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1.
S. A. Stern S. S. Kulkarni H. L. Frisch 《Journal of Polymer Science.Polymer Physics》1983,21(3):467-481
Permeability coefficients have been measured for CO2, CH4, C2H4, and C3H8 in polyethylene membranes at temperatures of 5, 20, and 35°C and at applied gas pressures of up to 30 atm. The temperature and pressure dependence of the permeability coefficients was represented satisfactorily by an extension of Fujita's free-volume model of diffusion of small molecules in polymers. The results of the present steady-state permeability measurements provide further support for the conclusion reached from previous unsteady-state diffusivity measurements that Fujita's model is applicable to the transport of small molecules, such as CO2, CH4, C2H4, and C3H8, in polyethylene. It was previously thought that this model is applicable only to the transport of larger molecules, such as of organic vapors, in polymers. 相似文献
2.
Diffusion and solubility coefficients have been determined for the CO2?, CH4?, C2H4?, and C3H8-polyethylene systems at temperatures of 5, 20, and 35°C and at gas pressures up to 40 atm. Diffusion coefficients were obtained from rates of gas absorption in polyethylene rods under isothermal-isobaric conditions by means of a new diffusivity apparatus. The concentration dependence of the diffusion coefficients was represented satisfactorily by Fujita's free-volume model, modified for semicrystalline polymers, while the solubility of all the penetrants in polyethylene was within the limit of Henry's law. Semiempirical correlations were found for the free-volume parameters in terms of physicochemical properties of the penetrant gases and the penetrant-polymer systems. These correlations, if confirmed, should permit the prediction of diffusion and permeability coefficients of other gases and of gas mixtures in polyethylene as functions of pressure and temperature. 相似文献
3.
S. A. Stern G. R. Mauze H. L. Frisch 《Journal of Polymer Science.Polymer Physics》1983,21(8):1275-1298
Steady-state permeability coefficients have been measured for equimolar mixtures of CO2-C2H4, CO2-C3H8, and C2H4-C3H8, as well as for a mixture of 74.9 mol % CO2 and 25.1 mol % C2H4 in polyethylene membranes. The measurements were made at 20, 35, and 50°C and at pressures of up to 28 atm. Each component of the permeating mixtures studied had the effect of increasing the permeability coefficient for the other component. Furthermore, at equal partial pressures and at the same temperature, the component exhibiting the highest solubility in the polymer had the largest effect in increasing the permeability coefficient of the other component. This behavior is in agreement with the predictions of a free-volume model for the permeation of gas mixtures proposed by Fang, Stern, and Frisch. From a quantitative viewpoint, the permeability coefficients for the components of the mixtures agreed, on the average, to better than 25% with the predicted values. The theoretical permeability coefficients can be estimated from the model by using parameters determined with the pure components only. 相似文献
4.
The kinetics of depletion of ground state Ti(a3F) and electronically excited state Ti(a5F) upon interactions with CH4, C2H2, C2H4, and C2H6 are studied in a fast-flow reactor at a He pressure of 0.70 Torr. No depletion of ground state Ti(a3F) was observed upon interaction with all hydrocarbons studied here. Two alkanes, CH4 and C2H6, were also quite inert for depletion of the excited state Ti(a5F), On the other hand, C2H2 and C2H4 deplete the excited state Ti(a5F) very efficiently. Rate constants were determined to be (266 ± 86) and (476 ± 88) × 10?12 cm3s?1 for Ti(a5F) + C2H4 and Ti(a5F) + C2H2, respectively. These large rate constants compared with the ground state Ti were explained by an electron donor-acceptor interaction model that works in the interaction between C2H4 or C2H2 and the excited state with unfilled 4s orbital. 相似文献
5.
