T–O–T skeletal vibration in CuZSM-5 zeolite: IR study and quantum chemical modeling

Brocławik, Ewa; Dátka, Jerzy; Gil, Barbara; Kozyra, Paweł

doi:10.1039/a908832f

Cited by 59 publications

(37 citation statements)

References 12 publications

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“…found the other geometry to be the local minimum slightly higher in energy. In addition, geometrical parameters of both sites agree perfectly with those obtained previously for smaller, single-ring models [15,16]. Therefore we regard the 7T basket model as the smooth extension of our previous single-ring models.…”

Section: Methodological Remarkssupporting

confidence: 88%

“…These models were capable of describing geometrical properties of the site, which was confirmed by very good correlation between calculated framework distortion imposed by the cation and shifts in T-O-T skeletal vibration measured by IR spectroscopy [15]. We have found that Cu 2+ prefers fourfold coordination in the centre of six-ring while Cu + becomes bonded to three bridging oxygens in a 5T ring.…”

Section: Methodological Remarkssupporting

confidence: 59%

“…Thus it was highly desirable to confirm its validity by testing against existing experiment in the similar manner to that utilised for the first time in the case of small models [15]. Table 2 shows that red shift in T-O-T frequency corresponds perfectly to global weakening of these T-O bonds, where the effect of Cu 2+ is the strongest.…”

Section: Figurementioning

confidence: 91%

“…In view of incompleteness of experimentally available information on cationexchanged ZSM-5 and the need to devise a model of such site, which would be helpful in validation of working hypotheses, we have undertaken quantum chemical calculations for the part of MFI framework capable of hosting copper cations. We have already tested several small cluster models built of 6T or 5T rings cut-off the MFI framework as prospective hosts for Cu 2+ and Cu + [15,16].…”

Section: Methodological Remarksmentioning

confidence: 99%

“…As already known, such information may be extracted both from the analysis of NO stretch and of T-O-T skeletal vibration [11][12][13][14][15]. In this paper, on the basis of our theoretical investigations related to experimentally available information, we discuss the problem of speciation of Cu ions in MFI framework and its migration in the course of a catalytic process.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Nature of Copper Active Sites in CuZSM-5: Theory and Experiment

Brocławik

Dátka

Gil

et al. 2002

IJMS

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Section: Methodological Remarkssupporting

confidence: 88%

Section: Methodological Remarkssupporting

confidence: 59%

Section: Figurementioning

confidence: 91%

Section: Methodological Remarksmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Nature of Copper Active Sites in CuZSM-5: Theory and Experiment

Brocławik

Dátka

Gil

et al. 2002

IJMS

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Oxidation of Methane to Methanol by Water Over Cu/SSZ‐13: Impact of Cu Loading and Formation of Active Sites

Xiong

Zhang

et al. 2022

ChemCatChem

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Cu/SSZ-13 catalysts with different Cu loadings (1-5 wt.%) were prepared by conventional impregnation via a slow step-dry process for the direct conversion of methane to methanol. Catalytic performance of the catalysts is found to depend on the Cu loading in both stepwise and continuous processes and 2 wt.% Cu presents the best performance. CuO nanoparticles, Cu x O y clusters and monomeric [CuOH] + species are found on Cu/SSZ-13 based on HRTEM, HAADF-STEM, DR UV-vis and FTIR spectroscopies. The high coverage of CuO nanoparticles on 5 wt.% Cu/SSZ-13 results in the loss of catalytic reactivity in spite of the existence of active Cu x O y and [CuOH] + sites. Besides, it is proposed that the formation of [Cu 2 O 2 ] 2 + and [Cu 2 O] 2 + active sites involves [CuOH] + intermediates. We further found that improved catalytic performance in cyclic stepwise process involves the re-dispersion of CuO nanoparticles and/or large clusters as well as the re-oxidation of Cu(I) cations from self-reduction of [CuOH] + species.

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Copper Affects the Location of Zinc in Bimetallic Ion‐Exchanged Mordenite

2018

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Bimetallic ion exchange on a zeolite often impacts its catalytic properties compared to its monometallic counterparts. Here, we address the synergistic effect of simultaneous copper and zinc ion exchange on mordenite (MOR), as found earlier for dimethyl ether (DME) carbonylation. Samples with various Cu/Zn ratios were characterized by diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS) in the 3600 and 720 cm regions, pore distribution analysis through Ar physisorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and transmission electron microscopy (TEM). When ion-exchanged alone, copper preferentially occupies 12-membered rings, whereas zinc occupies 8-membered rings. In bimetallic combinations, the zinc addition was found to prevent the copper from sintering into nanoparticles and to increase its coordination strength to the zeolite. At a Cu/Zn ratio of 0.25 (for MOR with Si/Al=6.5), copper promotes zinc ion exchange into 12-membered rings, more specifically, into T4 sites that are known for the formation of the coke precursor in DME carbonylation on a MOR. The sites became blocked during the bimetallic ion exchange, leading to suppressed catalyst deactivation. The study contributes to the understanding of mutual ion effects in bimetallic exchanged zeolites and highlights the major role of copper as a governing factor in determining the location of co-exchanged zinc on a MOR.

show abstract

T–O–T skeletal vibration in CuZSM-5 zeolite: IR study and quantum chemical modeling

Cited by 59 publications

References 12 publications

Nature of Copper Active Sites in CuZSM-5: Theory and Experiment

Nature of Copper Active Sites in CuZSM-5: Theory and Experiment

Oxidation of Methane to Methanol by Water Over Cu/SSZ‐13: Impact of Cu Loading and Formation of Active Sites

Copper Affects the Location of Zinc in Bimetallic Ion‐Exchanged Mordenite

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