Water Ether Research Articles

Effect of silver nanoparticles on the solubility of methane and ethane in water

In this work, the solubility of methane and ethane were studied in aqueous dispersion of silver nanoparticles (1, 5, and 10 ppm) at temperatures of 1, 2.5, 10, and 11.5 °C for methane and 2.5, 5, 10, 15.5 °C for ethane and at initial pressures 1 to 5.5 and 0.35–2.15 MPa for methane and ethane, respectively. The nanoparticles were synthesized and characterized through UV–vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM) image. The results demonstrated that silver nanoparticles increased the solubility of methane and ethane up to 13 and 16% compared with pure water, respectively. The solubility of methane and ethane were enhanced by increasing the nanoparticles mass loading. The effect of nanoparticles on ethane solubility was more significant than methane solubility.

Phase Equilibria of Water/CO2 and Water/n-Alkane Mixtures from Polarizable Models.

Phase equilibria of water/CO2 and water/n-alkane mixtures over a range of temperatures and pressures were obtained from Monte Carlo simulations in the Gibbs ensemble. Three sets of Drude-type polarizable models for water, namely the BK3, GCP, and HBP models, were combined with a polarizable Gaussian charge CO2 (PGC) model to represent the water/CO2 mixture. The HBP water model describes hydrogen bonds between water and CO2 explicitly. All models underestimate CO2 solubility in water if standard combining rules are used for the dispersion interactions between water and CO2. With the dispersion parameters optimized to phase compositions, the BK3 and GCP models were able to represent the CO2 solubility in water, however, the water composition in CO2-rich phase is systematically underestimated. Accurate representation of compositions for both water- and CO2-rich phases cannot be achieved even after optimizing the cross interaction parameters. By contrast, accurate compositions for both water- and CO2-rich phases were obtained with hydrogen bonding parameters determined from the second virial coefficient for water/CO2. Phase equilibria of water/n-alkane mixtures were also studied using the HBP water and an exponenial-6 united-atom n-alkanes model. The dispersion interactions between water and n-alkanes were optimized to Henry's constants of methane and ethane in water. The HBP water and united-atom n-alkane models underestimate water content in the n-alkane-rich phase; this underestimation is likely due to the neglect of electrostatic and induction energies in the united-atom model.

Mild oxidation of ethane to acetic acid by H2O2 catalyzed by supported μ-nitrido diiron phthalocyanines

Low temperature selective transformation of light alkanes of natural gas to useful products continues to be an important challenge in chemistry and industry. μ-Nitrido diiron phthalocyanines were recently identified as powerful oxidation catalysts capable of oxidizing methane, benzene and transforming poly- and perfluorinated aromatic compounds under oxidative conditions. Herein, we have supported two μ-nitrido diiron complexes onto silica, graphite or nafion and their catalytic performance has been evaluated in the heterogeneous oxidation of ethane in water. Acetic acid was obtained with selectivity up to 71%. Turnover number up to 58 and 50–65 % product yields can be achieved. The cleavage of C–C bond also occurred and formic acid was formed as side product. In contrast to methane oxidation, no strong influence of 75 mM acid was observed in ethane oxidation. The reactivities of C–H bonds in methane, ethane and propane were very similar when the reaction was performed in water. In contrast, in diluted acidic solution, the μ-nitrido diiron phthalocyanine – H2O2 system exhibits 5 times higher activity in the oxidation of the methane C–H bond compared to the ethane C–H bond.

