Adsorption of water on ZSM 5 zeolites

Jentys, Andreas; Warecka, Gerhard; Derewinski, Miroslav; Lercher, Johannes A.

doi:10.1021/j100349a032

Cited by 267 publications

(198 citation statements)

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“…Using the standard B3LYP-functional, the final co-adsorption energy amounts to only -14 kJ mol -1 in H-ZSM-5, and an almost negligible -3 kJ mol -1 in H-beta (Table 3). In experimental studies comparing benzene adsorption on H-ZSM-5 and silicalite, very similar gravimetrical uptakes and heats of adsorption were reported for both materials, indicating that the stabilization of benzene within the zeolite pores is mainly due to dispersive interactions with the pore walls 28 [53]. Standard DFT-functionals are unable to account for these van der Waals interactions, which are clearly crucial to describe the actual stabilization.…”

Section: Benzene Co-adsorption and Methylationmentioning

confidence: 69%

Methylation of benzene by methanol: Single-site kinetics over H-ZSM-5 and H-beta zeolite catalysts

Mynsbrugge

Visur

Olsbye

et al. 2012

Journal of Catalysis

129

126

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Benzene methylation by methanol is studied on acidic zeolites H-ZSM-5 (MFI) and H-beta (BEA) to investigate the influence of the catalyst topology on the reaction rate. Experimental kinetic measurements at 350 °C using extremely high feed rates to suppress side reactions show that methylation occurs considerably faster on H-ZSM-5 than on H-beta. Theoretical rate constants, obtained from first-principles simulations on extended zeolite clusters, reproduce a higher methylation rate on H-ZSM-5 and provide additional insight into the various molecular effects that contribute to the overall differences between the two catalysts. The calculations indicate this higher methylation rate is primarily due to an optimal confinement of the reacting species in the medium pore material. Co-adsorption of methanol and benzene is energetically favored in H-ZSM-5 compared with H-beta, to the extent that the stabilizing host-guest interactions outweigh the greater entropy loss upon benzene adsorption in H-ZSM-5 vs. in Hbeta.

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Section: Benzene Co-adsorption and Methylationmentioning

confidence: 69%

Methylation of benzene by methanol: Single-site kinetics over H-ZSM-5 and H-beta zeolite catalysts

Mynsbrugge

Visur

Olsbye

et al. 2012

Journal of Catalysis

129

126

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“…We have studied adsorption of water on both proton sites, 35 and we have found that a more stable complex is formed with the proton position O 3 than O 1 . In this paper all calculations for the bare zeolite clusters and complex with water have been done for the proton attached to O 3 .…”

Section: A Zeolite Cluster Without Watermentioning

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%

“…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%

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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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“…In zeolites, research has been made on methane," ethylene,20 acetylene,21,22 benzene,23 ethanal,24 carbon dioxide,25 oxygen,26 and water. 27 In special infrared cells, perturbed spectra have been recorded for a number of substituted ethylenes and acetylene^. '^-^^ These changes in infrared bands result in frequency shifts, line splittings, and intensity changes, which may lead to the appearance of new bands or disappearance of field-free bands.…”

Section: Introductionmentioning

confidence: 99%

Vibrational Stark effect: Theoretical determination through the semiempirical AM1 method

et al. 1992

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The vibrational Stark effect of a series of small molecules has been calculated by means of the semiempirical AM1 method through addition of the electron-field interaction term in the one-electron Hamiltonian. Optimized geometrical parameters along with harmonic frequencies and line intensities are determined for different strengths of the applied uniform electric field. The perturbed spectra are compared with theoretical studies carried out at the ab initio level and with experimental results. The vibrational Stark effect of the retinal molecule is also computed, showing that this kind of study is feasible in systems of biochemical interest.

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Adsorption of water on ZSM 5 zeolites

Abstract: clay interlayers is too narrow to accommodate large molecules such as capric acid, resulting in apparent poor activity of the photocatalyst. Studies to confirm this idea are under way.

Cited by 267 publications

References 0 publications

Methylation of benzene by methanol: Single-site kinetics over H-ZSM-5 and H-beta zeolite catalysts

Methylation of benzene by methanol: Single-site kinetics over H-ZSM-5 and H-beta zeolite catalysts

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

Vibrational Stark effect: Theoretical determination through the semiempirical AM1 method

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