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Catherine M. Zimmerman William J. Koros 《Journal of Polymer Science.Polymer Physics》1999,37(12):1235-1249
Despite efforts by the membrane community to develop polymeric materials with improved O2/N2 separation performance, limited progress has occurred for almost a decade. Molecular sieving media, which can exhibit gas separation properties superior to polymers, tend to be brittle and uneconomical to produce for large‐scale membrane separation processes. Considering this, the polymer structures investigated in this work were designed to mimic aspects of the structure of molecular sieving media such as zeolites and carbon molecular sieves while maintaining the processability associated with polymers. Significantly attractive gas separation material properties were obtained using hyper rigid polypyrrolone copolymers with controlled packing disruptions between flat, packable segments. The gas transport properties in the materials changed dramatically as a result of different average interchain spacing. Moreover, all of the polypyrrolones studied in this work exhibited performance lying on or above the existing O2/N2 upper bound trade‐off line between permselectivity and permeability. These results, therefore, may point the way to a new cycle of membrane materials improvements for gas separations. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1235–1249, 1999 相似文献
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Cover Picture: Maculatic Acids—Sex Attractant Pheromone Components of Bald‐Faced Hornets (Angew. Chem. Int. Ed. 36/2018) 下载免费PDF全文
Weiwu Ren Regine Gries Catherine McCaughey Nathan Derstine Santosh K. Alamsetti Kenji L. Kurita Lorna Tu Prof. Roger G. Linington Prof. Robert Britton Prof. Gerhard Gries 《Angewandte Chemie (International ed. in English)》2018,57(36):11473-11473
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尖海龙与日本海马脂肪的提取和分析 总被引:29,自引:3,他引:29
本采用快速脂肪提取法取代索氏提取法,提取时间仅需45min提取率98.8%以上,并利用50m×0.35mmi.d,PEG-20M玻璃毛细管柱,分析了山东黄海海域尖海龙与日本海马脂肪中的脂肪酸,其中,尖海龙分离出59个峰,鉴定了42个,日本海马分离出52个峰,鉴定了41个,分别占脂肪酸总量的97.3%和98.0%,测得尖海龙脂肪中的EPA+DHA占31.0%,日本海马为14.1%。 相似文献
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This work reports the transport of carbon dioxide, oxygen, and nitrogen in amorphous membranes of vulcanized natural rubber reinforced with regenerated cellulose. The values of the permeability coefficient of carbon dioxide, oxygen, and nitrogen in the composites with 25% of cellulose, measured at 25 °C and 15 cmHg of pressure, are roughly one‐third of those measured in the same conditions for these gases in natural rubber. The isotherms representing the variation of both the permeability and diffusion coefficients of the gases with pressure present a relatively sharp increase in the region of low pressures, attributed to changes in the free volume. The analysis of the permeability characteristics of the membranes in terms of the free‐volume theory suggests that gas transport is severely hindered in both the cellulose phase and the cellulose–rubber interphase of the composites. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 393–402, 2000 相似文献
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松毛虫性信息素微量成分鉴定方法的研究 总被引:9,自引:0,他引:9
采用气相色谱-质谱分析确认了顺-5-,反-7-十二碳二烯乙酸酯是思茅松毛虫性信息素腺体的主要成分(次要成分由于含量极微且受杂质干扰,未能获得全扫描质谱图)。利用高分辨率毛细管气相色谱分析了思茅松毛虫性信息素腺体提取物的酯基转移和乙酰化反应的衍生物,进一步确认了顺-5-,反-7-十二碳二烯醇是思茅松毛虫性信息素腺体中的微量成分。探讨了功能团相互转换微量化学反应法鉴定松毛虫性信息素腺体中微量成分功能团和立体构型的优点。强调了性信息素微量成分鉴定工作在昆虫化学通讯系统研究中的重要性。 相似文献
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Jean Rouchaud Olivier Neus Claude Moulard 《International journal of environmental analytical chemistry》2013,93(1):65-80
Abstract For the analysis of metsulfuron-methyl in the crop soils with a sensitivity limit of 0.3 μg kg?1 dry soil, in the soil extract metsulfuron-methyl was separated from its soil metabolites and the soil impurities by repeated thin-layer chromatographies (TLC). In the cleaned soil extract, diazomethane transformed metsulfuron-methyl 1 into N,N′ -dimethyl metsulfuron-methyl 2 (methyl 2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)methylamino]carbonyl]methylamino]sulfonyl]benzoate). In the gas-liquid chromatograph with detection by electron capture (GC-EC) and in the combined gas chromatograph-mass spectrometer (GC-MS), 2 was transformed into 1-dioxy-2-N-methyl-3-keto-1,2-benzisothiazole 3 which was measured by GC-EC with confirmation by GC-MS. The metsulfuron-methyl soil metabolites 2-sulfonamido-methylbenzoate 6, 1-dioxy-3-keto-1,2-benzisothiazole (saccharin) 7 and 2-sulfonamidobenzoic acid 8 were analyzed in the soil of winter wheat crops by a procedure similar to the one for metsulfuron-methyl. After their separation and purification in the soil extracts by TLC, 7 and 8 were methylated, and analyzed as 3 in the GC-EC and GC-MS apparatus where the generated 6 was quantitatively transformed into 3; 6 was analyzed as such with the GC and GC-MS apparatus wherein it was transformed into 3. The sensitivity limit for each metabolite was 0.3 μg of equivalents of metsulfuron-methyl kg?1dry soil. The syntheses of the analysis standards of the metsulfuron-methyl derivatives 2 and 3, and of the metsulfuron-methyl metabolites 6, 7 and 8 are described. The transformation pathways of metsulfuron-methyl and of its derivatives are different from those of the pyridine-pyrimidine sulfonylurea herbicides flupyrsulfuron-methyl and rimsulfuron. The soil analysis of a sulfonylurea -by means of one of its transformation product- needs a previous study of the chemical reactivity of the sulfonylurea. This leads to the analysis procedures for the main soil metabolites of the sulfonylurea. 相似文献
