Diffusion Model for Gas Replacement in an Isostructural CH 4 –CO 2 Hydrate System
Guest exchange in clathrates is a complex activated phenomenon of the guest–host cage interaction on the molecular-scale level. To model this process, we develop a mathematical description for the nonequilibrium binary permeation of guest molecules during gas replacement based on the microscopic “ho...
| Published in: | The Journal of Physical Chemistry C |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
ACS (American Chemical Society)
2017
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| Subjects: | |
| Online Access: | https://oceanrep.geomar.de/id/eprint/50441/ https://oceanrep.geomar.de/id/eprint/50441/1/Salamatin%20et%20al.pdf https://doi.org/10.1021/acs.jpcc.7b04391 |
| Summary: | Guest exchange in clathrates is a complex activated phenomenon of the guest–host cage interaction on the molecular-scale level. To model this process, we develop a mathematical description for the nonequilibrium binary permeation of guest molecules during gas replacement based on the microscopic “hole-in-cage-wall” diffusive mechanism. The transport of gas molecules is envisaged as a series of jumps between occupied and empty neighboring cages without any significant lattice restructuring in the bulk. The gas exchange itself is seen as two-stage swapping initiated by almost instantaneous formation of a mixed hydrate layer on the hydrate surface followed by a much slower permeation-controlled process. The model is constrained by and validated with available time-resolved neutron diffraction data of the isostructural CH4 guest replacement by CO2 in methane hydrate, a process of possible importance for the sequestration of CO2 with concomitant recovery of CH4 in marine gas hydrates. |
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