Sorption of argon and nitrogen on network types of zeolites and aluminophosphates

Reichert, H.; Müller, Ulrich; Unger, Klaus K.; Grillet, Y.; Rouquérol, F.; Rouquérol, J.; Coulomb, J.P.

doi:10.1016/s0167-2991(08)61359-2

Cited by 23 publications

(10 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Such a phenomenon cannot be observed at T = 77.3 K, because of the too-low-pressure value of the substep ( P sub = 4.0 × 10 -2 Torr), which prevents the possibility of measuring the substep desorption branch. In addition, we have to notice that the relative pressure of the substep adsorption branch increases when the temperature increases, P sub / P o = 4.5 10 -2 at T = 96.5 K. The hysteresis loop, related to the sorbed phase transition, has been already found for the system nitrogen/silicalite I …”

Section: Resultsmentioning

confidence: 68%

Sorption Properties of AlPO₄-5 and SAPO-5 Zeolite-like Materials

et al. 1998

View full text Add to dashboard Cite

We have studied by volumetric adsorption isotherm measurements the sorption properties of different AlPO4-5 or SAPO-5 samples, for sorbate species characterized by a large range of molecular size: D2, Kr, Ar, C2D2, CO2, CH4, CF4, and C(CH3)4. The highest sorption capacities, Q max, greatly depend on the sorbate molecular size. A difference of 1 order of magnitude is observed between hydrogen and neopentane. In addition, we have found that the sorption capacities of the four analyzed AlPO4-5 or SAPO-5 samples vary by almost a factor of 2. This result clearly shows that, as a consequence of the one-dimensional character of the AFI micropore network, Q max is very sensitive to small amounts of crystalline defects or impurities. For methane, Q max is equal to 6 mol/uc, a quantity that is not compatible with the commonly accepted value of the internal diameter of the AlPO4-5 micropore diameter, ⌀M = 7.3 Å. Moreover, an interesting phase transition phenomenon has been observed during the sorption of krypton and methane, a result that can be the consequence of the good parametric agreement between such sorbate species and the AlPO4-5 inner surface.

show abstract

Section: Resultsmentioning

confidence: 68%

Sorption Properties of AlPO₄-5 and SAPO-5 Zeolite-like Materials

et al. 1998

View full text Add to dashboard Cite

show abstract

“…But this does not necessarily mean that the distribution of different sorption centers between crystallographically determined sites, such as segments of 1 a" « 0.45 mmol/cm3 u" = 1.81 mmol/cm3 0.0091 1/Pa 0.14 1/Pa sinusoidal and straight channels, obeys that factor. In this respect, recent findings of sorption state transitions between "disordered phases" and "crystalline-like solid phases" for various gases in MFI,33 34 expressed also as isotherm hysteresis at low temperature and loading, are of interest. To correlate the above probability of distribution to any identified number of sorption centres or types of sorption states may well be a task of further studies.…”

Section: Resultsmentioning

confidence: 99%

Sorbate Immobilization in Molecular Sieves. Rate-Limiting Step for n-Hexane Uptake by Silicalite-I

Micke¹,

Buelow²,

Kočiřı́k³

et al. 1994

J. Phys. Chem.

View full text Add to dashboard Cite

Sorption uptake of hydrocarbons by molecular sieves with nonuniform micropore systems such as MFI-type zeolites may be governed by a complex of mechanisms instead of pure intracrystalline diffusion. In the particular case of sorption kinetics of n-hexane on silicalite-I, processes occur on the microcrystal level which comprise both Fickian diffusion and sorbate immobilization/mobilization. The rate processes connected with the immobilization of the sorbing species are due to both geometrical constraints and differences in the interaction potential topology between straight and sinusoidal channels within the zeolite crystals. A full quantitative description of this complex transport phenomenon has been derived. A strategy has been developed to reduce the three-parameter problem to that with one parameter only, which is the prerequisite of a practical parameter-fitting procedure. In this way, rate coefficients of the particular composite processes were calculated on the basis of experimental uptake data. The latter were fitted by use of a Volterra integral equation technique.The coefficient of intracrystalline diffusion of the system n-hexaneMFI structure at 323 K amounts to 5 x m2/s, which is a value independent of loading (as the product of the immobilization and mobilization rates is). It is impossible to interpret the measured uptake curves utilizing a model that encompasses intracrystalline diffusion only (Le., neglecting the presence of sorbate immobilization). Neglecting the strong deviation in uptake curve shape by utilizing equations for pure intracrystalline diffusion (e.g., the method of statistical moments), diffusivities were obtained that are lower by up to 3 orders of magnitude.

show abstract

“…As a matter of fact this time for N 2 in NaA is very long at 193 K; it is then difficult to perform isotherms at lower temperatures because of the temperature regulation. At 78 K, the diffusivity of N 2 in NaA is completely hindered, meanwhile O 2 continues to diffuse easily in this zeolite; the Na cations in the window aperture impede totally the intracrystalline diffusion of N 2 . − This fact has been used to verify the quantity which can be condensed in the intergrain volume.…”

Section: Methodsmentioning

confidence: 99%

Molecular Interactions in Nanoporous Adsorbents. Adsorption of N₂ and O₂ in Zeolites with Cavities or Channels: Na₁₂A, Ca₆A, NaX, and Decationated Mordenite

1996

View full text Add to dashboard Cite

The adsorption of two small molecules in porous crystals presenting void volumes of different shapes (cavities of ∼12 Å diameter, channels of ∼6 Å diameter) is measured in a large range of temperatures and pressures. The data analysis shows off the difference in the intermolecular forces between N2 and O2 molecules; in condensed phases the molecule-molecule interaction is repulsive and it is more repulsive for N2. The density of the adsorbed phase is compared with that of the liquid at three temperatures; that points out the confinement effect which is dominant in the channels.

show abstract

Sorption of argon and nitrogen on network types of zeolites and aluminophosphates

Cited by 23 publications

References 8 publications

Sorption Properties of AlPO₄-5 and SAPO-5 Zeolite-like Materials

Sorption Properties of AlPO₄-5 and SAPO-5 Zeolite-like Materials

Sorbate Immobilization in Molecular Sieves. Rate-Limiting Step for n-Hexane Uptake by Silicalite-I

Molecular Interactions in Nanoporous Adsorbents. Adsorption of N₂ and O₂ in Zeolites with Cavities or Channels: Na₁₂A, Ca₆A, NaX, and Decationated Mordenite

Contact Info

Product

Resources

About

Sorption of argon and nitrogen on network types of zeolites and aluminophosphates

Cited by 23 publications

References 8 publications

Sorption Properties of AlPO4-5 and SAPO-5 Zeolite-like Materials

Sorption Properties of AlPO4-5 and SAPO-5 Zeolite-like Materials

Sorbate Immobilization in Molecular Sieves. Rate-Limiting Step for n-Hexane Uptake by Silicalite-I

Molecular Interactions in Nanoporous Adsorbents. Adsorption of N2 and O2 in Zeolites with Cavities or Channels: Na12A, Ca6A, NaX, and Decationated Mordenite

Contact Info

Product

Resources

About

Sorption Properties of AlPO₄-5 and SAPO-5 Zeolite-like Materials

Sorption Properties of AlPO₄-5 and SAPO-5 Zeolite-like Materials

Molecular Interactions in Nanoporous Adsorbents. Adsorption of N₂ and O₂ in Zeolites with Cavities or Channels: Na₁₂A, Ca₆A, NaX, and Decationated Mordenite