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Zhou MY, Zhang XW, Yi H, Wang ZS, Zhou DD, Lin RB, Zhang JP, Chen XM. Molecular-Sieving Separation of Methanol/Benzene Azeotrope by a Flexible Metal-Organic Framework. J Am Chem Soc 2024; 146:12969-12975. [PMID: 38625041 DOI: 10.1021/jacs.3c13480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Separation of methanol/benzene azeotrope mixtures is very challenging not only by the conventional distillation technique but also by adsorbents. In this work, we design and synthesize a flexible Ca-based metal-organic framework MAF-58 consisting of cheap raw materials. MAF-58 shows selective methanol-induced pore-opening flexibility. Although the opened pores are large enough to accommodate benzene molecules, MAF-58 shows methanol/benzene molecular sieving with ultrahigh experimental selectivity, giving 5.1 mmol g-1 high-purity (99.99%+) methanol and 2.0 mmol g-1 high-purity (99.97%+) benzene in a single adsorption/desorption cycle. Computational simulations reveal that the preferentially adsorbed, coordinated methanol molecules act as the gating component to selectively block the diffusion of benzene, offering a new gating adsorption mechanism.
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Affiliation(s)
- Mu-Yang Zhou
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, School of Chemistry, IGCME, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xue-Wen Zhang
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, School of Chemistry, IGCME, Sun Yat-Sen University, Guangzhou 510275, China
| | - Heng Yi
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, School of Chemistry, IGCME, Sun Yat-Sen University, Guangzhou 510275, China
| | - Zhi-Shuo Wang
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, School of Chemistry, IGCME, Sun Yat-Sen University, Guangzhou 510275, China
| | - Dong-Dong Zhou
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, School of Chemistry, IGCME, Sun Yat-Sen University, Guangzhou 510275, China
| | - Rui-Biao Lin
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, School of Chemistry, IGCME, Sun Yat-Sen University, Guangzhou 510275, China
| | - Jie-Peng Zhang
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, School of Chemistry, IGCME, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xiao-Ming Chen
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, School of Chemistry, IGCME, Sun Yat-Sen University, Guangzhou 510275, China
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2
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Gao MY, Bezrukov AA, Song BQ, He M, Nikkhah SJ, Wang SQ, Kumar N, Darwish S, Sensharma D, Deng C, Li J, Liu L, Krishna R, Vandichel M, Yang S, Zaworotko MJ. Highly Productive C 3H 4/C 3H 6 Trace Separation by a Packing Polymorph of a Layered Hybrid Ultramicroporous Material. J Am Chem Soc 2023; 145:11837-11845. [PMID: 37204941 DOI: 10.1021/jacs.3c03505] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Ultramicroporous materials can be highly effective at trace gas separations when they offer a high density of selective binding sites. Herein, we report that sql-NbOFFIVE-bpe-Cu, a new variant of a previously reported ultramicroporous square lattice, sql, topology material, sql-SIFSIX-bpe-Zn, can exist in two polymorphs. These polymorphs, sql-NbOFFIVE-bpe-Cu-AA (AA) and sql-NbOFFIVE-bpe-Cu-AB (AB), exhibit AAAA and ABAB packing of the sql layers, respectively. Whereas NbOFFIVE-bpe-Cu-AA (AA) is isostructural with sql-SIFSIX-bpe-Zn, each exhibiting intrinsic 1D channels, sql-NbOFFIVE-bpe-Cu-AB (AB) has two types of channels, the intrinsic channels and extrinsic channels between the sql networks. Gas and temperature induced transformations of the two polymorphs of sql-NbOFFIVE-bpe-Cu were investigated by pure gas sorption, single-crystal X-ray diffraction (SCXRD), variable temperature powder X-ray diffraction (VT-PXRD), and synchrotron PXRD. We observed that the extrinsic pore structure of AB resulted in properties with potential for selective C3H4/C3H6 separation. Subsequent dynamic gas breakthrough measurements revealed exceptional experimental C3H4/C3H6 selectivity (270) and a new benchmark for productivity (118 mmol g-1) of polymer grade C3H6 (purity >99.99%) from a 1:99 C3H4/C3H6 mixture. Structural analysis, gas sorption studies, and gas adsorption kinetics enabled us to determine that a binding "sweet spot" for C3H4 in the extrinsic pores is behind the benchmark separation performance. Density-functional theory (DFT) calculations and Canonical Monte Carlo (CMC) simulations provided further insight into the binding sites of C3H4 and C3H6 molecules within these two hybrid ultramicroporous materials, HUMs. These results highlight, to our knowledge for the first time, how pore engineering through the study of packing polymorphism in layered materials can dramatically change the separation performance of a physisorbent.
