The statistical thermodynamics of sorption in zeolites is studied. The multicomponent sorbate is regarded as a localized assembly of quasi-independent subsystems each contained in a sorption cavity of the microporous sorbent. Molecular exchange among the subsystems as well as between the assembly and the gas phase that is in thermodynamic equilibrium with the sorbate is allowed. Molecular statistics of the sorbate is worked out in detail with respect to a few representative ensembles. In effecting thermodynamic association of theoretical results, a quasi-grand partition function is related to the sorption system which is in complete thermal and material but only in partial mechanical equilibrium with its surroundings. Fundamental thermodynamic equations of the sorbate are derived, and their conditions of integrability with respect to physical variables are interpreted in relation to 'surface effects' and certain operational restrictions connected with the sorption system. A study of small-system thermodynamics further helps to clarify the behaviour of individual subsystems, especially as regards fluctuations. A quantitative theoretical study of the sorption of krypton and methane in Linde molecular sieve 5A is attempted. By means of analytic mathematics and Monte Carlo methods, statistical thermodynamic functions of the subsystems are calculated from relevant physical parameters. Some interesting features of the techniques used are also discussed. Interactions of the sorbate and sorbent, and in particular the effects due to exchangeable cations in the sorption cavities, are investigated. To indicate the degree of localization of the sorbate, probability distribution functions of the sorbate molecules within a specific subsystem, together with their distribution densities among all the subsystems are presented. Thermodynamic functions of the assembly are then calculated and compared with available experimental data. Finally, the usefulness of various approaches to the study of sorption in zeolites is assessed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:623077 |
| Date | January 1968 |
| Creators | Limcharoen, Preedeeporn |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/15950 |
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