scholarly journals Non-Exponential 1H and 2H NMR Relaxation and Self-Diffusion in Asphaltene-Maltene Solutions

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5218
Author(s):  
Kevin Lindt ◽  
Bulat Gizatullin ◽  
Carlos Mattea ◽  
Siegfried Stapf
Keyword(s):  
Diffusion Coefficients ◽  
Relaxation Times ◽  
Chemical Species ◽  
Nmr Relaxation ◽  
Molecular Size ◽  
Relaxation Rates ◽  
Vast Number ◽  
Self Diffusion ◽  
Slowing Down ◽  
The Individual

The distribution of NMR relaxation times and diffusion coefficients in crude oils results from the vast number of different chemical species. In addition, the presence of asphaltenes provides different relaxation environments for the maltenes, generated by steric hindrance in the asphaltene aggregates and possibly by the spatial distribution of radicals. Since the dynamics of the maltenes is further modified by the interactions between maltenes and asphaltenes, these interactions—either through steric hindrances or promoted by aromatic-aromatic interactions—are of particular interest. Here, we aim at investigating the interaction between individual protonic and deuterated maltene species of different molecular size and aromaticity and the asphaltene macroaggregates by comparing the maltenes’ NMR relaxation (T1 and T2) and translational diffusion (D) properties in the absence and presence of the asphaltene in model solutions. The ratio of the average transverse and longitudinal relaxation rates, describing the non-exponential relaxation of the maltenes in the presence of the asphaltene, and its variation with respect to the asphaltene-free solutions are discussed. The relaxation experiments reveal an apparent slowing down of the maltenes’ dynamics in the presence of asphaltenes, which differs between the individual maltenes. While for single-chained alkylbenzenes, a plateau of the relaxation rate ratio was found for long aliphatic chains, no impact of the maltenes’ aromaticity on the maltene–asphaltene interaction was unambiguously found. In contrast, the reduced diffusion coefficients of the maltenes in presence of the asphaltenes differ little and are attributed to the overall increased viscosity.

scholarly journals Methyl Group Rotation and Tunnellingin Crystals of 5-Membered Ring Molecules

1988 ◽  
Vol 43 (1) ◽  
pp. 35-42 ◽  
Author(s):  
A.-S. Montjoie ◽  
W. Müller-Warmuth ◽  
Hildegard Stiller ◽  
J. Stanislawski
Keyword(s):  
Elevated Temperatures ◽  
Inelastic Neutron Scattering ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Inelastic Neutron ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Quantum Tunnelling ◽  
Spin Lattice

Abstract1H NMR spin-lattice relaxation times T1 and -if accessible -level-crossing peaks and inelastic neutron scattering spectra have been measured for solid 2-and 3-methylfuran, 2-and 3-methylthiophene, 3-and 4-methylpyrazole, 1-methylimidazole, and 5-methylisoxazole. From the tunnel splittings, the torsional excitations and the NMR relaxation rates, the molecular dynamics of the methyl rotators has been evaluated between the limits of quantum tunnelling at low temperatures and thermally activated random reorientation at elevated temperatures.

Relation and Correlation between NMR Relaxation Times, Diffusion Coefficients, and Viscosity of Heavy Crude Oils

2015 ◽  
Vol 119 (43) ◽  
pp. 24439-24446 ◽  
Author(s):  
Jean-Pierre Korb ◽  
Nopparat Vorapalawut ◽  
Benjamin Nicot ◽  
Robert G. Bryant
Keyword(s):  
Diffusion Coefficients ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Crude Oils ◽  
Nmr Relaxation Times ◽  
Heavy Crude

Self-diffusion in molten sodium chloride: a test of the applicability of the Nernst—Einstein equation

1957 ◽  
Vol 241 (1227) ◽  
pp. 554-567 ◽  
Keyword(s):  
Sodium Chloride ◽  
Einstein Equation ◽  
Diffusion Coefficients ◽  
Liquid Sodium ◽  
Einstein Relation ◽  
Transport Numbers ◽  
Self Diffusion ◽  
Capillary Method ◽  
Molten Sodium ◽  
The Individual

