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Ultrafast Long-Range Charge Separation in Organic Semiconductor Photovoltaic Diodes
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Catalytic molten metals for the direct conversion of methane to hydrogen and separable carbon
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Data for "Adsorptive Separation and Recovery of Triacetic Acid Lactone from Fermentation Broth"
Triacetic acid lactone (TAL) can be microbially produced and further chemically upgraded to several high-value chemicals. In this work, several acidic and basic ion-exchange resins and activated charcoal were evaluated for their ability to adsorb microbially produced TAL. Activated charcoal and a weak base resin, Dowex 66, showed similar TAL adsorption capacity of 0.18 ± 0.002 g/g. At 15% w/v activated charcoal, about 98% of TAL present in fermentation broth could be adsorbed. Further, ethanol washing allowed recovery of 72% of adsorbed TAL. A biorefinery producing TAL from sucrose was designed, simulated, and evaluated (through technoeconomic analysis) under uncertainty, for an estimated TAL minimum product selling price (MPSP) of $4.27/kg [$3.71−4.94/kg; 5th-95th percentiles] for the current state of technology and $2.83/kg [$2.46–3.29/kg] following potential near-term improvements to fermentation. Thus, this work provides an adsorptive process to recover microbially produced TAL that can be chemically upgraded to several industrial products.
A CFD Validation Challenge for Transonic Shock-Induced Separated Flow: Experimental Characterization.
Abstract not provided.
Performance of the Gemini Planet Imager Non-redundant Mask and Spectroscopy of Two Close-separation Binaries: HR 2690 and HD 142527
The Gemini Planet Imager (GPI) contains a 10-hole non-redundant mask (NRM), enabling interferometric resolution in complement to its coronagraphic capabilities. The NRM operates both in spectroscopic (integral field spectrograph, henceforth IFS) and polarimetric configurations. NRM observations were taken between 2013 and 2016 to characterize its performance. Most observations were taken in spectroscopic mode, with the goal of obtaining precise astrometry and spectroscopy of faint companions to bright stars. We find a clear correlation between residual wavefront error measured by the adaptive optic system and the contrast sensitivity by comparing phase errors in observations of the same source, taken on different dates. We find a typical 5σ contrast sensitivity of (2–3) × 10 –3 at $~λ/D$. We explore the accuracy of spectral extraction of secondary components of binary systems by recovering the signal from a simulated source injected into several data sets. We outline data reduction procedures unique to GPI's IFS and describe a newly public data pipeline used for the presented analyses. We demonstrate recovery of astrometry and spectroscopy of two known companions to HR 2690 and HD 142527. NRM+polarimetry observations achieve differential visibility precision of σ ~ 0.4% in the best case. We discuss its limitations on Gemini-S/GPI for resolving inner regions of protoplanetary disks and prospects for future upgrades. We summarize lessons learned in observing with NRM in spectroscopic and polarimetric modes.
Process for fabricating PBI hollow fiber asymmetric membranes for gas separation and liquid separation
The invention provides methods for preparing an asymmetric hollow fiber, the asymmetric hollow fibers prepared by such methods, and uses of the asymmetric hollow fibers. One method involves passing a polymeric solution through an outer annular orifice of a tube-in-orifice spinneret, passing a bore fluid though an inner tube of the spinneret, dropping the polymeric solution and bore fluid through an atmosphere over a dropping distance, and quenching the polymeric solution and bore fluid in a bath to form an asymmetric hollow fiber.