Synthesis and Characterization of the Fullerene Co-Crystals C60 · 12 C6H12, C70 · 12 C6H12, C60 · 12 CCl4, C60 · 2CHBr3, C60 · 2CHCl3, C60 · 2H2CCl2 By crystallization of fullerenes from non-polar solvents (C6H12, CCl4, CHBr3, CHCl3, H2CCl2) compounds of the following compositions were obtained: C60 · 12C6H12, C70 · 12C6H12, C60 · 12CCl4, C60 · 2CHCl3, C60 · 2CHBr3 and C60 · 2H2CCl2. Lattice parameters have been determined by X-ray diffraction of powder samples; according to single-crystal examinations on C60 · 12C6H12, C60 · 12CCl4 and C60 · 2CHBr3 the fullerene is orientationally disordered. C60 · 12C6H12, cubic, a = 28.167(1) Å; C70 · 12C6H12, cubic, a = 28.608(2) Å; C60 · 12CCl4, cubic, a = 27.42(1) Å; C60 · 2CHBr3, hexagonal, a = 10.212(1), c = 10.209(1) Å; C60 · 2CHCl3, hexagonal, a = 10.08(1), c = 10.11(2) Å; C60 · 2H2CCl2, tetragonal, a = 16.400(1) Å, c = 11.645(7) Å. 相似文献
6.
Yuhai Jiang Jinfeng Sun Linde Wan 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1995,34(1):29-33
A model complex optical potential (composed of static, exchange, polarization and absorption terms) is employed to calculate the total (elastic and inelastic) electron-atom scattering cross sections from the corresponding atomic wave function at the Hartree-Fock level. The total cross sections (TCS) for electron scattering by their corresponding molecules (C2H2, C2H4, C2H6, C3H6, C3H8 and C4H8) are firstly obtained by the use of the additivity rule over an incident energy range of 10–1000 eV. The qualitative molecular results are compared with experimental data and other calculations wherever available, good agreement is obtained in intermediate-and high-energy region. 相似文献
7.
Zusammenfassung Die vorliegende Arbeit beschreibt ein neues Verfahren zur gas-chromatographischen Simultananalyse von N2, O2, CO, CO2, N2O, SO2, CH4, C2H4 und C2H6 im Konzentrations-bereich von 10% bis 10 ppm ohne Voranreicherung. Die temperaturprogrammierte Trennung der Einzelkomponenten erfolgt nach Vorsäulensplitting auf zwei parallel geschalteten Säulen. Zur Emittlung der Retentionszeiten und der Peakflächen werden zwei voneinander unabhängige Ultraschalldetektoren verwendet, deren Analogsignale nach Digitalisierung in einem Mikrocomputer verarbeitet werden. Instrumentierung und chromatographische Einzelheiten werden beschrieben und diskutiert.
Simultaneous gas chromatographic determination of N2, O2, CO, CO2, N2O, SO2, CH4, C2H4 and C2H6 at the ppm-level. Part I
Summary A new procedure for the simultaneous determination of N2, O2, CO, CO2, N2O, SO2, CH4, C2H4 and C2H6 by gas chromatography is described. Concentrations from 10% down to 10 ppm can be determined without preconcentration. After a pre-column splitting the individual compounds of the sample are separated by a uniform temperature program on two different columns in parallel. Detection of the effluents is achieved by two individual ultrasonic detectors, the data from which are processed in a micro-computer. Instrumentation and gas chromatographic details are described and discussed.相似文献
8.
Organoantimony Compounds. VI. Crystalline Phenyl Antimony. Formation and Cleavage with Sodium and Lithium Butyl, respectively Reactions of C6H5SbH2 with C6H5CH ? CH2, C6H5C ? CH and other unsaturated compounds give the corresponding hydrogenated system and phenyl antimony as orange-red crystals and the formula (C6H5Sb)6 · 1 C6H6 1.1 reacts with sodium by cleavage of Sb–Sb bonds forming C6H5SbNa2 and C6H5(Na)Sb–Sb(Na)C6H5. These stibides are suitable materials to prepare tert. stibines, distibines and cyclic stibines. The cleavage of 1 with butyllithium is a complicated reaction and gives beside other stibides also C6H5(C4H9)SbLi which can be characterized as (CH3)3Si–Sb(C4H9)C6H5. The 1H-nmr data of the prepared stibines are discussed. 相似文献
9.
