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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Polymer-Infiltrated Metal–Organic Frameworks for Thin-Film Composite Mixed-Matrix Membranes with High Gas Separation Properties

Thin-film composite mixed-matrix membranes (TFC-MMMs) have potential applications in practical gas separation processes because of their high permeance (gas flux) and gas selectivity. In this study, we fabricated a high-performance TFC-MMM based on a rubbery comb copolymer, i.e., poly(2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] ethyl methacrylate)-co-poly(oxyethylene methacrylate) (PBE), and metal–organic framework MOF-808 nanoparticles. The rubbery copolymer penetrates through the pores of MOF-808, thereby tuning the pore size. In addition, the rubbery copolymer forms a defect-free interfacial morphology with polymer-infiltrated MOF-808 nanoparticles. Consequently, TFC-MMMs (thickness = 350 nm) can be successfully prepared even with a high loading of MOF-808. As polymer-infiltrated MOF is incorporated into the polymer matrix, the PBE/MOF-808 membrane exhibits a significantly higher CO 2 permeance (1069 GPU) and CO 2 /N 2 selectivity (52.7) than that of the pristine PBE membrane (CO 2 permeance = 431 GPU and CO 2 /N 2 selectivity = 36.2). Therefore, the approach considered in this study is suitable for fabricating high-performance thin-film composite membranes via polymer infiltration into MOF pores.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Relationship between microporous structure and light gas transport through glassy polymeric membranes revealed by molecular simulations

Microporous glassy polymers are attractive materials for gas separation membranes, due to their high permeability and tailorable selectivity, provided physical aging can be delayed. The archetypal microporous glassy polymer, PTMSP, can be blended with a hyper-crosslinked isatin–triptycene porous polymer network (PPN) to delay physical aging. However, while PPN is effective at reducing physical aging, it also affects the permeability of light gases through PTMSP. Molecular dynamics simulations were used here to shed fundamental light on the mechanisms responsible for these effects. Atomistic models are developed that satisfactorily reproduce experimental observations such as matrix density and cavity size distributions for neat PTMSP as well as for PTMSP–PPN blends. Analysis of the simulation results suggests that physical aging is delayed because the PPN inclusions slow down PTMSP relaxation while reducing the connectivity between free volume pockets. To understand how PPN inclusions affect light gas permeability, the atomistic models developed are used to probe CO 2 and CH 4 diffusion and sorption. These simulations are conducted for PTMSP matrices exhibiting varying density, towards reproducing experimental permeability data. Interrogating the simulation trajectories, it is discovered that while CH 4 travels preferentially through the free volume cavities, CO 2 preferentially interacts with the available surfaces, especially in the presence of PPN. These differences help interpret experimental observations. The transport of C 2 H 6 and H 2 S through PTMSP matrices was also investigated. These gases, and in particular H 2 S, were found to absorb within PTMSP, yielding very low diffusion coefficients. The ability to predict differences in diffusion pathways for various natural gas components unveils the possibility of engineering membranes to control permeability and selectivity towards large-scale applications.

Bao Le, Tran Thi [Univ. of Oklahoma, Norman, OK (U↗
DOE OSTI2024

CFD Modeling of High-Flux Plate-and-Frame Membrane modules for industrial carbon capture

In this work, we explore the use of CO2-selective flat sheet membranes for capturing CO2 from point sources. We employ Computational Fluid Dynamics (CFD) models to design high-flux plate-and-frame membrane modules to achieve uniform flow distribution among membrane elements, minimize dead-end zones, and ease the common concentration polarization issue for gas separation membranes. The goal is to drive membrane technology improvements by providing better module designs for given membrane properties and operating conditions.

Dosso, Cheick↗
DOE OSTI2024

CFD Modeling of High-Flux Plate-and-Frame Membrane Modules for Industrial Carbon Capture

In this work, we explore the use of CO2-selective flat sheet membranes for capturing CO2 from point sources. We employ Computational Fluid Dynamics (CFD) models to design high-flux plate-and-frame membrane modules to achieve uniform flow distribution among membrane elements, minimize dead-end zones, and ease the common concentration polarization issue for gas separation membranes. The goal is to drive membrane technology improvements by providing better module designs for given membrane properties and operating conditions.