Efficient Mesofluidic Separation of Large Particles in nuclear slurries - 20408
Efficient and effective particle separation is essential to cleanup of many nuclear wastes. For example, particle separation may be used to accelerate settle-decant bottlenecks that limit the throughput necessary to achieve the U.S. Department of Energy waste cleanup mission in a timely manner. Particle separation may be used to protect downstream processing equipment from pulses of solids that may be encountered near (within a few feet of) liquid-solid interfaces during waste transfer operations, thereby preventing work stoppages. Effective particle separation may permit efficient sludge washing. These are only a few of the ways in which particle separation is important. Yet, efficient and effective particle separation in nuclear processing environments remains challenging. For example, settle-decant operations permit larger and heavier particles to settle, leaving smaller, lighter particles suspended. However, settle-decant operations are slow, convection currents may resuspend solids, hindered settling of multicomponent slurries remains incompletely understood, and predictive models for settling in graduated cylinders fail to match limited observations of settling in large waste tanks. Additionally, pumping operations can cause turbulent resuspension of particles when the pump intake is close to the settled solids layer. Filtration techniques that use membranes or partially permeable barriers retain larger particles, permitting smaller particles to permeate. However, filters, including dead-end filtration, are prone to clogging and caking, operate at elevated pressures due to minimal void volume, and increase in pressure during operations, which require more control systems. Therefore, the need for high throughput particle separation techniques that operate with modest pressure drops persists. A novel mesofluidic separator presents the opportunity to effectively and efficiently accelerate the waste cleanup mission. The separator separates large particles from process streams across a broad range of particle sizes and has no moving parts or media to replace, regenerate, or clean. This separator design has an unusually large void volume, permitting operation at much higher flow rates (and lower pressures) than traditional filtration (e.g., dead-end filtration). Industrial-scale flow rates have been demonstrated. In performance testing, mesofluidic separators operate at might flow rates (>90 gpm (0.0006 m{sup 3}/s) in piping 3 inches (0.08 m) in diameter; Re>10{sup 5}), with modest pressure drop (∼25 psi (170 KPa) in testing). In complex, aggregating waste simulants, the separator loses <25% of flow projected over months without back pulsing or chemical cleaning. Mesofluidic separation presents infrastructure advantages, reduces risk, and provides mission impact. Infrastructure advantages include implementation within existing transfer systems, plug and play without facility modifications to safety systems, and operation at low pressures. The separator is flexible in location, may be positioned within or outside of waste tanks, and may replace or augment dead-end and cross-flow filters. Mesofluidic separation reduces risk by minimizing waste (no media to replace or regenerate and no cleaning chemicals to handle and dispose) and by minimizing filter change-out consistent with as low as reasonably achievable (ALARA) exposure to workers. The potential mission impact of these separators is substantial. The separator has potential to support, simplify, and accelerate in-farm transfers and waste feed delivery. Furthermore, the separator can free up settling and holding tanks in the Direct Feed Low-Activity Waste (DFLAW) mission by reducing or eliminating post-transfer settling and wait times with the potential to free up 1 Mgal (4000 m{sup 3}) of double-shell tank space. This paper quantitatively compares mesofluidic separation to dead-end filtration, discusses scale-up results, and considers the separator's potential to efficiently and effectively reduce the long-term environmental ability of particulate-rich nuclear wastes. (authors)
Center for Gas Separations (CGS)
The total energy consumption in the U.S. has been rising steadily for decades, and it currently amounts to ~98,000 TBtu/yr, with approximately 30% of this total attributable to the industrial sector. Reasonable estimates indicate that 45–55% of total industry energy consumption derives from chemical separations, and for example, over 120 TBtu/yr alone is used in carrying out olefin/paraffin separations via energy-intensive cryogenic distillation. Therefore, the pursuit of new, even radically different approaches to some of the most energy-intensive industrial separations processes is an imperative scientific pursuit for reducing energy consumption toward a more sustainable future. Adsorbent and membrane-based separations can require a fraction of the energy needed for distillation methods, and as such are considered promising solutions for balancing increasing energy demand in the U.S. with the need for a massive reduction in energy consumption. Although considerable research effort has been devoted to the design of materials capable of carrying out various gas separations, usually operating through size-selective, chemisorptive, or physisorptive mechanisms, it remains a great challenge to design materials that function adequately for real-world applications. Indeed, the chemical and physical differences between molecules in gas mixtures of interest are often small, and therefore it is necessary, through the use of nanoscience and synthetic chemistry, to engineer unprecedented molecular-level control in adsorbate–adsorbent interactions. The overarching mission of the Center for Gas Separations (CGS) was to discover fundamental innovations that have the potential to dramatically reduce the energy associated with critical gas separations. In particular, the CGS developed novel synthetic routes, guided by molecular chemistry principles, as well as advanced characterization and computational methods, that have enabled the discovery of new materials and membranes tailor-made to exhibit exceptional performance for a range of gas separations processes, as required in the clean use of fossil fuels and in reducing CO 2 emissions from industry. A challenge of this magnitude required the collaboration and synergy of a large team of researchers with expertise in materials synthesis, characterization, and computations. During the 11-year project period, the CGS created a range of new materials within the family of highly-tunable, porous solids known as metal–organic frameworks (MOFs). These new frameworks demonstrate novel mechanisms for key industrial gas separations, including revolutionary new cooperative adsorption processes that enable low-energy CO 2 and CO capture, and are capable of efficiently separating olefins from paraffins, O 2 from air, and the shape-selective separation of alkane isomers. In addition, the CGS developed new strategies for incorporating these materials into composite membranes toward highly efficient and selective membrane-based separations. As a testament to the success of the CGS, two start-up companies, Mosaic Materials,4 Inc. and Flux Technology, Inc., grew out of these research efforts, and these companies are seeking to commercialize MOF and composite membranes materials for key separations in industry, including large-scale CO 2 capture and hydrocarbon separations, respectively. Another company, framergy, Inc., licensed IP resulting from CGS research toward the commercialization of adsorbents for various energy-relevant applications.
