Adsorbed Molecules on Solvated Layer Silicates: Surface Mobility and Orientation from ESR Studies

McBride, Murray B.

doi:10.1346/ccmn.1977.0250102

Cited by 13 publications

(7 citation statements)

References 14 publications

(21 reference statements)

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“…There is evidence in other porous systems that molecules preferentially align along surfaces when adsorbed . Adsorption of fluids on clays also shows ordering with nonrandom tumbling of molecules close to the clay surface . If a system were to have no preferential orientation of the fluid molecules at pore surfaces, then the dipolar coupling will simply be an average over all angles and no anisotropy in the relaxation will occur.…”

Section: Homonuclear Dipolar Couplingmentioning

confidence: 99%

Relaxation mechanisms and shales

Washburn

2014

Concepts Magnetic Resonance

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Unconventional petroleum resources present in shales have recently seen increased development due to growing demand for energy worldwide, declining conventional petroleum discoveries, and improved technology for production. Shale reservoirs differ from more conventional reservoirs in both matrix composition and structure, tending to be low in porosity and ultralow in permeability, making traditional laboratory characterization methods difficult to apply. The noninvasiveness of nuclear magnetic resonance (NMR) makes it a favored technique for shale analysis. However, interpretation of NMR relaxometry results for shales is more complex than in traditional reservoirs. Surface relaxivity in conventional reservoirs is predominantly caused by the interaction of fluid molecules with paramagnetic impurities on pore surfaces. However, in shales, small pore sizes coupled with the presence of hydrogen-rich organic matter can result in more interactions. This article discusses different relaxation mechanisms that may be present in shales and situations where they are relevant. Surface relaxation in organic matter is likely caused by homonuclear dipolar coupling, not paramagnetic impurities, and as such, will have a significant temperature dependence. Due to the small pore sizes in shales, the effect of internal gradients on the signal appears negligible in almost all situations. Analysis of transverse relaxation resulting from organic solids by an inverse Laplace transform may lead to results that are anomalously short and overcall signal intensity. Diffusional coupling between the shale pores confounds interpretation of the NMR response as a pore size distribution. There also appears to be rapid exchange of magnetization between mobile and immobile phases in the samples.

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Section: Homonuclear Dipolar Couplingmentioning

confidence: 99%

Relaxation mechanisms and shales

Washburn

2014

Concepts Magnetic Resonance

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“…Evidence for the mechanisms by which metals are retained in exchangeable (or nonexchangeable) form may also be derived from the degree of surface mobility. Recent investigations of organic cation rotation at clay surfaces by electron spin resonance (ESR) spectroscopy (McBride, 1976a;McBride, 1977) have demonstrated that motion-dependent ESR spectra of adsorbed paramagnetic cations can provide useful information about adsorption processes. Spectra of the vanadyl ion, VO ~+, are particularly well suited to estimation of rates of rotational motion because of the strong dependence of spectral lineshape upon rotational correlation time, rR, where rR represents the time required for VO ~+ to reorient in solution by random thermal tumbling.…”

Section: Introductionmentioning

confidence: 99%

Mobility and Reactions of VO²⁺ on Hydrated Smectite Surfaces

McBride

1979

Clays and clay miner.

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Abstract--The electron spin resonance (ESR) spectra of varying quantities of vanadyl ion (VO 2+) adsorbed on hydrated hectorite indicated that hydrolysis of VO 2+ was promoted at low levels of adsorption. The hydrolyzed product was adsorbed on the clay surfaces, with a ligand environment that was partially aqueous and partially hydroxide in nature. Greater amounts of VO 2+ adsorbed on wetted hectorite obscured the ESR spectrum of the strongly adsorbed hydrolysis product with a solutiordike spectrum. An approximately 50% reduction in rotational mobility of VO 2+ relative to solution was indicated by the lincwidth of this spectrum. Loss in mobility occurred with reduction of the interlamellar spacing until, under strongly dehydrating conditions, the VO(HzO)52+ ions became aligned with the V =O bond axis normal to the plane of the clay platelets.

