1
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Stracke K, Evans JD. The use of collective variables and enhanced sampling in the simulations of existing and emerging microporous materials. NANOSCALE 2024. [PMID: 38647659 DOI: 10.1039/d4nr01024h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
Microporous materials, including zeolites, metal-organic frameworks, and cage compounds, offer diverse functionalities due to their unique dynamics and guest confinement properties. These materials play a significant role in separation, catalysis, and sensing, but their complexity hinders exploration using traditional atomistic simulations. This review explores collective variables (CVs) paired with enhanced sampling as a powerful approach to enable efficient investigation of key features in microporous materials. We highlight successful applications of CVs in studying adsorption, diffusion, phase transitions, and mechanical properties, demonstrating their crucial role in guiding material design and optimisation. The future of CVs lies in integration with techniques like machine learning, allowing for enhanced efficiency and accuracy. By tailoring CVs to specific materials and developing multi-scale approaches we can further unlock the intricacies of these fascinating materials. Simulations are a cornerstone in unravelling the complexities of microporous materials and are crucial for our future understanding.
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Affiliation(s)
- Konstantin Stracke
- School of Physics, Chemistry and Earth Science, The University of Adelaide, 5005 Australia.
| | - Jack D Evans
- School of Physics, Chemistry and Earth Science, The University of Adelaide, 5005 Australia.
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2
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Liu Y, Zuo J, Li Z, Li J, Zou X, Yang X, Yang B, Zhang C, Wang H, Pui DYH, Yang RT. Separation of SO 2 and NO 2 with the Zeolite Membrane: Molecular Simulation Insights into the Advantageous NO 2 Dimerization Effect. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:2751-2762. [PMID: 35192347 DOI: 10.1021/acs.langmuir.1c02290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
NO2 and SO2, as valuable chemical feedstock, are worth being recycled from flue gases. The separation of NO2 and SO2 is a key process step to enable practical deployment. This work proposes SO2 separation from NO2 using chabazite zeolite (SSZ-13) membranes and provides insights into the feasibility and advantages of this process using molecular simulation. Grand canonical ensemble Monte Carlo and equilibrium molecular dynamics methods were respectively adopted to simulate the adsorption equilibria and diffusion of SO2, NO2, and N2O4 on SSZ-13 at varying Si/Al (1, 5, 11, 71, +∞), temperatures (248-348 K), and pressures (0-100 kPa). The adsorption capacity and affinity (SO2 > N2O4 > NO2) demonstrated strong competitive adsorption of SO2 based on dual-site interactions and significant reduction in NO2 adsorption due to dimerization in the ternary gas mixture. The simulated order of diffusivity (NO2 > SO2 > N2O4) on SSZ-13 demonstrated rapid transport of NO2, strong temperature dependence of SO2 diffusion, and the impermeability of SSZ-13 to N2O4. The membrane permeability of each component was simulated, rendering a SO2/NO2 membrane separation factor of 26.34 which is much higher than adsorption equilibrium (6.9) and kinetic (2.2) counterparts. The key role of NO2-N2O4 dimerization in molecular sieving of SO2 from NO2 was addressed, providing a facile membrane separation strategy at room temperature.
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Affiliation(s)
- Yingshu Liu
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, PR China
| | - Jiayu Zuo
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, PR China
| | - Ziyi Li
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, PR China
| | - Jun Li
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, PR China
| | - Xiaoqin Zou
- Faculty of Chemistry, Northeast Normal University, Changchun 130024, PR China
| | - Xiong Yang
- School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, PR China
| | - Bentao Yang
- Zhongye Changtian International Engineering Co., Ltd., Changsha 410205, PR China
| | - Chuanzhao Zhang
- College of Biochemical Engineering, Beijing Union University, Beijing 100023, PR China
| | - Haoyu Wang
- College of Biochemical Engineering, Beijing Union University, Beijing 100023, PR China
| | - David Y H Pui
- Mechanical Engineering, University of Minnesota, 111 Church Street, S.E., Minneapolis, Minnesota 55455, United States
| | - Ralph T Yang
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, United States
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3
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Zuluaga-Bedoya CC, Dutta RC, Bhatia SK. Nonuniformity of Transport Coefficients in Ultrathin Nanoscale Membranes and Nanomaterials. ACS APPLIED MATERIALS & INTERFACES 2021; 13:59546-59559. [PMID: 34846839 DOI: 10.1021/acsami.1c18659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The quest to reduce transport resistance in separations using nanomaterials has led to considerable interest in nanoscale adsorbents and ultrathin membranes. It is now established that interfacial resistance limits the performance of such nanosized materials; however, the origin of this resistance is uncertain. While it is associated with surface pore blockages and distortions in some materials, its existence even in ideal materials is largely putative. Here, we report equilibrium molecular dynamics (EMD) simulations with ideal zeolite-based nanosheets, indicating the transport resistance to be entirely distributed within the solid, without contribution from an interfacial effect. We demonstrate the presence of an internal entry region over which fluid decorrelation occurs, and in which the local transport coefficient inside the crystal is nonuniform and position-dependent, increasing to the uniform value in the bulk material at larger distances. Our EMD-based diffusivity profiles within the nanomaterial enable us to unequivocally determine the entry length, and reveal an internal excess resistance, frequently assumed to be an interfacial resistance, due to significant reduction of the internal transport coefficient in the entrance and exit regions. A decrease in the entry length with loading in PON zeolite nanosheets is seen. We demonstrate a reduction in external resistance in the external bulk chambers used in simulations, triggered by the interplay of incomplete decorrelation in the nanosheet and periodic boundary conditions imposed on the system comprising the nanosheet and surrounding bulk reservoirs when the nanosheet thickness is less than the entry length. Our analysis of the transport dynamics within the nanosheet demonstrates that, at least for ideal systems, decomposition of the inhomogeneous diffusivity-based internal resistance into an interfacial and a uniform transport coefficient-based internal contribution is not appropriate for finite-sized systems. Our results will enable the improved design of nanoscale membranes and materials for applications in separation and other processes.