Porous Organic Cage Membranes for Molecular Gas Separations (Final Technical Report for DE-SC0021357)
This proposal aims at demonstrating the development of a novel family of membranes, composed of porous organic cages (POC) which offer the possibility of displaying high separation performance for challenging molecular gas separations relevant to natural gas purification, and olefin/paraffin separation. The proposed POCs synthesized in membrane form will display the most desirable properties of polymers (facile processability and flexibility) and inorganic materials (hierarchically ordered pores with molecular sieving properties) leading to highly selective and permeable membranes. POCs should display distinctive structural, compositional, adsorption and transport properties than those of conventional porous materials, opening the doors for a new research direction in membrane science, and gas separations. Our preliminary results demonstrate the feasibility of preparing POC crystals with controlled size, and continuous POC membranes with remarkable high permeances, and separation ability for CO 2 /CH 4 , N 2 /CH 4 and C 3 H 6 /C 3 H 8 separations serving as a solid foundation for our proposed work. Fundamentally, this proposal aims at elucidating separation mechanisms of different gas mixtures related to natural gas composition, and olefin/paraffin separation over porous organic cage membranes. The proposed research will result in fundamental understanding of adsorption and transport properties of industrially relevant gas molecules through novel microporous membranes, and may lead to the development of a cost effective membrane technology for natural gas purification, and olefin/paraffin separation surpassing the conventional benchmark technology distillation. Furthermore, we aim at demonstrating selective water transport through POC membranes, which can be positively impactful in numerous industrial applications in which water is present. The ability to fabricate thin, chemically and mechanically stable POC membranes for societal relevant gas separations constitute a new and distinctive direction in membrane science. Our proposed work aims at addressing some of the challenges recognized in the Research Agenda for Transforming Separation Science . Specifically: (a) advancing understanding of complex mixtures on separation performance; (b) exploring thermodynamic and kinetic mechanisms through the elucidation of separation mechanisms, and (c) study potential stability issues of the membranes to be assessed by evaluating the long term membrane stability and performance at various temperatures and pressures. The team is uniquely qualified to execute the proposed work. The PI has solid expertise in the rational molecular engineering design of porous crystalline membranes for molecular gas separations. The PNNL collaborator has extensive experience in the synthesis, characterization, and functional applications of microporous crystals, with particular emphasis on gas adsorption.
