Showing papers on "Gas separation published in 2011"

Polymer nanosieve membranes for CO2-capture applications

Abstract: Microporous organic polymers (MOPs) are of potential significance for gas storage, gas separation and low-dielectric applications. Among many approaches for obtaining such materials, solution-processable MOPs derived from rigid and contorted macromolecular structures are promising because of their excellent mass transport and mass exchange capability. Here we show a class of amorphous MOP, prepared by [2+3] cycloaddition modification of a polymer containing an aromatic nitrile group with an azide compound, showing super-permeable characteristics and outstanding CO(2) separation performance, even under polymer plasticization conditions such as CO(2)/light gas mixtures. This unprecedented result arises from the introduction of tetrazole groups into highly microporous polymeric frameworks, leading to more favourable CO(2) sorption with superior affinity in gas mixtures, and selective CO(2) transport by presorbed CO(2) molecules that limit access by other light gas molecules. This strategy provides a direction in the design of MOP membrane materials for economic CO(2) capture processes.

Metal-Organic Frameworks: Applications from Catalysis to Gas Storage

Abstract: Preface PART I: Design of Multifunctional Porous MOFs DESIGN OF POROUS COORDINATION POLYMER/METAL-ORGANIC FRAMEWORKS: PAST, PRESENT AND FUTURE Introduction Background and Ongoing Chemistry of Porous Coordination Polymers Multifunctional Frameworks Preparation of Multifunctional Frameworks Perspectives DESIGN OF FUNCTIONAL METAL-ORGANIC FRAMEWORKS BY POST-SYNTHETIC MODIFICATION Building a MOFs Toolbox by Post-Synthetic Modification Post-Functionalization of MOFs by Host-Guest Interactions Post-Functionalization of MOFs Based on Coordination Chemistry Post-Functionalization of MOFs by Covalent Bonds Tandem Post-Modification for the Immobilization of Organometallic Catalysts Critical Assessment Conclusion PART II: Gas Storage and Separation Applications THERMODYNAMIC METHODS FOR PREDICTION OF GAS SEPARATION IN FLEXIBLE FRAMEWORKS Introduction Theoretical Background Molecular Simulation Methods Analytical Methods Based on Experimental Data Outlook SEPARATION AND PURIFICATION OF GASES BY MOFS Introduction General Principles of Gas Separation and Purification MOFs for Separation and Purification Processes Conclusions and Perspectives OPPORTUNITIES FOR MOFS IN CO2 CAPTURE FROM FLUE GASES, NATURAL GAS, AND SYNGAS BY ADSORPTION Introduction General Introduction to Pressure Swing Adsorption Production of H2 from Syngas CO2 Removal from Natural Gas Post-Combustion CO2 Capture MOFs Conclusions MANUFACTURE OF MOF THIN FILMS ON STRUCTURED SUPPORTS FOR SEPARATION AND CATALYSIS Advantages and Limitations of Membrane Technologies for Gas and Liquid Separation Mechanisms of Mass Transport and Separation Synthesis of Molecular Sieve Membranes Application of MOF Membranes Limitations Conclusions and Outlook RESEARCH STATUS OF METAL-ORGANIC FRAMEWORKS FOR ON-BOARD CRYO-ADSORPTIVE HYDROGEN STORAGE APPLICATIONS Introduction - Research Problem and Significance MOFs as Adsorptive Hydrogen Storage Options Experimental Techniques and Methods for Performance and Thermodynamic Assessment of Porous MOFs for Hydrogen Storage Material Research Results From Laboratory-Scale Materials to Engineering Conclusion PART III: Bulk Chemistry Applications SEPARATION OF XYLENE ISOMERS Xylene Separation: Industrial Processes, Adsorbents, and Separation Principles Properties of MOFs Versus Zeolites in Xylene Separations Separation of Xylenes Using MIL-47 and MIL-53 Conclusions METAL-ORGANIC FRAMEWORKS AS CATALYSTS FOR ORGANIC REACTIONS Introduction MOFs with Catalytically Active Metal Nodes in the Framework Catalytic Functionalization of Organic Framework Linkers Homochiral MOFs MOF-Encapsulated Catalytically Active Guests Mesoporous MOFs Conclusions PART IV: Medical Applications BIOMEDICAL APPLICATIONS OF METAL-ORGANIC FRAMEWORKS Introduction MOFs for Bioapplications Therapeutics Diagnostics From Synthesis of Nanoparticles to Surface Modification and Shaping Discussion and Conclusion METAL-ORGANIC FRAMEWORKS FOR BIOMEDICAL IMAGING Introduction Gadolinium Carboxylate NMOFs Manganese Carboxylate NMOFs Iron Carboxylate NMOFs: The MIL Family Iodinated NMOFs: CT Contrast Agents Lanthanide Nucleotide NMOFs Guest Encapsulation within NMOFs Conclusion PART V: Physical Applications LUMINESCENT METAL-ORGANIC FRAMEWORKS Introduction Luminescence Theory Ligand-Based Luminescence Metal-Based Luminescence Guest-Induced Luminescence Applications of Luminescent MOFs Conclusion DEPOSITION OF THIN FILMS FOR SENSOR APPLICATIONS Introduction Literature Survey Signal Transduction Modes Considerations in Selecting MOFs for Sensing Applications MOF Thin Film Growth: Methods, Mechanisms, and Limitations Conclusions and Perspectives PART VI: Large-Scale Synthesis and Shaping of MOFs INDUSTRIAL MOF SYNTHESIS Introduction Raw Materials Synthesis Shaping Applications Conclusion and Outlook MOF SHAPING AND IMMOBILISATION Introduction MOF@Fiber Composite Materials Requirements of Adsorbents for Individual Protection MOFs in Monolithic Structures

