Exchange relaxometry of flow at small Péclet numbers in a glass bead pack

Olaru, Alexandra M.; Kowalski, Julia; Sethi, Vaishali; Blümich, Bernhard

doi:10.1016/j.jmr.2012.04.015

Cited by 9 publications

(2 citation statements)

References 33 publications

(43 reference statements)

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“…On the other hand, exchange in non-equilibrium leads to asymmetry in 2D NMR maps. This has been observed, for example, in 2D chemical exchange spectra for chemical reactions involving different sites (Lacabanne et al, 2022), for the spread of hyperpolarization by spin diffusion (Björgvinsdóttir et al, 2021), and for slow flow across porous media in relaxation exchange maps (Olaru et al, 2012).…”

Section: Introductionmentioning

confidence: 85%

Monte-Carlo Analysis of Asymmetry in Three-Site Relaxation Exchange: Probing Detailed Balance

Bluemich

Parziale

Augustine

2023

Preprint

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Abstract. The question is investigated if three-site diffusive relaxation exchange in thermodynamic equilibrium can lead to exchange maps, which are asymmetric for fluids confined to pores. Asymmetry reports circular flow of particles between the relaxation sites which disagrees with detailed balance according to which the particle exchange between any pair of sites must be balanced. Vacancy diffusion and gas diffusion of particles confined to two-dimensional pores were modeled in Monte-Carlo simulations. For each particle move in vacancy diffusion on a 2D checkerboard grid, one of the eight neighboring destination cells was identified on the basis the jump probability calculated from an empirical approximation of the free energy. Gas diffusion was simulated without thermodynamic interaction on a simulation grid which was up to 104 times finer than the particle diameter. It was found that up to 1 % of all particles moves coherently in closed paths. This motion is attributed to pore resonance corresponding to diffusion eigenmodes. The study shows that detailed balance of multi-site exchange does not apply for a small fraction of particles when the exchange is impacted by topological constraints.

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Section: Introductionmentioning

confidence: 85%

Monte-Carlo Analysis of Asymmetry in Three-Site Relaxation Exchange: Probing Detailed Balance

Bluemich

Parziale

Augustine

2023

Preprint

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“…Inverse Laplace Transform (ILT) by Venkataramanan, Song and Hürlimann [37] and Hürlimann and Venkataramanan [38], pseudo-3D experiments for the study of diffusive exchange, like , represent undoubtedly the most complex and detail-rich approaches [14,[39][40][41][42]. The pulse sequence consists of two CPMG loops separated by a longitudinal storage period called mixing time ( ), during which diffusive coupling and/or chemical exchange may take place [43][44][45].…”

Section: Introductionmentioning

confidence: 99%

Spatially-resolved 1H NMR relaxation-exchange measurements in heterogeneous media

Terenzi

Sederman

Mantle

et al. 2019

Journal of Magnetic Resonance

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In the last decades, the 1 H NMR relaxation-exchange (REXSY) technique has become an essential tool for the molecular investigation of simple and complex fluids in heterogeneous porous solids and soft matter, where the mixing-time-evolution of crosscorrelated peaks enables a quantitative study of diffusive exchange kinetics in multicomponent systems. Here, we present a spatially-resolved implementation of the correlation technique, named , based on one-dimensional spatial mapping along using a rapid frequency-encode imaging scheme. Compared to other phase-encoding methods, the adopted MRI technique has two distinct advantages: (i) is has the same experimental duration of a standard (bulk) measurement, and (ii) it provides a high spatial resolution. The proposed method is first validated against bulk measurements on homogeneous phantom consisting of cyclohexane uniformly imbibed in finely-sized α-Al 2 O 3 particles at a spatial resolution of 0.47 mm; thereafter, its performance is demonstrated, on a layered bed of multi-sized α-Al 2 O 3 particles, for revealing spatiallydependent molecular exchange kinetics properties of intra-and inter-particle cyclohexane as a function of particle size. It is found that localised spectra provide well resolved cross peaks whilst such resolution is lost in standard bulk data. Future prospective applications of the method lie, in particular, in the local characterisation of mass transport phenomena in multi-component porous media, such as rock cores and heterogeneous catalysts.3

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Quantifying Liquid-Solid Mass Transfer in a Trickle Bed Using $${T}_{2}-{T}_{2}$$ Relaxation Exchange NMR

Elgersma,

Zheng,

Avrantinis

et al. 2023

Appl Magn Reson

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Measurement of the liquid-solid mass transfer coefficient within a trickle bed (i.e. gas-liquid flow within a packed bed) of porous silica pellets is achieved through the use of $${T}_{2}-{T}_{2}$$ T 2 - T 2 relaxation exchange nuclear magnetic resonance (NMR). Compared to many conventional measurement techniques, the NMR method enables measurement of mass transport using pellets of real commercial interest. Mass transfer coefficients measured using the NMR technique over a range of liquid Reynolds number, 0.2 $$\le R{e}_{\mathrm{L}}\le $$ ≤ R e L ≤ 1.4, are compared to a number of literature correlations, with values measured using the NMR method falling within the range predicted by the correlations. The results demonstrate the importance of considering both the flow conditions and the type of pellets used to develop mass transport correlations in trickle beds. This novel NMR application may be utilized in the future to screen catalyst pellets in trickle beds for optimal mass transport properties.

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Exchange relaxometry of flow at small Péclet numbers in a glass bead pack

Cited by 9 publications

References 33 publications

Monte-Carlo Analysis of Asymmetry in Three-Site Relaxation Exchange: Probing Detailed Balance

Monte-Carlo Analysis of Asymmetry in Three-Site Relaxation Exchange: Probing Detailed Balance

Spatially-resolved 1H NMR relaxation-exchange measurements in heterogeneous media

Quantifying Liquid-Solid Mass Transfer in a Trickle Bed Using $${T}_{2}-{T}_{2}$$ Relaxation Exchange NMR

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