The Shape Selectivity of Paraffin Hydroconversion on TON-, MTT-, and AEL-Type Sieves

Maesen, Theo L. M.; Schenk, Merijn; Vlugt, Thijs J. H.; Jonge, J.P.de; Smit, Berend

doi:10.1006/jcat.1999.2673

Cited by 141 publications

(144 citation statements)

References 36 publications

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“…The CBMC simulations of the sorption isotherms at 403 K are shown in Figure 19. 190 The reason for the inversion of the hierarchy compared to the case of MFI is again entropic. AFI consists of cylindrical channels of 0.73 nm radius, which is large enough to accommodate the bulky 22DMB, and thus, there is no configurational penalty for these molecules.…”

Section: Other Zeolitesmentioning

confidence: 99%

“…32 This linear relationship between the Gibbs free energy of formation of transition states and that of products is an example of the semiempirical Brønsted-Evans-Polanyi relationship. 32,492,493 According to this relationship, the prohibitively high Gibbs free energy of formation (and adsorption) of RR-dimethylalkane products inside TON-type zeolites 190,490,491,494 is an indication of a similarly high Gibbs free energy of formation of the transition state for RR-dimethylalkane formation, so that transition state shape selectivity will inhibit RRdimethylalkane product formation inside TON-type zeolite Figure 53. The hydrocracking precursors and products obtained by applying the mechanism shown in Figure 52 to C 10 .…”

Section: Transition State Shape Selectivitymentioning

confidence: 99%

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Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

2008

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Section: Other Zeolitesmentioning

confidence: 99%

Section: Transition State Shape Selectivitymentioning

confidence: 99%

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

2008

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“…1,2,5,6,24,55,56 Zeolites exist in a wide variety of structures. Currently, over 130 different topologies are known.…”

Section: Zeolite Structuresmentioning

confidence: 99%

Loading Dependence of the Diffusion Coefficient of Methane in Nanoporous Materials

2006

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In this work, we use molecular simulations to study the loading dependence of the self-and collective diffusion coefficients of methane in various zeolite structures. To arrive at a microscopic interpretation of the loading dependence, we interpret the diffusion behavior in terms of hopping rates over a free-energy barrier. These free-energy barriers are computed directly from a molecular simulation. We show that these free-energy profiles are a convenient starting point to explain a particular loading dependence of the diffusion coefficient. On the basis of these observations, we present a classification of zeolite structures for the diffusion of methane as a function of loading: three-dimensional cagelike structures, one-dimensional channels, and intersecting channels. Structures in each of these classes have their loading dependence of the free-energy profiles in common. An important conclusion of this work is that diffusion in nanoporous materials can never be described by one single effect so that we need to distinguish different loading regimes to describe the diffusion over the entire loading range.

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“…[1][2][3][4] This adsorption behavior is usually quantified by means of the adsorption isotherm, which is the quantity of hydrocarbons adsorbed at a given temperature and pressure. Experimentally, the determination of adsorption isotherms can be quite time consuming, because of the slow diffusion of hydrocarbons in the pores of a zeolite.…”

Section: Introductionmentioning

confidence: 99%

Molecular simulations of the adsorption of cycloalkanes in MFI-type silica

Schenk

Smit

Maesen

et al. 2005

Phys. Chem. Chem. Phys.

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A new force field for the simulation of the adsorption of cycloalkanes in nanoporous silica affords a significant improvement over any previously employed force field. The simulated isotherms reproduce the most salient features in the experimental isotherms extremely well. The study of cyclo-pentane, -hexane, and -heptane adsorption in MFI-type silica indicates an inflection for cyclopentane but not for cyclohexane at intermediate pressure. If corroborated by experiments, such an inflection point would afford an excellent calibration point for further force field developments. At low pressures, mixture isotherms of cyclohexane and n-hexane show a temperature dependence on the selectivity in accordance with recent results by J. P. Fox and S. P. Bates, J. Phys. Chem., 2004, 108, 17136. This dependence is caused by a difference in temperature dependence of the Henry coefficient for both molecules. At high pressures entropy effects due to packing always favor the sorption of n-hexane. Furthermore, the influence of the flexibility of the zeolite framework on the adsorption of these rather bulky molecules is investigated. It is found that this influence of the flexibility on the adsorption of cyclohexane is as small as with n-alkanes.

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The Shape Selectivity of Paraffin Hydroconversion on TON-, MTT-, and AEL-Type Sieves

Cited by 141 publications

References 36 publications

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

Loading Dependence of the Diffusion Coefficient of Methane in Nanoporous Materials

Molecular simulations of the adsorption of cycloalkanes in MFI-type silica

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