Template-Free Synthesis of a Highly Porous Benzimidazole-Linked Polymer for CO2 Capture and H2 Storage

Abstract: A highly porous benzimidazole-linked polymer (SABET 1172 m2/g) exhibits very high gas selectivity CO2/N2 (70) and CO2/CH4 (10) and can store CO2 (19 wt %, 273 K, 1 bar) and H2 (1.9 wt %, 77 K, 1 bar) with Qst values of 26.7 and 7.9 kJ/mol, respectively.

Poly-/metal-benzimidazole nano-composite membranes for hydrogen purification

Abstract: In this study, a novel scheme to fabricate nano-composite membrane materials containing fully dispersed nano-size zeolitic imidazolate frameworks (ZIFs) has been proposed for the first time. By mixing the as-synthesized ZIF-7 nano-particles without the traditional drying process with polybenzimidazole (PBI), the resultant membranes not only achieve an unprecedented ZIF-7 loading as high as 50 wt%, but also overcome the low permeability nature of PBI. The membranes exhibit characteristics of high transparency and mechanical flexibility, together with enhanced H2 permeability and ideal H2/CO2 permselectivity surpassing both neat PBI and ZIF-7 membranes. Advanced instrument analyses have confirmed the unique ZIF–polymer interface and elucidated the mixed matrix structure that contributes to the high ZIF loading and enhanced gas separation performance superior to the prediction from the Maxwell model. The high thermal stability, good dispersion of ZIF nanoparticles with minimal agglomeration and the attractive gas separation performance at elevated temperatures up to 180 °C indicate the practicability of this nano-composite material for hydrogen production and CO2 capture in realistic industrial applications under harsh and extreme environments.