T. C. Merkel V. I. Bondar K. Nagai B. D. Freeman I. Pinnau 《Journal of Polymer Science.Polymer Physics》2000,38(3):415-434
The permeability of poly(dimethylsiloxane) [PDMS] to H2, O2, N2, CO2, CH4, C2H6, C3H8, CF4, C2F6, and C3F8, and solubility of these penetrants were determined as a function of pressure at 35 °C. Permeability coefficients of perfluorinated penetrants (CF4, C2F6, and C3F8) are approximately an order of magnitude lower than those of their hydrocarbon analogs (CH4, C2H6, and C3H8), and the perfluorocarbon permeabilities are significantly lower than even permanent gas permeability coefficients. This result is ascribed to very low perfluorocarbon solubilities in hydrocarbon‐based PDMS coupled with low diffusion coefficients relative to those of their hydrocarbon analogs. The perfluorocarbons are sparingly soluble in PDMS and exhibit linear sorption isotherms. The Flory–Huggins interaction parameters for perfluorocarbon penetrants are substantially greater than those of their hydrocarbon analogs, indicating less favorable energetics of mixing perfluorocarbons with PDMS. Based on the sorption results and conventional lattice solution theory with a coordination number of 10, the formation of a single C3F8/PDMS segment pair requires 460 J/mol more energy than the formation of a C3H8/PDMS pair. A breakdown in the geometric mean approximation of the interaction energy between fluorocarbons and hydrocarbons was observed. These results are consistent with the solubility behavior of hydrocarbon–fluorocarbon liquid mixtures and hydrocarbon and fluorocarbon gas solubility in hydrocarbon liquids. From the permeability and sorption data, diffusion coefficients were determined as a function of penetrant concentration. Perfluorocarbon diffusion coefficients are lower than those of their hydrocarbon analogs, consistent with the larger size of the fluorocarbons. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 415–434, 2000 相似文献
10.
T. C. Merkel V. Bondar K. Nagai B. D. Freeman 《Journal of Polymer Science.Polymer Physics》2000,38(2):273-296
Pure gas solubility and permeability of H2, O2, N2, CO2, CH4, C2H6, C3H8, CF4, C2F6, and C3F8 in poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) were determined as a function of pressure at 35°C. Permeability coefficients of the perfluorinated penetrants are approximately an order of magnitude lower than those of their hydrocarbon analogs, and lower even than those of the permanent gases. In striking contrast to hydrocarbon penetrants, PTMSP permeability to fluorocarbon penetrants decreases with increasing penetrant size. This unusual size‐sieving behavior in PTMSP is attributed to low perfluorocarbon solubilities in PTMSP coupled with low diffusion coefficients relative to those of their hydrocarbon analogs. In general, perfluorocarbon penetrants are less soluble than their hydrocarbon analogs in PTMSP. The difference in hydrocarbon and perfluorocarbon solubilities in high free volume, hydrocarbon‐rich PTMSP is much smaller than in hydrocarbon liquids and liquidlike polydimethylsiloxane. The low solubility of perfluorocarbon penetrants is ascribed to the large size of the fluorocarbons, which inhibits their dissolution into the densified regions of the polymer matrix and reduces the number of penetrant molecules that can be accommodated in Langmuir sites. From the permeability and sorption data, diffusion coefficients were calculated as a function of penetrant concentration. With the exception of H2 and the C3 analogs, all of the penetrants exhibit a maximum in their concentration‐dependent diffusion coefficients. Resolution of diffusion coefficients into a mobility factor and a thermodynamic factor reveals that it is the interplay between these two terms that causes the maxima. The mobility of the smaller penetrants (H2, O2, N2, CH4, and CO2) decreases monotonically with increasing penetrant concentration, suggesting that the net free volume of the polymer–penetrant mixture decreases as additional penetrant is added to PTMSP. For larger penetrants mobility either: (1) remains constant at low concentrations and then decreases at higher penetrant concentrations (C2H6, CF4, and C2F6); (2) remains constant for all concentrations examined (C3H8); or (3) increases monotonically with increasing penetrant concentration (C3F8). Presumably these results reflect the varying effects of these penetrants on the net free volume of the polymer–penetrant system. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 273–296, 2000 相似文献
11.
