An infrared study of H2O and D2O on HZSM-5 and DZSM-5

Parker, L.M.; Bibby, D.M.; Burns, Gary R.

doi:10.1016/0144-2449(93)90069-f

Cited by 61 publications

(53 citation statements)

References 22 publications

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“…In the harmonic approximation the ratio between the frequencies of the OD and OH groups is approximately 0.728 ͑Ϸ1/&͒. Experimentally, 2,3,6 the OD stretch frequency of a bare zeolite is observed in the interval of 2659-2670 cm Ϫ1 . The frequencies we have calculated are in a very good agreement with the experiment ͑see Figs.…”

Section: Isotope Effectmentioning

confidence: 93%

“…Also their intensity is decreased by a factor of almost 2 compared to the spectra of the zeolite hydroxyl groups. Parker et al 2 have observed a broad band with a maximum around 2150 cm Ϫ1 and another relatively narrow band at 1900 cm Ϫ1 . For adsorption of CD 3 CN on ͑Ref.…”

Section: Isotope Effectmentioning

confidence: 99%

“…The reaction can be studied by infrared spectroscopy because the frequencies of the vibrations of the zeolite hydroxyl group will change upon interaction with the water molecule. When water is adsorbed on H-ZSM-5, [1][2][3][4][5][6]21 HY, 7 H-MOR, 4 or chabazite 22 a triplet of bands appears at 2872-3000, 2403-2515, and 1700 cm Ϫ1 , known also as an ABC triplet. This triplet is accompanied by two peaks at 3700 and 3550 cm Ϫ1 .…”

Section: Introductionmentioning

confidence: 99%

“…During the last decade, adsorption of water on zeolites has been extensively studied both experimentally [1][2][3][4][5][6][7][8] and theoretically [9][10][11][12][13][14][15][16][17][18][19][20] in order to understand the nature of the interaction of basic molecules with the Brøn-sted sites in the zeolites. The reaction can be studied by infrared spectroscopy because the frequencies of the vibrations of the zeolite hydroxyl group will change upon interaction with the water molecule.…”

Section: Introductionmentioning

confidence: 99%

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Quantum chemical calculation of infrared spectra of acidic groups in chabazite in the presence of water

Mihaleva¹,

Santen

Jansen

2004

The Journal of Chemical Physics

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The changes in the spectra of the acidic group in chabazite are studied by quantum chemical calculations. The zeolite is modeled by two clusters consisting of eight tetrahedral atoms arranged in a ring and seven tetrahedral atoms coordinated around the zeolite OH group. The potential energy and dipole surfaces were constructed from the zeolite OH stretch, in-plane and out-of-plane bending coordinates, and the intermolecular stretch coordinate that corresponds to a movement of the water molecule as a whole. Both the anharmonicities of the potential energy and dipole were taken into account by calculation of the frequencies and intensities. The matrix elements of the vibrational Hamiltonian were calculated within the discrete variable representation basis set. We have assigned the experimentally observed frequencies at ϳ2900, ϳ2400, and ϳ1700 cm Ϫ1 to the strongly perturbed zeolite OH vibrations caused by the hydrogen bonding with the water molecule. The ABC triplet is a Fermi resonance of the zeolite OH stretch mode with the overtone of the in-plane bending ͑the A band͒ and the overtone of the out-of-plane bending ͑the C band͒. In the B band the stretch is also coupled with the second overtone of the out-of-plane bending. The frequencies at ϳ3700 and ϳ3550 cm Ϫ1 we have assigned to the OH stretch frequencies of a slightly perturbed water molecule.

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Section: Isotope Effectmentioning

confidence: 93%

Section: Isotope Effectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Quantum chemical calculation of infrared spectra of acidic groups in chabazite in the presence of water

Mihaleva¹,

Santen

Jansen

2004

The Journal of Chemical Physics

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“…Parker et al 8 50 Compared with IR spectroscopy this technique has the advantage that it selectively probes modes with a large component of proton motions. Since the INS intensities are proportional to the number of hydrogen atoms, it was possible to determine the loading to be about 1 water molecule/Brønsted site.…”

Section: Dependence Of the Proton-transfer Energy And The Heat Of Adsmentioning

confidence: 99%

Interaction of Water with Brønsted Acidic Sites of Zeolite Catalysts. Ab Initio Study of 1:1 and 2:1 Surface Complexes

1996

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The adsorption of one and two water molecules on cluster models of Brønsted acid sites of zeolite catalysts has been investigated by ab initio quantum chemical methods at the Hartree-Fock self-consistent field (HF), at the second-order Møller-Plesset perturbation theory (MP2), and at the density functional theory (DFT) levels. Among the two possible structures of the 1:1 adsorption complex, the water H-bonded to the zeolitic OH group (neutral complex) and the hydroxonium ion attached to the negatively charged zeolite surface (ion pair), only the former is a minimum. The ion pair complex is a transition structure for the proton transfer from one lattice oxygen to a neighboring one via the adsorbed water. However, the energy difference between both structures is only a few kJ/mol. For the neutral 1:1 adsorption complex we predict an average shift of the three protons involved of 7-8 ppm; the observed shifts are 6-7 ppm for one water molecule per site. The vibrational frequencies calculated for the ion pair structure do not permit an interpretation of the observed infrared spectrum. For the neutral structure (MP2) we predict frequencies of 1317 and 1022 cm -1 for the zeolitic in-plane and out-of-plane modes, respectively, while the zeolitic OH stretching mode is strongly red-shifted down to 2740-2850 cm -1 . These data support a recent interpretation of the IR spectrum which explains the observed triplet of bands as a result of Fermi resonance between the strongly perturbed zeolitic OH stretch and the OH bending overtones. The MP2 calculations for the neutral complex also provide a complete assignment of the peaks observed by inelastic neutron scattering for water on H-mordenite. Inclusion of electron correlation proves crucial, and comparison of MP2 and DFT (gradient corrected functionals) methods is made. While energy differences are very similar, the DFT approach yields by far too large frequency shifts for OH donor groups in H bonds. When a second water molecule is added (2:1 complex), both the neutral and the ion pair structure prove to be local minima on the potential energy surface. The adsorption energy is found to drop by 25%, and the ion pair structure becomes the more stable one. Predictions are made on how the vibrational spectra and the 1 H NMR chemical shifts change.

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Infrared Spectroscopy for the Characterization of Surface Acidity and Basicity

Knözinger

2008

Handbook of Heterogeneous Catalysis

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An infrared study of H2O and D2O on HZSM-5 and DZSM-5

Cited by 61 publications

References 22 publications

Quantum chemical calculation of infrared spectra of acidic groups in chabazite in the presence of water

Quantum chemical calculation of infrared spectra of acidic groups in chabazite in the presence of water

Interaction of Water with Brønsted Acidic Sites of Zeolite Catalysts. Ab Initio Study of 1:1 and 2:1 Surface Complexes

Infrared Spectroscopy for the Characterization of Surface Acidity and Basicity

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