High Ionic Liquid Content Polymeric Gel Membranes: Preparation and Performance

Abstract: Ionic liquid polymeric gel membranes containing from 20 wt % to 80 wt % of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ((EMIM)(TFSI)) in poly(vinylidene fluoride- co-hexafluoropropylene) (p(VDF-HFP)) were prepared by solvent casting from a solution in acetone. The effect of the ionic liquid on the performance and properties of the membranes was discussed and compared with the neat polymer. In the presence of an excess of ionic liquid, p(VDF-HFP) membranes swell in a significant way, especially above 70 C, becoming completely soluble above 90 C. DSC analysis shows a gradual decrease of the melting point of the gel and a decrease in the overall melting enthalpy with increasing ILcontent,whereasthemeltingenthalpynormalizedforthepolymerfractionshowsaninitialdropandthena gradual increase. In the presence of the ionic liquid, the elastic modulus and break strength decrease dramatically, while the maximum deformation first increases due to higher flexibility of the plasticized polymer and then rapidly decreases above 40 wt % of IL as a consequence of the progressive decrease of the number of entanglements. X-ray studies demonstrate a reduction in the overall crystal content. The position of the strongest diffraction peak remains unaltered in all samples, suggesting that only the polymer chains crystallize and that no cocrystallization of ionic liquid and polymer takes place. Preliminary gas permeation measurementsshowasignificantincreaseofthepermeabilityinthepresenceof(EMIM)(TFSI), especially for carbon dioxide. This suggests a potential application in gas separation membranes, for instance for natural gas treatment or for CO2 sequestration from flue gas.

Are MOF membranes better in gas separation than those made of zeolites

Abstract: Despite much progress in the development of zeolite molecular sieve membranes, there is so far no industrial gas separation by zeolite membranes, with the exception of the de-watering of bio-ethanol by steam permeation using LTA membranes. During the last 5 years, metal–organic framework (MOF) membranes have been developed and tested in gas separation. The complete tool box of techniques originally developed for the preparation of zeolite membranes could be applied for the preparation of MOF membranes, such as the use of macroporous ceramic or metal supports, seeding, intergrowth-supporting additives, and microwave heating. There are some structure-related properties of MOFs which recommend them as suitable material for molecular sieve membranes. On the other hand, the structural flexibility of MOFs apparently prevents a sharp molecular sieving with a pore size estimated from the ‘rigid’ crystallographic structure by size exclusion. An application of MOFs is predicted in so-called mixed matrix membranes which show improved performance in comparison with the pure polymer membranes. Different from zeolites as organic–inorganic material, the MOF nanoparticles can be easily embedded into organic polymers, and standard shaping technologies to hollow fibers or spiral wound geometries can be applied.

Tailoring the Separation Behavior of Hybrid Organosilica Membranes by Adjusting the Structure of the Organic Bridging Group

Abstract: Hybrid organically linked silica is a highly promising class of materials for the application in energy-efficient molecular separation membranes. Its high stability allows operation under aggressive working conditions. Herein is reported the tailoring of the separation performance of these hybrid silica membranes by adjusting the size, flexibility, shape, and electronic structure of the organic bridging group. A single generic procedure is applied to synthesize nanoporous membranes from bridged silsesquioxane precursors with different reactivities. Membranes with short alkylene (CH2 and C2H4) bridging groups show high H2/N2 permeance ratios, related to differences in molecular size. The highest CO2/H2 permeance ratios, related to the affinity of adsorption in the material, are obtained for longer (C8H16) alkylene and aryl bridges. Materials with long flexible alkylene bridges have a hydrophobic surface and show strongly temperature-dependent molecular transport as well as a high n-butanol flux in a pervaporation process, which is indicative of organic polymerlike properties. The versatility of the bridging group offers an extensive toolbox to tune the nanostructure and the affinity of hybrid silica membranes and by doing so to optimize the performance towards specific separation challenges. This provides excellent prospects for industrial applications such as carbon capture and biofuel production.

Oxygen separation from air using ceramic-based membrane technology for sustainable fuel production and power generation

Abstract: There has been tremendous progress in membrane technology for gas separation, in particular oxygen separation from air in the last 20 years providing an alternative route to the existing conventional separation processes such as cryogenic distillation and pressure swing adsorption. This paper covers the review of membrane separation process and recent developments of ceramic membranes for oxygen separation from air. This membrane based oxygen supply from air offers significant advantages for integration in power generation cycles with carbon dioxide (CO2) capture, coal gasification systems and gas-to-liquid (GTL) plants. The critical issues in the implementation of membrane technology for power generation and fuel production are also presented and discussed.