Noelia Calvar Elena Gómez Ángeles Domínguez Eugénia A. Macedo 《The Journal of chemical thermodynamics》2011,43(8):1256-1262
The osmotic and activity coefficients and vapour pressures of binary mixtures containing 1-propanol, or 2-propanol and imidazolium-based ionic liquids with bis(trifluoromethylsulfonyl)imide as anion (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, C2MimNTf2, 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide, C3MimNTf2, and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, C4MimNTf2) were determined at T = 323.15 K using the vapour pressure osmometry technique. The experimental osmotic coefficients were correlated using the extended Pitzer model modified by Archer and the MNRTL model, obtaining standard deviations lower than 0.033 and 0.064, respectively. The mean molal activity coefficients and the excess Gibbs free energy for the mixtures studied were calculated from the parameters of the extended Pitzer model modified by Archer. Besides the effect of the alkyl-chain of the cation, the effect of the anion can be assessed comparing the experimental results with those previously obtained for imidazolium ionic liquids with sulphate anions. 相似文献
12.
13.
Lin Yu Yong‐Qiang Ma Guo‐Cang Wang Hai‐Bin Song Hong‐Geng Wang Jin‐Shan Li Jing‐Rong Cui Rui‐Qing Wang 《应用有机金属化学》2004,18(4):187-190
A series of triarylbismuth(V) di(N‐p‐toluenesulfonyl)aminoacetates with the formula (4‐CH3C6H4SO2NHCH2CO2)2BiAr3 (Ar?C6H5, 4‐CH3C6H4, 4‐ClC6H4, 4‐BrC6H4) were synthesized and characterized by elemental analysis, IR, 1H NMR and mass spectra. The crystal structure of (4‐CH3C6H4SO2NHCH2CO2)2Bi(C6H4Cl‐4)3 was determined and shows the bismuth to exist in a distorted trigonal bipyramidal geometry. Four human neoplastic cell lines (HL‐60, PC‐3MIE8, BGC‐823 and MDA‐MB‐435) were used to screen these compounds. The results indicate that these compounds at 10 μM show cytotoxicity. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
14.
Inorganic-organic hybrid membranes containing silica as the structure matrix, poly(N-vinylpyrrolidone) (PVP) as the organic mediating agent and silver ions as olefinic carriers were prepared using sol–gel method and dip-coating process. The structure and permeances of the membranes for N2, He, C2H4, C2H6 at different temperatures indicated that defect-free membranes were obtained and the transportation of the C2H4 through the membranes followed the dissolution and diffusion mechanism. Ideal separation factors of C2H4/C2H6 through the membranes were evaluated at the temperature of 298, 373 and 423 K respectively using mixture gas of 50% C2H4-50% C2H6. The results showed that the ideal separation factors of C2H4/C2H6 through the membranes were obviously greater than the ratio of PC2H4/PC2H6 obtained from the single gas measurement due to the hindering effect by the adsorbed C2H4. The ideal separation factors of C2H4/C2H6 increased with temperature and reached 10 at 423 K, which suggested that C2H4 and C2H6 could be separated at lower humidity compared to the reported organic polymer/silver salt membranes in which humidified gases and higher silver loading were usually used. The transport of C2H4 in the inorganic-organic hybrid membrane was proposed to follow the hopping mechanism, that is, olefins moved across the fixed silver sites. 相似文献
15.