Self-diffusion coefficients of sodium and chlorine in molten sodium chloride have been determined by the capillary method with the aid of 22 Na and 36 Cl radio-tracers. The results can be represented by the expressions D Na = 8x 10 -4 exp (-4000/RT) and D Cl = 33 x 10 -4 exp (-8500/.RT). These values, when inserted in the Nernst-Einstein equation (A = (F 2 /RT) (D+ D-)), lead to a value of the equivalent conductance, A, which is about 40 % greater than that observed experimentally. The evidence that the diffusion coefficients of Na + and Cl - are similar in magnitude and that the activation energies are much smaller than the heat of vaporization of liquid sodium chloride, support the conclusions, derived from other evidence, that the free volume in the molten salt consists largely of holes, analogous to vacant lattice sites. On the basis of this model, the discrepancy in the Nernst-Einstein relation can readily be interpreted in terms of two diffusion mechanisms, one being normal vacancy diffusion of single ions, and the other a process in which no net charge is displaced in a unit step. It is suggested that the latter is the Seitz-Dienes mechanism of consecutive jumps of cation and anion in coupled vacancies. The interpretation mentioned enables the individual mobilities of Na + and Cl - ions to be determined, and hence their transport numbers can be calculated (t Na += 0.71, t Cl - = 0.29 at 935° C). The individual diffusion coefficients of the ions and of the coupled vacancies are in reasonable agreement with the Stokes-Einstein equation.

Ionic Dynamics in Plastic Crystal KNO2 Studied by 39K and 15N NMR

1994 ◽  
Vol 49 (1-2) ◽  
pp. 247-252 ◽  
Author(s):  
Motoko Kenmotsu ◽  
Hisashi Honda ◽  
Hiroshi Ohki ◽  
Ryuichi Ikeda ◽  
Tomoki Erata ◽  
...  
Keyword(s):  
Intermediate Phase ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
15N Nmr ◽  
Temperature Phase ◽  
Self Diffusion ◽  
Spin Lattice

AbstractThe spin-lattice relaxation time of 39K NMR observed in the low-temperature phase (T<264.1 K) of KNO2 is explained by the quadrupole mechanism contributed from a newly found NO2- motion. The in-plane C3 reorientation and the overvall NO2 rotation as well as the self-diffusion were shown in the intermediate phase (T ≤ 314.7 K) and the high-temperature plastic phase (T < melting point: 710 K), respectively, by observing 39K and 15N NMR relaxation times and 15N lineshapes.

Study of the Molecular Dynamics from Deuterium Zeeman and Quadrupolar NMR Relaxation of 4,4´-di-n-Heptylazoxybenzene in the Nematic and Smectic A Phases

1994 ◽  
Vol 49 (1-2) ◽  
pp. 311-319 ◽  
Author(s):  
C. Forte ◽  
M. Geppi ◽  
C. A. Veracini
Keyword(s):  
Diffusion Coefficients ◽  
Pulse Sequence ◽  
Pulse Sequences ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Aromatic Rings ◽  
Spin Lattice ◽  
Smectic A ◽  
Methylene Group ◽  
Negligible Contribution

Abstract The deuterium spin-lattice (T1Z) and quadrupolar (R1Q) relaxation times of the liquid crystal 4,4´-Heptyl-azoxybenzene (HAB), deuterated on the aromatic rings and the first methylene group of the chains, have been measured by means of the Jeener-Broekaert pulse sequence at two different frequencies (10 and 46.04 M Hz) and throughout the nematic and the smectic A phase. By applying suitable models, we have determined rotational and reorientational diffusion coefficients and evalu­ated the contribution of the different motions (internal, molecular and collective) to the relaxation. In particular we have found a non negligible contribution from order director fluctuations. A comparison between the T1Z and T1Q measurements performed by means of Jeener-Broekaert and Wimperis pulse sequences is also shown.

