Force Field Parametrization through Fitting on Inflection Points in Isotherms

Dubbeldam, David; Calero, Sofı́a; Vlugt, Thijs J. H.; Krishna, Rajamani; Maesen, Theo L. M.; Beerdsen, E.; Smit, Berend

doi:10.1103/physrevlett.93.088302

Cited by 158 publications

(209 citation statements)

References 24 publications

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“…23−25 A united-atom force field that uses the 12-6 Lennard-Jones potential model was developed for alkanes and alkenes in the zeolites by Smit and co-workers, and it has been validated to reproduce the vapor liquid equilibrium of guest molecules. 26,27 The simulated adsorption isotherms computed using this force field show excellent agreement with the experimental data for several different known zeolite structures, and thus, we assumed the force field to be transferable to all pure-silica zeolite structures.…”

Section: ■ Methodsologymentioning

confidence: 78%

Large-Scale Computational Screening of Zeolites for Ethane/Ethene Separation

et al. 2012

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Large-scale computational screening of thirty thousand zeolite structures was conducted to find optimal structures for separation of ethane/ethene mixtures. Efficient grand canonical Monte Carlo (GCMC) simulations were performed with graphics processing units (GPUs) to obtain pure component adsorption isotherms for both ethane and ethene. We have utilized the ideal adsorbed solution theory (IAST) to obtain the mixture isotherms, which were used to evaluate the performance of each zeolite structure based on its working capacity and selectivity. In our analysis, we have determined that specific arrangements of zeolite framework atoms create sites for the preferential adsorption of ethane over ethene. The majority of optimum separation materials can be identified by utilizing this knowledge and screening structures for the presence of this feature will enable the efficient selection of promising candidate materials for ethane/ethene separation prior to performing molecular simulations. ■ INTRODUCTIONEthene is one of the largest production chemical products today due in large part to the demand for polyethylene. Global annual production capacity exceeds 152 million tonnes and is projected to grow by 20% over the next 5 years. 1 Large-scale production of ethene involves separating it from other light hydrocarbons, including methane, ethane, and propane. To achieve acceptable purity, these compounds are typically separated using a series of low-temperature distillations at high pressure. 2 The low relative volatility of the ethane-ethene mixture makes the separation energy and capital intensive. Several other approaches for separating light olefins and paraffins have been proposed in the literature. These include physical and chemical absorption processes, extractive distillation, membranes, and adsorption onto porous materials. 2−8 The similarity of molecular sizes in these mixtures contributes to the difficulty of the separation. Adsorbent materials can potentially provide better separation of these components. By interacting more strongly with one component of the mixture, an adsorbent may provide an adsorbed mixture richer in one component or limit the diffusion of one component for a kinetic separation. 3 Previous efforts with porous materials have looked into both physically adsorbing materials, such as zeolites, 7 and chemically adsorbing materials, such as metal−organic frameworks (MOFs) with open metal sites. 5,6 In addition, zeolitic imidazolate frameworks and specifically ZIF-8 has been investigated as a potential candidate for performing kinetic separation via the enhanced diffusivity of ethene compared to ethane within the material. 4 For this work, we focus on zeolite structures as a possible candidate for adsorption-based separation and focus on ethane/ethene separation.Zeolites are porous aluminosilicates with pore diameters on the order of 0.5 to 5 nm. While roughly 200 zeolite topologies have been identified in experiments, only a handful of these materials are used on an industrial scale...

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Section: ■ Methodsologymentioning

confidence: 78%

Large-Scale Computational Screening of Zeolites for Ethane/Ethene Separation

et al. 2012

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“…17 The positions of the framework atoms are fixed during the MC simulations as the rigidity of zeolite framework has been shown to be a reasonable approximation in obtaining accurate adsorption properties. 18 All of the force fields in this work come from Garcia-Perez et al and Dubbeldam et al 19,20 The gas−host interactions are precomputed and stored inside an energy grid in GPU global memory before the MC simulation, and utilized as a lookup table during the MC cycles. 21 The creation of the energy grid is especially important to block out (i.e., set to high energy) regions within porous materials that are diffusively inaccessible within the experimental time scale.…”

Section: ■ Grand Canonical Monte Carlo Methods For Porous Materialsmentioning

confidence: 99%

Efficient Monte Carlo Simulations of Gas Molecules Inside Porous Materials

Kim

Smit

2012

J. Chem. Theory Comput.

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Monte Carlo (MC) simulations are commonly used to obtain adsorption properties of gas molecules inside porous materials. In this work, we discuss various optimization strategies that lead to faster MC simulations with CO 2 gas molecules inside host zeolite structures used as a test system. The reciprocal space contribution of the gas−gas Ewald summation and both the direct and the reciprocal gas−host potential energy interactions are stored inside energy grids to reduce the wall time in the MC simulations. Additional speedup can be obtained by selectively calling the routine that computes the gas−gas Ewald summation, which does not impact the accuracy of the zeolite's adsorption characteristics. We utilize two-level densitybiased sampling technique in the grand canonical Monte Carlo (GCMC) algorithm to restrict CO 2 insertion moves into lowenergy regions within the zeolite materials to accelerate convergence. Finally, we make use of the graphics processing units (GPUs) hardware to conduct multiple MC simulations in parallel via judiciously mapping the GPU threads to available workload. As a result, we can obtain a CO 2 adsorption isotherm curve with 14 pressure values (up to 10 atm) for a zeolite structure within a minute of total compute wall time.

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“…38 The interaction parameters of alkanes listed in Table I for use in molecular simulations of confined systems are obtained uniquely and accurately through fitting on experimental isotherms with inflection points. 39,40 Recently, it was shown that these parameters also give near-quantitative agreement for collective diffusivities for ethane in silicalite compared to neutron-scattering experiments. 41 Details on the simulations can be found in Refs.…”

Section: A Force Field Parameters For Adsorption and Diffusion Of Almentioning

confidence: 99%

Molecular simulation of loading-dependent diffusion in nanoporous materials using extended dynamically corrected transition state theory

Dubbeldam

Beerdsen

Vlugt

et al. 2005

The Journal of Chemical Physics

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209

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A dynamically corrected transition state theory method is presented that is capable of computing quantitatively the self-diffusivity of adsorbed molecules in confined systems at nonzero loading. This extention to traditional transition state theory is free of additional assumptions and yields a diffusivity identical to that obtained by conventional molecular-dynamics simulations. While molecular-dynamics calculations are limited to relatively fast diffusing molecules, our approach extends the range of accessible time scales significantly beyond currently available methods. We show results for methane, ethane, and propane in LTL-and LTA-type zeolites over a wide range of temperatures and loadings, and demonstrate the extensibility of the method to mixtures.

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Force Field Parametrization through Fitting on Inflection Points in Isotherms

Cited by 158 publications

References 24 publications

Large-Scale Computational Screening of Zeolites for Ethane/Ethene Separation

Large-Scale Computational Screening of Zeolites for Ethane/Ethene Separation

Efficient Monte Carlo Simulations of Gas Molecules Inside Porous Materials

Molecular simulation of loading-dependent diffusion in nanoporous materials using extended dynamically corrected transition state theory

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