Permeability and diffusion coefficients of O2, He, CO2 and C4H6 were measured in water,swollen poly(vinylalcohol-co-itaconic acid) membranes having various water contents from 0.48 to 0.83. The permeability coefficients of CO2 and C4H6 were found to depend on the upstream pressure, while the permeability coefficients of O2 and He were independent of the pressure. With decreasing pressure the permeability coefficients of CO2 and C4H6 increased, and the pressure dependence became larger with decreasing water content of the membranes. A parallel permeation model based on the two states of water in the water-swollen membranes could be applied successfully to CO2 and C4H6. 相似文献
16.
Nela Farkaov Juraj ernk Milagros Toms Larry R. Falvello 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(5):477-481
The reaction of NiCl2, K2C2O4·H2O and 2,2′‐bipyridine (bpy) in water–ethanol solution at 281 K yields light‐purple needles of the new pentahydrate of bis(2,2′‐bipyridine)oxalatonickel(II), [Ni(C2O4)(C10H8N2)2]·5H2O or [Ni(ox)(bpy)2]·5H2O, while at room temperature, deep‐pink prisms of the previously reported tetrahydrate [Ni(ox)(bpy)2]·4H2O [Román, Luque, Guzmán‐Miralles & Beitia (1995), Polyhedron, 14 , 2863–2869] were gathered. The asymmetric unit in the crystal structure of the new pentahydrate incorporates the discrete molecular complex [Ni(ox)(bpy)2] and five solvent water molecules. Within the complex molecule, all three ligands are bonded as chelates. The complex molecules are involved in an extended system of hydrogen bonds with the solvent water molecules. Additionally, π–π interactions also contribute to the stabilization of the extended structure. The dehydration of the pentahydrate starts at 323 K and proceeds in at least two steps as determined by thermal analysis. 相似文献
17.
Equilibrium geometries, bond dissociation energies and relative energies of axial and equatorial iron tetracarbonyl complexes of the general type Fe(CO)4L (L = CO, CS, N2, NO+, CN–, NC–, η2‐C2H4, η2‐C2H2, CCH2, CH2, CF2, NH3, NF3, PH3, PF3, η2‐H2) are calculated in order to investigate whether or not the ligand site preference of these ligands correlates with the ratio of their σ‐donor/π‐acceptor capabilities. Using density functional theory and effective‐core potentials with a valence basis set of DZP quality for iron and a 6‐31G(d) all‐electron basis set for the other elements gives theoretically predicted structural parameters that are in very good agreement with previous results and available experimental data. Improved estimates for the (CO)4Fe–L bond dissociation energies (D0) are obtained using the CCSD(T)/II//B3LYP/II combination of theoretical methods. The strongest Fe–L bonds are found for complexes involving NO+, CN–, CH2 and CCH2 with bond dissociation energies of 105.1, 96.5, 87.4 and 83.8 kcal mol–1, respectively. These values decrease to 78.6, 64.3 and 64.2 kcal mol–1, respectively, for NC–, CF2 and CS. The Fe(CO)4L complexes with L = CO, η2‐C2H4, η2‐C2H2, NH3, PH3 and PF3 have even smaller bond dissociation energies ranging from 45.2 to 37.3 kcal mol–1. Finally, the smallest bond dissociation energies of 23.5, 22.9 and 18.5 kcal mol–1, respectively are found for the ligands NF3, N2 and η2‐H2. A detailed examination of the (CO)4Fe–L bond in terms of a semi‐quantitative Dewar‐Chatt‐Duncanson (DCD) model is presented on the basis of the CDA and NBO approach. The comparison of the relative energies between axial and equatorial isomers of the various Fe(CO)4L complexes with the σ‐donor/π‐acceptor ratio of their respective ligands L thus does not generally support the classical picture of π‐accepting ligands preferring equatorial coordination sites and σ‐donors tending to coordinate in axial positions. In particular, this is shown by iron tetracarbonyl complexes with L = η2‐C2H2, η2‐C2H4, η2‐H2. Although these ligands are predicted by the CDA to be stronger σ‐donors than π‐acceptors, the equatorial isomers of these complexes are more stable than their axial pendants. 相似文献
18.
