GCMC simulations in zeolite MFI and activated carbon for benzene removal from exhaust gaseous streams

Cosoli, Paolo; Fermeglia, Maurizio; Ferrone, Marco

doi:10.1080/08927020802350919

Cited by 4 publications

(3 citation statements)

References 31 publications

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“…All carbon atoms in the graphite surface model were fixed at their crystallographic coordinates. Although an approximate approach, this method has been used successfully to model adsorption phenomena on carbon surfaces. ,− …”

Section: Simulation Methodsmentioning

confidence: 99%

Alcohol and Thiol Adsorption on (Oxy)hydroxide and Carbon Surfaces: Molecular Dynamics Simulation and Desorption Experiments

2012

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Classical molecular dynamics simulations were used to investigate the interaction of methyl, ethyl, and n-propyl alcohols and thiols with the hydroxylated basal surfaces of aluminum hydroxide and iron oxyhydroxide, as well as a model graphite surface. Comparisons were made to concurrently run desorption experiments investigating the interaction of methyl, ethyl, and n-propyl alcohols with aluminum hydroxide and activated carbon. The metal (oxy)hydroxide surfaces represent the basal surfaces of the neutral end-member layered double hydroxides gibbsite and lepidocrocite, respectively, while the graphite surface is a simplified model of the pore walls in activated carbon used in the chemisorption experiment. Adsorption enthalpies obtained from simulations at infinite adsorbate dilution show that adsorption is greatly favored on the hydroxylated surfaces compared to the graphite surface, with the ethyl molecules adsorbing most favorably. Heats of desorption calculated from chemisorption experiments show the same increased interaction strength for the alcohols on the aluminum hydroxide surface compared with activated carbon, with the most favorable interaction being ethanol with the aluminum hydroxide surface. In general, simulations show that alcohols adsorb more strongly than thiols on the hydroxylated surfaces, while the reverse is true on the graphite surface. The structure of adsorbed monolayers was obtained from simulations of a liquidlike layer above each surface. As expected, monolayer surface densities decreased with increasing molecule size. The hydroxylated surfaces were found to be amphoteric with respect to both alcohol and thiol adsorption, and primary adsorption sites facilitate hydrogen bonding between the adsorbate and several surface hydroxyl groups. Alcohols and thiols adsorb at much larger distances to the graphite surface, resulting in the smaller adsorption enthalpies.

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Section: Simulation Methodsmentioning

confidence: 99%

Alcohol and Thiol Adsorption on (Oxy)hydroxide and Carbon Surfaces: Molecular Dynamics Simulation and Desorption Experiments

2012

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“…The adsorption of aromatics in MFI-type zeolites has also been studied by molecular simulations. Commonly, Monte Carlo (MC) simulations in the grand-canonical ensemble (GCMC) are used to compute sorbate loadings as a function of temperature and pressure in a zeolite framework. − Several studies where MC is used to investigate adsorption of aromatics in MFI-type zeolites can be found in the literature. − Snurr et al computed adsorption isotherms of benzene and p -xylene in MFI-type zeolites. Large differences in the loadings are found when using the MFI Ortho and Para structures.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Aromatics in MFI-Type Zeolites: Experiments and Framework Flexibility in Monte Carlo Simulations

et al. 2020

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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 MFItype 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.

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“…The adsorption and diffusion of aromatics in MFI-type zeolites has also been studied by molecular simulations . Commonly, Monte Carlo (MC) simulations in the grand-canonical ensemble are used to compute sorbate loadings as a function of temperature and pressure in a zeolite framework. − Several studies where MC is used to study the adsorption of aromatics in MFI-type zeolites can be found in the literature. ,− Zeolites are commonly considered as very rigid structures as their atomic bonds and angles are highly constrained. , Computer simulations of the adsorption of hydrocarbons in zeolites are typically performed assuming that the zeolite framework taken from crystallographic data is a rigid structure. ,, Nevertheless, Clark and Snurr showed that the computed adsorption isotherms are sensitive to small differences in the atom positions of the zeolite. Framework flexibility is observed to play a role only if the adsorbate fits tightly in the zeolite pore .…”

Section: Introductionmentioning

confidence: 99%

Effects of Framework Flexibility on the Adsorption and Diffusion of Aromatics in MFI-Type Zeolites

et al. 2020

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We systematically study how the degree of framework flexibility affects the adsorption and diffusion of aromatics in MFI-type zeolites as computed by Monte Carlo simulations. It is observed that as the framework is more flexible, the zeolite structure is inherently changed. We have found that framework flexibility has a significant effect on the adsorption of aromatics in MFI-type zeolites, especially at high pressure. Framework flexibility allows the zeolite framework to accommodate to the presence of guest aromatic molecules. For very flexible zeolite frameworks, loadings up to two times larger than that in a rigid zeolite framework are obtained at a given pressure. We assessed the “flexible snapshot” method, which captures framework flexibility using independent snapshots of the framework. We have found that this method only works well when the loadings are low. This suggests that the effect of the guest molecules on the zeolite framework is important. Framework flexibility lowers the free-energy barriers between low energy states, increasing the rate of diffusion of aromatics in the straight channel of MFI-type zeolites for many orders of magnitude compared to a rigid zeolite framework. The simulations show that framework flexibility should not be neglected and that it significantly affects the diffusion and adsorption properties of aromatics in an MFI-type zeolite.

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GCMC simulations in zeolite MFI and activated carbon for benzene removal from exhaust gaseous streams

Cited by 4 publications

References 31 publications

Alcohol and Thiol Adsorption on (Oxy)hydroxide and Carbon Surfaces: Molecular Dynamics Simulation and Desorption Experiments

Alcohol and Thiol Adsorption on (Oxy)hydroxide and Carbon Surfaces: Molecular Dynamics Simulation and Desorption Experiments

Adsorption of Aromatics in MFI-Type Zeolites: Experiments and Framework Flexibility in Monte Carlo Simulations

Effects of Framework Flexibility on the Adsorption and Diffusion of Aromatics in MFI-Type Zeolites

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