Can alkane isomers be separated? Adsorption equilibrium and kinetic data for hexane isomers and their binary mixtures on MFI |
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Authors: | Alexandre F P Ferreira Marjo C Mittelmeijer-Hazeleger Alfred Bliek |
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Institution: | (1) HIMS—Van ’t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands |
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Abstract: | In this study we present a global overview of the adsorption behavior of hexane isomers on MFI. With an experimental approach
that couples a manometric technique with Near Infrared (NIR) spectroscopy, which has been recently developed, we did address
adsorption kinetic properties of n-hexane, 2-methylpentane, 2,2-dimethylbutane and 2,3-dimethylbutane, and their binary mixtures. The adsorption equilibrium
properties of the binary mixtures were also assessed using the same technique. Whereas the adsorption isotherms and heats
of adsorption for single components have been studied by a manometric technique coupled with a micro calorimeter. The differential
heats of adsorption of n-hexane increase slightly with loading, on the other hand the heat of adsorption of branched hexanes exhibits a decrease with
loading. The diffusion rates on MFI of n-hexane, 2-methylpentane and 2,3-dimethylbutane are in the same order of magnitude. However, the diffusion rate of 2,2-dimethylbutane
is two orders of magnitude lower than rates of the other isomers. In the binary mixtures the components interact and the difference
between the diffusion rates of the components decreases. The MFI zeolite presents equilibrium selectivity towards the less
branched isomers. In conclusion, a separation process for linear/mono-branched alkanes + double-branched alkanes, has to be
based on its equilibrium properties and not based on adsorption kinetics. |
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Keywords: | Zeolites Alkanes Isotherms Differential heat of adsorption |
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