Dosso, Cheick↗
DOE OSTI2024

CFD modeling of high-flux plate-and-frame membrane modules for industrial carbon capture

In this work, we explore the use of CO2-selective flat sheet membranes for capturing CO2 from point sources. We employ Computational Fluid Dynamics (CFD) models to design high-flux plate-and-frame membrane modules to achieve uniform flow distribution among membrane elements, minimize dead-end zones, and ease the common concentration polarization issue for gas separation membranes. The goal is to drive membrane technology improvements by providing better module designs for given membrane properties and operating conditions.

Dosso, Cheick↗
NASA NTRS2016

Advanced Supported Liquid Membranes for Carbon Dioxide Control in Cabin Applications

The development of new, robust, life support systems is critical to NASA's continued progress in space exploration. One vital function is maintaining the carbon dioxide (CO2) concentration in the cabin at levels that do not impair the health or performance of the crew. The CO2 removal assembly (CDRA) is the current CO2 control technology on-board the International Space Station (ISS). Although the CDRA has met the needs of the ISS to date, the repeated cycling of the molecular sieve sorbent causes it to break down into small particles that clog filters or generate dust in the cabin. This reduces reliability and increases maintenance requirements. Another approach that has potential advantages over the current system is a membrane that separates CO2 from air. In this approach, cabin air contacts one side of the membrane while other side of the membrane is maintained at low pressure to create a driving force for CO2 transport across the membrane. In this application, the primary power requirement is for the pump that creates the low pressure and then pumps the CO2 to the oxygen recovery system. For such a membrane to be practical, it must have high CO2 permeation rate and excellent selectivity for CO2 over air. Unfortunately, conventional gas separation membranes do not have adequate CO2 permeability and selectivity to meet the needs of this application. However, the required performance could be obtained with a supported liquid membrane (SLM), which consists of a microporous material filled with a liquid that selectively reacts with CO2 over air. In a recently completed Phase II SBIR project, Reaction Systems, Inc. fabricated an SLM that is very close to meeting permeability and selectivity objectives for use in the advanced space suit portable life support system. This paper describes work carried out to evaluate its potential for use in spacecraft cabin application.

Wickham, David T.↗
NASA NTRS2016

Advanced Supported Liquid Membranes for Carbon Dioxide Control in Cabin Applications

The development of new, robust, life support systems is critical to NASA's continued progress in space exploration. One vital function is maintaining the carbon dioxide (CO2) concentration in the cabin at levels that do not impair the health or performance of the crew. The carbon dioxide removal assembly (CDRA) is the current CO2 control technology on-board the International Space Station (ISS). Although the CDRA has met the needs of the ISS to date, the repeated cycling of the molecular sieve sorbent causes it to break down into small particles that clog filters or generate dust in the cabin. This reduces reliability and increases maintenance requirements. Another approach that has potential advantages over the current system is a membrane that separates CO2 from air. In this approach, cabin air contacts one side of the membrane while other side of the membrane is maintained at low pressure to create a driving force for CO2 transport across the membrane. In this application, the primary power requirement is for the pump that creates the low pressure and then pumps the CO2 to the oxygen recovery system. For such a membrane to be practical, it must have high CO2 permeation rate and excellent selectivity for CO2 over air. Unfortunately, conventional gas separation membranes do not have adequate CO2 permeability and selectivity to meet the needs of this application. However, the required performance could be obtained with a supported liquid membrane (SLM), which consists of a microporous material filled with a liquid that selectively reacts with CO2 over air. In a recently completed Phase II SBIR project, Reaction Systems, Inc. fabricated an SLM that is very close to meeting permeability and selectivity objectives for use in the Portable Life Support System (PLSS). This paper describes work carried out to evaluate its potential for use in the cabin.

Wickham, David T.↗
DOE OSTI2022

Gas Separations using Nanoporous Atomically Thin Membranes: Recent Theoretical, Simulation, and Experimental Advances

Abstract Porous graphene and other atomically thin 2D materials are regarded as highly promising membrane materials for high‐performance gas separations due to their atomic thickness, large‐scale synthesizability, excellent mechanical strength, and chemical stability. When these atomically thin materials contain a high areal density of gas‐sieving nanoscale pores, they can exhibit both high gas permeances and high selectivities, which is beneficial for reducing the cost of gas‐separation processes. Here, recent modeling and experimental advances in nanoporous atomically thin membranes for gas separations is discussed. The major challenges involved, including controlling pore size distributions, scaling up the membrane area, and matching theory with experimental results, are also highlighted. Finally, important future directions are proposed for real gas‐separation applications of nanoporous atomically thin membranes.