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Affiliation(s)
| | - Ravi C Dutta
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Suresh K Bhatia
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
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4
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Daglar H, Erucar I, Keskin S. Recent advances in simulating gas permeation through MOF membranes. MATERIALS ADVANCES 2021; 2:5300-5317. [PMID: 34458845 PMCID: PMC8366394 DOI: 10.1039/d1ma00026h] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 07/21/2021] [Indexed: 05/20/2023]
Abstract
In the last two decades, metal organic frameworks (MOFs) have gained increasing attention in membrane-based gas separations due to their tunable structural properties. Computational methods play a critical role in providing molecular-level information about the membrane properties and identifying the most promising MOF membranes for various gas separations. In this review, we discuss the current state-of-the-art in molecular modeling methods to simulate gas permeation through MOF membranes and review the recent advancements. We finally address current opportunities and challenges of simulating gas permeation through MOF membranes to guide the development of high-performance MOF membranes in the future.
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Affiliation(s)
- Hilal Daglar
- Department of Chemical and Biological Engineering, Koc University, Rumelifeneri Yolu Sariyer 34450 Istanbul Turkey +90-(212)-338-1362
| | - Ilknur Erucar
- Department of Natural and Mathematical Sciences, Faculty of Engineering, Ozyegin University, Cekmekoy 34794 Istanbul Turkey
| | - Seda Keskin
- Department of Chemical and Biological Engineering, Koc University, Rumelifeneri Yolu Sariyer 34450 Istanbul Turkey +90-(212)-338-1362
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5
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Kallo M, Lennox MJ. Understanding CO 2/CH 4 Separation in Pristine and Defective 2D MOF CuBDC Nanosheets via Nonequilibrium Molecular Dynamics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:13591-13600. [PMID: 33161715 PMCID: PMC7685532 DOI: 10.1021/acs.langmuir.0c02434] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The separation of CO2/CH4 gas mixtures is a key challenge for the energy sector and is essential for the efficient upgrading of natural gas and biogas. A new emerging field, that of metal-organic framework nanosheets (MONs), has shown the potential to outperform conventional separation methods and bulk metal-organic frameworks (MOFs). In this work, we model the CO2/CH4 separation in both defect-free and defective 2D CuBDC nanosheets and compare their performance with the bulk CuBDC MOF and experimental data. We report the results of external force nonequilibrium molecular dynamics (EF-NEMD) for pure components and binary mixtures. The EF-NEMD simulations reveal a pore blocking separation mechanism, in which the CO2 molecules occupy adsorption sites and significantly restrict the diffusion of CH4. The MON structure achieves a better selectivity of CO2 over CH4 compared to the bulk CuBDC MOF which is due to the mass transfer resistance of the methane molecules on the surface of the nanosheet. Our results show that it is essential to consider the real mixture in these systems rather than relying solely on pure component data and ideal selectivity. Furthermore, the separation is shown to be sensitive to the presence of missing linker defects in the nanosheets. Only 10% of missing linkers result in nonselective nanosheets. Hence, the importance of a defect-free synthetic method for CuBDC nanosheets is underlined.
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6
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Qian Q, Asinger PA, Lee MJ, Han G, Mizrahi Rodriguez K, Lin S, Benedetti FM, Wu AX, Chi WS, Smith ZP. MOF-Based Membranes for Gas Separations. Chem Rev 2020; 120:8161-8266. [PMID: 32608973 DOI: 10.1021/acs.chemrev.0c00119] [Citation(s) in RCA: 461] [Impact Index Per Article: 115.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Metal-organic frameworks (MOFs) represent the largest known class of porous crystalline materials ever synthesized. Their narrow pore windows and nearly unlimited structural and chemical features have made these materials of significant interest for membrane-based gas separations. In this comprehensive review, we discuss opportunities and challenges related to the formation of pure MOF films and mixed-matrix membranes (MMMs). Common and emerging separation applications are identified, and membrane transport theory for MOFs is described and contextualized relative to the governing principles that describe transport in polymers. Additionally, cross-cutting research opportunities using advanced metrologies and computational techniques are reviewed. To quantify membrane performance, we introduce a simple membrane performance score that has been tabulated for all of the literature data compiled in this review. These data are reported on upper bound plots, revealing classes of MOF materials that consistently demonstrate promising separation performance. Recommendations are provided with the intent of identifying the most promising materials and directions for the field in terms of fundamental science and eventual deployment of MOF materials for commercial membrane-based gas separations.