Methodology for assessing the maximum potential impact of separations opportunities in industrial processes
Separation technologies currently used in U.S. manufacturing industries are estimated to account for more than 20% of plant energy consumption. However, accurately determining the impact of new separation technology solutions can sometimes be difficult, especially when evaluating a slate of new candidate separation technologies, each of which has its own separation performance, energy demand, and capital cost. In these cases, a typical approach is to assess each new separation technology by collecting performance and cost information and then using that information to develop a techno-economic analysis to identify overall benefits. While this approach is thorough, it can be time consuming and can hinder reaching a critical understanding of the potential of a given separation challenge, especially when there is no known solution. To address these issues, we developed an assessment methodology, using industrial screening processes, that can be used to better understand the potential impacts of addressing a given separation challenge. This paper presents an overview of our separation challenge stream assessment methodology. The methodology involves defining an “ideal” separator and deriving the associated minimum separation energy. The “ideal” separator represents the most optimistic outlook of a given opportunity so the maximum impact from existing and not-yet-developed solutions can be assessed. Using established biorefinery models, we applied the methodology to 10 different separation challenge streams from two different biomass conversion platforms to identify the type of information that can be obtained. Three of the ten challenge streams assessed had maximum possible cost savings predictions >20%, and associated reductions in process energy carbon intensity ranging from 0 to 54%. Two streams had cost and energy savings potential that were < 5%. Some of the opportunity drivers from the various assessments include higher product yields, reduction or elimination of downstream equipment, new co-products, and cost savings associated with raw materials and energy consumption. The information from these assessments can help guide the selection or development of new separation technology solutions based on the various potential factors that drive the projected benefits.
Enhanced separation of rare earth elements
Industrial rare earth separation processes utilize PC88A, a phosphonic acid ligand, for solvent extraction separations. The separation factors of the individual rare earths, the equipment requirements, and chemical usage for these flowsheets are well characterized. Alternative ligands such as Cyanex® 572 and the associated flowsheets are being investigated at the pilot scale level to determine if significant improvements to the current separation processes can be realized. These improvements are identified as higher separation factors, reduced stage requirements, or reduced chemical consumption. Any of these improvements can significantly affect the costs associated with these challenging separation proccesses. A mid/heavy rare earth element (REE) separations flowsheet was developed and tested for each ligand in a 30 stage mixer-settler circuit to compare the separation performance of PC88A and Cyanex® 572. The ligand-metal complex strength of Cyanex® 572 provides efficient extraction of REE while significantly reducing the strip acid requirements. Reductions in chemical consumption have a significant impact on process economics for REE separations. Partitioning results summarized Table 1 indicate that Cyanex® 572 offers the same separation performance as PC88A while reducing acid consumption by 30% in the strip section for the mid/heavy REE separation. Flowsheet Effluent Compositions PC88A Cyanex® 572 Raffinate Mid REE Heavy REE 99.40% 0.60% 99.40% 0.60% Rich Mid REE Heavy REE 2.20% 97.80% 0.80% 99.20% Liquor Strip Acid Required 3.4 M 2.3 M Table 1 – Flowsheet results comparing separation performance of PC88A and Cyanex® 572 for a mid/heavy REE separation.
Kr/Xe SeparatioKr/Xe Separation over Metal Organic Framework Membranes
The central thrust of this project is to develop a novel family of continuous membranes, composed of porous crystalline membranes (mainly metal organic frameworks) which offer the possibility of demonstrating high separation performance for Kr/Xe gas mixtures. The specific objectives of the proposed work are: (1) The development of continuous and reproducible MOF membranes on porous tubular supports displaying high Kr permeabilities and high Kr/Xe separation selectivities.(2) Demonstrating the membrane performance long term stability.(3) Establish the basic structure/separation relationships of MOF membranes in Kr/Xe separations, and (4) Demonstrating that membrane synthesis could be amenable to large scale production. We have demonstrated that porous crystalline molecular sieve membranes including metal organic frameworks, zeolites, and alumino phosphates can effectively separate Kr/Xe gas mixtures ate industrially relevant compositions. Specifically, these three compositions correspond to a different family of microporous crystals, namely zeolites (SAPO-34), metal organic frameworks (ZIF-8) and alumino phosphates (AlPO-18). SAPO-34 membranes displayed the best overall separation performance, while AlPO-18 membranes displayed the highest Kr permeances. The key factors affecting the separation selectivity and permeance of these membranes were identified, and decoupled. The presence of rigid micropores with size lying between Kr and Xe atomic sizes, lower Xe/Kr uptakes (adsorption selectivity), and lower concentration of non-selective pores led to the highest observed Kr/Xe separation selectivities among these three microporous crystals, which corresponded to SAPO-34. The Kr permeances for these three microporous crystalline membrane compositions decreased exponentially with membrane thickness. The best membranes separated Kr/Xe gas mixtures with separation selectivities as high as 45 and Kr permeances ~ as high as 1.2 x 10 -7 mol/m 2 s Pa. In addition, SAPO-34 and ZIF-8 membranes were effective in separating Air/Xe mixtures. With separation selectivities as high as 30, and air permeances of 2.3 x 10 -7 mol/m 2 s Pa. Finally, we explore the synthesis in powder form of other potentially suitable porous crystals that if prepared in membrane form could be highly appealing candidates for Kr/Xe and Air/Xe separation. These crystals are porous organic cages which potentially can molecular sieve Kr and air from Xenon based on the unimodal pore sizes lying between the size of the permeant molecules.
