FTIR analysis of the hydroxyl region in US-Y zeolites

Макарова, М. А.; Dwyer, John

doi:10.1021/j100126a004

Cited by 69 publications

(28 citation statements)

References 7 publications

(8 reference statements)

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“…The less acidic hydroxyls restoring at lowest desorption temperatures 473 and 523 K are represented by 3620 and 3550 cm −1 bands, whereas most acidic hydroxyls restoring at highest temperatures: 573–673 K are represented by 3600 and 3520 cm −1 maxima. This result agrees well with the conclusions proposed by several authors, e. g. Makarova and Dwyer . It was also concluded that the very high acid strength of 3600 and 3520 cm −1 hydroxyls was the result of the interaction of Si−O 1 H−Al, and Si−O 3 H−Al with extra‐framework Al.…”

Section: Resultssupporting

confidence: 92%

“…3600 cm À1 in zeolites USY steamed (non-treated with acid and not desilicated) show extremely acid strength. This was reported by several authors, [14] and 3600 cm À1 hydroxyls in USY were interpreted as SiÀO 1 HÀAl interacting with extra-framework Al extracted from zeolite by water treatment during steaming procedure. We suppose, that 3600 cm À1 groups present in zeolite Y desilicated above 318 K may also show very high acid strength (as in USY).…”

Section: Introductionsupporting

confidence: 72%

“…This result agrees well with the conclusions proposed by several authors, e. g. Makarova and Dwyer. [14] It was also concluded that the very high acid strength of 3600 and 3520 cm À1 hydroxyls was the result of the interaction of SiÀO 1 HÀAl, and SiÀO 3 HÀAl with extra-framework Al.…”

Section: Acid Strength Of Oh Groups In Zeolite Usymentioning

confidence: 99%

“…It was postulated by many authors, e. g ref. [14]. Water interacting with zeolite framework caused the extraction of some Al.…”

Section: Acid Strength Of Hydroxyls In Desilicated Zeolite Y Measuredmentioning

confidence: 99%

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Hydroxyl Groups of Exceptionally High Acidity in Desilicated Zeolites Y

et al. 2018

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The desilication of dealuminated zeolite Y in NaOH/tetrabutylammonium hydroxide mixtures produces hierarchical zeolite Y containing a micropore system as well as mesopores of significant volume and surface. IR studies evidenced that a new kind of hydroxyls was formed if desilication was realized above 318 K. This new kind of acidic hydroxyls is characterized by IR band at 3600 cm−1. IR studies showed, that these new hydroxyls showed extremely high acidity. This was evidenced by very high frequency shifts of IR bands of OH interacting with probe molecules: CO and N2: ΔνnormalOnormalH···normalCnormalO =411 cm−1 and ΔνOH···N2 =164 cm−1, resp. These frequency shift are the highest in all the chemistry of zeolites including very strongly acidic dealuminated mazzite and steamed zeolite USY (ΔνnormalOnormalH···normalCnormalO =ca. 380 cm−1) indicating that 3600 cm−1 hydroxyls are the most acidic in all the zeolites.

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Section: Resultssupporting

confidence: 92%

Section: Introductionsupporting

confidence: 72%

Section: Acid Strength Of Oh Groups In Zeolite Usymentioning

confidence: 99%

“…It was postulated by many authors, e. g ref. [14]. Water interacting with zeolite framework caused the extraction of some Al.…”

Section: Acid Strength Of Hydroxyls In Desilicated Zeolite Y Measuredmentioning

confidence: 99%

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Hydroxyl Groups of Exceptionally High Acidity in Desilicated Zeolites Y

et al. 2018

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“…Distribution of unexchanged BAS in 8‐ and 12‐MR structures can be evaluated from diffuse‐reflectance infrared Fourier transform spectroscopy (DRIFTS) in the 3700–3500 cm −1 range. Hydroxyl groups in 12‐MR are characterized by wavelength at 3609–3625 cm −1 and the hydroxyl groups in 8‐MR at 3581–3590 cm −1 ,. The deconvoluted DRIFT spectra are presented in Figure , and the ratio of peaks areas of 12‐MR BAS (3623–3631 cm −1 ) to 8‐MR BAS (3583–3587 cm −1 ) is shown in Table .…”

Section: Resultsmentioning

confidence: 99%

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.

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Infrared Spectroscopy on Powder Catalysts

Stavitski¹

2013

In‐situ Characterization of Heterogeneous Catalysts

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FTIR analysis of the hydroxyl region in US-Y zeolites

Cited by 69 publications

References 7 publications

Hydroxyl Groups of Exceptionally High Acidity in Desilicated Zeolites Y

Hydroxyl Groups of Exceptionally High Acidity in Desilicated Zeolites Y

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

Infrared Spectroscopy on Powder Catalysts

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