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Affiliation(s)
- Qihui Qian
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Patrick A Asinger
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Moon Joo Lee
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Gang Han
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Katherine Mizrahi Rodriguez
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Sharon Lin
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Francesco M Benedetti
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Albert X Wu
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Won Seok Chi
- School of Polymer Science and Engineering, Chonnam National University, Buk-gu, Gwangju 61186, Korea
| | - Zachary P Smith
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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7
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Wan Z, Zhou G, Dai Z, Li L, Hu N, Chen X, Yang Z. Separation Selectivity of CH 4/CO 2 Gas Mixtures in the ZIF-8 Membrane Explored by Dynamic Monte Carlo Simulations. J Chem Inf Model 2020; 60:2208-2218. [PMID: 32208717 DOI: 10.1021/acs.jcim.0c00114] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Here we report a series of nonequilibrium dynamic Monte Carlo simulations combined with dual control volume (DCV-DMC) to explore the separation selectivity of CH4/CO2 gas mixtures in the ZIF-8 membrane with a thickness of up to about 20 nm. Meanwhile, an improved DCV-DMC approach coupled with the corresponding potential map (PM-DCV-DMC) is further developed to speed up the computational efficiency of conventional DCV-DMC simulations. Our simulation results provide the molecular-level density and selectivity profiles along the permeation direction of both CH4 and CO2 molecules in the ZIF-8 membrane, indicating that the parts near membrane surfaces at both ends play a key role in determining the separation selectivity. All densities initially show a sharp increase in the individual maximum within the first outermost unit cell at the feed side and follow a long fluctuating decrease process. Accordingly, the corresponding selectivity profiles initially display a long fluctuating increase in the individual maximum and follow a sharp decrease near the membrane surface at the permeation side. Furthermore, the effects of feed composition, temperature, and pressure on the relevant separation selectivity are also discussed in detail, where the temperature has a greater influence on the separation selectivity than the feed composition and pressure. More importantly, the predicted separation selectivities from our PM-DCV-DMC simulations are well consistent with previous experimental results.
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Affiliation(s)
- Zheng Wan
- Institute of Advanced Materials (IAM), State-Province Joint Engineering Laboratory of Zeolite Membrane Materials, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, People's Republic of China
| | - Guobing Zhou
- Institute of Advanced Materials (IAM), State-Province Joint Engineering Laboratory of Zeolite Membrane Materials, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, People's Republic of China.,School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Zhongyang Dai
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China.,National Supercomputing Center in Shenzhen, Shenzhen 518055, People's Republic of China
| | - Li Li
- Institute of Advanced Materials (IAM), State-Province Joint Engineering Laboratory of Zeolite Membrane Materials, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, People's Republic of China
| | - Na Hu
- Institute of Advanced Materials (IAM), State-Province Joint Engineering Laboratory of Zeolite Membrane Materials, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, People's Republic of China
| | - Xiangshu Chen
- Institute of Advanced Materials (IAM), State-Province Joint Engineering Laboratory of Zeolite Membrane Materials, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, People's Republic of China
| | - Zhen Yang
- Institute of Advanced Materials (IAM), State-Province Joint Engineering Laboratory of Zeolite Membrane Materials, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, People's Republic of China
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8
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Dutta RC, Bhatia SK. Interfacial barriers to gas transport: probing solid-gas interfaces at the atomistic level. MOLECULAR SIMULATION 2019. [DOI: 10.1080/08927022.2019.1635694] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Ravi C. Dutta
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD, Australia
| | - Suresh K. Bhatia
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD, Australia
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9
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Velioglu S, Keskin S. Simulation of H 2/CH 4 mixture permeation through MOF membranes using non-equilibrium molecular dynamics. JOURNAL OF MATERIALS CHEMISTRY. A 2019; 7:2301-2314. [PMID: 30931122 PMCID: PMC6395021 DOI: 10.1039/c8ta10167a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 12/19/2018] [Indexed: 05/05/2023]
Abstract
Grand canonical Monte Carlo (GCMC) simulations are widely used with equilibrium molecular dynamics (EMD) to predict gas adsorption and diffusion in single-crystals of metal-organic frameworks (MOFs). Adsorption and diffusion data obtained from these simulations are then combined to predict gas permeabilities and selectivities of MOF membranes. This GCMC + EMD approach is highly useful to screen a large number of MOFs for a target membrane-based gas separation process. External field non-equilibrium molecular dynamics (NEMD) simulations, on the other hand, can directly compute gas permeation by providing an accurate representation of MOF membranes but they are computationally demanding and require long simulation times. In this work, we performed NEMD simulations to investigate H2/CH4 separation performances of MOF membranes. Both single-component and binary mixture permeabilities of H2 and CH4 were computed using the NEMD approach and results were compared with the predictions of the GCMC + EMD approach and experimental measurements reported in the literature. Our results showed that there is a good agreement between NEMD simulations and experiments for the permeability and selectivity of MOF membranes. NEMD simulations provided the direct observation of the mass transfer resistances on the pore mouth of MOF membranes, which is neglected in the GCMC + EMD approach. Our results suggested that once the very large numbers of MOF materials were screened using the GCMC + EMD approach, more detailed NEMD calculations can be performed for the best membrane candidates to unlock the actual gas transport mechanism before the experimental fabrication of MOF membranes.
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Affiliation(s)
- Sadiye Velioglu
- Department of Chemical and Biological Engineering , Koc University , Rumelifeneri Yolu, Sariyer , 34450 , Istanbul , Turkey . ; Tel: +90-212-338-1362
| | - Seda Keskin
- Department of Chemical and Biological Engineering , Koc University , Rumelifeneri Yolu, Sariyer , 34450 , Istanbul , Turkey . ; Tel: +90-212-338-1362
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10
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Dutta RC, Bhatia SK. Interfacial barriers to gas transport in zeolites: distinguishing internal and external resistances. Phys Chem Chem Phys 2018; 20:26386-26395. [DOI: 10.1039/c8cp05834b] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The gas separation performance of ultrathin membranes is dictated by the interfacial barriers that exist on the solid side of the interface.