Solution and Diffusion in Silicone Rubber. I. A Comparison with Natural Rubber

1963 ◽  
Vol 36 (3) ◽  
pp. 642-650 ◽  
Author(s):  
R. M. Barrer ◽  
J. A. Barrie ◽  
N. K. Raman
Keyword(s):  
Statistical Theory ◽  
Natural Rubber ◽  
Silicone Rubber ◽  
Diffusion Coefficients ◽  
Molecular Size ◽  
Low Energy ◽  
Kcal Mole ◽  
Self Diffusion ◽  
Order Of Magnitude ◽  
And Diffusion

Abstract The diffusion and solubility of n- and isobutane and of n- and neopentane has been studied in the range 30° to 70° C, in polydimethylsiloxane rubbers. The solubilities are very similar to those in natural rubbers and show comparable agreement with the statistical theory of polymer penetrant mixtures. Diffusion coefficients are at least an order of magnitude greater in silicone than in natural rubbers. The very low energy of activation, ED, of about 4 kcal/mole is almost invariant among the hydrocarbons studied and is the same as for self-diffusion and viscous flow in this rubber. The low value of ED means that permeabilities of the hydrocarbons increase as the temperature falls. Because diffusion in silicones is less dependent upon molecular size and shape of penetrant than in natural rubber, the silicones are less selective though much more permeable separation barriers.

Boron-11, boron-10, and nitrogen-14 NMR relaxation rates and quadrupole coupling constants in BH3NH3

1992 ◽  
Vol 70 (9) ◽  
pp. 2420-2423 ◽  
Author(s):  
Glenn H. Penner ◽  
Stephen I. Daleman ◽  
Angela R. Custodio
Keyword(s):  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Coupling Constants ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Orbital Theory ◽  
Spin Lattice ◽  
Quadrupolar Coupling ◽  
Field Gradients

The 11B, 10B, and 14N spin–lattice relaxation times (T1) for aqueous solutions of BH3NH3 were measured by NMR spectroscopy. The results of this investigation are consistent with the nuclear quadrupolar coupling constants reported in previous nuclear quadrupolar resonance and microwave studies. The activation energy associated with rotational reorientation of BH3NH3 in aqueous solution is 11.7 ± 0.6 kJ/mol. Electric field gradients were calculated at various levels of abinitio molecular orbital theory, in order to obtain theoretical 14N and 11B quadrupolar coupling constants. At the highest level of calculation (CI(SD)/6-31G**//MP2/6-31G**), these are in agreement with recently reported microwave results but not with previously reported NQR experiments.

Characterisation of the Structure and Flow Behaviour of Model Chocolate Systems by Means of NMR and Rheology

2005 ◽  
Vol 15 (2) ◽  
pp. 98-111 ◽  
Author(s):  
Joachim Götz ◽  
Hartmut Balzer ◽  
Ruth Hinrichs
Keyword(s):  
Relaxation Times ◽  
Nmr Relaxation ◽  
Flow Behaviour ◽  
Model Systems ◽  
Capillary Rheometry ◽  
Self Diffusion ◽  
Relaxation Experiments ◽  
Nmr Relaxation Times ◽  
Flow Functions ◽  
Online Process

Abstract In order to characterise the structure and flow behaviour of model chocolate systems Nuclear Magnetic Resonance (NMR) and rheometry were used to determine the T1 - and T2 - NMR relaxation times and their corresponding flow functions. T1 and T2 characterise the molecular mobility of fluids and correlate with both the zero-shear-rate and infinity viscosity of various chocolate model systems (determined with rotational rheometry and capillary rheometry). Based on this correlation, NMR provides the possibility to determine characteristic viscosities of chocolate masses by means of NMR-relaxation experiments. The viscosities of chocolate masses are important process parameters, as they are used for quality control of the production process. An online process viscosimetry via T2 relaxation would allow the installation of an efficient process control and, thus, a process automation. This NMR application with comparatively short measuring times is especially interesting for disperse systems where the use of conventional rheometric techniques may cause large errors. The only prerequisite for the measurement of the viscosities using NMR is a previous calibration. This was performed with the help of rotational and capillary rheometry. The NMR self-diffusion experiments are especially appropriate to characterise the influence of emulsifiers on the structure and the flow behaviour of chocolate masses.

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