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Monte Carlo simulations in the grand canonical and Gibbs ensembles were carried out to predict the adsorption isotherms of argon, nitrogen, and n-perfluorohexane in BCR-704, a faujasite-type calcium aluminosilicate with a Si/Al ratio of 1.6. Starting from existing force fields for the sorbate molecules and a transferable force field for all-silica zeolites, attempts were made to develop a force field that would reproduce the experimentally determined argon and nitrogen adsorption isotherms in BCR-704. However, good agreement for the nitrogen adsorption isotherm could only be obtained either for a set of force field parameters with a greatly reduced partial charge on the calcium cation or using a larger partial charge and assuming that co-adsorbed water molecules are present at the temperature used for the argon and nitrogen adsorption isotherms. Predictions of the adsorption isotherm for n-perfluorohexane in BCR-704 using the latter force field parameters and the FAU-X structure with a water/calcium ratio of 1 yield good agreement with the experimental benchmark data.
Bibliographical noteFunding Information:
Financial support from the National Science Foundation ( CBET-1159837 for the development of the TraPPE-zeo force field and part of the initial simulations carried out at the University of Minnesota), the Defense Threat Reduction Agency ( HDTRA1-10-1-0023 for research at Northwestern University), the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Award DE-FG02-12ER16362 (for research at the University of Minnesota and Northwestern University enabling the longer simulations), and a graduate School Fellowship (P.B.) is gratefully acknowledged. Part of the computer resources was provided by the Minnesota Supercomputing Institute.
- Adsorption isotherm
- Monte Carlo simulation