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Affiliation(s)
- Ravi C. Dutta
- School of Chemical Engineering
- The University of Queensland
- Brisbane
- Australia
| | - Suresh K. Bhatia
- School of Chemical Engineering
- The University of Queensland
- Brisbane
- Australia
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11
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Chae K, Huang L. Computational study of pressure-driven methane transport in hierarchical nanostructured porous carbons. J Chem Phys 2016; 144:044708. [PMID: 26827229 DOI: 10.1063/1.4940427] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Using the reflecting particle method together with a perturbation-relaxation loop developed in our previous work, we studied pressure-driven methane transport in hierarchical nanostructured porous carbons (HNPCs) containing both mesopores and micropores in non-equilibrium molecular dynamics simulations. The surface morphology of the mesopore wall was systematically varied by tuning interaction strength between carbon atoms and the template in a mimetic nanocasting process. Effects of temperature and mesopore size on methane transport in HNPCs were also studied. Our study shows that increased mesopore wall surface roughness changes the character of the gas-wall interaction from specular to diffuse, while the gas-gas interaction is diminished due to the decrease of adsorption density. Effects of the mesopore wall surface morphology are the most significant at low temperatures and in small channels. Our systematic study provides a better understanding of the transport mechanisms of light gases through carbon nanotube composite membranes in experiments.
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Affiliation(s)
- Kisung Chae
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Liping Huang
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
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12
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Glavatskiy KS, Bhatia SK. Thermodynamic Resistance to Matter Flow at The Interface of a Porous Membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:3400-3411. [PMID: 27010213 DOI: 10.1021/acs.langmuir.6b00375] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Nanoporous materials are important in industrial separation, but their application is subject to strong interfacial barriers to the entry and transport of fluids. At certain conditions the fluid inside and outside the nanoporous material can be viewed as a two-phase system, with an interface between them, which poses an excess resistance to matter flow. We show that there exist two kinds of phenomena which influence the interfacial resistance: hydrodynamic effects and thermodynamic effects, which are independent of each other. Here, we investigate the role of the thermodynamic effects in carbon nanotubes (CNTs) and slit pores and compare the associated thermodynmic resistance with that due to hydrodynamic effects traditionally modeled by the established Sampson expression. Using CH4 and CO2 as model fluids, we show that the thermodynamic resistance is especially important for moderate to high pressures, at which the fluid within the CNT or slit pore is in the condensed state. Further, we show that at such pressures the thermodynamic resistance becomes comparable with the internal resistance to fluid transport at length scales typical of membranes used in fuel cells, and of importance in membrane-based separation, and nanofluidics in general.
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Affiliation(s)
- K S Glavatskiy
- School of Chemical Engineering, The University of Queensland , St Lucia, Queensland 4072, Australia
| | - Suresh K Bhatia
- School of Chemical Engineering, The University of Queensland , St Lucia, Queensland 4072, Australia
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13
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Chae K, Huang L. Computational Study of Pressure-Driven Gas Transport in Nanostructured Carbons: An Alternative Approach. J Phys Chem B 2015; 119:12299-307. [PMID: 26309067 DOI: 10.1021/acs.jpcb.5b05464] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We demonstrated a computationally efficient method in nonequilibrium molecular dynamics (NEMD) simulations to study pressure-driven gas transport in porous media. The reflecting particle method (RPM)14 was used to establish a steady-state gas flow along the transport channel, and the gas density in the feed chamber was properly adjusted to allow a constant pressure drop under various conditions by using a perturbation-relaxation loop developed here. This method was validated for methane flow through carbon nanotubes over a wide range of temperatures, giving results comparable to those of the commonly used dual control volume grand canonical molecular dynamics (DCV-GCMD) method but at least 20 times more efficient, even though the transport condition tested is favorable for the latter. This made it possible to perform systematic studies on the effects of temperature, pressure, and channel size on the transport behaviors. Our study shows that adsorption density varies significantly with temperature, which dramatically influences the transport mechanisms, especially in small channels at low temperatures and under high pressures. This newly developed NEMD method can be readily extended to study gas transport through channels with more complex surface morphology.
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Affiliation(s)
- Kisung Chae
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute , Troy, New York 12180, United States
| | - Liping Huang
- Department of Materials Science and Engineering, Rensselaer Polytechnic Institute , Troy, New York 12180, United States
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14
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Atci E, Keskin S. Atomically Detailed Models for Transport of Gas Mixtures in ZIF Membranes and ZIF/Polymer Composite Membranes. Ind Eng Chem Res 2012. [DOI: 10.1021/ie202530f] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Erhan Atci
- Department of Chemical and Biological Engineering, Koç University Rumelifeneri Yolu, Sariyer, 34450
Istanbul, Turkey
| | - Seda Keskin
- Department of Chemical and Biological Engineering, Koç University Rumelifeneri Yolu, Sariyer, 34450
Istanbul, Turkey
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15
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Affiliation(s)
- Jian-Rong Li
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, USA
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16
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Heinke L, Kärger J. Correlating surface permeability with intracrystalline diffusivity in nanoporous solids. PHYSICAL REVIEW LETTERS 2011; 106:074501. [PMID: 21405519 DOI: 10.1103/physrevlett.106.074501] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Indexed: 05/30/2023]
Abstract
The rates of uptake and release of guest molecules in nanoporous solids are often strongly influenced or even controlled by transport resistances at the external surface ("surface barriers") rather than by intraparticle diffusion, which was assumed to be rate controlling in many of the earlier kinetic studies. By correlating the surface resistance with the intracrystalline diffusivity, we develop here a microkinetic model which closely reproduces the experimentally observed results for short-chain alkanes in Zn(tbip), a member of the novel metal-organic framework family of nanoporous materials. It seems likely that this mechanism, which is shown to provide a rational explanation of the commonly observed discrepancies between "macro" and "micro" measurements of intracrystalline diffusion, may be fairly general.
