For the trans-2-butene-NaA zeolite system, the rate of adsorption was determined by the intracrystalline diffusion. The effect of transfer in the transport pores and the final rate of dissipation of the heat of adsorption could be neglected. The effective intra-crystalline diffusion coefficient at 303K was equal to 0.8·x 10-16m2/s. Adsorption of trans-2-butene by Na8Mg2A zeolite with stepwise change in pressure gave kinetic curves described by an internal equation for the kinetics of isothermal adsorption. The effective intracrystalline coefficients were a function of the degree of filling and increased from 2.5·10-16 to 32·x 10-16m2/s with increasing filling from 0.44 to 1.93mmol/g. Self-diffusion coefficients calculated using the Darken equation also increased slightly with filling from 2.3 x 10-16 to 3.7·x 10-16m2/s. Significant differences between calculated and experimental curves for adsorption of trans-2-butene by microcrystalline NaA in the case of very convex adsorption isotherms was attributed to the effect of heat upon intracrystalline diffusion.

Study of Intracrystalline Diffusion and Conduction in Zeolites. Communication 3. Kinetics of Adsorption of Trans-2-Butene by NaA and NaMgA Zeolites. R.Broddak, A.M.Voloshchuk, V.A.Gorlov, M.M.Dubinin, B.Kuhlmann, L.A.Falko, R.Scholner: Bulletin of the Academy of Sciences of the USSR Division of Chemical Science, 1985, 34[3], 455-60

Figure 2

Diffusivity of Alkanes in NaCaA Zeolite

(a: methane, b: ethane, c: n-propane, d: n-butane, lines without data-points

are for [downwards]: n-pentane, n-hexane, n-heptane)