Hydrogen Isotope Separation from Aqueous Streams using Zeolite Membranes
Efficient separation of heavy hydrogen isotopes {sup 3}H (or T, tritium) and {sup 2}H (or D, deuterium) from {sup 1}H has been a long-standing endeavor in nuclear fuel cycle research and development. For example, tritium (half-life 12.3 years) is a fission product from nuclear plants and is found as tritiated water (HTO) in effluent streams from nuclear installations. Tritium must be concentrated and removed from such aqueous streams for waste storage. The separation of deuterium from deuterated water (HDO) has applications in heavy water production, and can also be used as a nonradioactive simulant in HTO separation research. Several methods have been explored such as ion exchange/adsorption and membrane permeation. Adsorption by molecular sieving materials such as zeolites can separate tritiated water from water with moderate selectivity (HTO/H{sub 2}O separation factor∼1.2-1.4) due to a subtle difference in adsorption characteristics between the two species. However, there remains a requirement for high-selectivity continuous separation of heavy hydrogen isotopes from water. Here we demonstrate new results on the use of zeolite membranes as a potential high-performance, low-cost, radiation-stable candidate for such separations. In zeolite membranes, separation of HTO (or HDO) from water would take place by a combination of adsorption and diffusion characteristics. Here we describe the hydrogen isotope separation properties of silicoaluminophosphate (SAPO-34) membranes synthesized on porous α-alumina supports. D{sub 2}O/H{sub 2}O feed mixtures of realistic compositions are used as a non-radioactive simulant for tritiated water feeds. Our results show promising applications of zeolite membranes for hydrogen isotope separation and recovery. In summary, SAPO-34 membranes were fabricated and investigated to demonstrate their pervaporative separation properties for D{sub 2}O-H{sub 2}O binary systems. These membrane exhibit high selectivity (up to ∼19) for D{sub 2}O and good permeance (> 600 GPU) even at low concentrations of D{sub 2}O in the feed, making them highly interesting candidates for capture of heavy hydrogen isotopes (D and T) from aqueous streams encountered in the nuclear fuel cycle. The mechanism of separation appears to involve both diffusivity and adsorption differences as expected in nanoporous materials, even though detailed identification of their respective contributions is a subject of future work. We also hypothesize that tritiated (T{sub 2}O/H{sub 2}O) mixtures will also show similar performance in relation to the present deuterated mixtures. This is planned to be further investigated through pervaporation measurements. (authors)
Chabazite Zeolite Membranes for Krypton/Xenon Separation: Control of Membrane Properties and Process Modeling
Nuclear energy is considered to be a clean and economical means of carbon-free energy. As part of the overall process for recycling used nuclear fuel (UNF), it is necessary to develop technologies to separate the off-gases formed during the fission of uranium and plutonium in nuclear power reactors. The off-gas stream is generated during the shearing and chopping, voloxidation, and acid dissolution steps, and would have a flow rate of ∼2500 L/min assuming a typical 800 tons heavy metal/yr reprocessing facility. Kr separation from Xe is one of the steps in a proposed UNF off-gas processing flowsheet. The Kr/Xe mixture is approximately 10/90 by volume and hence the separation of Kr would reduce the volume of radioactive {sup 85}Kr waste by a factor of 10. Kr/Xe separation is challenging since they are both chemically inert species and physically very similar (0.036 nm size difference). There is no existing process for this separation that is suitable for use in UNF recycling since conventional cryogenic distillation requires highly intensive power and large system volume. Membrane-based separation using radiation-stable materials such as zeolites could be an attractive separation method, if membranes with sufficient Kr flux and selectivity can be fabricated. Zeolite membranes offer an opportunity to exploit the size difference of Kr (kinetic diameter 0.36 nm) and Xe (0.396 nm) to achieve preferential permeation of the minority component (Kr) from the mixture, leading to an efficient separation with very low energy requirements. An ideal membrane process would permeate a stream of pure