Transport and sorption studies in beta and USY zeolites via temporal analysis of products (TAP)

Single pulse TAP experiments were chosen for obtaining estimates of intra-particle diffusion coefficients and better insight into adsorption–desorption dynamics and equilibria for isobutane and n-butane in commercially available beta and USY zeolite. This technique provides a unique way of directly estimating transport and sorption processes at extremely low surface coverage (θi → 0), 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 enables the use of small zeolite particles without causing high bed resistance. A theoretical model that considers transport and adsorption–desorption phenomena in the inter-particle and intra-particle space is developed and numerically solved. Numerical experiments demonstrate the ability of the model to represent the actual experimental response curves. It is shown that reliable values of intra-particle diffusivity and adsorption–desorption constants can be obtained from the TAP single pulse experiments when the three dimensionless constants of the model τpiτpi (the ratio of characteristic diffusion time in the micro-reactor to characteristic diffusion time in zeolite pore), KeqiKeqi (the ratio of characteristic desorption time to characteristic adsorption time), and kdi∗ (the ratio of characteristic diffusion time in the micro-reactor to characteristic desorption time) fall within a prescribed range.

Our paper reports the methodology to obtain reliable estimates of intra-particle diffusivities and adsorption–desorption constants in large pore beta and USY zeolites by using single pulse TAP response experiments.Figure optionsDownload high-quality image (89 K)Download as PowerPoint slide