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Affiliation(s)
- Mei-Yan Gao
- Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Republic of Ireland
| | - Andrey A Bezrukov
- Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Republic of Ireland
| | - Bai-Qiao Song
- Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Republic of Ireland
| | - Meng He
- Department of Chemistry, University of Manchester, Manchester, M13 9PL, U.K
| | - Sousa Javan Nikkhah
- Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Republic of Ireland
| | - Shi-Qiang Wang
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way 138634, Singapore
| | - Naveen Kumar
- Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Republic of Ireland
| | - Shaza Darwish
- Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Republic of Ireland
| | - Debobroto Sensharma
- Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Republic of Ireland
| | - Chenghua Deng
- Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Republic of Ireland
| | - Jiangnan Li
- Department of Chemistry, University of Manchester, Manchester, M13 9PL, U.K
| | - Lunjie Liu
- Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Rajamani Krishna
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands
| | - Matthias Vandichel
- Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Republic of Ireland
| | - Sihai Yang
- Department of Chemistry, University of Manchester, Manchester, M13 9PL, U.K
| | - Michael J Zaworotko
- Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick V94 T9PX, Republic of Ireland
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Li C, Zhang Z, Heinke L. Mass transfer of toluene in a series of metal-organic frameworks: molecular clusters inside the nanopores cause slow and step-like release. Phys Chem Chem Phys 2022; 24:3994-4001. [PMID: 35103267 DOI: 10.1039/d1cp05560g] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The mass transfer of the guest molecules in the pores is fundamental for the application of nanoporous materials like metal-organic frameworks, MOFs. In the present work, we explore the uptake and release of toluene in a series of Zr-based MOFs with different pore sizes. We find that intermolecular guest-guest interaction, sterically controlled by the pore size, has a substantial impact on the release kinetics. While the adsorption is rather fast, the desorption process is many orders of magnitude slower. Depending on the pore size, molecular clusters form, here (most likely) toluene dimers, which are rather stable and their break-up is rate-limiting during the desorption process. This results in a step-like desorption kinetics, deviating from the plain Fickian-diffusion-controlled release. Temperature-dependent experiments show that the minimum and maximum of the release rates are obtained at the same toluene loadings, independent of the temperature. Moreover, the activation energy for the release coincides with the binding energy of a toluene dimer. The work shows the importance of intermolecular guest-guest interaction, controlled by the MOF-nanoconfinement, for the uptake and release from nanoporous materials.
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Affiliation(s)
- Chun Li
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
| | - Zejun Zhang
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
| | - Lars Heinke
- Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
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Joulazadeh M, Rahimi A, Mirmohammadi SJ, Kanani M, Dadkhah S, Zarean M. Feasibility Study of Benzene Dehydration through an Adsorption Process: Isotherm Determination, Kinetics, and Fixed-Bed Column Studies. Ind Eng Chem Res 2022. [DOI: 10.1021/acs.iecr.1c03081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mehrnaz Joulazadeh
- Research and Development Department, Iran Chemical Industries Investment Co. (ICIIC), Isfahan 8335144114, Iran
| | - Amir Rahimi
- Chemical Engineering Department, College of Engineering, University of Isfahan, Isfahan 8174673441, Iran
| | - S. Javad Mirmohammadi
- Research and Development Department, Iran Chemical Industries Investment Co. (ICIIC), Isfahan 8335144114, Iran
| | - Masoud Kanani
- Research and Development Department, Iran Chemical Industries Investment Co. (ICIIC), Isfahan 8335144114, Iran
| | - Saeed Dadkhah
- Research and Development Department, Iran Chemical Industries Investment Co. (ICIIC), Isfahan 8335144114, Iran
| | - Mostafa Zarean
- Research and Development Department, Iran Chemical Industries Investment Co. (ICIIC), Isfahan 8335144114, Iran
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Screening Metal-Organic Frameworks for Separation of Binary Solvent Mixtures by Compact NMR Relaxometry. Molecules 2021; 26:molecules26123481. [PMID: 34201035 PMCID: PMC8228364 DOI: 10.3390/molecules26123481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 06/04/2021] [Accepted: 06/05/2021] [Indexed: 01/18/2023] Open
Abstract
Metal–organic frameworks (MOFs) have great potential as an efficient alternative to current separation and purification procedures of a large variety of solvent mixtures—a critical process in many applications. Due to the huge number of existing MOFs, it is of key importance to identify high-throughput analytical tools, which can be used for their screening and performance ranking. In this context, the present work introduces a simple, fast, and inexpensive approach by compact low-field proton nuclear magnetic resonance (NMR) relaxometry to investigate the efficiency of MOF materials for the separation of a binary solvent mixture. The mass proportions of two solvents within a particular solvent mixture can be quantified before and after separation with the help of a priori established correlation curves relating the effective transverse relaxation times T2eff and the mass proportions of the two solvents. The new method is applied to test the separation efficiency of powdered UiO-66(Zr) for various solvent mixtures, including linear and cyclic alkanes and benzene derivate, under static conditions at room temperature. Its reliability is demonstrated by comparison with results from 1H liquid-state NMR spectroscopy.