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Affiliation(s)
- Lars Heinke
- Faculty of Physics and Geosciences, Department of Interface Physics, University of Leipzig, Germany
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17
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Hibbe F, Chmelik C, Heinke L, Pramanik S, Li J, Ruthven DM, Tzoulaki D, Kärger J. The Nature of Surface Barriers on Nanoporous Solids Explored by Microimaging of Transient Guest Distributions. J Am Chem Soc 2011; 133:2804-7. [DOI: 10.1021/ja108625z] [Citation(s) in RCA: 146] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Florian Hibbe
- Faculty of Physics and Geosciences, Department of Interface Physics, University of Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany
| | - Christian Chmelik
- Faculty of Physics and Geosciences, Department of Interface Physics, University of Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany
| | - Lars Heinke
- Faculty of Physics and Geosciences, Department of Interface Physics, University of Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany
- Fritz-Haber-Institute of the Max-Planck-Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Sanhita Pramanik
- Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
| | - Jing Li
- Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854, United States
| | - Douglas M. Ruthven
- Department of Chemical Engineering, University of Maine, Orono, Maine 04469, United States
| | - Despina Tzoulaki
- Faculty of Physics and Geosciences, Department of Interface Physics, University of Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany
- Technical University of Munich, Faculty of Chemistry, Lichtenbergstrasse 4, 85748 Garching, Germany
| | - Jörg Kärger
- Faculty of Physics and Geosciences, Department of Interface Physics, University of Leipzig, Linnéstrasse 5, 04103 Leipzig, Germany
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18
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Li YS, Bux H, Feldhoff A, Li GL, Yang WS, Caro J. Controllable synthesis of metal-organic frameworks: From MOF nanorods to oriented MOF membranes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2010; 22:3322-6. [PMID: 20533422 DOI: 10.1002/adma.201000857] [Citation(s) in RCA: 209] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Affiliation(s)
- Yan-Shuo Li
- Institute of Physical Chemistry and Electrochemistry, Center for Solid State Research and New Materials, Leibniz University Hannover, Germany.
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19
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Knauth M, Vasenkov S, Kärger J, Fritzsche S. Molecular dynamics study of sorbate diffusion in a simple porous membrane containing microporous nanocrystals and mesopores. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.07.106] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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20
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Zang J, Konduri S, Nair S, Sholl DS. Self-diffusion of water and simple alcohols in single-walled aluminosilicate nanotubes. ACS NANO 2009; 3:1548-1556. [PMID: 19545168 DOI: 10.1021/nn9001837] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Understanding transport phenomena of fluids through nanotubes (NTs) is of great interest in order to enable potential application of NTs as separation devices, encapsulation media for molecule storage and delivery, and sensors. Single-walled metal oxide NTs are interesting materials because they present a well-defined solid-state structure, precisely tunable diameter and length, as well as a hydrophilic and functionalizable interior for tuning transport and adsorption selectivity. Here, we study the transport properties of hydrogen-bonding liquids (water, methanol, and ethanol) through a single-walled aluminosilicate NT to investigate the influence of liquid-surface and liquid-liquid interactions and the effects of competitive transport of different chemical species using molecular dynamics (MD) simulations. The self-diffusivities (D(s)) for all the three species decrease with increasing loading and are comparable to bulk liquid diffusivities at low molecular loadings. We show that the hydrogen-bond network associated with water makes its diffusion behavior different from methanol and ethanol. Mixtures of water and methanol show segregation in the NT, with water located closer to the tube wall and the alcohol molecules localized near the center of the NT. D(s) values of water in an analogous aluminogermanate NT are larger than those in the aluminosilicate NT due to a larger pore diameter.
