Specific Feature of Copper Ion-Exchanged Mordenite for Dinitrogen Adsorption at Room Temperature

Kuroda, Yasushige; Yoshikawa, Yuzo; Konno, Shin Ichi; Hamano, Hideaki; Maeda, Hironobu; Kumashiro, Ryotaro; Nagao, Mahiko

doi:10.1021/j100026a028

Cited by 96 publications

(112 citation statements)

References 11 publications

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“…Therefore, there is no doubt that after reduction in CO, the predominant part of copper was transformed into Cu þ ions. This conclusion also well agrees with the previously reported literature data on self-reduction of bivalent copper after vacuum treatment at high temperature or reduction in CO [9][10][11][12][13].…”

Section: Resultssupporting

confidence: 93%

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Unusual Forms of Molecular Hydrogen Adsorption by Cu+1 Ions in the Copper-Modified ZSM-5 Zeolite

Kazansky

Serykh

2004

Catalysis Letters

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DRIFT and IR transmittance spectra of H 2 adsorbed at 77 K or at room temperature by the copper-modified ZSM-5 zeolite pre-evacuated or pre-reduced in CO at 873 K indicated several unusual forms of adsorbed hydrogen. H-H stretching frequencies of adsorbed species at 3075-3300 cm À1 are by about 1000 cm À1 lower than in the free hydrogen molecules. This indicates unusually strong perturbation of adsorbed hydrogen by reduced Cu þ1 ions that has been never before reported neither for hydrogen nor for adsorption of other molecules by any cationic form of zeolites or oxides.KEY WORDS: Cu loaded ZSM-5 zeolite; molecular hydrogen adsorption; IR spectra of adsorbed hydrogen.

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Section: Resultssupporting

confidence: 93%

“…It was also reported in Refs. [9][10][11][12][13] that reduced Cu þ ions very strongly adsorb CO and nitrogen. In Ref.…”

Section: Introductionmentioning

confidence: 99%

Unusual Forms of Molecular Hydrogen Adsorption by Cu+1 Ions in the Copper-Modified ZSM-5 Zeolite

Kazansky

Serykh

2004

Catalysis Letters

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“…The XANES spectra of the dehydrated material are peculiar because the 1s f 4p pre-edge transition is a distinct well-resolved band: this fact is rather unusual for Cu(II) species where the 1s f 4p transition is observed as a shoulder of the edge in most of the cases. 11,22,27,28,[30][31][32][33] The evolution of the XANES features upon progressive outgassing is in accordance with the removal of water: (i) the decrease of white line is classically interpreted with a decrease in coordination; (ii) the red shift and increase in intensity of the 1s f 4p peak is interpreted as an increase of covalency in the ligand-copper bond. It is worth noticing that this transition is better described as a shakedown transition [1s(2)...3d(9)4p(0) L 0 ] f [1s(1)...3d(10)4p(1) L + ] where the internal electronic transition of the metal is accompanied by a ligand to metal electron transfer, 26,35,36 L 0 and L + representing the neutral and charged ligands, respectively.…”

Section: Xanes Spectroscopymentioning

confidence: 75%

Local Structure of Framework Cu(II) in HKUST-1 Metallorganic Framework: Spectroscopic Characterization upon Activation and Interaction with Adsorbates

et al. 2006

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XRD, UV-Vis, EXAFS, XANES, and Raman techniques have been used to study the removal of water molecules coordinated to the Cu(II) framework atoms of the novel HKUST-1 metal-organic framework. The dehydration process preserves the crystalline nature of the material, just causing a reduction of the cell volume due to the shrinking of the [Cu 2 C 4 O 8 ] cage. The removal of adsorbed H 2 O molecule makes the framework Cu(II) sites available for interaction with other probe molecules. In situ IR spectroscopy has evidenced the formation at liquid nitrogen temperature of labile Cu(II)‚‚‚CO adducts characterized by a ν(C-O) ) 2178 cm -1 and at 15 K of Cu(II)‚‚‚H 2 adducts characterized by a ν(H-H) ) 4100 cm -1 . To the best of our knowledge, we have observed for the first time a clear signal of Cu(II) carbonyl and dihydrogen complexes formed inside a crystalline microporous hosting matrix. The sinking of the oxygens of the carboxyl units, undergone by the Cu(II) framework ions in the dehydration process, is responsible for the rather low coordinative unsaturation of Cu(II). The important shielding effect of the four oxygen framework atoms is testified by the low polarization factor of the Cu(II) site probed by both CO and H 2 molecules.