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“…Extensive ESR work has been undertaken on the dynamical behaviour ofnitroxide spin probes such as TEMPO +, the cationic form of 4-amino-2,2,6,6-tetramethylpiperdine-Noxide, in the interlamellar region of smectites. (McBride 1976c(McBride , 1976d(McBride , 1977a(McBride , 1977b. Rotational correlation times were derived from the theory of Sachs & Latorre (1974).…”

Section: Nitroxide Spin Probesmentioning

confidence: 99%

“…4 illustrates the ESR spectra of orientated films of TEMPO +-doped Na +-hectorite solvated with water, methanol and ethanol. For the fully hydrated Na+-hectorite, McBride (1977b) related the calculated value of zc to an effective diffusion coefficient of D = 5 • 10 -6 cmZs -l using the relationship D = 12/4Zc, where/is the mean jump distance, i.e. the diameter of the probe molecule.…”

Section: Nitroxide Spin Probesmentioning

confidence: 99%

The application of electron spin resonance spectroscopy to studies of clay minerals: II. Interlamellar complexes—structure, dynamics and reactions

Hall

1980

Clay miner.

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A BSTRACT: A review is given of the application of ESR spectroscopy to the study of hydrated transition metal ions and nitroxide spin probes in the interlamellar region of smectites and vermiculites. These investigations have not only provided information regarding the structure and mobility of the intracrystalline water-cation layers but have also demonstrated the reactivity and catalytic properties of certain transition metal exchange forms of smectites. Several novel coordination complexes and redox reactions between the exchange ions and a variety of simple organic molecules have been characterized.The application of ESR spectroscopy to studies of paramagnetic ions and defect centres occurring in aluminosilicate lattices or on external clay particle surfaces was discussed in Part I of this review (Hall, 1980). Apart from these investigations, considerable attention has also been focussed on the characterization by ESR of the nature of the interlamellar water-cation layers in hydrated smectites and vermiculites. These studies, which are reviewed here, are based on the fact that when paramagnetic (transition metal) exchange cations are present in these clays, their ESR spectra serve as sensitive probes of both structural and dynamic properties of the local environment of the ions.Structural information may be derived from the symmetry and orientation-dependence of the ESR spectra. Information regarding the orientation of the symmetry axes of the complex ions can be obtained by working with preferentially-orientated films aligned either parallel or perpendicular to the magnetic field (Angel & Hall, 1973;Clementz et al., 1973).ESR spectra can also probe the dynamic properties of ions or radicals in solution-like environments, yielding information such as rotational correlation times or diffusion coefficients. In general, the elucidation of such information requires the presence of a species having anisotropic g-values (and preferably also anisotropic hyperfine splittings). If the paramagnetic ion is in a quasi-crystalline environment, i.e. is effectively immobile on the time-scale of observation of the ESR experimenL the direction-dependence of the spectrum will be seen in oriented samples. In contrast, if the ion is in a solution-like environment of low viscosity, and rapidly tumbling with a correlation time considerably shorter than the observation time, complete averaging of the anisotropic components of the spectrum will occur, giving effective spectral parameters g -l(gx+gy+gz) and A = 13(A~ + Ay + A~). In intermediate cases, where the mobility is on a time-scale comparable with the observation time, only a partial averaging of the spectrum will occur. In

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Adsorbed Molecules on Solvated Layer Silicates: Surface Mobility and Orientation from ESR Studies

Cited by 13 publications

References 14 publications

Relaxation mechanisms and shales

Relaxation mechanisms and shales

Mobility and Reactions of VO²⁺ on Hydrated Smectite Surfaces

The application of electron spin resonance spectroscopy to studies of clay minerals: II. Interlamellar complexes—structure, dynamics and reactions

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Adsorbed Molecules on Solvated Layer Silicates: Surface Mobility and Orientation from ESR Studies

Cited by 13 publications

References 14 publications

Relaxation mechanisms and shales

Relaxation mechanisms and shales

Mobility and Reactions of VO2+ on Hydrated Smectite Surfaces

The application of electron spin resonance spectroscopy to studies of clay minerals: II. Interlamellar complexes—structure, dynamics and reactions

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Mobility and Reactions of VO²⁺ on Hydrated Smectite Surfaces