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Gas‐transport properties in crosslinked polymers. I. Aliphatic polyurethane–acrylate‐based adhesives
P. Tiemblo J. Guzmn E. Riande E. F. Salvador C. Peinado 《Journal of Polymer Science.Polymer Physics》2001,39(7):786-795
The gas‐transport properties of one of a family of well‐known adhesives, Loctite 350®, were studied. Permeability, solubility, and diffusivity coefficients, together with the activation energies of diffusion and permeation and the solution enthalpy, were determined from 20 to 40 °C for oxygen, nitrogen, carbon dioxide, and methane. Loctite 350® showed relatively high permselectivity and permeability for the gas pairs O2/N2 and CO2/CH4, especially for the former. The possibility of preparing very thin layers on various kinds of supports from these photocurable polymers makes them promising materials for gas‐separation devices. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 786–795, 2001 相似文献
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The author gives a detailed survey on thermogravimetric investigations under quasi-isothermal — quasi-isobaric conditions (Q-TG). According to the principle of the technique the heating of the sample is governed by the transformation itself according to the feed-back principle in a way that the transformations should take place at a strictly constant rate, slower by orders of magnitude than in the case of the conventional techniques. Due to this, the transformations take place under ideal conditions, near to physico-chemical requirements.Based on the obtained advantageous results further methods were elaborated, like thermo-dilatometry (Q-TD), evolved gas analysis (Q-EGA) and microdistillation under quasi-isothermal conditions.The second part of the present review deals with DTA and DSC techniques under quasi-isothermal conditions elaborated recentlyThis revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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Cover Picture: para‐Xylene Ultra‐selective Zeolite MFI Membranes Fabricated from Nanosheet Monolayers at the Air–Water Interface (Angew. Chem. Int. Ed. 2/2018) 下载免费PDF全文
Dr. Donghun Kim Mi Young Jeon Prof. Benjamin L. Stottrup Prof. Michael Tsapatsis 《Angewandte Chemie (International ed. in English)》2018,57(2):361-361
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Summary Inverse gas chromatography with olefinic stationary phases, containing oxidation inhibitors, and air as carrier gas is shown
to yield characteristic plots of retention index versus time, which may be explained in terms of the present knowledge of
antioxidant action. A new technique for the evaluation of antioxidant efficiency is described that is sensitive to loss of
antioxidant due to vaporization. Further evidence of the role of the support phase in inverse gas chromatography is presented
and the adsorption of a hindered phenol used to give an estimate of the concentration of active sites on diatomaceous supports. 相似文献
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M. J. Reimers M. J. Cibulsky T. A. Barbari 《Journal of Polymer Science.Polymer Physics》1993,31(5):537-543
A series of vinyl alcohol/vinyl butyral copolymers was examined to assess the effect of internal hydrogen bonding on gas sorption and diffusion. Sorption and permeation measurements for carbon dioxide and methane were performed on four vinyl alcohol/vinyl butyral copolymers. Upon comparing the various data, it was found that hydrogen-bonded copolymers exhibit a much wider variation in diffusion coefficient than non-hydrogen-bonded copolymers. The fractional free volumes of the studied copolymers were considerably lower than expected based on values of the diffusion coefficient. This may be due to the fact that predicted occupied volumes are too large and that the effect of internal hydrogen bonding is not accounted for properly. Using a relationship between infrared spectral shift and hydrogen-bond length, fractional free volumes in the hydrogen bonded copolymers were correlated with the interatomic spacing associated with the hydrogen bond. This implies that the average length of a hydrogen bond can be used as a measure of chain packing in hydrogen-bonded polymers. © 1993 John Wiley & Sons, Inc. 相似文献
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This article evaluates the influence of temperature on the sorption of gases in two isomers of polynorbornene. The subject polymers were stereoisomers with nearly identical bulk density and total free volume. Because of differences in the mobility of the polymer backbone, the isomers packed differently resulting in differences in the average free‐volume element size within the matrix. The influence of these differences on free‐volume element size was characterized by the heat of sorption of gases in the matrix. The most pronounced differences were observed in the isosteric heats of sorption of condensable carbon dioxide and methane in the polymer isomers. This analysis suggests that the relative space available for sorption into free‐volume elements is higher in the methyl II isomer relative to methyl III. These conclusions support the physical characterizations reported in Part I of this series suggesting that the methyl II isomer has larger average free‐volume elements but fewer of them than the methyl III isomer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1939–1946, 2003 相似文献