Adsorption of Aromatics in MFI-Type Zeolites

Experiments and Framework Flexibility in Monte Carlo Simulations

Journal article (2020)

Authors

S.A. Caro Ortiz Engineering Thermodynamics - Mechanical, Maritime and Materials Engineering
Erik Zuidema Shell Global Solutions B.V.
Desmond Dekker Shell Global Solutions International B.V.
Marcello S. Rigutto Shell Global Solutions International B.V.
D. Dubbeldam Engineering Thermodynamics - Mechanical, Maritime and Materials Engineering , Universiteit van Amsterdam
T.J.H. Vlugt Engineering Thermodynamics - Mechanical, Maritime and Materials Engineering
Research Group
Engineering Thermodynamics (Mechanical, Maritime and Materials Engineering) (TU Delft)
Copyright: © 2020 S.A. Caro Ortiz, Erik Zuidema, Desmond Dekker, Marcello Rigutto, D. Dubbeldam, T.J.H. Vlugt
DOI
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https://doi.org/10.1021/acs.jpcc.0c06096
More Info
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Published Date

2020

Language

English

Faculty

Mechanical, Maritime and Materials Engineering

Department

Process and Energy

Research Group

Engineering Thermodynamics

Abstract

Computer simulations of adsorption of aromatics in zeolites are typically performed using rigid zeolite frameworks. However, adsorption isotherms for aromatics are very sensitive to small differences in the atomic positions of the zeolite (Chem. Phys. Lett., 1999, 308, 155-159). This article studies the effect of framework flexibility on the adsorption of aromatics in MFI-type zeolites computed by grand-canonical Monte Carlo simulations. New experimental data of adsorption of ethylbenzene in a MFI-type zeolite at 353 K is presented. The adsorption of n-heptane, ethylbenzene, and xylene isomers is computed in three MFI-type zeolite structures. It is observed that the intraframework interactions in flexible framework models induce small but important changes in the atom positions of the zeolite and hence in the adsorption isotherms. Framework flexibility is differently "rigid": flexible force fields produce a zeolite structure that vibrates around a new equilibrium configuration with limited capacity to accommodate to a bulky guest molecule. The vibration of the zeolite atoms only plays a role at high loadings, and the adsorption is mainly dependent on the average positions of the atoms. The simulations show that models for framework flexibility should not be blindly applied to zeolites and a general reconsideration of the parametrization schemes for such models is needed.