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Title page for ETD etd-03202014-111806

Type of Document Dissertation
Author Mitchell, Lucas Alexander
Author's Email Address lucas.a.mitchell@vanderbilt.edu
URN etd-03202014-111806
Title Adsorption of light gases and gas mixtures on zeolites and nanoporous carbons
Degree PhD
Department Chemical Engineering
Advisory Committee
Advisor Name Title
M. Douglas LeVan Committee Chair
G. Kane Jennings Committee Member
Peter T. Cummings Committee Member
Sandra J. Rosenthal Committee Member
  • DFT
  • Henrys Law
  • mixtures
  • adsorption
  • zeolites
  • carbon
Date of Defense 2014-03-13
Availability unrestricted
The ability to accurately predict mixture adsorption equilibrium is vital for

future gas separation technologies. This research concentrates on the investigation

and prediction of adsorption equilibrium of pure components and gas mixtures. The

systems studied are of importance to the field of personal medical oxygen generation.

Two commercial adsorbents are investigated: a LiLSX zeolite and a carbon

molecular sieve. Adsorption equilibria are measured on the LiLSX zeolite for nitrogen

and oxygen, both as pure gases and binary mixtures. The binary measurements

consist of Henry’s law behavior with one component in excess as well as binary

isotherms for a range of compositions. Binary Henry’s law behavior is modeled by

adding virial excess mixture coefficients to the ideal adsorbed solution theory. The

mixture coefficients are evaluated solely from the binary Henry’s law behavior, and

the binary isotherms for a range of compositions are predicted accurately. Adsorption

isotherms are measured on the carbon molecular sieve for oxygen, nitrogen, and argon

at pressures up to 100 bar. The capacities of the gases are higher than expected, with

the carbon molecular sieve having capacities higher than BPL activated carbon and

capacities similar to a superactivated carbon.

An approach to model adsorption of pure gases using classical density functional

theory is developed. Fundamental measure theory is used as an accurate

method to describe the hard sphere interaction potential. To address the intermolecular

and intramolecular attractive potentials, a version of the statistical associating

fluid theory is used. The new approach models adsorption of molecules of increasing

complexity on flat walls, with predictions comparing well with simulation data in the

literature. The new approach is extended by incorporating the 10-4-3 Steele potential

to describe slit-shaped carbon pores. Nitrogen is first modeled inside the pores, where

the density profiles are combined to produce a pore size distribution and describe the

nitrogen isotherm. Pore density profiles are modeled for n-pentane and, using the

pore size distribution obtained from nitrogen, a pentane isotherm is shown to agree

well with experimental data.

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