(207b) Transport in Nanoporous Beta and Ultrastable – Y Zeolites

The key role of nanopore diffusion (especially in pore sizes < 2 nm) and adsorption/ desorption in zeolites on catalytic processes and adsorptive separation techniques is widely acknowledged (Karger and Ruthven, 1992). Diffusion in zeolites is not as straightforward as diffusion in gas and liquid, in the sense that the molecules have to move through channels of molecular dimensions. The diffusivities in zeolites strongly depend on pore morphology, interaction of guest molecules with pore wall, the size of the guest molecule, the chemical properties of guest molecules, and channel loading. As a result, major discrepancies are observed in diffusivity values calculated for different hydrocarbons in different zeolite structures. The objectives of this work are to understand and quantify the nanopore diffusivities and adsorption/ desorption constants at zero channel loading for light hydrocarbons. This study is mainly based on the experimental evidence provided by temporal analysis of products (TAP) (Gleaves et al., 1988) method and the interpretation of data by appropriate theoretical models.

References:

Gleaves, J. T., Ebner, J. R., Kuechler, T. C. 1988. Temporal analysis of products (TAP)-a unique catalyst evaluation system with submillisecond time resolution. Catal. Rev. Sci. Engng., (30), 49-116.

Karger J., and Ruthven D. M., 1992, ?Diffusion in Zeolites? Wiley, New York, U.S.A