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Affiliation(s)
- Ji Zang
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, GA 30332-0100, USA
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21
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Thompho S, Chanajaree R, Remsungnen T, Hannongbua S, Bopp PA, Fritzsche S. The Permeation of Methane Molecules through Silicalite-1 Surfaces. J Phys Chem A 2009; 113:2004-14. [DOI: 10.1021/jp808588n] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Somphob Thompho
- Institut für Theoretische Physik, Universität Leipzig, Vor dem Hospitaltore 1, D-04103 Leipzig, Germany, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand, Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand, and Department of Chemistry, Université Bordeaux 1, Building A12, 351 Cours de la Libération, F-33405 Talence CEDEX, France
| | - Rungroj Chanajaree
- Institut für Theoretische Physik, Universität Leipzig, Vor dem Hospitaltore 1, D-04103 Leipzig, Germany, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand, Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand, and Department of Chemistry, Université Bordeaux 1, Building A12, 351 Cours de la Libération, F-33405 Talence CEDEX, France
| | - Tawun Remsungnen
- Institut für Theoretische Physik, Universität Leipzig, Vor dem Hospitaltore 1, D-04103 Leipzig, Germany, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand, Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand, and Department of Chemistry, Université Bordeaux 1, Building A12, 351 Cours de la Libération, F-33405 Talence CEDEX, France
| | - Supot Hannongbua
- Institut für Theoretische Physik, Universität Leipzig, Vor dem Hospitaltore 1, D-04103 Leipzig, Germany, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand, Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand, and Department of Chemistry, Université Bordeaux 1, Building A12, 351 Cours de la Libération, F-33405 Talence CEDEX, France
| | - Philippe A. Bopp
- Institut für Theoretische Physik, Universität Leipzig, Vor dem Hospitaltore 1, D-04103 Leipzig, Germany, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand, Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand, and Department of Chemistry, Université Bordeaux 1, Building A12, 351 Cours de la Libération, F-33405 Talence CEDEX, France
| | - Siegfried Fritzsche
- Institut für Theoretische Physik, Universität Leipzig, Vor dem Hospitaltore 1, D-04103 Leipzig, Germany, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand, Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand, and Department of Chemistry, Université Bordeaux 1, Building A12, 351 Cours de la Libération, F-33405 Talence CEDEX, France
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22
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Eun Jee S, McGaughey AJ, Sholl DS. Molecular simulations of hydrogen and methane permeation through pore mouth modified zeolite membranes. MOLECULAR SIMULATION 2009. [DOI: 10.1080/08927020802162900] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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23
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Garate JA, English N, MacElroy J. Carbon nanotube assisted water self-diffusion across lipid membranes in the absence and presence of electric fields. MOLECULAR SIMULATION 2009. [DOI: 10.1080/08927020802353491] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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24
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Keskin S, Sholl DS. Assessment of a Metal−Organic Framework Membrane for Gas Separations Using Atomically Detailed Calculations: CO2, CH4, N2, H2 Mixtures in MOF-5. Ind Eng Chem Res 2008. [DOI: 10.1021/ie8010885] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Seda Keskin
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - David S. Sholl
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
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25
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Smit B, Maesen TLM. Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity. Chem Rev 2008; 108:4125-84. [DOI: 10.1021/cr8002642] [Citation(s) in RCA: 586] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Berend Smit
- Department of Chemical Engineering, University of California, Berkeley, California 94720-1462, Van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, and Centre Européen de Calcul Atomique et Moléculaire (CECAM), Ecole Normale Supérieure, 46 Allée d’Italie, 69007 Lyon France
| | - Theo L. M. Maesen
- Chevron, Energy Technology Company, 100 Chevron Way, Richmond, California 94802-0627
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26
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Sun J, Zhang LT. Temperature control algorithms in dual control volume grand canonical molecular dynamics simulations of hydrogen diffusion in palladium. J Chem Phys 2008; 127:164721. [PMID: 17979385 DOI: 10.1063/1.2794343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effectiveness of five temperature control algorithms for dual control volume grand canonical molecular dynamics is investigated in the study of hydrogen atom diffusion in a palladium bulk. The five algorithms, namely, Gaussian, generalized Gaussian moment thermostat (GGMT), velocity scaling, Nosé-Hoover (NH), and its enhanced version Nosé-Hoover chain (NHC) are examined in both equilibrium and nonequilibrium simulation studies. Our numerical results show that Gaussian yields the most inaccurate solutions for the hydrogen-palladium system due to the high friction coefficient generated from the large velocity fluctuation of hydrogen, while NHC, NH, and GGMT produce the most accurate temperature and density profiles in both equilibrium and nonequilibrium cases with their feedback control mechanisms. However, this feedback control also overestimates the self-diffusion coefficients in equilibrium systems and the diffusion coefficient in nonequilibrium systems. Velocity scaling thermostat produces slight inhomogeneities in the temperature and density profiles, but due to the dissipated heat accumulated in the control volumes it still yields accurate self-diffusion coefficients that are in good agreement with the experimental data at a wide range of temperatures while others tend to deviate.
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Affiliation(s)
- Jianwei Sun
- Department of Mechanical Engineering, Tulane University, New Orleans, Louisiana 70118, USA
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27
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Hierarchische Nanofertigung: von geformten Zeolithnanopartikeln zu hochleistungsfähigen Trennmembranen. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200604910] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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28
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Snyder MA, Tsapatsis M. Hierarchical Nanomanufacturing: From Shaped Zeolite Nanoparticles to High-Performance Separation Membranes. Angew Chem Int Ed Engl 2007; 46:7560-73. [PMID: 17694585 DOI: 10.1002/anie.200604910] [Citation(s) in RCA: 307] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Despite more than a decade of intense research on the high-resolution selectivity of thin zeolite films as alternatives to energy-intensive industrial separations, membranes consisting of intergrown, oriented zeolite crystals have fallen short of gaining wide commercial application. Factors including poor performance, high cost, and difficulties in scale up have contributed to this, and have also stunted their application in other niche markets. Until recently, rational design of these materials was limited because of the elusive mechanism of zeolite growth, and forced more empirical approaches. New understanding of zeolite growth along with recent advances in the molecular engineering of crystal microstructure and morphology, assembly of crystal monolayers, and synthesis of ordered films constitute a strong foundation for meeting stringent industrial demands in the future. Together with new processing capabilities, such a foundation should make it possible to synthesize commercially viable zeolite membranes through hierarchical approaches. Such advances open exciting prospects beyond the realm of separations for assembly of novel and complex functional materials including molecular sensors, mechanically stable dielectrics, and novel reaction-diffusion devices.