Rapid Analysis of Dissolved Methane, Ethylene, Acetylene and Ethane using Partition Coefficients and Headspace-Gas Chromatography

Analysis of dissolved methane, ethylene, acetylene, and ethane in water is crucial in evaluating anaerobic activity and investigating the sources of hydrocarbon contamination in aquatic environments. A rapid chromatographic method based on phase equilibrium between water and its headspace is developed for these analytes. The new method requires minimal sample preparation and no special apparatus except those associated with gas chromatography. Instead of Henry's Law used in similar previous studies, partition coefficients are used for the first time to calculate concentrations of dissolved hydrocarbon gases, which considerably simplifies the calculation involved. Partition coefficients are determined to be 128, 27.9, 1.28, and 96.3 at 30°C for methane, ethylene, acetylene, and ethane, respectively. It was discovered that the volume ratio of gas-to-liquid phase is critical to the accuracy of the measurements. The method performance can be readily improved by reducing the volume ratio of the two phases. Method validation shows less than 6% variation in accuracy and precision except at low levels of methane where interferences occur in ambient air. Method detection limits are determined to be in the low ng/L range for all analytes. The performance of the method is further tested using environmental samples collected from various sites in Nova Scotia.

Simultaneous measurement of ethane diffusivity and skin resistance of ‘Jonica’ apples by efflux experiment

An experiment was carried out to simultaneously measure the diffusivity and skin resistance of ethane in ‘Jonica’ apples by equilibrating them in an ethane–air mixture, transferring them to an ethane-free jar and monitoring the concentration of the air in the jar as the ethane is released. The concentration curve is then curve fitted by a finite element model using a realistic axisymmetric geometry to determine the diffusivity and mass transfer coefficient (inverse of skin resistance). The solubility (Henry’s law constant) of ethane in apple tissue was determined at equilibrium and was the same as that of ethane in water. The diffusivity of ethane in apple tissue was 19.4 × 10 −8 m 2 s −1, the skin resistance 1.26 × 10 6 s m −1 and the mass transfer Biot number (ratio of internal to external resistance) 0.61. The values of these parameters for O 2, CO 2 and neon were calculated from those for ethane using a two phase co-diffusion model. They disagree with results from previous efflux experiments but are consistent with direct measurement on cut tissue samples using the diffusion cell method. This can be explained by the hypothesis that the diffusivity determined by curve fitting is that of the inner cortex, while the resistance of the outer cortex is treated as part of skin resistance. Taken in combination with previous tests, the present results give an indication of the diffusivity profile across the apples.

Hydrophobic Interactions by Monte Carlo Simulations

The structural and thermodynamic properties of liquid water and of the dilute solutions of methane and ethane in water were calculated by Monte Carlo simulations in the temperature range 298 K to 318 K and 298 K to 333 K, respectively. The nonpolar molecules were modeled as one- and two-center Lennard–Jones particles; for the interaction potential of water a modified TIP5P model was used. The results indicate that the nonpolar solutes tend to aggregate with increasing temperature. Methane molecules preferably form water-separated pairs, even at higher temperatures, whereas for ethane contact pairs are more likely. For the thermodynamic conditions studied here, the residual chemical potential of water is a linear function of temperature.

Measurements and Thermodynamic Modeling of Vapor−Liquid Equilibria in Ethane−Water Systems from 274.26 to 343.08 K

In this paper, new experimental data on the solubility of gaseous ethane in water are reported in the 274.26−343.08 K temperature range for pressures up to 4.952 MPa. A static−analytic apparatus, taking advantage of a pneumatic capillary sampler, is used for fluid sampling. The Valderrama modification of the Patel−Teja equation of state, combined with non-density-dependent mixing rules, is used for modeling the vapor−liquid equilibrium. The new solubility data generated in this work are used for tuning of the binary interaction parameters between ethane and water. Then, these data are compared with some literature data and the results of the thermodynamic model. To further evaluate the performance of the model, a comparison is made between the predicted water content data and some experimental data in the literature. These comparisons show the reliability of the techniques and model presented in this work.

