Partially Decarbonylated Tetrairidium Clusters on γ-Al2O3: Structural Characterization and Catalysis of Toluene Hydrogenation

Alexeev, Oleg S.; Panjabi, Ghansham; Gates, Bruce C.

doi:10.1006/jcat.1997.1907

Cited by 64 publications

(87 citation statements)

References 37 publications

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“…EXAFS spectroscopy is one of the most powerful techniques for investigation of small clusters because it provides direct evidence of metal-metal bonds. It has been used to characterize tetra-and hexairidium clusters on the surfaces of porous oxides (g-Al 2 O 3 , [13,14,32,33] MgO, [23,[26][27][28]34] and TiO 2 [24] ) and zeolites. [9,[10][11][12]19] Tetrairidium clusters have been routinely found to have IrÀIr first-shell coordination numbers of nearly 3, consistent with a tetrahedral metal framework, and IrÀIr bonding distances of typically 2.67 AE 0.02 , essentially matching the IrÀIr bonding distance in coordinatively saturated iridium clusters such as [Ir 4 (CO) 12 ].…”

Section: Determination Of Structures Of Supported Iridium Clustersmentioning

confidence: 99%

Prototype Supported Metal Cluster Catalysts: Ir₄ and Ir₆

2010

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Section: Determination Of Structures Of Supported Iridium Clustersmentioning

confidence: 99%

Prototype Supported Metal Cluster Catalysts: Ir₄ and Ir₆

2010

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“…4 Many supports have been used to disperse iridium particles in surface science studies, such as MgO, 5,6 g-Al 2 O 3 7,8 and TiO 2 . [5][6][7][8][9][10][11] Argo et al investigated the hydrogenation reactions of ethene, propene, and toluene on small clusters of iridium (Ir 4 and Ir 6 ) on oxide supports (g-Al 2 O 3 and MgO). Heterogeneous catalysts containing iridium clusters on different supports have been examined in a number of previous experimental and theoretical studies.…”

Section: Introductionmentioning

confidence: 99%

The properties of Ir_n (n = 2–10) clusters and their nucleation on γ-Al₂O₃ and MgO surfaces: from ab initio studies

Chen

Huo

Chen

et al. 2015

Phys. Chem. Chem. Phys.

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The structural stability and magnetic properties of iridium clusters Irn (n = 2-10) and their interaction on γ-Al2O3(001) and MgO(100) surfaces have been investigated from first principles calculations. It is found that the adsorption energy of Irn (n = 2-10)/γ-Al2O3(001) is lower than that of Irn/MgO(100); meanwhile, the strongest adsorption energy cluster for γ-Al2O3(001) is the tetrahedral Ir4 cluster, while for MgO(100) is a cubic Ir8 cluster. On the other hand, the nucleation of Irn (n = 2-10) clusters on both surfaces is thermodynamically favorable and exothermic. Moreover, the nucleation energy of Irn (n = 2-10) clusters on the γ-Al2O3(001) surface is close to the corresponding energy on the MgO(100) surface, except for Ir3, Ir4 and Ir6 clusters. Interestingly, the nucleation of Ir3 and Ir6 clusters on the MgO(100) surface is more favorable than that on the γ-Al2O3(001) surface, while the nucleation of the Ir4 cluster is reverse and very close to the gas phase Ir4 cluster. More importantly, deformation energy and charge density analysis show that the adsorbed Ir4 cluster on the γ-Al2O3(001) surface has obviously charge transfer between Ir atoms and surface Al, O atoms with negligible deformation. However, for the MgO(100) surface, the Ir4 cluster connects directly to three surface O atoms with severe distortion, which inhibits the activity of the tetrahedral Ir4 cluster as a catalyst.

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“…The procedures to obtain the EXAFS function from the raw data are the same as those reported by Koningsberger [25,27]. EXAFS spectra were analyzed using theoretical reference files obtained from materials with well known structures [28][29][30]. The theoretical reference files were generated using FEFF7.0 software for Ir-Ir, Ir-Cl, Ir-O, Ir-N, and Ir-C from Ir metallic bulk data,…”

Section: Discussionmentioning

confidence: 99%

“…Typically, it is observed that alumina supported Ir catalysts have two types of Ir-O contributions [28,47,48,53,54]. The oxygen at short distance (*1.99 Å ) is mainly due to IrO 2 crystallites [32,38,49], while the second Ir-O at longer distances (between 2.1 and 2.9) are oxygen contributions from the alumina.…”

Section: Dendrimer Removal and Catalyst Activationmentioning

confidence: 98%

PAMAM Dendrimer-Derived Ir/Al2O3 Catalysts: An EXAFS Characterization

Jesús

Williams

2009

Catal Lett

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Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to characterize several synthesis stages of hydroxyl-terminated generation four (G4OH) PAMAM dendrimer-derived Ir/c-Al 2 O 3 catalyst. The EXAFS results indicate that Ir 3? forms complexes with dendrimer functional groups through displacement of two Cl -ion ligands. These complexes are very stable in solution, and no reduction of Ir 3? to Ir nanoparticles or clusters is observed after introduction of reducing agents such as NaBH 4 or H 2 . These Ir 3? -dendrimer complexes remain essentially intact after support impregnation. The formation of 1-2 nm particles occurs when the catalysts are treated with O 2 /H 2 or H 2 , and the dendrimer-derived catalysts exhibit a lower degree of metal support interaction.

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Partially Decarbonylated Tetrairidium Clusters on γ-Al2O3: Structural Characterization and Catalysis of Toluene Hydrogenation

Cited by 64 publications

References 37 publications

Prototype Supported Metal Cluster Catalysts: Ir₄ and Ir₆

Prototype Supported Metal Cluster Catalysts: Ir₄ and Ir₆

The properties of Ir_n (n = 2–10) clusters and their nucleation on γ-Al₂O₃ and MgO surfaces: from ab initio studies

PAMAM Dendrimer-Derived Ir/Al2O3 Catalysts: An EXAFS Characterization

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Partially Decarbonylated Tetrairidium Clusters on γ-Al2O3: Structural Characterization and Catalysis of Toluene Hydrogenation

Cited by 64 publications

References 37 publications

Prototype Supported Metal Cluster Catalysts: Ir4 and Ir6

Prototype Supported Metal Cluster Catalysts: Ir4 and Ir6

The properties of Irn (n = 2–10) clusters and their nucleation on γ-Al2O3 and MgO surfaces: from ab initio studies

PAMAM Dendrimer-Derived Ir/Al2O3 Catalysts: An EXAFS Characterization

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Prototype Supported Metal Cluster Catalysts: Ir₄ and Ir₆

Prototype Supported Metal Cluster Catalysts: Ir₄ and Ir₆

The properties of Ir_n (n = 2–10) clusters and their nucleation on γ-Al₂O₃ and MgO surfaces: from ab initio studies