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Krishna R, van Baten JM. Water/Alcohol Mixture Adsorption in Hydrophobic Materials: Enhanced Water Ingress Caused by Hydrogen Bonding. ACS OMEGA 2020; 5:28393-28402. [PMID: 33163823 PMCID: PMC7643331 DOI: 10.1021/acsomega.0c04491] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Accepted: 10/09/2020] [Indexed: 06/11/2023]
Abstract
Microporous crystalline porous materials such as zeolites, metal-organic frameworks, and zeolitic imidazolate frameworks (ZIFs) have potential use for separating water/alcohol mixtures in fixed bed adsorbers and membrane permeation devices. For recovery of alcohols present in dilute aqueous solutions, the adsorbent materials need to be hydrophobic in order to prevent the ingress of water. The primary objective of this article is to investigate the accuracy of ideal adsorbed solution theory (IAST) for prediction of water/alcohol mixture adsorption in hydrophobic adsorbents. For this purpose, configurational bias Monte Carlo (CBMC) simulations are used to determine the component loadings for adsorption equilibrium of water/methanol and water/ethanol mixtures in all-silica zeolites (CHA, DDR, and FAU) and ZIF-8. Due to the occurrence of strong hydrogen bonding between water and alcohol molecules and attendant clustering, IAST fails to provide quantitative estimates of the component loadings and the adsorption selectivity. For a range of operating conditions, the water loading in the adsorbed phase may exceed that of pure water by one to two orders of magnitude. Furthermore, the occurrence of water-alcohol clusters moderates size entropy effects that prevail under pore saturation conditions. For quantitative modeling of the CBMC, simulated data requires the application of real adsorbed solution theory by incorporation of activity coefficients, suitably parameterized by the Margules model for the excess Gibbs free energy of adsorption.
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Krishna R. Metrics for Evaluation and Screening of Metal-Organic Frameworks for Applications in Mixture Separations. ACS OMEGA 2020; 5:16987-17004. [PMID: 32724867 PMCID: PMC7379136 DOI: 10.1021/acsomega.0c02218] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 07/01/2020] [Indexed: 05/29/2023]
Abstract
For mixture separations, metal-organic frameworks (MOFs) are of practical interest. Such separations are carried out in fixed bed adsorption devices that are commonly operated in a transient mode, utilizing the pressure swing adsorption (PSA) technology, consisting of adsorption and desorption cycles. The primary objective of this article is to provide an assessment of the variety of metrics that are appropriate for screening and ranking MOFs for use in fixed bed adsorbers. By detailed analysis of several mixture separations of industrial significance, it is demonstrated that besides the adsorption selectivity, the performance of a specific MOF in PSA separation technologies is also dictated by a number of factors that include uptake capacities, intracrystalline diffusion influences, and regenerability. Low uptake capacities often reduce the efficacy of separations of MOFs with high selectivities. A combined selectivity-capacity metric, Δq, termed as the separation potential and calculable from ideal adsorbed solution theory, quantifies the maximum productivity of a component that can be recovered in either the adsorption or desorption cycle of transient fixed bed operations. As a result of intracrystalline diffusion limitations, the transient breakthroughs have distended characteristics, leading to diminished productivities in a number of cases. This article also highlights the possibility of harnessing intracrystalline diffusion limitations to reverse the adsorption selectivity; this strategy is useful for selective capture of nitrogen from natural gas.