Perfluoroalkanes in Water: Experimental Henry's Law Coefficients for Hexafluoroethane and Computer Simulations for Tetrafluoromethane and Hexafluoroethane

The solubility of hexafluoroethane in water was determined experimentally and, together with that of tetrafluoromethane, calculated by molecular simulation. A high-precision apparatus based on an extraction method was used to measure the solubility of hexafluoroethane in water in the temperature range of 287−328 K at pressures close to atmospheric. The experimental data obtained were used to calculate Henry's law coefficients H2,1(p1sat,T), whose temperature dependence was represented by appropriate correlations. The imprecision of the results was characterized by average deviations of H2,1 from these smoothing equations and is of ±0.17%. From the temperature variation of the Henry's law coefficients, partial molar solution quantities such as the variation of the Gibbs energy, enthalpy, entropy, and heat capacity were derived. Monte Carlo simulations, associated with Widom's test particle insertion method and the finite−difference thermodynamic integration technique, were used to calculate the residual chemical potential of low molecular weight alkanes and perfluoroalkanes in water leading to Henry's law coefficients. Simulations were performed from 280 to 500 K along the saturation line of the pure solvent. The simulation method was validated by the calculation of H2,1(p1sat,T) for methane and ethane in water for which quantitative predictions were attained even at the lowest temperatures. The calculations for tetrafluoromethane and hexafluoroethane in water were compared with experimental values, when available, to test intermolecular potential models. Solute−solvent radial distribution functions were obtained from simulation at low and high temperatures.

Solubility measurements of methane and ethane in water at and near hydrate conditions

The isobaric solubility of pure methane and ethane gases in liquid water was measured under different conditions, including hydrate formation points, using a ramping method in which measurements are made through the entire and continuous hydrate formation/decomposition cycle. The work was conducted for methane at 3.45 MPa (500 psia) and temperatures ranging from 17.0 to 0.0°C (290.2 to 273.2 K), and for ethane at 0.66 MPa (95 psia) and a temperature range of 17.0 to 0.0°C (290.2 to 273.2 K). The isobaric solubilities obtained show a significant divergence from (normal) Henry's law solubility as the temperature is lowered. The increase in the solubility is presumably the result of the onset of a sorption process that traps the gas molecules in the water structure. Several sub-processes were observed as the hydrate formation was taking place: (1) the dissolution of the gas in the liquid water, or interstitial solubility, (2) the onset of the sorption sub-process and build-up of the hydrate precursors, (3) the catastrophic formation and the existence of the solid phase with its slushy characteristics, and (4) the solidification of the hydrates, therefore causing the total plugging of the experimental cell.

The Solubility of Ethane in Water up to 473 K

AbstractThe Henry constants for the dissolution of ethane in water have been determined with two experimental methods up to 473 K and with an overall precision of 2%. From this data it was possible to calculate the thermodynamic properties of the dissolution process and using the results of our previous study of the thermodynamics of dissolution of methane in water, it was possible to calculate the contribution of the so‐called hydrophobic effect over a wide temperature range. It is shown that a Percus‐Yevick plus Lennard‐Jones perturbation theory accounts reasonably well for the observed behaviour.

Thermodynamic Carbon Isotope Effect for Solubility of Ethane in Water

Experimental determination of the carbon isotope effect in the ethane-water system was carried out using the modified Rayleigh method. The investigations were carried out with regard to the temperature dependence of the isotope effect in the temperature range between 13 and 80 °C under atmospheric pressure. The experimental results are discussed in details.

Antigens of Pasteurella tularensis: Preparative Procedures

Ether-water (EW) extraction of Pasteurella tularensis produced better antigens than five other chemical procedures. EW extracts produced from stationary-phase, liquid-grown, saline suspensions of strain SCHU S4 cells regularly induced agglutinin and precipitin formation in rabbits. Mice, guinea pigs, and monkeys also responded to EW extracts but with lower antibody levels. The use of strains of lower virulence, acetone-dried cells, organisms grown on a solid medium, and abbreviated extraction conditions all resulted in extracts with a diminished antigenicity, but logarithmic-phase and stationary-phase cells yielded equivalent EW extracts. The use of adjuvant, hyperimmunization, and large doses of antigen increased the precipitin responses of rabbits without appreciably altering the agglutinin response. By the appropriate combination of centrifugal fractionation of EW extracts, use of adjuvant, and vaccination schedule, rabbit antisera with either predominantly agglutinating or precipitating activities were obtained.

