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.

Adsorption isotherms of n-pentane to n-decane were measured gravimetrically on silicalite crystals at temperatures ranging from 30 to 150 °C and at pressures up to 1333 Pa. The virial equation was used to correlate the experimental data and to calculate the Henry's law constants and the heats of adsorption at zero loading. The limiting heats of adsorption of hexane and heptane are slightly higher than those reported in literature. The isotherms of these two compounds also exhibit an unusual convex region in a certain temperature range. The saturation capacities decrease from pentane to decane with a significant drop observed from heptane to octane.

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How many guests? Interference microscopy is used to monitor the concentration of guest molecules in a ferrierite zeolite. The micropore diffusivities are determined as a function of loading through the microscopic application of Fick's second law. This method can be used to study isotropic and anisotropic diffusion, as well as to locate and quantify surface barriers and internal defects.

Evolution of internal concentration profiles of methanol in 2-D pore structure of ferrierite crystal was measured in the pressure range of 0 to 80 mbar with the help of the recently developed interference microscopy technique. The measured profiles showed that both a surface barrier and internal diffusion controlled the kinetics of adsorption/desorption. Furthermore, they indicated that in the main part of the crystal, the z-directional 10-ring channels were not accessible to methanol and that the transport of methanol mainly occurred via 8-ring y-directional channels. The roof-like part of the crystal was almost instantaneously filled/emptied during adsorption/desorption, indicating accessible 10-ring channels in this section. The measured profiles were analyzed microscopically with the direct application of Fick's second law, and the transport diffusivity of methanol in ferrierite was determined as a function of adsorbed phase concentration. The transport diffusivity varied by more than 2 orders of magnitude over the investigated pressure range. Transport diffusivities, calculated from measured profiles from small and large pressure step changes, were all found to be consistent. Simulated concentration profiles obtained from the solution of Fick's second law with the calculated functional dependence of diffusivities on concentration compared very well with the measured concentration profiles, indicating validity and consistency of the measured data and the calculated diffusivities. The results indicate the importance of measuring the evolution of concentration profiles as this information is vital in determining (1) the direction of internal transport, (2) the presence of internal structural defects, and (3) surface/internal transport barriers. Such detailed information is available neither from common macroscopic methods since, they measure changes in macroscopic properties and use model assumptions to predict the concentration profiles inside, nor from microscopic methods, since they only provide information on average displacement of diffusing molecules.