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Affiliation(s)
- Rajamani Krishna
- Van ‘t Hoff Institute for Molecular
Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
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Krishna R, van Baten JM. Elucidation of Selectivity Reversals for Binary Mixture Adsorption in Microporous Adsorbents. ACS OMEGA 2020; 5:9031-9040. [PMID: 32337468 PMCID: PMC7178797 DOI: 10.1021/acsomega.0c01051] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 03/31/2020] [Indexed: 06/01/2023]
Abstract
The adsorption selectivity, S ads, is a key metric that quantifies the efficacy of any adsorbent in mixture separations. It is common practice to use ideal adsorbed solution theory (IAST) for estimating the value of S ads, using unary isotherm data inputs. In a number of experimental investigations, the phenomena of selectivity reversals and adsorption azeotropy (S ads = 1) have been reported in the published literature; such reversals may result from changes in mixture compositions, pressures, or pore loadings. In many cases, IAST is unable to anticipate such selectivity reversals. In this article, configurational-bias Monte Carlo simulations are used to gain insights into the phenomena of selectivity reversals. Two fundamentally different scenarios of selectivity reversals have been identified. In the first scenario, selectivity reversals are caused by inhomogeneous distribution of adsorbates due to preferential location and siting of a guest species in the pore space. For example, CO2 locates preferentially in the side pockets of mordenite and in window regions of DDR, CHA, and LTA zeolites. CO2 also congregates around the extra-framework cations of NaX zeolite. IAST fails to anticipate such selectivity reversals because its development relies on the assumption that the competition between guest species is uniform within the pore space. In the second scenario, selectivity reversals are caused by entropy effects that manifest near pore saturation conditions; the component that is preferentially adsorbed is the one that has the higher packing efficiency. For a homologous series of compounds, the component with the smaller chain length is favored at high pore occupancies. For adsorption of mixtures of alkane isomers within the intersecting channel network of MFI zeolite, the linear isomer is favored on the basis of entropic considerations.
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Shen WC, Chien IL. Design and Control of Ethanol/Benzene Separation by Energy-Saving Extraction–Distillation Process Using Glycerol as an Effective Heavy Solvent. Ind Eng Chem Res 2019. [DOI: 10.1021/acs.iecr.9b03095] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Wei-Cheng Shen
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - I-Lung Chien
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
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Krishna R, van Baten JM. Investigating the non-idealities in adsorption of CO2-bearing mixtures in cation-exchanged zeolites. Sep Purif Technol 2018. [DOI: 10.1016/j.seppur.2018.06.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Guevara-Carrion G, Gaponenko Y, Mialdun A, Janzen T, Shevtsova V, Vrabec J. Interplay of structure and diffusion in ternary liquid mixtures of benzene + acetone + varying alcohols. J Chem Phys 2018; 149:064504. [PMID: 30111131 DOI: 10.1063/1.5044431] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The Fick diffusion coefficient matrix of ternary mixtures containing benzene + acetone + three different alcohols, i.e., methanol, ethanol, and 2-propanol, is studied by molecular dynamics simulation and Taylor dispersion experiments. Aiming to identify common features of these mixtures, it is found that one of the main diffusion coefficients and the smaller eigenvalue do not depend on the type of alcohol along the studied composition path. Two mechanisms that are responsible for this invariant behavior are discussed in detail, i.e., the interplay between kinetic and thermodynamic contributions to Fick diffusion coefficients and the presence of microscopic heterogeneities caused by hydrogen bonding. Experimental work alone cannot explain these mechanisms, while present simulations on the molecular level indicate structural changes and uniform intermolecular interactions between benzene and acetone molecules in the three ternary mixtures. The main diffusion coefficients of these ternary mixtures exhibit similarities with their binary subsystems. Analyses of radial distribution functions and hydrogen bonding statistics quantitatively evidence alcohol self-association and cluster formation, as well as component segregation. Furthermore, the excess volume of the mixtures is analyzed in the light of intermolecular interactions, further demonstrating the benefits of the simultaneous use of experiment and simulation. The proposed framework for studying diffusion coefficients of a set of ternary mixtures, where only one component varies, opens the way for further investigations and a better understanding of multicomponent diffusion. The presented numerical results may also give an impulse to the development of predictive approaches for multicomponent diffusion.
