EXAFS studies on the origin of high catalytic activity in nickel Y zeolite

Sano, Mitsuru; Maruo, Tetsuya; Yamatera, Hideo; Suzuki, Minoru; Saito, Yasukazu

doi:10.1021/ja00235a008

Cited by 49 publications

(33 citation statements)

References 3 publications

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“…The bond angles are close to octahedral: O′3-Ni1′2-O3′ ) 88°, O5-Ni1′2-O5 ) 79°, and O3′-Ni1′2-O5 ) 96°and 174°(again mean values). The presence of the Ni 4 O 4 unit shown in Figures 5 and 6 is supported by the EXAFS studies of Sano et al 7 and Dooryhee et al 14 who reported the presence of "oligomeric nickel oxides" in Ni-Y. 6,7 About each Ni 2+ ion, they found 3.0-3.5 oxygens at 2.08 or 2.02 Å and 3.0 Ni 2+ ions at 2.99 Å.…”

Section: Trigonal Ni 2+ Ions At the First Site I′supporting

confidence: 60%

“…7 Table 7). Additional H + ions, beyond the numbers given in Table 7, would be present if some of the water molecules that coordinate to Ni 2+ have dissociated.…”

Section: Discussionmentioning

confidence: 99%

“…7,9 They suggested that extraframework nickel oxides had formed within the zeolite. These nickel-oxide clusters were shown to be at least partly responsible for the high catalytic activity found in CO oxidation.…”

Section: Catalysismentioning

confidence: 99%

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Crystal Structures of Vacuum-Dehydrated Ni²⁺-Exchanged Zeolite Y (FAU, Si/Al = 1.69) Containing Three-Coordinate Ni²⁺, Ni₈O₄·xH₂O⁸⁺, x ≤ 4, Clusters with Near Cubic Ni₄O₄ Cores, and H⁺

Kim¹,

Jung²,

Heo³

et al. 2009

J. Phys. Chem. C

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Five single crystals of vacuum-dehydrated Ni 2+ -exchanged zeolite Y (Ni-Y) were variously prepared by the exchange of Na-Y or K-Y (Na 71 -or K 71 -Si 121 Al 71 O 384 , Si/Al ) 1.69) with Ni 2+ using flowing aqueous 0.05 M Ni(NO 3 ) 2 at 294 or 353 K, followed by vacuum dehydration at 2.0 × 10 -6 Torr and 623 or 723 K. Their crystal structures and chemical compositions were determined using synchrotron X-radiation and energy dispersive X-ray (EDX) analyses to give Ni n -Y, where 25.3 e n e 34.1 per unit cell:121+z Al 71-z O 384 ]-FAU, where 21.4 e u e 24.2, M ) Na and/or Ca, 3.3 e V e 13.1, 9.5 e w e 21.6, 2 e x e 4, 0.3 e y e 3.2, and 0 e z e 2.5. In each of the five crystal structures (space group Fd3 j m; mean a ) 24.47 Å), Ni 2+ is found at sites I, I′, a second I′, II′, and sometimes II; unexpectedly, Na + and Ca 2+ are found at another site II. Two extra-framework oxygen positions (O e ), one in the sodalite cavity and the other nearby in the supercage, are seen on 3-fold axes in all crystals. They bond to Al 3+ and Ni 2+ ions in the sodalite cavities to form Al(O e H) 4 -and Ni 8 (O e ) 4 · xH 2 O e 8+ clusters with Ni 4 (O e ) 4 cores, and with framework oxygens (O f ) to give trigonal bipyramidal Ni(O f ) 3 (O e ) 2 2+ and trigonal pyramidal Ni(O f ) 3 O e 2+ . At site I (centers of double 6-rings) in the Na-Y crystal that was Ni 2+ -exchanged at 294 K, ∼14 Ni 2+ ions per unit cell each coordinate octahedrally to six framework oxygen atoms. The Ni 2+ ions at the first I′ site are 3-coordinate near planar in all crystals. The Ni 2+ ions at the second I′ site are members of the Ni 4 O 4 cores, tetrahedrally distorted cubes with Ni-O ) 2.199(13) Å and O-Ni-O ) 79.6(9)°in a representative crystal; these Ni 2+ ions are distorted octahedral with three O e 's of the cluster and three O f 's. The Ni 2+ ions at sites II′ and II are 3-, 4-, or 5-coordinate. Al(OH) 4-from framework dealumination centers some sodalite cavities in four of the five crystals; their number increased with both ion-exchange and dehydration temperatures, suggesting that dealumination occurred during both processes. The number of Ni 2+ ions per unit cell increases with Ni 2+ -exchange temperature and is greater with K-Y than with Na-Y, perhaps because the larger K + ions are more loosely held. The leaving cation affects the Ni 2+ distribution over the available sites, perhaps via the level of Ni 2+ -exchange. Both a greater degree of Ni 2+ -exchange and a higher dehydration temperature cause more Ni 8 O 4 · xH 2 O 8+ clusters to form, leaving fewer Ni 2+ ions at sites I and II. As more Ni 8 O 4 · xH 2 O 8+ formed, more H + ions were produced. Some H + and some 3-and 4-coordinate Ni 2+ ions are easily accessible for catalysis.