Kr for storage and also produce pure Xe which has commercial value (> $8000/kg at 99+% purity). SAPO-34 is a silico-alumino-phosphate zeolite molecular sieve with CHA framework topology and containing uniform micropores (0.38 nm), intermediate in size between the kinetic diameters of Kr and Xe. It was hypothesized that SAPO-34 membranes can separate krypton and xenon by diffusivity differences. Previously we fabricated SAPO-34 membranes and showed that they are capable of separating Kr from Xe. Our previous work also indicated that there is much potential for engineering the separation properties of these membranes with a view to improving permeance and selectivity and evaluating the expected process performance. The main objectives of the present study are: 1) development of SAPO-34 membranes with enhanced membrane performance via thickness reduction and ion exchange, and 2) process modeling for technic-economic analysis of zeolite membrane systems for Kr/Xe separation.
Designer Metal–Organic Frameworks for Size–Exclusion–Based Hydrocarbon Separations: Progress and Challenges
The separation of hydrocarbons is of primary importance in the petrochemical industry but remains a challenging process. Hydrocarbon separations have traditionally relied predominantly on costly and energy intensive heat-driven procedures such as low temperature distillations. Adsorptive separation based on porous solids represents an alternative technology that is potentially more energy efficient for the separation of some hydrocarbons. Great efforts have been made recently not only on the development of adsorbents with optimal separation performance but also towards the subsequent implementation of adsorption-based separation technology. Emerging as a relatively new class of multifunctional porous materials, metal-organic frameworks hold substantial promise as adsorbents for highly efficient separation of hydrocarbons. This is because of their exceptional and intrinsic porosity tunability which enables size-exclusion based separations that render the highest possible separation selectivity. In this review, we highlight the recent advances in the development of MOFs for separation of selected groups of hydrocarbons, including methane/C2 hydrocarbons, normal alkanes, alkane isomers, alkane/alkene/alkyne, and C8 alkylaromatics, with a particular focus on separations based on size-exclusion mechanism. Insights into tailor-made structures, material design strategies, and structure-property relations will be elucidated. In addition, the existing challenges and possible future directions of this important research field will be discussed.
Silver-mediated separations: A comprehensive review on advancements of argentation chromatography, facilitated transport membranes, and solid-phase extraction techniques and their applications
The use of silver(I) ions in chemical separations, also known as argentation separations, is a powerful approach for the selective separation and analysis of many natural and synthetic organic compounds. In this review, a comprehensive discussion of the most common argentation separation techniques, including argentation-liquid chromatography (Ag-LC), argentation-gas chromatography (Ag-GC), argentation-facilitated transport membranes (Ag-FTMs), and argentation-solid phase extraction (Ag-SPE) is provided. For each of these techniques, notable advancements, optimized separations, and innovative applications are discussed. The review begins with an explanation of the fundamental chemistry underlying argentation separations, mainly the reversible π-complexation between silver(I) ions and carbon-carbon double bonds. Within Ag-LC, the use of silver(I) ions in thin-layer chromatography, high-performance liquid chromatography, as well as preparative LC are explored. This discussion focuses on how silver(I) ions are employed in the stationary and mobile phase to separate unsaturated compounds. For Ag-GC and Ag-FTMs, different silver compounds and supporting media are discussed, often with relation to olefin-paraffin separations. Ag-SPE has been widely employed for the selective extraction of unsaturated compounds from complex matrices in sample preparation. This comprehensive review of Ag-LC, Ag-GC, Ag-FTMs, and Ag-SPE techniques emphasizes the immense potential of argentation separations in separations science and serves as a valuable resource for researchers seeking to learn, optimize, and utilize argentation separations.