Precursor Selection and Process Conditions in the Preparation of Carbon Membrane for Gas Separation: A Review

Abstract: Carbon membranes prepared by pyrolysis/carbonization of polymeric precursors have been studied in the last few years as a promising candidate for gas separation process. As the aim of this paper, a review on polymer precursor selection and effect of pyrolysis conditions on carbon membrane characteristics and performances were discussed in detail. A number of different polymer precursors have been surveyed for their utility as materials in carbon membrane fabrication. The gas transport properties of various types of carbon membrane that produced by different researchers was summarized. Furthermore, the potential applications and future directions of carbon membrane in gas separation processes were also briefly identified.

Thermally Rearranged (TR) Poly(ether-benzoxazole) Membranes for Gas Separation

Abstract: Thermal rearrangement of hydroxyl-containing polyimides in solid state formed microporous polybenzoxazoles showing extraordinarily fast molecular transport for small gas molecules. Their microporous structure and size distribution can be tuned easily by varying the chemical structure of the precursor hydroxyl−polyimide and by using different thermal treatment protocols. This manuscript reports, for the first time, the synthesis of ether containing polybenzoxazole, that is, poly(ether−benzoxazole) (PEBO) membranes by thermal rearrangement of a novel fluorinated poly(o-hydroxy ether−imide). The effect of increased chain flexibility on the physical and transport properties of the resultant thermally rearranged (TR) polymer membranes for different thermal treatment protocols (e.g., final temperature and thermal dwell time) have been examined and reported in detail.

Sorption studies of CO 2 , CH 4 , N 2 , CO, O 2 and Ar on nanoporous aluminum terephthalate [MIL-53(Al)]

Abstract: Aluminum terephthalate, MIL-53(Al), metal–organic framework synthesized hydrothermally and purified by solvent extraction method was used as an adsorbent for gas adsorption studies. The synthesized MIL-53(Al) was characterized by powder X-Ray diffraction analysis, surface area measurement using N2 adsorption–desorption at 77 K, FTIR spectroscopy and thermo gravimetric analysis. Adsorption isotherms of CO2, CH4, CO, N2, O2 and Ar were measured at 288 and 303 K. The absolute adsorption capacity was found in the order CO2>CH4>CO>N2>Ar>O2. Henry’s constants, heat of adsorption in the low pressure region and adsorption selectivities for the adsorbate gases were calculated from their adsorption isotherms. The high selectivity and low heat of adsorption for CO2 suggests that MIL-53(Al) is a potential adsorbent material for the separation of CO2 from gas mixtures. The high selectivity for CH4 over O2 and its low heat of adsorption suggests that MIL-53(Al) could also be a compatible adsorbent for the separation of methane from methane–oxygen gas mixtures.

High performance polyimide with high internal free volume elements.

Abstract: This paper reports a new polyimide design with high internal free volume elements for fast mass transport simultaneously with high selectivity. Here, we show that the polymer design using a three-dimensional rigid molecular structure having internal void space can lead to the formation of high fractional free volume with proper cavity size to separate small gas molecules with high selectivities as high permeabilities. These findings could strongly impact emerging gas separation applications using polymeric membranes such as natural gas purification and biogas purification to get clean energy resources.

Facile synthesis of an ultramicroporous MOF tubular membrane with selectivity towards CO(2)

Abstract: A substituted imidazolate-based MOF (SIM-1) membrane has been crystallized in situ on a tubular asymmetric alumina support that can be exploited for gas separation through preferential adsorption.