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Section: Trigonal Ni 2+ Ions At the First Site I′supporting

confidence: 60%

“…7 Table 7). Additional H + ions, beyond the numbers given in Table 7, would be present if some of the water molecules that coordinate to Ni 2+ have dissociated.…”

Section: Discussionmentioning

confidence: 99%

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Crystal Structures of Vacuum-Dehydrated Ni²⁺-Exchanged Zeolite Y (FAU, Si/Al = 1.69) Containing Three-Coordinate Ni²⁺, Ni₈O₄·xH₂O⁸⁺, x ≤ 4, Clusters with Near Cubic Ni₄O₄ Cores, and H⁺

Kim¹,

Jung²,

Heo³

et al. 2009

J. Phys. Chem. C

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“…The corresponding spectra for metal oxides are given for comparison. The XANES pre-edge peak is attributed to the 1s-3d dipolar forbidden transition [21]. Principally, this 1s-3d forbidden transition gains additional intensity when the metal center is in a non-centrally symmetric environment through mixing of 3d and 4p orbitals caused by the breakdown of inversion symmetry due to the structure distortion.…”

Section: Resultsmentioning

confidence: 98%

Synthesis, Characterization and Catalytic Performance of Well-Ordered Crystalline Heteroatom Mesoporous MCM-41

Qin

Yan

2017

Crystals

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Abstract:Mesoporous heteroatom molecular sieve MCM-41 bulk crystals with the crystalline phase were synthesized via a one-step hydrothermal method using an ionic complex as template. The ionic complex template was formed by interaction between cetyltrimethylammonium ions and metal complex ion [M(EDTA)] 2− (M = Co or Ni)]. The materials were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, N 2 adsorption-desorption isotherms, and X-ray absorption fine structure spectroscopy. The results showed that the materials possess a highly-ordered mesoporous structure with a crystalline phase and possess highly uniform ordered arrangement channels. The structure is in the vertical cross directions with a crystalline size of about 12 µm and high specific surface areas. The metal atoms were incorporated into the zeolite frameworks in the form of octahedral coordinate and have a uniform distribution in the materials. The amount of metal complexes formed by metal ion and EDTA is an essential factor for the formation of the vertical cross structure. Compared to Si-MCM-41, the samples exhibited better conversion and higher selectivity for cumene cracking.

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“…Taking into account sites occupancies [3], a corrected Ni-O value of 2.16 Å was estimated [5]. This value is significantly higher than the Ni-O distances (from 1.87 to 2.05 Å ) determined for dehydrated samples by EXAFS (Extended X-ray Absorption Fine Structure) [5][6][7], the number of nearest oxygen neighbours being furthermore lower (between 3 and 4). These discrepancies prompted us to analyse precisely the evolution upon rehydration of the coordination shell around Ni 2+ in a NiNaX sample and this was made possible owing to the recent development of dispersive-EXAFS for the in situ study of catalytic materials, allowing the recording of complete absorption spectra in very short times [8,9].…”

Section: Introductionmentioning

confidence: 95%

Real time monitoring of the evolution of Ni2+ environment in faujasite upon rehydration by in situ dispersive-EXAFS

et al. 2005

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EXAFS studies on the origin of high catalytic activity in nickel Y zeolite

Cited by 49 publications

References 3 publications

Crystal Structures of Vacuum-Dehydrated Ni²⁺-Exchanged Zeolite Y (FAU, Si/Al = 1.69) Containing Three-Coordinate Ni²⁺, Ni₈O₄·xH₂O⁸⁺, x ≤ 4, Clusters with Near Cubic Ni₄O₄ Cores, and H⁺

Crystal Structures of Vacuum-Dehydrated Ni²⁺-Exchanged Zeolite Y (FAU, Si/Al = 1.69) Containing Three-Coordinate Ni²⁺, Ni₈O₄·xH₂O⁸⁺, x ≤ 4, Clusters with Near Cubic Ni₄O₄ Cores, and H⁺

Synthesis, Characterization and Catalytic Performance of Well-Ordered Crystalline Heteroatom Mesoporous MCM-41

Real time monitoring of the evolution of Ni2+ environment in faujasite upon rehydration by in situ dispersive-EXAFS

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EXAFS studies on the origin of high catalytic activity in nickel Y zeolite

Cited by 49 publications

References 3 publications

Crystal Structures of Vacuum-Dehydrated Ni2+-Exchanged Zeolite Y (FAU, Si/Al = 1.69) Containing Three-Coordinate Ni2+, Ni8O4·xH2O8+, x ≤ 4, Clusters with Near Cubic Ni4O4 Cores, and H+

Crystal Structures of Vacuum-Dehydrated Ni2+-Exchanged Zeolite Y (FAU, Si/Al = 1.69) Containing Three-Coordinate Ni2+, Ni8O4·xH2O8+, x ≤ 4, Clusters with Near Cubic Ni4O4 Cores, and H+

Synthesis, Characterization and Catalytic Performance of Well-Ordered Crystalline Heteroatom Mesoporous MCM-41

Real time monitoring of the evolution of Ni2+ environment in faujasite upon rehydration by in situ dispersive-EXAFS

Contact Info

Product

Resources

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Crystal Structures of Vacuum-Dehydrated Ni²⁺-Exchanged Zeolite Y (FAU, Si/Al = 1.69) Containing Three-Coordinate Ni²⁺, Ni₈O₄·xH₂O⁸⁺, x ≤ 4, Clusters with Near Cubic Ni₄O₄ Cores, and H⁺

Crystal Structures of Vacuum-Dehydrated Ni²⁺-Exchanged Zeolite Y (FAU, Si/Al = 1.69) Containing Three-Coordinate Ni²⁺, Ni₈O₄·xH₂O⁸⁺, x ≤ 4, Clusters with Near Cubic Ni₄O₄ Cores, and H⁺