Xenon sorption

Davis and coworkers [104] studied " Xe NMR of xenon adsorbed in several SAPOs, ALPOs, and Y zeolites. From a comparison of the xenon chemical shift extrapolated to zero pressure, these authors concluded that Xe atoms feel significantly smaller electrostatic fields and field gradients in the aluminophosphates compared to aluminosilicates. The extrapolated chemical shift decreased from 97 ppm in erionite to 60 ppm in Y zeolite and to 27 ppm in AIPO4-5, with the values for SAPOs being intermediate to Y zeolites and AlPOs as would be expected from the acidity trends. They concluded as well that SAPO-37 does not contain separate aluminophosphate and aluminosilicate islands. Dumont et al. [105] also carried out xenon NMR experiments in SAPO-37. From xenon sorption capacity and the decrease in the chemical shift, their conclusion was that the framework of calcined SAPO-37 is unstable when exposed to moist air. 

Xenon has also been applied to the study of humic substances. Previously, there had only been one study on the investigation of surface of soil materials using xenon, namely a study of xenon sorption on to the montmorillonite clay surface. Magusin et al. explored the use of xenon NMR to probe the average volume to area ratio in the pore networks of humidified sand as well as carbon black and kaolin model systems. High-pressure xenon NMR experiments were carried out and showed a broad resonance around 45-55 ppm for three different samples of carbon black with different particle sizes. By comparison, the kaolin and humidified sand showed broad resonances near 8 ppm and zero, respectively. The humidified sand spectrum showed xenon spectral intensity at negative ppm values. The authors derived an expression for the pore size given the measured xenon chemical shift and a constant related to xenon adsorption on the surface. 

SE-measurements were done with a Spectral Ellip-someter ES4G from Sopra, with a Xenon high-pressure 1 2174-01 light source from Hamamatsu, a double monochromator with a slit width of 400 xm, a spectral range from 230-930 nm and a spectral resolution of 0.05 nm. The evaluation of the measurements was carried out by Film Wizard 32 with the Cauchy-model. The observation of the relative changes in the refractive index at 589.3 nm was sufficient to monitor the sorption of the analytes. 

Wacker J. F. (1989) Laboratory simulation of meteoritic noble gases III. Sorption of neon, argon, krypton, and xenon on carbon elemental fractionation. Geochim. Cosmochim. Acta 53, 1421-1433. 

The nature of xenon adsorbed on a metal single crystal surface (Ir(l 11)) was studied by 129Xe NMR spectroscopy.669 2H and 129Xe NMR spectra were used to follow the sorption of CD4 or Xe by a flexible microporous polymer, catena-bis(dibenzoylmethanato)(4,4 -bipy)nickel(II).670... 

At MAS speeds above 5 kHz, two major fluorine-19 resonances can be resolved in the acid form of the perfluorosulfonate ionomer Nafion (DuPont trademark). Xenon-129 NMR is used as an alternative probe of morphologically based sorption environments in Nafion. The xenon-129 spectrum of xenon sorbed into Nafion under a pressure of 12 atm shows two resonances corresponding to two sorption environments. ... 

Wacker JF, Zadnik MG, Anders E (1985) Laboratory simrrlation of meteoritic noble gases. I. Sorption of xenon on carbon Trapping experiments. Geochim Cosmochim Acta 49 1035-1048 Walter FM, Barry DC (1991) Pre- and main sequence evolution of solar activity. In The Sun in Time. Sonett CP, Giampapa MS, Matthews MS (eds) University of Arizona Press, Tucson, Arizona, p633-657... 

Zadnik MG, Wacker JF, Lewis RS (1985) Laboratory simulation of meteoiitic noble gases. II. Sorption of xenon on carbon Etching and heating experiments. Geochim Cosmochim Acta 49 1049-1059... 

Nanopore Structure Analysis. - MRI has provided direct visualization of gaseous xenon and methane in the void spaces of aerogels, offering unique information and insights into the pore structure and molecular diffusivities of occluded sorbates. Pore structure and sorption properties of silica aerogels... 

Xenon-129 NMR as a Probe of Polymer Sorption Sites A New View of Structure and Transport... 

At the lowest temperature (-900C) and at the lowest pressure (3 atm), the xenon spectrum for the sorbed line is rather broad, possibly asymmetric or bimodal. This would indicate an asymmetric or bimodal distribution of sorption environments on a fairly short length scale. More complicated descriptions of amorphous environments might consider the effects of the presence of an amorphous/crystalline interfacial region or of two sorption environments as proposed in the dual mode model. The low pressure, low temperature spectra being discussed have the poorest signal to noise and better spectra are needed to characterize this situation properly. 

The spectra of xenon-129 in high density polyethylene are relatively simple, with only a single resonance about 200 ppm for the free gas resonance. The sorbed xenon-129 is present in the amorphous phase and the line width increases with decreasing temperature and xenon pressure. At the lowest temperature and pressure, the line width is about 50 ppm and the line shape is asymmetric, indicating a distribution of sorption environments in the amorphous component. 

PIMl-COl-40 show outstanding sorption capacities for xenon, even greater than for the highly permeahle polymer poly[l-(trimethylsilyl)-l-propyne] (PTMSP Figure... 

The pore structure of a solid is generally characterized by its porosity, the pore diameter, the pore shape, the pore connectivity, the pore size distribution, the specific pore volume, and the specific surface area [8], These parameters are obtained from sorption measurements with nitrogen, intrusion techniques, radiation scattering, pycnometry, thermoporometry, calorimetric measurements, xenon... 

Xe NMR spectra in some heterogeneous polymer systems consist of two resonances which collapse to a single resonance as a function of temperature. Two different resonances arise from spatially separated, distinct sorption environments and spectral collapse occurs when xenon atoms diffuse from one environment to the other at a sufficiently fast rate. ... 

C NMR spectra of CH4 in an AIPO4-II molecular sieve have revealed exchange effects between adsorbed and nonadsorbed methane gas. The diffusion of a mixture of methane and xenon in the zeoHte siUcahte has been studied by pulsed field gradient NMR spectroscopy. In situ H MAS NMR studies of the H/D exchange of deuterated propane adsorbed on H-ZSM-5 have been reported. C MAS NMR spectroscopy has been used to study the initial stages of propane activation over H-ZSM-5, and sorption properties of hnear alkanes in ferrierite. Protonated sites on sulfate-promoted zirconium oxide catalysts have been studied using H NMR spectroscopy. NMR relaxation and self-diffusion of pentane, neopentane, dodecane, benzene, cyclohexane, and... 

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