2D materials↗
DOE OSTI2023

High Performance Ionene Architectures for Membrane Separations (Final Technical Report)

Our DOE BES research grant (DE-SC0018181, 8/15/17-2/28/22) focused on the synthesis, characterization, and performance of a new class of polymers known as high-performance (HP)-ionenes as gas separation membranes, including associated computational studies. This research resulted in 11 peer-reviewed journal publications with an additional ~7 manuscripts currently in review or under preparation for submission. This DOE BES funding has also resulted in 3 U.S. patent applications.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Nanofilm Composite Membranes of Bottlebrush Poly(1,3‐Dioxolane) Plasticized by Poly(Ethylene Glycol) for CO 2 /N 2 Separation

Abstract Poly(1,3‐dioxolane) has emerged as a leading membrane material for post‐combustion CO 2 capture due to its high ether oxygen content and strong affinity toward CO 2 . However, they are often cross‐linked to inhibit crystallization, which makes them impossible to fabricate into industrial thin‐film composite membranes. Herein, soluble and high molecular weight bottlebrush polymers ( b PDXLA) are synthesized using reversible addition‐fragmentation chain transfer polymerization and demonstrate the feasibility of fabricating nanofilm (≈100 nm) composite membranes (NCMs). Furthermore, b PDXLA can be plasticized using a miscible additive of poly(ethylene glycol) dimethyl ether (PEGDME) to improve CO 2 permeability while retaining good CO 2 /N 2 selectivity. For example, adding 20 mass% PEGDME improves CO 2 permeance from 930 to 1300 GPU and decreases CO 2 /N 2 selectivity from 74 to 53 at 25 °C; the membrane exhibits stable separation performance competitive with state‐of‐the‐art commercial membranes. This work unveils a practical approach to designing uncross‐linked, highly polar polymers for practical membrane gas separation and highlights a facile way to enhance performance by incorporating miscible plasticizers using industrial manufacturing processes.

Zhang, Gengyi [Department of Chemical and Biologic↗
DOE OSTI2022

In Situ Growth of Crystalline and Polymer-Incorporated Amorphous ZIFs in Polybenzimidazole Achieving Hierarchical Nanostructures for Carbon Capture

We report mixed matrix materials (MMMs) hold great potential for membrane gas separations by merging nanofillers with unique nanostructures and polymers with excellent processability. In situ growth of the nanofillers is adapted to mitigate interfacial incompatibility to avoid the selectivity loss. Surprisingly, functional polymers have not been exploited to co-grow the nanofillers for membrane applications. Herein, in situ synergistic growth of crystalline zeolite imidazole framework-8 (ZIF-8) in polybenzimidazole (PBI), creating highly porous structures with high gas permeability, is demonstrated. More importantly, PBI contains benzimidazole groups (similar to the precursor for ZIF-8, i.e., 2-methylimidazole) and induces the formation of amorphous ZIFs, enhancing interfacial compatibility and creating highly size-discriminating bottlenecks. For instance, the formation of 15 mass% ZIF-8 in PBI improves H- 2 permeability and H- 2 /CO 2 selectivity by approximate to 100% at 35 degrees C, breaking the permeability/selectivity tradeoff. This work unveils a new platform of MMMs comprising functional polymer-incorporated amorphous ZIFs with hierarchical nanostructures for various applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Fine-tuned thermally cross-linkable 6FDA-based polyimide membranes for aggressive natural gas separation

Glassy 6FDA-based polyimides are attractive membrane materials for many industrially important gas separations; however, plasticization in aggressive natural gas often causes significant loss in CO 2 /CH 4 selectivity. In this study, a family of thermally cross-linkable 6FDA-based polyimides containing carboxyl groups were synthesized and cross-linked as dense films via decarboxylation-induced thermal crosslinking. As well as chemical structure, crosslinking temperatures above and below T g are shown to be synergistic tools. Our results demonstrate that structure evolution during the decarboxylation-induced crosslinking process is affected significantly by the 3,5-diaminobenzoic acid (DABA) content in the polymer backbone. Even for a 50/50 CO 2 /CH 4 binary mixture with feed pressure up to 800 psia, decarboxylation-induced crosslinking provides attractive gas separation performance and plasticization resistance. Combined facile structure tunability, crosslinkability and high asymmetric fiber spinnability make the cross-linkable 6FDA-based polyimides a versatile platform for diverse aggressive natural gas feeds encountered in practice. Finally, our study provides insights into material design of thermally cross-linkable polymer membranes for such a broad spectrum of aggressive gas separations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Precisely segmented PEEK–ionene + ionic liquid composite membranes for CO 2 separation

