Sorption and diffusion parameters from vacuum-TPD of ammonia on H-ZSM-5

This work aims at filling the gap in vacuum-TPD modeling methodology for microporous samples. The specific objective was to assess and distinguish external and internal mass transfer effects from the intrinsic sorption dynamics during temperature-programmed desorption, as illustrated by ammonia on H...

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Bibliographic Details
Published in:Chemical engineering science 2013-02, Vol.89, p.40-48
Main Authors: Kouva, Sonja, Kanervo, Jaana, Schüβler, Florian, Olindo, Roberta, Lercher, Johannes A., Krause, Outi
Format: Article
Language:English
Subjects:
adsorption
Ammonia
Chemical engineering
desorption
Dynamic tests
Dynamical systems
Dynamics
heat
Kinetics
Mass transfer
Mathematical modeling
NH3-TPD
Porous materials
Sorption
temperature
Transient response
Zeolites
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Summary:This work aims at filling the gap in vacuum-TPD modeling methodology for microporous samples. The specific objective was to assess and distinguish external and internal mass transfer effects from the intrinsic sorption dynamics during temperature-programmed desorption, as illustrated by ammonia on H-ZSM-5. The external mass transfer pattern was confirmed to be free of bed-depth effects, the intraparticle mass transfer resistance proved to be significant in the ammonia-TPD system, and equipment-related artefacts showed to be negligible based on preliminary experiments. Thus a consistent set of 10 TPD curves was collected, including two adsorption temperatures, three heating rates and two separate particle fractions. The experimental data was successfully modeled with a system including intraparticle mass transfer phenomena and intrinsic sorption kinetics. By combining a transient kinetic approach to a well-designed set of high-quality experiments vacuum-TPD can provide decoupled information on mass transfer and sorption for porous materials as we demonstrate in this work. [Display omitted] ► TPD is widely used to characterize porous solids; also provides kinetic information. ► Novel modeling methodology is established to describe the vacuum-TPD system. ► TPD modeling results: intraparticle diffusion and adsorption equilibrium parameters. ► Example: NH3-TPD of H-ZSM-5—adsorption and mass transfer parameters are reported.
ISSN:0009-2509
1873-4405
DOI:10.1016/j.ces.2012.11.025