Quasi-elastic neutron scattering study of the molecular motions of methanol adsorbed on H-ZSM-5

Jobic, H.; Renouprez, A.J.; Bée, M.; Poinsignon, C.

doi:10.1021/j100278a020

Cited by 56 publications

(65 citation statements)

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“…The peak temperatures they report agree with the present experiment. Quasi-elastic neutron scattering [21] and NMR [12] studies had shown the presence of two types of methanol -one which was strongly bound and the other a loosely bound, diffusive methanol. The former would correspond to the methanol species desorbing at 557 K, observed in the present studies, while the loosely bound diffusive methanol species to the low temperature desorbing methanol.…”

Section: Methodsmentioning

confidence: 99%

Temperature Programmed Surface Reaction Studies of the Methanol to Gasoline (MTG) Conversion over ZSM‐5

Jayamurthy

Vasudevan

1995

Ber Bunsenges Phys Chem

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The~ethanol to gasoline conversion over ZSM-5 has been studied by the Temperature Programmed Surface Reaction (TP~R) technique. The technique is able to delineate the two steps in the process: the dehydration of methanol to dimethyl ether and the subsequent conversion of dimethyl ether to hydrocarbons. The activation barr~ers associated with each step was evaluated from the TPSR profiles and are 108 kJ/mol and 195 kJ/mol respectively, The methanol desorption profile shows considerable change with the amount of methanol molecules adsorbed per Bronsted site of the zeolite. The energy associated with the desorption process (CH OH) H + -ZSM-.-H 30H)n_t H -ZSM-5 + CH 30H, shows a spectrum of values depending on n. The spectrum is not connnuous and has a gap for n = 1. The trend is similar to that for the corresponding gas-phase reaction, (CH30H)nH+-(CH30H)n_IH+ +CH 30H. The present investigation highlights the importance of the prot~nated methanol cluster, (CH30H)nH + -ZSM-5, in the primary step of the MTG process, the formation of dimethyl ether. The reaction is compared with the corresponding gas phase ion-molecule reaction of CH 30H{ .

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Section: Methodsmentioning

confidence: 99%

Temperature Programmed Surface Reaction Studies of the Methanol to Gasoline (MTG) Conversion over ZSM‐5

Jayamurthy

Vasudevan

1995

Ber Bunsenges Phys Chem

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“…25,26 Quasielastic neutron scattering (QENS) is particularly effective in the study of microporous catalysts, 27 allowing the measurement of molecular movements taking place over timescales of 2 ps-100 ns depending on the instrument, and thus it may be employed to measure both nanoscale diffusion, [28][29][30] and also local motions such as rotation. [31][32][33][34] Crucially, this technique can be employed on sub-micron crystals, in contrast to other methods, such as PFG-NMR, which have timescales from micro-to milliseconds and hence need crystal sizes in the order of micrometres or larger to be able to measure intracrystalline diffusion.…”

Section: Introductionmentioning

confidence: 99%

Molecular behaviour of phenol in zeolite Beta catalysts as a function of acid site presence: a quasielastic neutron scattering and molecular dynamics simulation study

Hernandez‐Tamargo

O’Malley

Silverwood

et al. 2019

Catal. Sci. Technol.

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“…The experimentally measured anisotropy factor (1/2)(D x + D y )/D z was found to be close to 5. 10 The diffusion of methanol 11 and of a series of n-alkanes, methane, ethane, propane, butane, and hexane, [12][13][14] was studied by QENS in the MFI structure, but only the mean diffusivity could be extracted from the data.…”

Section: Introductionmentioning

confidence: 99%

Unidirectional and Single-File Diffusion of Molecules in One-Dimensional Channel Systems. A Quasi-Elastic Neutron Scattering Study

et al. 1997

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Translational diffusion of molecules in one-dimensional channel systems has been measured by quasi-elastic neutron scattering. The scattering function for a single-file diffusion model has been derived in order to differentiate this transport model from normal 1D diffusion. In the AlPO 4 -5 structure, ordinary 1D diffusion is observed for methane and ethane, whatever the loading, which indicates that the molecules are able to pass each other. The diffusion coefficients for both molecules are on the order of 10 -9 m 2 s -1 . On the other hand, a quite different regime is obtained by varying cyclopropane concentration in the same structure. At low loading, normal 1D diffusion is observed because the molecules can be considered as isolated, but at higher concentration cyclopropane is found to follow single-file diffusion. However, the mobility is too small to be determined. In the less open channel system of ZSM-48, ordinary 1D diffusion is found for small methane concentration, the diffusion coefficient being 2.5 × 10 -9 m 2 s -1 , at 155 K. At medium loading, single-file diffusion is observed with a mobility factor of 2 × 10 -12 m 2 s -1/2 . This is the first time that this technique has provided experimental evidence of single-file diffusion in zeolites.

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Quasi-elastic neutron scattering study of the molecular motions of methanol adsorbed on H-ZSM-5

Cited by 56 publications

References 1 publication

Temperature Programmed Surface Reaction Studies of the Methanol to Gasoline (MTG) Conversion over ZSM‐5

Temperature Programmed Surface Reaction Studies of the Methanol to Gasoline (MTG) Conversion over ZSM‐5

Molecular behaviour of phenol in zeolite Beta catalysts as a function of acid site presence: a quasielastic neutron scattering and molecular dynamics simulation study

Unidirectional and Single-File Diffusion of Molecules in One-Dimensional Channel Systems. A Quasi-Elastic Neutron Scattering Study

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