Ionenes, polymers with ionic groups incorporated directly within the backbone are a highly versatile class of materials, although they have received much less attention than polyelectrolytes which have ionic groups pendant from the polymer backbone. By designing ionenes that incorporate robust properties of poly(ether ether ketone) (PEEK), we have achieved new imidazolium-containing PEEK–ionene architectures that create opportunities for enhanced CO 2 separation membranes. To achieve these materials, an new imidazole-functionalized PEEK oligomer (ImK(EEK) 2 KIm) was synthesized through facile and straightforward routes. This molecule was then polymerized via condensation reactions with two different aromatic (α,α'-dibromo-p-xylene) and aliphatic (dibromohexyl containing-bis(imidazolium)hexane dibromide salt) comonomers and exchanged with bistriflimide ([Tf 2 N]) anion to obtain two unique PEEK–ionenes containing distinct PEEK and ionic segments: p([ImK(EEK) 2 Im-p-xyl][Tf 2 N] 2 ) and p([ImK(EEK) 2 (ImC 6 ) 3 ][Tf 2 N] 4 ). While the neat PEEK–ionenes exhibited high molecular weight but were not able to form high-quality films, adding stoichiometric amounts of “free” IL (1-methyl-3-butylimidazolium bistriflimide, [C 4 mIm][Tf 2 N]), greatly improved the flexibility and processability of the resultant membranes. Further, the structure–property relationships of bulk PEEK–ionenes and corresponding composites were extensively characterized by different analytical techniques (thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, and solid-state NMR). In conclusion, the gas separation properties were investigated, with the PEEK–ionenes + IL composites exhibiting CO 2 permeabilities of 14–94 barrer and good CO 2 /N 2 permselectivities of 26–35, indicating that new designs of segmented ionenes and composites with ILs a promising material design strategy for developing gas separation membranes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2015

Continued Advancement of Supported Liquid Membranes for Carbon Dioxide Control in Extravehicular Activity Applications

The Development of a new, robust, portable life support system (PLSS) is currently a high NASA priority in order to support longer and safer extravehicular activity (EVA) missions that will be necessary as space travel extends to near-Earth asteroids and eventually Mars. One of the critical PLSS functions is maintaining the carbon dioxide (CO2) concentration in the suit at acceptable levels. The Metal Oxide (MetOx) canister has a finite CO2 adsorption capacity and therefore in order to extend mission times, the unit would have to be larger and heavier, which is undesirable; therefore new CO2 control technologies must be developed. While recent work has centered on the use of alternating sorbent beds that can be regenerated during the EVA, this strategy increases the system complexity and power consumption. A simpler approach is to use a membrane that vents CO2 to space but retains oxygen(O2). A membrane has many advantages over current technology: it is a continuous system with no theoretical capacity limit, it requires no consumables, and it requires no hardware for switching beds between absorption and regeneration. Conventional gas separation membranes do not have adequate selectivity for use in the PLSS, but the required performance could be obtained with a supported liquid membrane (SLM), which consists of a microporous film filled with a liquid that selectively reacts with CO2 over oxygen (O2). In a recently completed Phase II Small Business Innovative Research project, Reaction Systems developed a new reactive liquid that has effectively zero vapor pressure, making it an ideal candidate for use in an SLM. Results obtained with the SLM in a flat sheet configuration with representative pressures of CO2, O2, and water (H2O) have shown that the CO2 permeation rate and CO2/O2 selectivity requirements have been met. In addition, the SLM vents moisture to space very effectively. The SLM has also been prepared and tested in a hollow fiber form, which will be necessary to meet size requirements in the PLSS. In initial tests, the required CO2 permeance values have been obtained, while the current CO2/O2 selectivity values are somewhat lower than needed. However, the performance of the SLM is a strong function of the method used to impregnate the sorbent in the hollow fiber walls and rapid progress is being made in that area.

