Quantification of Brønsted Acidity in Mordenites

Макарова, М. А.; Wilson, A.E.; Liemt, B.J. van; Mesters, C.M.A.M.; Winter, A.; Williams, C.

doi:10.1006/jcat.1997.1849

Cited by 68 publications

(73 citation statements)

References 16 publications

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“…The in situ FTIR spectra in the $\tilde \nu $ =3900–3400 cm −1 region are presented in Figure 4 a for HY, Au/HY, and NaY. A strong peak at $\tilde \nu $ =3630 cm −1 and a weak broad peak around $\tilde \nu $ =3550 cm −1 are observed; they are assigned to high‐frequency (HF) acidic OH groups located in the supercage and acidic OH groups in the sodalite cage respectively 42–45. It is obvious that the peak at $\tilde \nu $ =3630 cm −1 is strong for the HY sample but weak for NaY, indicating that the OH groups inside the supercage are abundant in HY but are nearly zero in NaY.…”

Section: Resultsmentioning

confidence: 97%

“…A strong peak at ñ = 3630 cm À1 and a weak broad peak around ñ = 3550 cm À1 are observed; they are assigned to high-frequency (HF) acidic À OH groups located in the supercage and acidic À OH groups in the sodalite cage respectively. [42][43][44][45] It is obvious that the peak at ñ = 3630 cm À1 is strong for the HY sample but weak for NaY, indicating that the À OH groups inside the supercage are abundant in HY but are nearly zero in NaY. In the case of Au/HY, the intensity of the band at ñ = 3630 cm À1 decreased, suggesting that the ÀOH groups are consumed when Au clusters were introduced into the supercage.…”

Section: Resultsmentioning

confidence: 99%

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Gold Nanoclusters Confined in a Supercage of Y Zeolite for Aerobic Oxidation of HMF under Mild Conditions

Cai

Zhang

et al. 2013

Chemistry A European J

192

104

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Au nanoclusters with an average size of approximately 1 nm size supported on HY zeolite exhibit a superior catalytic performance for the selective oxidation of 5‐hydroxymethyl‐2‐furfural (HMF) into 2,5‐furandicarboxylic acid (FDCA). It achieved >99 % yield of 2,5‐furandicarboxylic acid in water under mild conditions (60 °C, 0.3 MPa oxygen), which is much higher than that of Au supported on metal oxides/hydroxide (TiO2, CeO2, and Mg(OH)2) and channel‐type zeolites (ZSM‐5 and H‐MOR). Detailed characterizations, such as X‐ray diffraction, transmission electron microscopy, N2‐physisorption, and H2‐temperature‐programmed reduction (TPR), revealed that the Au nanoclusters are well encapsulated in the HY zeolite supercage, which is considered to restrict and avoid further growing of the Au nanoclusters into large particles. The acidic hydroxyl groups of the supercage were proven to be responsible for the formation and stabilization of the gold nanoclusters. Moreover, the interaction between the hydroxyl groups in the supercage and the Au nanoclusters leads to electronic modification of the Au nanoparticles, which is supposed to contribute to the high efficiency in the catalytic oxidation of HMF to FDCA.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Gold Nanoclusters Confined in a Supercage of Y Zeolite for Aerobic Oxidation of HMF under Mild Conditions

Cai

Zhang

et al. 2013

Chemistry A European J

192

104

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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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“…These, in turn, are determined by the catalyst preparation process [7,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. Most of the papers under discussion provide only scant information on the catalyst preparation and characterization, so that it is not possible to evaluate the contributions of each of the critical parameters to the resultant (de)hydrogenation efficiency.…”

Section: Does Selectivity Relate To the Relative (De)hydrogenation Efmentioning

confidence: 99%

“…An equitable comparison between the performance of MAZand MOR-type zeolites turned out to be remarkably complicated, for the accessibility [21][22][23][24][25][26][27], density, and strength [7,28,29] of the Brønsted acid sites all appear critically dependent on the zeolite synthesis [23,[30][31][32][33][34] and modification [23,35,36] processes. After nearly a decade of research, it was concluded that the improvement of MAZ-over MORtype zeolites was too small to merit commercialization of the former [29,37].…”

Section: Introductionmentioning

confidence: 99%

The selectivity of -hexane hydroconversion on MOR-, MAZ-, and FAU-type zeolites

Calero

Schenk

Dubbeldam

et al. 2004

Journal of Catalysis

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Analyses of a series of published n-hexane hydroisomerization product slates suggest that MAZ-type zeolites yield more dimethylbutane and less methylpentane than either FAU-or MOR-type zeolites. Molecular simulations do not corroborate the traditional view that these selectivity differences are specifically related to the MAZ-, FAU-, or MOR-type zeolite topology. A scrutiny of the literature indicates that reported variation in selectivity relates to a variation in the efficiency of the (de)hydrogenation function relative to the acid function. The FAU-type zeolite catalyst had the most efficient hydrogenation function. The efficiency of the hydrogenation function on the MAZ-type zeolite was low enough to significantly enhance the 2,3-dimethylbutane yield relative to the methylpentane yield, but not low enough to decrease the 2,2-dimethylbutane yield. The efficiency of the hydrogenation function on the MOR-type zeolite was low enough to do both. Only at a sufficiently high n-hexane hydroconversion does the catalyst with the most efficient hydrogenation function exhibit the highest dimethylbutane yield. This new perspective on the reported hexane hydroconversion selectivities suggests that a FAU-type zeolite catalyst with a highly efficient hydrogenation function is best suited for n-hexane hydroisomerization. The FAU topology has the highest porosity which should afford the highest activity without impairing selectivity.  2004 Elsevier Inc. All rights reserved.

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Quantification of Brønsted Acidity in Mordenites

Cited by 68 publications

References 16 publications

Gold Nanoclusters Confined in a Supercage of Y Zeolite for Aerobic Oxidation of HMF under Mild Conditions

Gold Nanoclusters Confined in a Supercage of Y Zeolite for Aerobic Oxidation of HMF under Mild Conditions

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

The selectivity of -hexane hydroconversion on MOR-, MAZ-, and FAU-type zeolites

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