Kinetic patterns of adsorption and desorption in silicalite-1 were studied for linear and branched C6 alkanes of uniform shape and size by using the tapered element oscillating microbalance method (table 39). Unlike the conventional gravimetric method, the present technique minimized external mass and heat transfer limitations in transient experiments, due to the high flow-rate of the carrier gas through the sample bed, without affecting measurements. Model equations in which the thermodynamic factor for intracrystalline diffusivities was taken into account, permitted the determination of diffusivities from adsorption and desorption patterns in the non-linear adsorption range. The diffusivities determined at zero coverage for the studied adsorptives, which covered 3 orders of magnitude (10−12 to 10-15m2/s), were in good agreement with those obtained using zero-length column and chromatography methods. It was shown that the present technique could be easily used not only for steady-state and equilibrium measurements, but also for transient up-take and desorption experiments.

Diffusion of Linear and Branched C6 Alkanes in Silicalite-1 Studied by the Tapered Element Oscillating Microbalance. W.Zhu, F.Kapteijn, J.A.Moulijn: Microporous and Mesoporous Materials, 2001, 47[2–3], 157–71

Table 39

Diffusion of Alkanes in Silicalite-1

continued

Table 39 (continued)

Diffusion of Alkanes in Silicalite-1