Subramanya Nayak1, John Gleaves2, P. A. Ramachandran2, and MIlorad P. Dudukovic3. (1) Energy, Environment and Chemical Engineering, Washington University in St Louis, St Louis, MO 63130, (2) Energy, Environment and Chemical Engineering, Washington University in St. Louis, Saint Louis, MO 63130, (3) Energy, Environmental and Chemical Engineering, Washington University in Saint Louis, One Brookings Drive, Saint Louis, MO 63130
This study seeks to develop a fundamental understanding of the diffusion and adsorption-desorption mechanism of hydrocarbon molecules in nanopores zeolites, specifically beta and ultrastable Y (USY) zeolites. Macroscopic TAP (Temporal Analysis of Products) pulse response experiments (1), along with appropriate theoretical models, was used to study transport and interactions of probe molecules on nanopores zeolites. In TAP pulse response experiments small amount of probe molecule were pulsed in TAP microreactor under high vacuum (10-8 torr), as a result transport through the bed of zeolites happens in Knudsen regime. Under high vacuum condition external mass transfer resistance was completely absent and molecules move independently. TAP pulse response experiments were very reproducible and the diffusivities estimated using this macroscopic technique compares well with those determined using microscopic techniques, such as Pulse-Field Gradient NMR (2).
References
1. 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.
2. Nijhuis T. A., van den Broeke., Linder M. J. G., van de Graf, Kapteijn, Makke K, Moulijn J. A. 1999, “Measurement and modeling of transient adsorption and diffusion process in microporous materials” Chem Engg Sci., 54 4423.