Single-pulse temporal analysis of products experiments were used to obtain estimates of intra-particle diffusion coefficients and a better insight into adsorption–desorption dynamics and equilibria for isobutane and n-butane in commercially available beta and USY zeolites. This technique provided a unique way of directly estimating transport and sorption processes at extremely low surface coverages, in the absence of an inert carrier stream, with no external mass transfer resistance, and with a negligible thermal effect. The use of a thin zone TAP reactor configuration permitted the use of small zeolite particles without causing high bed resistance. A theoretical model that considered transport and adsorption–desorption phenomena in the inter-particle and intra-particle space was developed and solved numerically. Numerical experiments demonstrated the ability of the model to represent the actual experimental response curves. It was shown that reliable values of intra-particle diffusivity (figure 8) and adsorption–desorption constants could be obtained from the TAP single pulse experiments when the three dimensionless constants of the model (ratio of characteristic diffusion time in the micro-reactor to characteristic diffusion time in zeolite pore, ratio of characteristic desorption time to characteristic adsorption time, ratio of characteristic diffusion time in the micro-reactor to characteristic desorption time) fell within a prescribed range.

Transport and Sorption Studies in Beta and USY Zeolites via Temporal Analysis of Products (TAP). S.V.Nayak, M.Morali, P.A.Ramachandran, M.P.Dudukovic: Journal of Catalysis, 2009, 266[2], 169–81

Table 11

Diffusivity of Na in Al-Doped Zeolite