Dynamics of CO<sub>2</sub> Adsorption on Amine Adsorbents.
2. Insights Into Adsorbent Design
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Abstract
Packed bed breakthrough experiments are reported for
commercial
zeolite 13X and 3-aminopropyl-functionalized SBA-15 silica materials
with three different amine loadings. Mass and heat transfer dynamics
for all four materials are modeled successfully. Amine adsorbents
with open pores are found to exhibit faster mass diffusion rates compared
to zeolite 13X. When amine loading is increased by coupling aminopropyl
groups, premature breakthrough combined with a long tail is observed.
Contrary to conventional physisorbants, finite heat losses to the
column wall do not explain the long breakthrough tail. A rate model
that accounts for heterogeneity in diffusion was found to accurately
capture the breakthrough shape of the high loading material. Batch
uptake measurements support the hypothesis that slow diffusion through
the polymer phase is what hampers adsorption kinetics in the high
amine loading adsorbent. The results emphasize the importance of designing
materials that are not overloaded with amine sites, as excessive amine
loadings can lead to depressed adsorption kinetics and premature column
breakthrough