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Affiliation(s)
- Mark A Snyder
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
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29
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Ling C, Sholl DS. Using first-principles calculations to predict surface resistances to H2 transport through metal alloy membranes. J Memb Sci 2007. [DOI: 10.1016/j.memsci.2007.07.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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30
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Simon JM, Inzoli I, Bedeaux D, Kjelstrup S. Numerical evidence for a thermal driving force during adsorption of butane in silicalite. MOLECULAR SIMULATION 2007. [DOI: 10.1080/08927020701370620] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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31
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Molecular Modelling in Zeolite Science. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s0167-2991(07)80807-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/22/2023]
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32
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Newsome DA, Sholl DS. Molecular Dynamics Simulations of Mass Transfer Resistance in Grain Boundaries of Twinned Zeolite Membranes. J Phys Chem B 2006; 110:22681-9. [PMID: 17092016 DOI: 10.1021/jp063287g] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The net mass transfer resistance for gas molecules permeating through zeolite membranes includes contributions from intracrystalline diffusion and contributions from interfacial effects. These interfacial effects can arise either from gas-zeolite interfaces or from interfaces that exist within zeolite crystals due to grain boundaries. We present the first atomically detailed simulations that examine interfacial mass transfer resistance due to internal grain boundaries in zeolites that are relevant for membrane applications. Our calculations examine twinned silicalite crystals in crystallographic configurations that have been identified in previous experiments. We used the dual control volume grand canonical molecular dynamics method to simulate the permeance of CH(4) and CF(4) through thin twinned silicalite crystals. The magnitudes of the grain boundary resistances are quite substantial, at least for the thin crystals that are accessible in our simulations.
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Affiliation(s)
- David A Newsome
- Department of Chemical Engineering, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213, USA
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33
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Gulín-González J, Schüring A, Fritzsche S, Kärger J, Vasenkov S. The influence of the desorption barrier on the transport of molecules through the external surface of nanoporous crystals. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.07.102] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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34
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Chen H, Johnson JK, Sholl DS. Transport diffusion of gases is rapid in flexible carbon nanotubes. J Phys Chem B 2006; 110:1971-5. [PMID: 16471771 DOI: 10.1021/jp056911i] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular dynamics simulations of rigid, defect-free single-walled carbon nanotubes have previously suggested that the transport diffusivity of gases adsorbed in these materials can be orders of magnitude higher than any other nanoporous material (A. I. Skoulidas et al., Phys. Rev. Lett. 2002, 89, 185901). These simulations must overestimate the molecular diffusion coefficients because they neglect energy exchange between the diffusing molecules and the nanotube. Recently, Jakobtorweihen et al. have reported careful simulations of molecular self-diffusion that allow nanotube flexibility (Phys. Rev. Lett. 2005, 95, 044501). We have used the efficient thermostat developed by Jakobtorweihen et al. to examine the influence of nanotube flexibility on the transport diffusion of CH4 in (20,0) and (15,0) nanotubes. The inclusion of nanotube flexibility reduces the transport diffusion relative to the rigid nanotube by roughly an order of magnitude close to zero pressure, but at pressures above about 1 bar the transport diffusivities for flexible and rigid nanotubes are very similar, differing by less than a factor or two on average. Hence, the transport diffusivities are still extremely large compared to other known materials when flexibility is taken into account.
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Affiliation(s)
- Haibin Chen
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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35
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Newsome DA, Sholl DS. Influences of interfacial resistances on gas transport through carbon nanotube membranes. NANO LETTERS 2006; 6:2150-3. [PMID: 16968042 DOI: 10.1021/nl061181r] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Carbon nanotubes have significant promise as gas separation membranes. Gas permeation through nanopores involves mass transfer resistances from molecules entering and leaving pores (so-called surface resistances) and diffusion within the pores. We use molecular simulations to give the first estimates of surface resistances for gas transport through nanotubes. For CH4 transport through (20,0) carbon nanotubes at 300 K, surface resistances are small for nanotubes 5-10 mum in length but can be significant for shorter nanotubes.
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Affiliation(s)
- David A Newsome
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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36
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Sholl DS. Understanding macroscopic diffusion of adsorbed molecules in crystalline nanoporous materials via atomistic simulations. Acc Chem Res 2006; 39:403-11. [PMID: 16784218 DOI: 10.1021/ar0402199] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The diffusion rates of molecules inside nanoporous materials lie at the heart of many large-scale industrial applications of these materials. Quantitatively describing this diffusion, particularly diffusion of chemical mixtures in situations leading to net mass transport, remains challenging. Molecular dynamics (MD) simulations can play an important complementary role to experiments in this area. This Account describes applications of MD to diffusion in nanoporous materials with a particular focus on macroscopic diffusion, that is, diffusion involving mass transport. These methods have made useful contributions to developing mixing theories for predicting multicomponent diffusion from single-component data and to screening new classes of materials for practical applications.