Single crystals of Sr[B(C6H5O7)2](H2O)4 · 3H2O, a new borate‐citrate material, were grown with sizes up to 8 × 6 × 2 mm by slow evaporation of water at room temperature. The structure of Sr[B(C6H5O7)2](H2O)4 · 3H2O was determined by single‐crystal X‐ray diffraction. It crystallizes in the monoclinic space group P21/c, with a = 11.363(3) Å, b = 18.829(4) Å, c = 11.976(3) Å, β = 110.736(3)°, and Z = 4. The SrO8 dodecahedra, BO4 tetrahedra and citrate groups are linked together to form chains. The compound was characterized by IR and UV/Vis/NIR transmittance spectroscopy as well as thermal analysis. 相似文献
19.
《Fluid Phase Equilibria》1999,155(1):127-137
Solubilities of 15 nonpolar gases (He, Ne, Ar, Kr, Xe, H2, D2, N2, O2, CH4, C2H4, C2H6, CF4, SF6, and CO2) in 2-methyl-2-propanol (tert-butanol) have been measured at the temperature 303.15 K and 101.33 kPa partial pressure of gas. Standard changes of the Gibbs energy of solution have been also determined from experimental data. The Lennard–Jones 6,12 pair potential parameters have been estimated for that solvent using the Scaled Particle Theory (SPT) and these parameters have been compared with those corresponding to the other isomers of butanol. It can be concluded that the derived energy parameters provide a measurement of the association of the alkanol. A version of the UNIFAC model has been applied and the corresponding interaction parameters for alkanes and alkanols have been determined. 相似文献
20.
The pyrolysis of 2-methylbut-1-ene-3-yne (C5H6) has been studied from 375 to 450°C in a quartz reaction vessel in the absence and presence of O2 or NO. From 375 to 425°C, the rates of disappearance of reactant and of formation of dimers are second order in C5H6. The major product is polymer, with the dimers accounting for about 3% of the C5H6 consumed. In addition, toluene and p-xylene are produced, their production coming, at least in part, from decomposition of the C5H6 dimers (C10H12). Also, trace amounts of CH4, C2H4, C2H6, are formed. The rate coefficients for C5H6 removal and C10H12 formation in the absence of O2 or NO are where the uncertainties are one standard deviation. The reaction mechanism for dimer formation is analogous to that in vinyl acetylene (C4H4) pyrolysis (5), except that in the C4H4 system cyclooctatetraene is seen as an unstable product that isomerizes to styrene, whereas in the C5H6 system, the dimethylcyclooctatetraene apparently is too unstable to be detected. The dimers detected were 2,6-dimethylstyrene (P4), p-isopropenyltoluene (P5), and two other unidentified dimers (P3) with nearly identical gas chromatographic retention times. From the effect of the radical scavengers and by comparison of the C4H4 and C5H6 systems, the following mechanistic characteristics were determined: (1) The direct formation of styrene in the C4H4 system comes from a head-to-head modified Diels-Alder six-member cycloaddition that proceeds through a diradical intermediate. (2) There is no positive evidence for a direct head-to-tail modified Diels-Alder six-member cycloaddition. However, if it does occur, it does not involve diradicals but must be concerted. (3) Cyclooctatetraene is formed in concerted, non-free-radical mechanisms that may proceed both by head-to-head and head-to-tail eight-member cycloadditions. For the C5H6 system, the head-to-head adduct isomerizes to P3, whereas the head-to-tail adduct isomerizes to P3, P4, and/or P5. and/or P5. Kinetic data suggest that P3 is not produced from the cyclooctatetraene intermediate, in which case, head-to-head addition would not occur. It appears that the head-to-head additions are free radical in nature and proceed mainly through a six-membered ring intermediate, while head-to-tail additions are a concerted molecular process and proceed mainly through an eight-membered ring intermediate. 相似文献