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“…4p electronic transitions in Cu + . 9,[34][35][36][37][38][39] In contrast, Cu 2+ species show three features in the near-edge region: a weak absorption at about 8978 eV, attributed to dipole-forbidden 1s ! 3d transitions and a shoulder at 8988 eV and an intense peak at 8998 eV, both arising from 1s !…”

Section: Reduction Of Cumentioning

confidence: 99%

Spectroscopic and chemical characterization of active and inactive Cu species in NO decomposition catalysts based on Cu-ZSM5

Costa

Modén

Meitzner

et al. 2002

Phys. Chem. Chem. Phys.

148

145

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The number and type of Cu 2+ species present on O 2 -treated Cu-ZSM5 catalysts (Si/Al ¼ 13.1-14.6) with varying Cu/Al ratios (0.12-0.60) were measured using temperature-programmed reduction in H 2 or CO and desorption of O 2 with He as the carrier. The effluent stream was monitored using mass spectrometry and the structure and oxidation state was determined in parallel by X-ray absorption spectroscopy. Isolated Cu 2+ monomers and oxygen-bridged Cu 2+ dimers interacting with Al-Al next nearest neighbor pairs were the predominant Cu species on these catalysts. The fraction of Cu present as dimers increased from 0.46 to 0.78 as Cu/Al ratios increased from 0.12 to 0.60, as expected from the decreasing average Cu-Cu distance with increasing Cu content. In contrast, monomers reached a plateau of $0.15 Cu 2+ /Al, suggesting that only some Al-Al pairs can interact with small Cu 2+ monomer structures, while a much larger fraction can bind with larger oxygen-bridged Cu 2+ dimers. The measured distribution of Cu dimers and monomers is consistent with the number and bond distances of Al-Al pairs for the Si/Al ratio in these ZSM5 samples. The distributions of Cu species obtained from the amount of CO 2 formed (from CO), the amount of H 2 O formed (from H 2 ), and the amount of CO adsorbed after reduction in CO are in excellent agreement. The number of oxygen atoms removed as O 2 was significantly smaller than that removed with H 2 or CO, suggesting that only proximate Cu dimers autoreduce via recombinative desorption steps. NO decomposition turnover rates (normalized per Cu dimer) were nearly independent of Cu content, except at the lowest Cu/Al ratio, consistent with the involvement of Cu dimers as the active Cu species in NO decomposition redox cycles on Cu-ZSM5. Multiple O 2 and CO 2 peaks during desorption and reduction in CO suggest the presence of Cu dimers with varying oxygen binding energy and reactivity. The Cu dimers initially formed at low Cu/Al contents during exchange are less reducible, consistent with their lower NO decomposition turnover rates.

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Specific Feature of Copper Ion-Exchanged Mordenite for Dinitrogen Adsorption at Room Temperature

Cited by 96 publications

References 11 publications

Unusual Forms of Molecular Hydrogen Adsorption by Cu+1 Ions in the Copper-Modified ZSM-5 Zeolite

Unusual Forms of Molecular Hydrogen Adsorption by Cu+1 Ions in the Copper-Modified ZSM-5 Zeolite

Local Structure of Framework Cu(II) in HKUST-1 Metallorganic Framework: Spectroscopic Characterization upon Activation and Interaction with Adsorbates

Spectroscopic and chemical characterization of active and inactive Cu species in NO decomposition catalysts based on Cu-ZSM5

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