Inhomogeneity of Broensted acid sites in H-mordenite

Zholobenko, Vladimir L.; Макарова, М. А.; Dwyer, John

doi:10.1021/j100124a030

Cited by 128 publications

(125 citation statements)

References 2 publications

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“…A recent paper proposed that-similar to Y-zeolitethe absorption peak of the ͑deuterated͒ hydroxyls in Mordenite consists of two contributions: a low-frequency ͑LF͒ and a high-frequency ͑HF͒ subpeak, resulting from hydroxyls in the small 8-ring cages and in the larger 12-ring cages, respectively. 13 This decomposition was carried out for the absorption spectrum and the result ͑see Fig. 1͒ is in agreement with Ref.…”

Section: Resultssupporting

confidence: 81%

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Fast energy delocalization upon vibrational relaxation of a deuterated zeolite surface hydroxyl

Bonn

Brugmans

Kleyn

et al. 1995

The Journal of Chemical Physics

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. (1995). Fast energy delocalization upon vibrational relaxation of a deuterated zeolite surface hydroxyl. Chemical Physics, 102(5), 2181-2185. DOI: 10.1063/1.468740 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. In this time-resolved study of vibrational dynamics of deuterated surface hydroxyls at acid sites in the zeolite Mordenite, we investigate the O-D T 1 vibrational lifetime and transient band shifts. It is shown that after infrared excitation of the stretching mode of a surface hydroxyl, the excess energy is rapidly distributed over delocalized low-energy lattice modes upon de-excitation. This is asserted from the observation that nonexcited hydroxyls are perturbed by the relaxation of their excited counterparts immediately after this relaxation. This observation can be made owing to better resolution in transient transmission spectroscopy obtained by deuteration of the surface hydroxyls. This assignment allows for accurate estimates of lattice temperatures after relaxation of the vibration. Further, from the observation that the vibrational lifetime is dependent on frequency ͑increasing from 25 to 70 ps with increasing frequency͒, it is concluded that the deuterated acidic protons are hydrogen bonded to lattice oxygen atoms in the zeolite.

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Section: Resultssupporting

confidence: 81%

“…8 Recently, the acidity of the zeolite Mordenite has been the subject of much research. [9][10][11][12][13][14] In order to gain better insight into the dynamics of vibrational relaxation and the properties of this surface hydroxyl, we performed a time-resolved vibrational study of deuterated hydroxyls.…”

Section: Introductionmentioning

confidence: 99%

Fast energy delocalization upon vibrational relaxation of a deuterated zeolite surface hydroxyl

Bonn

Brugmans

Kleyn

et al. 1995

The Journal of Chemical Physics

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“…The band at 3610 cm −1 for acidic bridging −OH stretching vibration was actually the combination of the bands for two types of acid sites in the 12-MR channels (∼3612 cm −1 ) and the 8-MR channels (∼3590 cm −1 ). 4,25,26 It is obvious that the band at 3610 cm −1 of the Cu-HMOR sample decreased significantly in comparison with that of the HMOR sample, indicating that the acidic bridging −OH groups might be exchanged by Cu ions. 27 Figure 3b shows the 1 H MAS NMR spectra of the HMOR and Cu-HMOR samples.…”

Section: Resultsmentioning

confidence: 99%

Dimethyl Ether Carbonylation to Methyl Acetate over Nanosized Mordenites

Xue

Huang

Ditzel³

et al. 2013

Ind. Eng. Chem. Res.

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Nanosized mordenites were found to show significantly enhanced reaction efficiency in dimethyl ether (DME) carbonylation to methyl acetate (MA) because of a greatly facilitated diffusion process. Copper incorporation into the channels of the nanosized mordenites further promoted the reaction rate, selectivity, and stability. Moreover, upon the addition of a small amount of H 2 (5−19 vol %) to the feed gas, deactivation was suppressed during DME carbonylation, whereas the catalyst stability and rate of formation of MA increased.

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“…14A), upon ammonia adsorption, shows a band at 3677 cm À1 , which can be assigned to either a P-OH or an Al-OH group [26,27]. On sorption of ammonia this appears as a negative peak for the parent material.…”

Section: Exafs and Xanes Studies-local Symmetry Of Cobalt And Manganesementioning

confidence: 99%

“…The catalysts were activated and reduced in situ at 400°C under vacuum (10 À5 mbar). The detailed experimental procedure was described elsewhere [26,27].…”

Section: Characterizationmentioning

confidence: 99%

Framework cobalt and manganese in MeAPO-31 (Me=Co, Mn) molecular sieves

Tušar

Mali

Arčon

et al. 2002

Microporous and Mesoporous Materials

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Pure phases of CoAPO-31 and MnAPO-31 were synthesized hydrothermally using di-n-propylamine as a structuredirecting agent. The incorporation of manganese(II) and cobalt(II) into framework aluminum sites of AlPO 4 -31 was suggested from elemental, thermogravimetric and X-ray powder diffraction analysis. Isomorphous aluminum substitution with cobalt(II) was confirmed from static 31 P NMR spectra. UV-VIS and XANES spectra revealed a partial oxidation of framework cobalt(II) and manganese(II) into cobalt(III) and manganese(III) in the calcined MeAPO-31 and thus the presence of redox centers in the products. The generation of acid sites (Brønsted and Lewis) in MeAPO-31 was supported by IR measurements of pyridine and by ammonium adsorption/desorption. The strength of the acid sites in the catalysts studied decreased in the following order: MnAPO-31 > CoAPO-31 > AlPO 4 -31.

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Inhomogeneity of Broensted acid sites in H-mordenite

Cited by 128 publications

References 2 publications

Fast energy delocalization upon vibrational relaxation of a deuterated zeolite surface hydroxyl

Fast energy delocalization upon vibrational relaxation of a deuterated zeolite surface hydroxyl

Dimethyl Ether Carbonylation to Methyl Acetate over Nanosized Mordenites

Framework cobalt and manganese in MeAPO-31 (Me=Co, Mn) molecular sieves

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