Helium Group Gases

Hwang, Shuen‐cheng; Weltmer, William R.

doi:10.1002/0471238961.0701190508230114.a01

Cited by 5 publications

(6 citation statements)

References 40 publications

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“…Thus, concentration polarization was not observed in the present experiments with the SW membrane. Two different sweeping gases, i.e., N 2 and Ar, gave completely identical results, because both gas molecules have a spherical shape, are inert [27], and do not interfere with the membrane or with the other gases. However, nitrogen is somewhat cheaper and thus more practical in technology.…”

Section: Influence Of Sweep Stream On Membrane Separationmentioning

confidence: 91%

Biomethane Production from Biogas by Separation Using Thin‐Film Composite Membranes

et al. 2017

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Raw biogas obtained from a sewage plant was successfully purified by a single‐step method to a quality compatible with compressed natural gas (CNG) standards. For this purpose, thin‐film composite membranes with polyamide skin layer were evaluated at varying temperatures, pressures, feed and sweep flow rates. The wetting of the polyamide skin layer was analyzed under different experimental conditions. Optimization of the purification process resulted in a better separation than that in previous studies. The achieved CH4 and H2S levels are conform to the required standards for commercialization in the Czech Republic. A unique feature of the presented approach, distinguishing the water‐swollen thin‐film composite membranes from polymeric membranes under dry conditions, is that the condensing water absorbs a significant amount of the minor impurities of biogas, such as H2S.

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Section: Influence Of Sweep Stream On Membrane Separationmentioning

confidence: 91%

Biomethane Production from Biogas by Separation Using Thin‐Film Composite Membranes

et al. 2017

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“…Both xenon and krypton are used in lighting, in lasers, , in double glazing for insulation, , and as carrier gases in analytical chemistry . Since krypton and xenon are present in Earth’s atmosphere at concentrations of 1.14 and 0.087 ppm, respectively, the conventional method to obtain xenon and krypton is as a byproduct of the separation of air into oxygen and nitrogen by cryogenic distillation . This byproduct stream from air separation consists of 80% krypton and 20% xenon .…”

Section: Introductionmentioning

confidence: 99%

“…Cryogenic distillation for the separation of krypton and xenon has a very high energy and capital requirement, reflected by the cost of high-purity xenon, about $5000/kg . An alternative, potentially energy- and cost-saving Xe/Kr separation process is to use a nanoporous material as an adsorbent to selectively adsorb either Kr or Xe at ambient temperature through a temperature- or pressure-swing adsorption process. , Xenon and krypton are also products of the nuclear fission of uranium and plutonium; porous materials could be used to capture the radioactive xenon and krypton in the processing of used nuclear fuel. − Experiments regarding xenon and krypton adsorption ,,− suggest that it may be feasible to use nanoporous materials in an adsorption-based process to separate a Xe/Kr mixture.…”

Section: Introductionmentioning

confidence: 99%

What Are the Best Materials To Separate a Xenon/Krypton Mixture?

Simon¹,

Mercado²,

et al. 2015

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Accelerating progress in the discovery and deployment of advanced nanoporous materials relies on chemical insight and structure property relationships for rational design. Because of the complexity of this problem, trial-and-error is heavily involved in the laboratory today. A cost-effective route to aid experimental materials discovery is to construct structure models of nanoporous materials in silico and use molecular simulations to rapidly test them and elucidate data-driven guidelines for rational design. For example, highly-tunable nanoporous materials have shown promise as adsorbents for separating an industrially relevant gaseous mixture of xenon and krypton. In this work, we characterize, screen, and analyze the Nanoporous Materials Genome, a database of ca. 670,000 porous material structures, for candidate adsorbents for xenon/krypton separations. For over half a million structures, the computational resources required for a brute-force screening using grand-canonical Monte Carlo simulations of Xe/Kr adsorption are prohibitive.To overcome the computational cost, we used a hybrid approach combining machine learning algorithms (random forests) with molecular simulations. We compared the results from our large-scale screening with simple pore models to rationalize the strong link between pore size and selectivity. With this insight, we then analyzed the anatomy of the binding sites of the most selective materials. These binding sites can be constructed from tubes, pockets, rings, or cages and are often composed of non-discrete chemical fragments. The complexity of these binding sites emphasizes the importance of high-throughput computational screenings to discover new materials. Interestingly, our screening study predicts that the two most selective materials in the database are an aluminophosphate zeolite analogue and a calcium based coordination network, both of which have already been synthesized but not yet tested for Xe/Kr separations.

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“…For gaseous radioactive krypton and xenon, the long half‐life of 85 Kr ( t 1/2 ≈10.8 years) urges its separation and capture from the off‐gas to avoid radioactive contamination, while the radioactive 135 Xe can capture a neutron to transmute to stable 136 Xe, which can be used in the field from lighting, laser, medical imaging to anaesthesia [5] . Furthermore, the capture of Xe in the treatment of nuclear fuel waste can significantly lower the price of the Xe since the concentration of Xe in the nuclear fission gas is 4500 times higher than in the atmosphere [6] . Currently, cryogenic distillation technology is mostly used to separate Xe and Kr from nuclear reprocessing off‐gas, [7] which is energy‐intensive and uneconomic.…”

Section: Methodsmentioning

confidence: 99%

Self‐Adjusting Metal–Organic Framework for Efficient Capture of Trace Xenon and Krypton

et al. 2022

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The capture of the xenon and krypton from nuclear reprocessing off‐gas is essential to the treatment of radioactive waste. Although various porous materials have been employed to capture Xe and Kr, the development of high‐performance adsorbents capable of trapping Xe/Kr at very low partial pressure as in the nuclear reprocessing off‐gas conditions remains challenging. Herein, we report a self‐adjusting metal‐organic framework based on multiple weak binding interactions to capture trace Xe and Kr from the nuclear reprocessing off‐gas. The self‐adjusting behavior of ATC‐Cu and its mechanism have been visualized by the in‐situ single‐crystal X‐ray diffraction studies and theoretical calculations. The self‐adjusting behavior endows ATC‐Cu unprecedented uptake capacities of 2.65 and 0.52 mmol g−1 for Xe and Kr respectively at 0.1 bar and 298 K, as well as the record Xe capture capability from the nuclear reprocessing off‐gas. Our work not only provides a benchmark Xe adsorbent but proposes a new route to construct smart materials for efficient separations.

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Helium Group Gases

Cited by 5 publications

References 40 publications

Biomethane Production from Biogas by Separation Using Thin‐Film Composite Membranes

Biomethane Production from Biogas by Separation Using Thin‐Film Composite Membranes

What Are the Best Materials To Separate a Xenon/Krypton Mixture?

Self‐Adjusting Metal–Organic Framework for Efficient Capture of Trace Xenon and Krypton

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