TPD–IR studies of CO desorption from zeolites CuY and CuX

Dátka, Jerzy; Kozyra, Paweł

doi:10.1016/j.molstruc.2004.12.033

Cited by 31 publications

(30 citation statements)

References 23 publications

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“…We suggest that a slightly red-shifted experimental LF band for CuX can be assigned to site II in the 6T rings with three Al atoms, with strongly bound copper and weakly adsorbed CO (Table 8, result for the 6T ring with three Al in high silica model). This assignment also explains the observation 27 for Cu(I)-X that the LF band gains intensity with increasing CO coverage; for it belongs to those sites (site II in the 6T ring with three Al atoms) at which CO binds significantly less strongly. We associate the HF band in Cu(I)-X with Cu(I) ions in site III, which we expect to be occupied in X zeolites with high Cu loading.…”

Section: Co Stretching Frequenciessupporting

confidence: 67%

“…27 The two bands point to the presence of two different copper sites in Cu(I)-FAU. TPD experiments 27 showed that in Cu(I)-X zeolite CO binding is stronger for the high-frequency site.…”

Section: Co Stretching Frequenciesmentioning

confidence: 99%

“…[22][23][24][25][26][27][28] Stretching modes of monocarbonyl species in different Cu(I)-zeolites are in the range of 2160-2122 cm À1 compared to 2143 cm À1 for gas phase CO. 28 DFT calculations for the high-silica Cu(I)-FER and Cu(I)-MFI zeolites have shown that CO adsorption on both types of Cu(I) sites results in the same CO frequency (2156 and 2159-2164 cm À1 for Cu(I)-FER 29 and Cu(I)-MFI, 30 respectively) in agreement with the observation of only one CO band around 2157 and 2157-2159 cm À1 , respectively, in the IR spectra for CO loadings below 1 per Cu(I) site. [22][23][24][25][26][27][28] Stretching modes of monocarbonyl species in different Cu(I)-zeolites are in the range of 2160-2122 cm À1 compared to 2143 cm À1 for gas phase CO. 28 DFT calculations for the high-silica Cu(I)-FER and Cu(I)-MFI zeolites have shown that CO adsorption on both types of Cu(I) sites results in the same CO frequency (2156 and 2159-2164 cm À1 for Cu(I)-FER 29 and Cu(I)-MFI, 30 respectively) in agreement with the observation of only one CO band around 2157 and 2157-2159 cm À1 , respectively, in the IR spectra for CO loadings below 1 per Cu(I) site.…”

Section: Introductionmentioning

confidence: 99%

“…[24][25][26][27] This points to the presence of different Cu(I) sites persisting even after CO adsorption which may either belong to different cation positions of the FAU lattice, I, II and III (see Fig. Faujasites with a high Si : Al ratio (B3) are called zeolite Y, those with a low Si : Al ratio (B1.3) are called zeolite X. High-silica FAU structures (ultra-stable Y zeolite) are also known.…”

Section: Introductionmentioning

confidence: 99%

“…[24][25][26][27] Knowing the properties of Cu(I) sites is essential for understanding the catalytic behavior of the Cu(I)-zeolites and can enable more rational searching for new zeolite based catalysts or sorbents in the future. In particular, we want to assign the two observed CO stretching bands.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical studies of Cu(i) sites in faujasite and their interaction with carbon monoxide

Rejmak

Sierka

Sauer

2007

Phys. Chem. Chem. Phys.

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Sitting, coordination, and properties of Cu(I) cations in zeolite faujasite are investigated using a combined quantum mechanics-interatomic potential function method. The coordination of Cu(I) ions depends on their location within the zeolite lattice. Cu(I) located inside the hexagonal prisms (site I') and in the plane of six-membered aluminosilicate rings on the walls of sodalite units (site II) is threefold coordinated, whereas Cu(I) located in the supercages (site III) is twofold coordinated. In agreement with available experimental data Cu(I) appears to be more strongly bound in sites I' and II than in site III. The binding energy of site II Cu(I) ions increases with the number of Al atoms, but only closest Al atoms have a substantial influence. The CO molecule binds more strongly onto sites with weaker bound cations and lower coordination. We assign the two CO stretching IR bands observed for Cu(I)-Y zeolites to sites II with one Al (2157-2161 cm(-1)) and two Al atoms (2140-2148 cm(-1)) in the six-membered aluminosilicate ring. For Cu(I)-X we tentatively assign the high frequency band to site III (2156-2168 cm(-1)) and the low-frequency band to site II with three Al atoms in the six-membered ring (2136-2138 cm(-1)).

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Section: Co Stretching Frequenciessupporting

confidence: 67%

“…27 The two bands point to the presence of two different copper sites in Cu(I)-FAU. TPD experiments 27 showed that in Cu(I)-X zeolite CO binding is stronger for the high-frequency site.…”

Section: Co Stretching Frequenciesmentioning

confidence: 99%