Dynamics of the Cyclohexadienyl Radical Adsorbed in Porous Silica and NaZSM‐5

Roduner, Emil; Schwager, Martina; Tregenna‐Piggott, Philip L. W.; Dilger, Herbert; Shelley, Mee; Reid, I. D.

doi:10.1002/bbpc.199500081

Cited by 19 publications

(33 citation statements)

References 16 publications

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“…As noted in previous work, 5,21,22 in the absence of viscous friction, the frequency factor for the reorientational correlation time is expected to approach that of a classical free rotator: FR D 2 I/81kT 1/2 . Taking a value of I D 1.56 ð 10 45 kg m 2 for a benzene molecule, values of FR D 6.5 ð 10 13 and 5.2 ð 10 13 s are obtained at 130 and 205 K, respectively, which are the mid-points of the two temperature ranges over which the LF measurements were made.…”

Section: Energetics and Mobilitiesmentioning

confidence: 87%

Spin-labelling studies of benzene sorbed in carbon particles using muonium: a molecular view of sorption by environmental carbons

Rhodes¹,

Dintinger²,

Reid³

et al. 2000

Magn. Reson. Chem.

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Section: Energetics and Mobilitiesmentioning

confidence: 87%

Spin-labelling studies of benzene sorbed in carbon particles using muonium: a molecular view of sorption by environmental carbons

Rhodes¹,

Dintinger²,

Reid³

et al. 2000

Magn. Reson. Chem.

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“…Fast wobbling of the long molecular axis with a temperature dependent amplitude resulted in a partly averaged hyperfine tensor. A restricted type of motion was also observed for the cyclohexadienyl radical adsorbed in NaZSM-5 with a benzene loading close to eight molecules per unit cell [6].…”

Section: Introductionmentioning

confidence: 73%

“…The A l line width observed from benzene in NaZSM-5 is 47 mT FWHM (full width at half maximum) at 433 K which is slightly larger than the resonance observed for axially anisotropic benzene in its ALC%tSR powder spectrum (42 mT FWHM) [6], but considerably smaller than that for a rhombic benzene crystal (64 mT FWHM) [6]. The anisotropy of the hyperfine tensor is also reflected in the A 0 line width of 60 mT, which is far larger than that in the isotropic limit (12 mT FWHM).…”

Section: Resultsmentioning

confidence: 99%

Dynamics of cyclohexadienyl radicals in NaZSM-5 and LiZSM-5

Stolmár

1997

Appl. Magn. Reson.

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“…The correlation time corresponding to a free rotor, t FR ¼ 2pðI y81k B TÞ 1y2 , has been used as a benchmark comparison for the reciprocal attempt frequency, t ? [31]. The moment of inertia, I, may be obtained as the sum of the constituent masses multiplied by the square of their displacement from the centre of rotation, I ¼ Sm i r i 2 .…”

Section: Discussionmentioning

confidence: 99%

Radiolabelling Measurements of Free Radicals Derived from Aromatic Volatile Organic Compounds Adsorbed in Zeolite Nanomaterials to and above Saturation Loadings

Rhodes¹,

Dintinger

2011

Progress in Reaction Kinetics and Mechanism

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Benzene, para-xylene and mesitylene were adsorbed into silicalite, Na -mordenite, Na -ZSM5 and Li -X zeolites, and studied using the longitudinal field muon spin relaxation (LF-mSRx) technique. The zeolites ZSM5=silicalite and mordenite contain microporous channels while zeolite X has only supercages. For cyclohexadienyl radicals=benzene adsorbed in Na -ZSM5, silicalite and Na -mordenite, a fraction was detected with a common reorientational activation energy in the region of ca 5 kJ mol À 1 ; however, in all cases there appeared a second fraction with an activation energy of ca 12 kJ mol À 1 . [In Li -X only a single fraction was observed with E a ¼ 8:1 kJ mol À 1 , from molecules adsorbed in supercages]. Given that high loadings of benzene, beyond the saturation capacities of the zeolites were employed, we believe the two distinct motional distributions represent the channel intersection and channel=external-surface niche locations in ZSM5=silicalite, the latter having the higher activation energy. An extraneous fraction may also be present (possibly as a thin film coating the zeolite grains), which probably also contributes to the detected ca 5 kJ mol À 1 component in which, as at the channel-intersections, the motion tends toward bulk behaviour. Mordenite has only a single accessible channel structure and is hence devoid of the relatively unrestricting channel intersecting pores that are present in ZSM5=silicalite. However, the channels are wider (ca 7 Å diameter) and we may ascribe therefore, the ca 5 kJ mol À 1 fraction to the formation of benzene clusters within these channels that exhibit bulk-type behaviour, while we assign, in analogy with the results for ZSM5=silicalite, the ca 12 kJ mol À 1 fraction to molecules adsorbed in niches on the external surface. It is thought that the essential difference between the two activation energies is that the ca 5 kJ mol À 1 processes involve molecular motion within clusters of benzene molecules with properties similar to the bulk phase (6.6 kJ mol À 1 was measured in pure benzene), while those characterised at ca 12 kJ mol À 1 reflect single benzene molecules or small, ordered molecular clusters interacting with a zeolite surface. The results for dimethylcyclohexadienyl radicals (derived from p-xylene) are rather similar, but indicate slightly reduced activation energies. The larger mesitylene molecules can penetrate zeolite X and (more slowly) mordenite, but are excluded from the internal pores of ZSM5=silicalite.

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Dynamics of the Cyclohexadienyl Radical Adsorbed in Porous Silica and NaZSM‐5

Cited by 19 publications

References 16 publications

Spin-labelling studies of benzene sorbed in carbon particles using muonium: a molecular view of sorption by environmental carbons

Spin-labelling studies of benzene sorbed in carbon particles using muonium: a molecular view of sorption by environmental carbons

Dynamics of cyclohexadienyl radicals in NaZSM-5 and LiZSM-5

Radiolabelling Measurements of Free Radicals Derived from Aromatic Volatile Organic Compounds Adsorbed in Zeolite Nanomaterials to and above Saturation Loadings

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