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

Smit, Berend; Maesen, Theo L. M.

doi:10.1021/cr8002642

Cited by 669 publications

(676 citation statements)

References 532 publications

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“…The Henry's constant and the pure component adsorption isotherms for CO 2 , CH 4 and N 2 gas molecules were computed using our highly efficient graphics processing unit code 26,27 , and the Ideal Adsorbed Solution Theory was then applied to estimate the mixture component uptake to reproduce the aforementioned conditions relevant to methane separations 39 . In our simulations, all interactions between gas molecules and the zeolite framework were described at the classical force field level with atomic partial charges (for Coulombic interactions) and 12-6 Lennard-Jones parameters (for van der Waals interactions) taken from Garcia-Perez et al 40 The framework was assumed to be rigid throughout the simulations, an assumption that is considered to be reasonable in zeolite structures 41 .…”

Section: Methodsmentioning

confidence: 99%

New materials for methane capture from dilute and medium-concentration sources

et al. 2013

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Methane (CH 4 ) is an important greenhouse gas, second only to CO 2 , and is emitted into the atmosphere at different concentrations from a variety of sources. However, unlike CO 2 , which has a quadrupole moment and can be captured both physically and chemically in a variety of solvents and porous solids, methane is completely non-polar and interacts very weakly with most materials. Thus, methane capture poses a challenge that can only be addressed through extensive material screening and ingenious molecular-level designs. Here we report systematic in silico studies on the methane capture effectiveness of two different materials systems, that is, liquid solvents (including ionic liquids) and nanoporous zeolites. Although none of the liquid solvents appears effective as methane sorbents, systematic screening of over 87,000 zeolite structures led to the discovery of a handful of candidates that have sufficient methane sorption capacity as well as appropriate CH 4 /CO 2 and/or CH 4 /N 2 selectivity to be technologically promising.

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Section: Methodsmentioning

confidence: 99%

New materials for methane capture from dilute and medium-concentration sources

et al. 2013

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“…In fact, the assumption of constant diffusion coefficient is commonly used in applications. 32 Grand Canonical Monte Carlo Simulations. GCMC simulations were utilized to obtain the gas uptake value as a function of fugacity.…”

Section: ■ Methodsmentioning

confidence: 99%

Large-Scale Screening of Zeolite Structures for CO₂ Membrane Separations

Kim

Abouelnasr²,

Lin³

et al. 2013

J. Am. Chem. Soc.

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ABSTRACT:We have conducted large-scale screening of zeolite materials for CO 2 /CH 4 and CO 2 /N 2 membrane separation applications using the free energy landscape of the guest molecules inside these porous materials. We show how advanced molecular simulations can be integrated with the design of a simple separation process to arrive at a metric to rank performance of over 87 000 different zeolite structures, including the known IZA zeolite structures. Our novel, efficient algorithm using graphics processing units can accurately characterize both the adsorption and diffusion properties of a given structure in just a few seconds and accordingly find a set of optimal structures for different desired purity of separated gases from a large database of porous materials in reasonable wall time. Our analysis reveals that the optimal structures for separations usually consist of channels with adsorption sites spread relatively uniformly across the entire channel such that they feature well-balanced CO 2 adsorption and diffusion properties. Our screening also shows that the top structures in the predicted zeolite database outperform the best known zeolite by a factor of 4−7. Finally, we have identified a completely different optimal set of zeolite structures that are suitable for an inverse process, in which the CO 2 is retained while CH 4 or N 2 is passed through a membrane. ■ INTRODUCTIONElevated CO 2 concentrations in the atmosphere are considered to be the primary cause of global warming. 1 Because of the ever-increasing amount of CO 2 emissions and our continuing reliance on fossil fuels, it remains imperative to search for various methods to mitigate the emission process. Among many suggested solutions, carbon capture and sequestration (CCS) is emerging as a viable technique: 2 CCS consists of utilizing materials to capture CO 2 emissions from point sources such as electric power plants, cement and steel plants, or natural gas field and injecting the adsorbed CO 2 molecules to geological reservoirs. Some of the main barriers for the large-scale implementation of CCS are the energy requirements and cost of the capture process.The currently available technology uses amines to selectively absorb CO 2 . These amines are very efficient in absorption of CO 2 , but the regeneration of the amine solution is relatively energy intensive. Alternative technologies, such as adsorption by adsorbents 3 or separations using membranes, 4 have the potential to significantly reduce the energy costs. Both technologies depend on the development of novel materials that have optimal properties for a given separation, with important classes of materials being nanoporous solids, such as zeolites and metal−organic frameworks. 3,5−8 By changing the pore topology and chemical composition, one could, in principle, synthesize millions of different materials, making it difficult to experimentally characterize and test all these materials. This gives a great opportunity for molecular simulations to identify the optimal materials in silico and gui...

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

Cited by 669 publications

References 532 publications

New materials for methane capture from dilute and medium-concentration sources

New materials for methane capture from dilute and medium-concentration sources

Large-Scale Screening of Zeolite Structures for CO₂ Membrane Separations

Efficient Monte Carlo Simulations of Gas Molecules Inside Porous Materials

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

Cited by 669 publications

References 532 publications

New materials for methane capture from dilute and medium-concentration sources

New materials for methane capture from dilute and medium-concentration sources

Large-Scale Screening of Zeolite Structures for CO2 Membrane Separations

Efficient Monte Carlo Simulations of Gas Molecules Inside Porous Materials

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Large-Scale Screening of Zeolite Structures for CO₂ Membrane Separations