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Affiliation(s)
- Gabriela Guevara-Carrion
- Thermodynamics and Energy Technology, University of Paderborn, Warburger Str. 100, D-33098 Paderborn, Germany
| | - Yuri Gaponenko
- Microgravity Research Center, Université Libre de Bruxelles, CP-165/62, Ave. F.D. Roosevelt, 50, B-1050 Brussels, Belgium
| | - Aliaksandr Mialdun
- Microgravity Research Center, Université Libre de Bruxelles, CP-165/62, Ave. F.D. Roosevelt, 50, B-1050 Brussels, Belgium
| | - Tatjana Janzen
- Thermodynamics and Energy Technology, University of Paderborn, Warburger Str. 100, D-33098 Paderborn, Germany
| | - Valentina Shevtsova
- Microgravity Research Center, Université Libre de Bruxelles, CP-165/62, Ave. F.D. Roosevelt, 50, B-1050 Brussels, Belgium
| | - Jadran Vrabec
- Thermodynamics and Energy Technology, University of Paderborn, Warburger Str. 100, D-33098 Paderborn, Germany
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Krishna R. Methodologies for screening and selection of crystalline microporous materials in mixture separations. Sep Purif Technol 2018. [DOI: 10.1016/j.seppur.2017.11.056] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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13
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Farzaneh A, DeJaco RF, Ohlin L, Holmgren A, Siepmann JI, Grahn M. Comparative Study of the Effect of Defects on Selective Adsorption of Butanol from Butanol/Water Binary Vapor Mixtures in Silicalite-1 Films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:8420-8427. [PMID: 28767246 DOI: 10.1021/acs.langmuir.7b02097] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A promising route for sustainable 1-butanol (butanol) production is ABE (acetone, butanol, ethanol) fermentation. However, recovery of the products is challenging because of the low concentrations obtained in the aqueous solution, thus hampering large-scale production of biobutanol. Membrane and adsorbent-based technologies using hydrophobic zeolites are interesting alternatives to traditional separation techniques (e.g., distillation) for energy-efficient separation of butanol from aqueous mixtures. To maximize the butanol over water selectivity of the material, it is important to reduce the number of hydrophilic adsorption sites. This can, for instance, be achieved by reducing the density of lattice defect sites where polar silanol groups are found. The density of silanol defects can be reduced by preparing the zeolite at neutral pH instead of using traditional synthesis solutions with high pH. In this work, binary adsorption of butanol and water in two silicalite-1 films was studied using in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy under equal experimental conditions. One of the films was prepared in fluoride medium, whereas the other one was prepared at high pH using traditional synthesis conditions. The amounts of water and butanol adsorbed from binary vapor mixtures of varying composition were determined at 35 and 50 °C, and the corresponding adsorption selectivities were also obtained. Both samples showed very high selectivities (100-23 000) toward butanol under the conditions studied. The sample having low density of defects, in general, showed ca. a factor 10 times higher butanol selectivity than the sample having a higher density of defects at the same experimental conditions. This difference was due to a much lower adsorption of water in the sample with low density of internal defects. Analysis of molecular simulation trajectories provides insights on the local selectivities in the zeolite channel network and at the film surface.
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Affiliation(s)
| | - Robert F DeJaco
- Department of Chemical Engineering and Materials Science and Department of Chemistry and Chemical Theory Center, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Lindsay Ohlin
- Chemical Technology, Luleå University of Technology , SE-971 87 Luleå, Sweden
| | - Allan Holmgren
- Chemical Technology, Luleå University of Technology , SE-971 87 Luleå, Sweden
| | - J Ilja Siepmann
- Department of Chemical Engineering and Materials Science and Department of Chemistry and Chemical Theory Center, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Mattias Grahn
- Chemical Technology, Luleå University of Technology , SE-971 87 Luleå, Sweden
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Krishna R. Screening metal–organic frameworks for mixture separations in fixed-bed adsorbers using a combined selectivity/capacity metric. RSC Adv 2017. [DOI: 10.1039/c7ra07363a] [Citation(s) in RCA: 96] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
For screening purposes, mixture separations with MOFs are evaluated on the basis of a combined selectivity/capacity metric.
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Affiliation(s)
- Rajamani Krishna
- Van't Hoff Institute for Molecular Sciences
- University of Amsterdam
- 1098 XH Amsterdam
- The Netherlands
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