The recycling or sequestration of carbon dioxide (CO2) from the waste gas of fossil-fuel power plants is widely acknowledged as one of the most realistic strategies for delaying or avoiding the ...severest environmental, economic, political, and social consequences that will result from global climate change and ocean acidification. For context, in 2013 coal and natural gas power plants accounted for roughly 31% of total U.S. CO2 emissions. Recycling or sequestering this CO2 would reduce U.S. emissions by ca. 1800 million metric tonseasily meeting the U.S.’s currently stated CO2 reduction targets of ca. 17% relative to 2005 levels by 2020. This situation is similar for many developed and developing nations, many of which officially target a 20% reduction relative to 1990 baseline levels by 2020. To make CO2 recycling or sequestration processes technologically and economically viable, the CO2 must first be separated from the rest of the waste gas mixturewhich is comprised mostly of nitrogen gas and water (ca. 85%). Of the many potential separation technologies available, membrane technology is particularly attractive due to its low energy operating cost, low maintenance, smaller equipment footprint, and relatively facile retrofit integration with existing power plant designs. From a techno-economic standpoint, the separation of CO2 from flue gas requires membranes that can process extremely high amounts of CO2 over a short time period, a property defined as the membrane “permeance”. In contrast, the membrane’s CO2/N2 selectivity has only a minor effect on the overall cost of some separation processes once a threshold permeability selectivity of ca. 20 is reached. Given the above criteria, the critical properties when developing membrane materials for postcombustion CO2 separation are CO2 permeability (i.e., the rate of CO2 transport normalized to the material thickness), a reasonable CO2/N2 selectivity (≥20), and the ability to be processed into defect-free thin-films (ca. 100-nm-thick active layer). Traditional polymeric membrane materials are limited by a trade-off between permeability and selectivity empirically described by the “Robeson upper bound”placing the desired membrane properties beyond reach. Therefore, the investigation of advanced and composite materials that can overcome the limitations of traditional polymeric materials is the focus of significant academic and industrial research. In particular, there has been substantial work on ionic-liquid (IL)-based materials due to their gas transport properties. This review provides an overview of our collaborative work on developing poly(ionic liquid)/ionic liquid (PIL/IL) ion-gel membrane technology. We detail developmental work on the preparation of PIL/IL composites and describe how this chemical technology was adapted to allow the roll-to-roll processing and preparation of membranes with defect-free active layers ca. 100 nm thick, CO2 permeances of over 6000 GPU, and CO2/N2 selectivity of ≥20properties with the potential to reduce the cost of CO2 removal from coal-fired power plant flue gas to ca. $15 per ton of CO2 captured. Additionally, we examine the materials developments that have produced advanced PIL/IL composite membranes. These advancements include cross-linked PIL/IL blends, step-growth PIL/IL networks with facilitated transport groups, and PIL/IL composites with microporous additives for CO2/CH4 separations.
Metabolomics is the study of metabolite profiles at the system level. Since its introduction in the early 2000s, metabolomics has greatly contributed to the understanding of the distribution of ...metabolites in organisms under various physiological conditions. In this comment, we show our research on the temporal development of metabolomics in general and in agricultural, food, and nutritional sciences. According to our investigation, metabolomics develops in a sigmoid kinetics. On the basis of the analysis, we made a prediction on the future of the metabolomics study, which may benefit the research community in the field.
Triply switchable CoII(dpzca)2 shows an abrupt, reversible, and hysteretic spin crossover (T 1/2↓ = 168 K, T 1/2↑ = 179 K, and ΔT 1/2 = 11 K) between the high-spin (HS) and low-spin (LS) states of ...cobalt(II), both of which have been structurally characterized. The spin transition is also reversibly triggered by pressure changes. Moreover, in a third reversible switching mechanism for this complex, the magnetic properties can be switched between HS cobalt(II) and LS cobalt(III) by redox.
Phosphonium poly(ionic liquid)s (PILs) have been studied as alternatives to more common ammonium and imidazolium PILs for potential transport and separation applications. This work characterizes the ...CO2, H2, N2, O2, CH4, and C2H4 single-gas permeability, diffusivity, solubility, and selectivity of free-standing films of poly((tri-n-alkyl)vinylbenzylphosphoniumbis(trifluoromethylsulfonyl)imide) PILs (i.e., poly(PnnnVBTf2N) where n=4, 6, 8). The gas permeability was found to increase approximately linearly with increasing alkyl chain length on the phosphonium group. To our knowledge, the CO2 permeability of 186 barrers observed for poly(P888VBTf2N) is the highest reported for neat PIL materials. In contrast, gas selectivity was observed to decrease with an increase in phosphonium alkyl chain length from n=4 to n=6, then remain approximately constant between n=6 and n=8. Additionally, the ionic conductivity of these materials was observed to increase from ca. 10−8 to ca. 10−5Scm−1 as the measurement temperature was increased from 25 to 105°C. At 25°C, the PIL with the shortest cation alkyl chain (n=4) was observed to have the lowest ionic conductivity. However at ca. 90°C, the expected trend of increasing ionic conductivity in the order n=4>n=6>n=8 was observed.
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•Light gas transport properties of phosphonium poly(ionic liquid) membranes.•Relatively high gas permeability for neat poly(ionic liquids).•Inverse H2/CO2 and N2/CH4 selectivity.•Ionic conductivity between 25 and 105°C.
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