduction by H2 on heterogeneous catalysts is an important class of reactions that has been studied for decades. However, atomic scale details of structure-function relationships are still poorly understood. Particularly, it has been suggested that metal particle size plays a unique role in controlling the stability of CO2 hydrogenation catalysts and the distribution of active sites, which dictates reactivity and selectivity. These studies often have not considered the possible role of isolated metal active sites in the observed dependences. Here, we utilize probe molecule diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with known site-specific extinction coefficients to quantify the fraction of Rh sites residing as atomically dispersed isolated sites (Rhiso), as well as Rh sites on the surface of Rh nanoparticles (RhNP) for a series of TiO2 supported Rh catalysts. Strong correlations were observed between the catalytic reverse water gas shift turn over frequency (TOF) and the fraction of Rhiso sites and between catalytic methanation TOF and the fraction of RhNP sites. Furthermore, it was observed that reaction condition-induced disintegration of Rh nanoparticles, forming Rhiso active sites, controls the changing reactivity with time on stream. This work demonstrates that isolated atoms and nanoparticles of the same metal on the same support can exhibit uniquely different catalytic selectivity in competing parallel reaction pathways and that disintegration of nanoparticles under reaction conditions can play a significant role in controlling stability.

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“…In regard to nitrile synthesis from hydrocarbon feedstocks, the challenge of potentially practical and sustainable routes rely on activating C-H bonds at mild temperatures, as well as hindering the side reactions to selectively form nitriles. Today in the chemical industry, metal catalysts dominate the technology for producing chemicals 25 26 27 28 29 30 31 , and significant advances in green synthesis processes are mostly combined by the development of new catalysts. The metal catalysts for efficiently oxidative cyanation of C-H bonds are in great demand but extremely difficult to achieve.…”

mentioning

confidence: 99%

Controllable cyanation of carbon-hydrogen bonds by zeolite crystals over manganese oxide catalyst

Wang

Zhang

et al. 2017

Nat Commun

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The synthesis of organic nitriles without using toxic cyanides is in great demand but challenging to make. Here we report an environmentally benign and cost-efficient synthesis of nitriles from the direct oxidative cyanation of primary carbon-hydrogen bonds with easily available molecular oxygen and urea. The key to this success is to design and synthesize manganese oxide catalysts fixed inside zeolite crystals, forming a manganese oxide catalyst with zeolite sheath (MnOx@S-1), which exhibits high selectivity for producing nitriles by efficiently facilitating the oxidative cyanation reaction and hindering the side hydration reaction. The work delineates a sustainable strategy for synthesizing nitriles while avoiding conventional toxic cyanide, which might open a new avenue for selective transformation of carbon-hydrogen bonds.

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A Bifunctional Mechanism for Ethene Dimerization: Catalysis by Rhodium Complexes on Zeolite HY in the Absence of Halides

Cited by 12 publications

References 35 publications

Molecular Rhodium Complexes Supported on the Metal-Oxide-Like Nodes of Metal Organic Frameworks and on Zeolite HY: Catalysts for Ethylene Hydrogenation and Dimerization

Molecular Rhodium Complexes Supported on the Metal-Oxide-Like Nodes of Metal Organic Frameworks and on Zeolite HY: Catalysts for Ethylene Hydrogenation and Dimerization

Isolated Metal Active Site Concentration and Stability Control Catalytic CO₂ Reduction Selectivity

Controllable cyanation of carbon-hydrogen bonds by zeolite crystals over manganese oxide catalyst

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A Bifunctional Mechanism for Ethene Dimerization: Catalysis by Rhodium Complexes on Zeolite HY in the Absence of Halides

Cited by 12 publications

References 35 publications

Molecular Rhodium Complexes Supported on the Metal-Oxide-Like Nodes of Metal Organic Frameworks and on Zeolite HY: Catalysts for Ethylene Hydrogenation and Dimerization

Molecular Rhodium Complexes Supported on the Metal-Oxide-Like Nodes of Metal Organic Frameworks and on Zeolite HY: Catalysts for Ethylene Hydrogenation and Dimerization

Isolated Metal Active Site Concentration and Stability Control Catalytic CO2 Reduction Selectivity

Controllable cyanation of carbon-hydrogen bonds by zeolite crystals over manganese oxide catalyst

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Product

Resources

About

Isolated Metal Active Site Concentration and Stability Control Catalytic CO₂ Reduction Selectivity