Measurement of the intracrystalline self-diffusion of xenon in zeolites by the NMR pulsed field gradient technique

Heink, W.; Kaerger, Joerg; Pfeifer, H.; Stallmach, Frank

doi:10.1021/ja00162a019

Cited by 87 publications

(49 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Pulsed-field gradient measurements give Xe diffusion rate constants in zeolites (A, Y and ZSM-5) of the order of 10-8-10 -9 m2/s [20][21][22]. This means that, in these materials, at room temperature the movement of the xenon averages its interactions over a great number of zeolite cages and channels on the NMR timescale.…”

Section: Influence Of Diffusionmentioning

confidence: 99%

129Xe-NMR of physisorbed xenon used as a probe for the study of microporous solids

1995

View full text Add to dashboard Cite

show abstract

Section: Influence Of Diffusionmentioning

confidence: 99%

129Xe-NMR of physisorbed xenon used as a probe for the study of microporous solids

1995

View full text Add to dashboard Cite

show abstract

“…One approach is the Pulse Field Gradient (PFG) technique, the utility of which has already been demonstrated [11][12][13]. However, the PFG technique requires specialized apparatus and therefore has not seen widespread use.…”

Section: Introductionmentioning

confidence: 99%

Application of129Xe 2D-EXSY NMR to intra- and interparticle exchange in zeolites

1995

View full text Add to dashboard Cite

2D-EXSY NMR methods were used to explore diffusion between different domains in zeolites on two very different length scales. Measurements were made on xenon-containing samples consisting of a mixture of NaX and NaY zeolite particles which give distinct resonance lines. The cross peaks observed were interpreted in terms of interparticle exchange, and exchange rates were measured as a function of particle size. This kind of experiment with a length scale of microns to mm should be useful in model studies of diffusion in packed catalyst beds. Measurements also were made to study exchange on a much smaller length scale between the main-channel and side-pocket sites in samples of microcrystalline Na-mordenite. Exchange rates and site occupancies were measured as a function of ternperature, yielding activation energies for xenon desorption and intersite diffusion. Also, information was obtained on the distribution of inequivalent side-pocket sites which leads to the large xenon NMR linewidths for this type of site.

show abstract

“…; PFG NMR technique Heink et al 1990) attributed to the utilized method. For many systems the apparent intra-crystalline diffusivity depends upon the length scale over which the diffusivity is measured (Cejka et al 2007).…”

Section: Fig 11mentioning

confidence: 99%

Adsorption and diffusion of Xenon in a granulated nano-NaY zeolite

et al. 2012

View full text Add to dashboard Cite

Henry's law constant and crystal diffusivity of xenon in the granulated nano-NaY zeolite were measured by the pulse gas chromatography method. For this purpose the moments of response peaks of xenon were analyzed. The effect of extra column parts of the utilized chromatographic system was also considered by analyzing the moments of the response peak which was obtained by pulse injection of inert gas of helium into the carrier gas of nitrogen. In addition, the measurement of average velocity of the carrier gas regarding the pressure drop in the extra column parts of the system attributed to precise results. By carrying out the experiments at various temperatures in the range of 30-110°C the heat of adsorption and activation energy of crystal diffusivity were estimated. In order to find the binder effect on the adsorption of and diffusion into granules, the aforementioned parameters were also measured for the binderless granules of macron sized NaY zeolite. Results revealed that although the adsorption of xenon on the binder of bentonite was negligible, the diffusion resistance created by this binder was significant such that the effective crystal diffusivity in the granules with 25 % binder was determined to be 96 percent lower than the granules with no binder. NomenclatureD AB Molecular diffusivity (m 2 /s) D ax The axial dispersion coefficient (m 2 /s) D p Diffusion coefficient in pores of granules (m 2 /s) D μ The effective diffusivities (m 2 /s) D μ0 Crystal diffusivity constant (m 2 /s) E μ The activation energy of crystal diffusivity (kJ/mol) K Dimensionless Henry's law constant based upon the crystal volume K 0 Adsorption constant K m External mass transfer coefficient (m/s) L Length of packed column (m) Q 0 The heat of adsorption (kJ/mol) R Radius of granules (m) Re Reynolds number (ρV ·2R)/µ R μ Radius of zeolitic crystal (m) Sc Schmidt number (μ/ρD AB ) Sh Sherwood number (K m 2R/D AB ) T Temperature (K) V Superficial velocity (m/s) under non-isobaric conditions Greek Letter ε b The bed porosity ε p Granule porosity μ Fluid viscosity (kg/m s) μ 1 The first normalized moment (s) μ 2 The second central moment (s 2 ) ρ Density (kg/m 3 ) σ Standard deviation τ Tortuosity factor 76 Adsorption (2012) 18:75-86

show abstract

Measurement of the intracrystalline self-diffusion of xenon in zeolites by the NMR pulsed field gradient technique

Cited by 87 publications

References 0 publications

129Xe-NMR of physisorbed xenon used as a probe for the study of microporous solids

129Xe-NMR of physisorbed xenon used as a probe for the study of microporous solids

Application of129Xe 2D-EXSY NMR to intra- and interparticle exchange in zeolites

Adsorption and diffusion of Xenon in a granulated nano-NaY zeolite

Contact Info

Product

Resources

About