Grafting thermally labile molecules on cross-linkable polyimide to design membrane materials for natural gas purification and CO2 capture

Abstract: A novel strategy to design molecularly the cavity size and free volume of flexible polyimide materials via thermal treatment of rigid and cross-linkable polyimides grafted with thermal liable side beta-cyclodextrin (CD) molecules is demonstrated in this study. The spaces occupied by the labile groups may become microvoids after low-temperature thermal degradation while the rigid polyimide backbone prevails. The thermal induced cross-linking reaction among polyimide chains may create ultra-fine micro-pores that integrally connect with microvoids. As a result, the thermally cured membranes fabricated from dense polyimide precursors show gas separation performance surpassing the trade-off lines, with tough and flexible mechanical properties. Thermal annealing at 425 °C produces polyimide membranes with the best CO2 permeability of 4016 Barrer with reasonable gas pair selectivity.

Evaluation and fabrication of pore‐size‐tuned silica membranes with tetraethoxydimethyl disiloxane for gas separation

Abstract: Organic/inorganic hybrid silica membranes were prepared from 1,1,3,3-tetraethoxy-1,3-dimethyl disiloxane (TEDMDS) by the sol-gel technique with firing at 300–550°C in N2. TEDMDS-derived silica membranes showed high H2 permeance (0.3–1.1 × 10−6 mol m−2 s−1 Pa−1) with low H2/N2 (∼10) and high H2/SF6 (∼1200) perm-selectivity, confirming successful tuning of micropore sizes larger than TEOS-derived silica membranes. TEDMDS-derived silica membranes prepared at 550°C in N2 increased gas permeances as well as pore sizes after air exposure at 450°C. TEDMDS had an advantage in tuning pore size by the “template” and “spacer” techniques, due to the pyrolysis of methyl groups in air and SiOSi bonding, respectively. For pore size evaluation of microporous membranes, normalized Knudsen-based permeance, which was proposed based on the gas translation model and verified with permeance of zeolite membranes, reveals that pore sizes of TEDMDS membranes were successfully tuned in the range of 0.6–1.0 nm. © 2011 American Institute of Chemical Engineers AIChE J, 2011

Three-Dimensional Pillar-Layered Copper(II) Metal−Organic Framework with Immobilized Functional OH Groups on Pore Surfaces for Highly Selective CO2/CH4 and C2H2/CH4 Gas Sorption at Room Temperature

Abstract: A new three-dimensional microporous metal−organic framework Cu(BDC−OH)(4,4′-bipy)·Gx (UTSA-15; H2BDC−OH = 2-hydroxy-benzenedicarboxylic acid, 4,4′-bipy =4,4′-bipyridine, G = guest molecules) with functional −OH groups on the pore surfaces was solvothermally synthesized and structurally characterized. UTSA-15 features a three-dimensional structure having 2D intercrossed channels of about 4.1 × 7.8 and 3.7 × 5.1 A2, respectively. The small pores and the functional −OH groups on the pore surfaces within the activated UTSA-15a have enabled their strong interactions with CO2 and C2H2 which have been revealed in their large adsorption enthalpies of 39.5 and 40.6 kJ/mol, respectively, highlighting UTSA-15a as the highly selective microporous metal−organic framework for the CO2/CH4 and C2H2/CH4 gas separation with separation selectivity of 24.2 and 55.6, respectively, at 296 K.

Fluorinated and Nanoporous Graphene Materials As Sorbents for Gas Separations

Abstract: The physisorption of gases on surfaces depends on the electrostatic and dispersion interactions with adsorbates. The former can be tuned by introducing charge variations in the material, and the latter can be tuned by chemical substitution. Using atomistic Monte Carlo calculations, the Henry’s law constants, and isosteric heats of adsorption of CH4, CO2, N2, O2, H2S, SO2, and H2O on graphene, two-dimensional polyphenylene (2D-PP), fluorographene, and fluoro(2D-PP) surfaces are used to demonstrate the tunability of these two types of interaction. With the exception of H2O, fluorination and nanoporosity-induced charge variations reduce the binding of the adsorbates. Gas separations relevant for CO2 sequestration, biogas upgrading, SO2 pollution control, and air dehumidification are considered, and in most cases, the nanoporosity and fluorination reduce the selectivity of adsorption. The exceptions are separations involving adsorption of H2O and the SO2/N2 separation, where the large dipole moments of the ad...