In-Situ Determination by ESR of the Oxidation State of Copper in Cu-ZSM-5 in Flowing He and O2 up to 500 .degree.C

Кучеров, А. В.; Gerlock, John L.; Jen, Hung-Wen; Shelef, M.

doi:10.1021/j100069a020

Cited by 68 publications

(43 citation statements)

References 2 publications

(2 reference statements)

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“…This means that all copper is present as EPR active tetragonally coordinated monomeric complexes. Others have also confirmed this observation on other zeolite samples [11,30,32]. This observation can be utilized extensively in catalyst research of hydrophilic Cu-zeolites, since the hydrated state is the starting point of all ex situ, in situ or operando experiments and the knowledge of the EPR signal intensity at this point will enable quantification of the EPR active copper species, e.g.…”

Section: Hydrated Cu-zeolitessupporting

confidence: 57%

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Identification and Quantification of Copper Sites in Zeolites by Electron Paramagnetic Resonance Spectroscopy

et al. 2016

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Recent quantitative electron paramagnetic resonance spectroscopy (EPR) data on different copper species present in copper exchanged in CHA zeolites are presented and put into context with the literature on other copper zeolites. The information were obtained using ex-situ and in-situ EPR on copper ion exchanged into a CHA zeolite with Si/Al = 14±1 to obtain Cu/Al = 0.46 ±0.02. The results shed light on the identity of different copper species present after activation in air. Since the EPR signal is quantifiable, the content of the different EPR active species has been elucidated and Cu 2+ in 2Al positions in the 6-membered rings (6mr) of the CHA structure has been characterized. sites of the CHA structure under the applied conditions.

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Section: Hydrated Cu-zeolitessupporting

confidence: 57%

“…The particular sitings of Cu in the 6mr depending on the different Al distributions are not resolved in the X-ray experiment. [30]. The MFI zeolite have a much more complex structure than FAU, and cation sites are positioned in combinations of 5mr and 6mr…”

Section: Cu-faumentioning

confidence: 99%

Identification and Quantification of Copper Sites in Zeolites by Electron Paramagnetic Resonance Spectroscopy

et al. 2016

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“…Since the minimum g-factor of the catalyst is 2.11 (g DPPH factor ) 2.0037 at 298 K), it is likely that the Cu(II) species has a square-planar structure in the channels of ZSM-5 (Scheme 2). Square-planar structures of CuO in ZSM-5 were also observed by Kucherov, Tanabe, and Larsen et al [31][32][33] Figure 5a shows that the EPR spectrum of the CuO/ZSM-5 catalyst at 463 K is broad and structureless. On the contrary, at 77 K the spectrum ( Figure 5c) exhibits a sharp signal and characteristic structure of Cu(II) complexes where the hyperfine coupling between the 3d unpaired electron and the copper (I ) 3 / 2 ) nuclear spin is well resolved.…”

Section: Methodssupporting

confidence: 74%

Byproduct Shape Selectivity in Supercritical Water Oxidation of 2-Chlorophenol Effected by CuO/ZSM-5

and

Wang

2000

Langmuir

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Reduction of trace polycyclic aromatic hydrocarbon (PAH) byproducts in supercritical water oxidation (SCWO) of 2-chlorophenol (2CP) effected by CuO/ZSM-5 has been investigated in the present work. In the channels of ZSM-5, due to a restricted environment, formation of undesired PAH byproducts in the SCWO of 2CP was significantly suppressed. Only trace light-PAHs with a molecular size less than 6 Å were formed in the SCWO of 2CP. Carcinogenic PAHs (heavy-PAHs) were not found. Structures of CuO and Cu2O in the channels of ZSM-5 that involved in the catalytic SCWO of 2CP were studied by X-ray photoelectron spectroscopy (XPS). The Cu2O-to-CuO ratio was approximately 0.15. Existence of the Cu(I) and Cu(II) was also confirmed by the preedge X-ray absorption near edge structural (XANES) spectroscopy. The copper oxides with a square-plane structure were observed by electron paramagnetic resonance (EPR) spectra. Furthermore, the extended X-ray absorption fine structural (EXAFS) spectra suggest that the copper oxides in the channels of ZSM-5 may form Cu3O2 clusters with Cu-Cu and Cu-O bond distances of 2.79 and 1.91 Å, respectively. The Cu3O2 clusters were oxidized to Cu3O4 by H2O2 in supercritical water.

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“…'~-'~ The catalytic cycle likely consists of Cu2+ to Cu+ reduction through spontaneous desorption of 0 2 and subsequent reoxidation by NO leading to the regeneration of Cu2+ sites upon N2 formation. Both extralattice oxygen and mobile lattice oxygen may participate in the overall chemistry of NO decomposition.13 However, Kucherov et al 14 have reported that they were unable to detect spontaneous reduction of Cu2+ at temperatures as high as 500 "C using ESR.…”

Section: Introductionmentioning

confidence: 99%

Formation of Cu-MFI NO Decomposition Catalyst via Reductive Solid-State Ion Exchange

Price¹,

Kanazirev²,

Church³

1995

J. Phys. Chem.

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High-temperature treatment of a mechanical mixture of CuO and H-MFI zeolite in the absence of 0 2 produced a Cu ion-exchanged zeolite catalyst with a high activity for the catalytic decomposition of NO to NZ and 02. Cu is probably introduced as Cu+ cations in zeolite ion-exchange sites via a solid-state ion-exchange process which includes CuO autoreduction to Cu+. ESR, 1-propanamine thermal desorption, and TPR characterization are consistent with this model. This preparation technique has a theoretical exchange limit of 1 Cu/framework Al, which is double the limit theoretically imposed on Cu2+ exchange. The preferred preparation conditions give rise to a material which approaches this theoretical limit, and there are probably similarities between catalysts prepared by this method and "overexchanged" Cu2+-MFI materials often reported for NO decomposition.

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In-Situ Determination by ESR of the Oxidation State of Copper in Cu-ZSM-5 in Flowing He and O2 up to 500 .degree.C

Cited by 68 publications

References 2 publications

Identification and Quantification of Copper Sites in Zeolites by Electron Paramagnetic Resonance Spectroscopy

Identification and Quantification of Copper Sites in Zeolites by Electron Paramagnetic Resonance Spectroscopy

Byproduct Shape Selectivity in Supercritical Water Oxidation of 2-Chlorophenol Effected by CuO/ZSM-5

Formation of Cu-MFI NO Decomposition Catalyst via Reductive Solid-State Ion Exchange

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