Fossil Fuels

Botto, Robert E.

doi:10.1002/9780470034590.emrstm0175

Cited by 3 publications

(2 citation statements)

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“…In this context, the additional interpretation of T 1rH and T 1rC may help to assign physical and structural properties of this coal. Competing relaxation mechanisms may complicate a proper assignment in terms of mobility and modification [18,37]. A comparison of T 1rH for alkyl (T 1rH ¼ 1:1 ms) and aryl (T 1rH ¼ 8:2 ms) carbons within the crystalline domain of C1 indicates limited spin diffusion, explainable by differing mobility.…”

Section: Structural Information Obtained From the Cross Polarization mentioning

confidence: 99%

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CP dynamics of heterogeneous organic material: characterization of molecular domains in coals

Abelmann

Totsche

Knicker

et al. 2004

Solid State Nuclear Magnetic Resonance

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Simplified equations are used in common approaches to describe cross polarization (CP) dynamics of solids. The CP behavior may be modulated by several nuclei interactions and physicochemical sample properties. At high magnetic fields and spinning speeds, these modulations can obscure the results. To elucidate their impact on the CP behavior of natural organic materials variable contact time (VCT) experiments were acquired with a high temporal resolution for two coal samples. The measurements were distinctly influenced by interfering fluctuations. Conventional approaches showed insufficient flexibility in terms of degrees of freedom to calculate the CP dynamics. The use of an original fundamental equation as model resulted in sufficient flexibility for such heterogeneous systems. The best results were obtained assuming a two component system. On these conditions a differentiation between amorphous and crystalline domains within the coal samples was enabled.

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Section: Structural Information Obtained From the Cross Polarization mentioning

confidence: 99%

“…protonated and non-protonated carbons. Non-protonated aromatic carbons require a longer polarization transfer time due to weak 1 H-13 C interactions than protonated aromatic carbons [17][18][19]. The intensity decay with T 1rH is sensitive to dipolar interactions caused by motions in the corresponding time frame (10 À4 , 10 À5 s).…”

Section: Introductionmentioning

confidence: 99%