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Thermodynamically Consistent Methodology for Estimation of Diffusivities of Mixtures of Guest Molecules in Microporous Materials.

ABSTRACT: The Maxwell-Stefan (M-S) formulation, that is grounded in the theory of irreversible thermodynamics, is widely used for describing mixture diffusion in microporous crystalline materials such as zeolites and metal-organic frameworks (MOFs). Binary mixture diffusion is characterized by a set of three M-S diffusivities: ? ₁, ? ₂, and ? ₁₂. The M-S diffusivities ? ₁ and ? ₂ characterize interactions of guest molecules with pore walls. The exchange coefficient ? ₁₂ quantifies correlation effects that result in slowing-down of the more mobile species due to correlated molecular jumps with tardier partners. The primary objective of this article is to develop a methodology for estimating ? ₁, ? ₂, and ? ₁₂ using input data for the constituent unary systems. The dependence of the unary diffusivities ? ₁ and ? ₂ on the pore occupancy, ?, is quantified using the quasi-chemical theory that accounts for repulsive, or attractive, forces experienced by a guest molecule with the nearest neighbors. For binary mixtures, the same occupancy dependence of ? ₁ and ? ₂ is assumed to hold; in this case, the occupancy, ?, is calculated using the ideal adsorbed solution theory. The exchange coefficient ? ₁₂ is estimated from the data on unary self-diffusivities. The developed estimation methodology is validated using a large data set of M-S diffusivities determined from molecular dynamics simulations for a wide variety of binary mixtures (H₂/CO₂, Ne/CO₂, CH₄/CO₂, CO₂/N₂, H₂/CH₄, H₂/Ar, CH₄/Ar, Ne/Ar, CH₄/C₂H₆, CH₄/C₃H₈, and C₂H₆/C₃H₈) in zeolites (MFI, BEA, ISV, FAU, NaY, NaX, LTA, CHA, and DDR) and MOFs (IRMOF-1, CuBTC, and MgMOF-74).

SUBMITTER: Krishna R

PROVIDER: S-EPMC6705243 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Thermodynamically Consistent Methodology for Estimation of Diffusivities of Mixtures of Guest Molecules in Microporous Materials.

Krishna Rajamani R

ACS omega 20190802 8

The Maxwell-Stefan (M-S) formulation, that is grounded in the theory of irreversible thermodynamics, is widely used for describing mixture diffusion in microporous crystalline materials such as zeolites and metal-organic frameworks (MOFs). Binary mixture diffusion is characterized by a set of three M-S diffusivities: Đ 1, Đ 2, and Đ 12. The M-S diffusivities Đ 1 and Đ 2 characterize interactions of guest mo ...[more]

PMID: 31460481

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Thermodynamically Consistent Methodology for Estimation of Diffusivities of Mixtures of Guest Molecules in Microporous Materials.

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Thermodynamically Consistent Methodology for Estimation of Diffusivities of Mixtures of Guest Molecules in Microporous Materials.

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