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Affiliation(s)
- David S Sholl
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
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37
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Arora G, Sandler SI. Mass transport of O2 and N2 in nanoporous carbon (C168 schwarzite) using a quantum mechanical force field and molecular dynamics simulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:4620-8. [PMID: 16649773 DOI: 10.1021/la053062h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
A hierarchical approach is used to calculate the single-component fluxes of N2 and O2 in nanoporous carbon molecular sieves (represented by C168 schwarzite) over a wide range of pressures and pressure drops. The self- and corrected diffusivities are calculated using equilibrium molecular dynamics simulations with force fields for the gas-carbon interactions obtained from quantum mechanical calculations. These results are combined with previously reported adsorption isotherms of N2 and O2 in C168 to obtain transport diffusivities and, by use of the Fick's equation of mass transport, to obtain single-component fluxes across the membrane. The diffusion coefficients and fluxes are also calculated using an empirical potential, which has been obtained by fitting low coverage adsorption data of N2 and O2 on a planar graphite sheet. By analyzing the diffusivities calculated with the ab initio potential in the limit of infinite dilution over the temperature range from 80 to 450 K, it is observed that the N2/O2 separation is energetically driven and a high selectivity of O2 over N2 can be obtained at low temperatures. However, with the empirical potential both the energetic and entropic contributions to selectivity were found to be close to unity. Similarly, by calculating single-component fluxes and ideal selectivities at 300 K and finite pressures it is found that the ab initio potential better explains the large O2/N2 selectivities of similarly sized molecules that have been observed experimentally. An interesting reversal in ideal selectivity is observed by adjusting the pressure at the two ends of the membrane. As a consequence, we predict that a highly selective kinetic separation in favor of either nitrogen or oxygen could be obtained with the same membrane depending on the operating conditions.
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Affiliation(s)
- Gaurav Arora
- Center for Molecular and Engineering Thermodynamics, Department of Chemical Engineering, University of Delaware, Newark, Delaware 19716, USA
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38
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Abstract
Carbon nanotubes show exceptional physical properties that render them promising candidates as building blocks for nanostructured materials. Many ambitious applications, ranging from gene therapy to membrane separations, require the delivery of fluids, in particular aqueous solutions, through the interior of carbon nanotubes. To foster these and other applications, it is necessary to understand the thermodynamic and transport properties of water confined within long narrow carbon nanotubes. Previous theoretical work considered either short carbon nanotubes or short periods of time. By conducting molecular dynamics simulations in the microcanonical ensemble for water confined in infinitely long carbon nanotubes of diameter 1.08 nm, we show here that confined water molecules diffuse through a fast ballistic motion mechanism for up to 500 ps at room temperature. By comparing the results obtained for the diffusion of water to those obtained for the diffusion of a reference Lennard-Jones fluid, we prove here that long-lasting hydrogen bonds are responsible for the ballistic diffusion of water clusters in narrow carbon nanotubes, as opposed to spatial mismatches between pore-fluid and fluid-fluid attractive interactions which, as shown previously by others, are responsible for the concerted motion of simple fluids in molecular sieves. Additionally we prove here for the first time that, despite the narrow diameter of the carbon nanotubes considered which may suggest the existence of single-file diffusion, when the trajectories of confined water are studied at time scales in excess of 500 ps, a Fickian-type diffusion mechanism prevails. Our results are important for designing nano fluidic apparatuses to develop, for example, novel drug-delivery devices.
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Affiliation(s)
- Alberto Striolo
- School of Chemical Biological and Materials Engineering, The University of Oklahoma, Norman, Oklahoma 73019, USA.
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Skoulidas AI, Sholl DS, Johnson JK. Adsorption and diffusion of carbon dioxide and nitrogen through single-walled carbon nanotube membranes. J Chem Phys 2006; 124:054708. [PMID: 16468902 DOI: 10.1063/1.2151173] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We have used atomically detailed simulations to examine the adsorption and transport diffusion of CO2 and N2 in single-walled carbon nanotubes at room temperature as a function of nanotube diameter. Linear and spherical models for CO2 are compared, showing that representing this species as spherical has only a slight impact in the computed diffusion coefficients. Our results support previous predictions that transport diffusivities of molecules inside carbon nanotubes are extremely rapid when compared with other porous materials. By examining carbon nanotubes as large as the (40,40) nanotube, we are able to compare the transport rates predicted by our calculations with recent experimental measurements. The predicted transport rates are in reasonable agreement with experimental observations.
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40
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Chen H, Sholl DS. Predictions of selectivity and flux for CH4/H2 separations using single walled carbon nanotubes as membranes. J Memb Sci 2006. [DOI: 10.1016/j.memsci.2005.06.030] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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41
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Zhu W, Hrabanek P, Gora L, Kapteijn F, Moulijn JA. Role of Adsorption in the Permeation of CH4 and CO2 through a Silicalite-1 Membrane. Ind Eng Chem Res 2005. [DOI: 10.1021/ie0507427] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Weidong Zhu
- Reactor & Catalysis Engineering, DelftChemTech, and Ceramic Membrane Centre, The Pore, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
| | - Pavel Hrabanek
- Reactor & Catalysis Engineering, DelftChemTech, and Ceramic Membrane Centre, The Pore, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
| | - Leszek Gora
- Reactor & Catalysis Engineering, DelftChemTech, and Ceramic Membrane Centre, The Pore, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
| | - Freek Kapteijn
- Reactor & Catalysis Engineering, DelftChemTech, and Ceramic Membrane Centre, The Pore, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
| | - Jacob A. Moulijn
- Reactor & Catalysis Engineering, DelftChemTech, and Ceramic Membrane Centre, The Pore, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
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