Structural Analysis by Neutron Diffraction of Nitrogen Sorbed Phases on Silicalite I and ZSM-5 (Si / Al = 23) Zeolites

Coulomb, J.P.; Llewellyn, Philip; Martin, Céline; Grillet, Y.; Rouquérol, J.

doi:10.1007/978-1-4613-1375-5_25

Cited by 4 publications

(2 citation statements)

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“…In a recent study by Coulomb et al, the N 2 and CO adsorption in silicalite was shown to have two phase transitions or three different adsorbed phases. The adsorption of Ar, Kr, O 2 , and H 2 has one phase transition or two adsorbed phases, and other small molecules such as CH 4 , C 2 H 6 , Xe, and SiF 4 have no phase transition.…”

Section: Introductionmentioning

confidence: 96%

Adsorption Equilibria of C₁to C₄Alkanes, CO₂, and SF₆on Silicalite

et al. 1998

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Adsorption isotherms of methane, ethane, propane, n-butane, isobutane, carbon dioxide, and sulfur hexafluoride were measured gravimetrically on silicalite crystals at temperatures ranging from 3 to 81 °C and at pressures up to 2000 kPa. A virial equation was used to correlate the experimental data and to calculate the isosteric heats of adsorption and the limiting heats of adsorption at zero loading. The adsorption isotherms of isobutane exhibit inflection points at loadings of 4−6 molecules/unit cell in a certain temperature range. This unusual adsorption behavior is attributed to adsorption of isobutane in different locations of the channel system.

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Section: Introductionmentioning

confidence: 96%

Adsorption Equilibria of C₁to C₄Alkanes, CO₂, and SF₆on Silicalite

et al. 1998

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“…In MFI zeolites, this is the case for various adsorbates. For long alkanes, the stepped behavior of the adsorption isotherm has been attributed to entropic or packing effect in the microporous network. , For other adsorbates such as argon, krypton, dioxygen, dinitrogen or carbon monoxide, , but also for larger ones like benzene, toluene, ethylbenzene, p -xylene, and bromobenzene, − the origin of these stepped isotherms was largely debated in the literature. One of the explanations is a structural transition of the host framework taking place upon fluid adsorption.…”

Section: Introductionmentioning

confidence: 99%

Structural Changes in Nanoporous MFI Zeolites Induced by Tetrachloroethene Adsorption: A Joint Experimental and Simulation Study

et al. 2011

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A joint experimental and molecular simulation study was performed to investigate the adsorption of tetrachloroethene on two MFI zeolites, ZSM-5 with a Si/Al ratio of 26.5, and silicalite-1, which is the pure silica form of ZSM-5. Adsorption isotherms and isosteric heats of adsorption of tetrachloroethene were measured and compared to molecular simulation results. Experimental curves for both MFI zeolites show a step at loading of 4 molecules 3 uc -1 that was interpreted in terms of a structural change of the host framework. A thermodynamic analysis based on the osmotic ensemble scheme allowed attributing this step to a symmetry change from ORTHO (orthorhombic form with Pnma symmetry) to PARA (orthorhombic form with P2 1 2 1 2 1 symmetry) of both adsorbents upon micropore filling. The adsorption mechanism was also characterized. The first tetrachloroethene molecules adsorbs in the channel intersections of the MONO (monoclinic form with P2 1 /n11 symmetry) and ORTHO structures of silicalite-1 and ZSM-5, respectively. Then, the above-mentioned structural change from ORTHO to PARA occurs, leading to a filling of sinusoidal channels until saturation was reached, i.e. ∼8 molecules.uc -1 for silicalite-1 and 6 molecules 3 uc -1 for ZSM-5. In addition, simulation results indicate that the sodium cations in the ZSM-5 zeolite are located at the channel intersections during the whole adsorption process.

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