Wickham, David T.↗
NASA NTRS2014

Advanced Supported Liquid Membranes for CO2 Control in Extravehicular Activity Applications

Developing a new, robust, portable life support system (PLSS) is currently a high priority for NASA in order to support longer and safer extravehicular activity (EVA) missions. One of the critical PLSS functions is maintaining the carbon dioxide (CO2) concentration in the suit at acceptable levels. Although the Metal Oxide (MetOx) canister has worked well, it has a finite CO2 adsorption capacity. Consequently, the unit would have to be larger and heavier to extend EVA times. Therefore, new CO2 control technologies must be developed to meet mission objectives without increasing the size of the PLSS. Although recent work has centered on sorbents that can be regenerated during the EVA, this strategy increases the system complexity and power consumption. A simpler approach is to use a membrane that selectively vents CO2 to space. A membrane has many advantages over current technology: it is a continuous system with no theoretical capacity limit, it requires no consumables, and it requires no hardware for switching beds between absorption and regeneration. Unfortunately, conventional gas separation membranes do not have adequate selectivity for use in the PLSS. However, the required performance could be obtained with a supported liquid membrane (SLM), which consists of a micro porous material filled with a liquid that selectively reacts with CO2 over oxygen (O2). In a current Phase II SBIR project, Reaction Systems has developed a new reactive liquid, which has effectively zero vapor pressure making it an ideal candidate for use in an SLM. The SLM function has been demonstrated with representative pressures of CO2, O2, and water (H2O). In addition to being effective for CO2 control, the SLM also vents moisture to space. Therefore, this project has demonstrated the feasibility of using an SLM to control CO2 in an EVA application. 1 President

Wickham, David T.↗
NASA NTRS2014

Advanced Supported Liquid Membranes for CO2 Control in Extravehicular Activity Applications

Developing a new, robust, portable life support system (PLSS) is currently a high priority for NASA in order to support longer and safer extravehicular activity (EVA) missions. One of the critical PLSS functions is maintaining the carbon dioxide (CO2) concentration in the suit at acceptable levels. Although the Metal Oxide (MetOx) canister has worked well, it has a finite CO2 adsorption capacity. Consequently, the unit would have to be larger and heavier to extend EVA times. Therefore, new CO2 control technologies must be developed to meet mission objectives without increasing the size of the PLSS. Although recent work has centered on sorbents that can be regenerated during the EVA, this strategy increases the system complexity and power consumption. A simpler approach is to use a membrane that selectively vents CO2 to space. A membrane has many advantages over current technology: it is a continuous system with no theoretical capacity limit, it requires no consumables, and it requires no hardware for switching beds between absorption and regeneration. Unfortunately, conventional gas separation membranes do not have adequate selectivity for use in the PLSS. However, the required performance could be obtained with a supported liquid membrane (SLM), which consists of a micro porous material filled with a liquid that selectively reacts with CO2 over oxygen (O2). In a current Phase II SBIR project, Reaction Systems has developed a new reactive liquid, which has effectively zero vapor pressure making it an ideal candidate for use in an SLM. The SLM function has been demonstrated with representative pressures of CO2, O2, and water (H2O). In addition to being effective for CO2 control, the SLM also vents moisture to space. Therefore, this project has demonstrated the feasibility of using an SLM to control CO2 in an EVA application.

Wickham, David T.↗
NASA NTRS2015

Continued Advancement of Supported Liquid Membranes for Carbon Dioxide Control in Extravehicular Activity Applications

The development of a new, robust, portable life support system (PLSS) is a high priority for NASA in order to support longer and safer extravehicular activity (EVA) missions. One of the critical PLSS functions is maintaining the carbon dioxide (CO2) concentration in the suit at acceptable levels. Although the Metal Oxide (MetOx) canister has historically performed very well, it has a finite CO2 adsorption capacity. Therefore, the size and weight of the unit would have to be increased to extend EVA times. Consequently, new CO2 control technologies must be developed in order to meet mission objectives without increasing the size of the PLSS. Recent work has centered on sorbents that can be regenerated during the EVA; however, this strategy increases the system complexity and power consumption. A much simpler approach is to employ a membrane that vents CO2 to space and retains oxygen (O2). A membrane has many advantages over current technology: it is a continuous system with no limit on capacity, it requires no consumables, and it does not need any hardware to switch beds between absorption and regeneration. Unfortunately, conventional gas separation membranes do not have the needed selectivity for use in the PLSS. However, the required performance could be obtained with a supported liquid membrane (SLM), which consists of a microporous material filled with a liquid that selectively reacts with CO2 over O2. In a recently completed Phase II SBIR project, Reaction Systems, Inc. achieved the required CO2 permeance and selectivity with an SLM in a flat sheet configuration. This paper describes work to convert the SLM into a more compact form and to scale it up to handle more representative process flow rates.

Wickham, David T.↗