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Quantitating Diffusion Enhancement in Pore Hierarchies
D Schneider1, S Hwang2, J Haase2,3
1Innovation Center Computer Assisted Surgery (ICCAS), Institute at the Medical Faculty, Leipzig University, Semmelweisstraße 14, 04103 Leipzig, Germany.
Langmuir : the ACS Journal of Surfaces and Colloids
|September 15, 2022
Summary
This study models hierarchically porous zeolites using a channel system. Kinetic Monte Carlo simulations confirm the two-region model for molecular diffusion, providing analytical expressions for transport enhancement.
Area of Science:
- Materials Science
- Chemical Engineering
- Physical Chemistry
Background:
- Hierarchically porous materials, such as mesoporous zeolites, are crucial in catalysis and separation.
- Understanding molecular transport within these complex structures is key to optimizing their performance.
- Existing models often simplify the intricate pore network, necessitating more accurate simulation approaches.
Purpose of the Study:
- To develop and validate a model for molecular diffusion in hierarchically porous systems.
- To compare simulation results with established diffusion models.
- To derive analytical expressions for quantifying transport enhancement in such materials.
Main Methods:
- Utilizing a microporous continuum model with perpendicular channels.
- Employing kinetic Monte Carlo (kMC) simulations to determine transient molecular uptake profiles.
- Applying the two-region (Kärger) model for molecular diffusion analysis.
Main Results:
- kMC simulation results show excellent agreement with the two-region model.
- Identified two limiting cases: fast exchange and slow exchange.
- Derived simple analytical expressions for molecular uptake rate and transport enhancement in these limiting cases.
Conclusions:
- The developed model accurately represents molecular diffusion in hierarchically porous zeolites.
- Analytical expressions provide a straightforward method for quantifying transport enhancement.
- The findings offer valuable insights for designing and optimizing porous materials for various applications.
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