Phase Equilibria in Hydrocarbon-Water Systems II - The Solubility of Ethane in Water at Pressures to 10,000 psi

Abstract A preliminary investigation was made to determine the time required to attainequilibrium within the equilibrium cell for this system. Experimental and smoothed data are presented for the solubility of ethane inwater for temperatures of 100', 160', 220', 280' and 340'F at pressures to10,000 psia. The minimum solubility phenomenon disappears at 10,000 psia within thistemperature range. As a continuation of the investigation of the behavior of hydrocarbon-watersystems, the experimental data on the solubility of ethane in water have beenextended to 10,000 psia. The experimental apparatus, technique, materials, andanalytical methods are essentially the same as previously reported. Time-Concentration Study Prior to the initial determinations of solubility in the ethane-water system, it was desired to establish the time necessary to agitate the liquid and vapor at equilibrium temperature andpressure in order to have equilibrium between the phases. This was done bybringing the equilibrium cell to the equilibrium temperature, charging it withethane to a pressure of 800 psia, and then charging with water to a pressurewhich was the same for each time-solubility determination. The temperature ofthe determinations was 100'F and the pressure, having been 6,330 psia for thefirst determination, was maintained at this same value on each subsequentdetermination. When the water was charged to the equilibrium cell, the celltemperature departed from 100'F and a period of time averaging about 40 minuteshad to elapse before the cell came back to equilibrium temperature. During thistime, the cell and its contents were not agitated. When the system had returnedto equilibrium temperature, agitation was started and timing was begun. Theresults of the time-solubility determinations are given in Table I. Readingdown a column in Table I, the figures represent respectively: the time ofagitation for the particular run; the time at which water was charged to thecell, taken as zero; the time elapsing after charging the water and until thecell returned to equilibrium temperature where agitation was begun; the hoursrelative to zero time elapsing before agitation was stopped; and the solubilitydetermined for the particular run. Since the ethane and water were in contactduring the period when the temperature was returning to the equilibriumtemperature, the time measured against the solubility values determined is nota true measure. Considerable diffusion undoubtedly occurred under the pressuresinvolved; however, the technique used was necessary in view of the fact thatfor the shorter runs, the system may not have been at equilibrium temperaturewhen the desired time had elapsed. From Table I it may be seen that equilibriumwas attained within one hour after agitation was begun. T.P. 2932

Phase Equilibria in Hydrocarbon-Water Systems

The Solubility of Ethane in Water at Pressures to 1200 Pounds Per SquareInch Abstract Since water is present in natural gas and petroleum reservoirs, it is ofengineering value to have accurate experimental data regarding the behavior ofwater in hydro-carbon systems. Since experimental data of this nature are soscarce in literature, a program is under way at the University of Texas toobtain experimental data regarding the distribution of water in petroleum hydrocarbons. This initial paper is subdivided into three parts:The apparatus and analytical procedure are discussed.The equipment has been checked by comparing the experimental data with dataof literature on the solubility of methane in water at 77'F and pressures to10,000 psia.Experimental data are presented at 100, 160, 220, 280, and 340'F on thesolubility of ethane in water at pressures to 1200 psia. As the temperature isincreased the solubility of ethane in water first exhibits a minimum and then amaximum solubility. The range of applicability of Henry's Law is discussed. Introduction Although considerable experimental data have been published onwater-hydrocarbon systems in the hydrate region, the information on thesesystems in the vapor-liquid and the vapor-liquid-liquid regions at elevatedpressures is extremely scarce. A survey of the literature on hydrocarbon-watersystems at elevated pressures was presented by McKetta and Katz showing thesystems and phases investigated. In addition to these existing published data, Poettman and Dean have reported the water content of propane in the three-phaseregion (only the propane-rich liquid and the vapor phases were studied) andMichels, et al. have reported the solubility of methane in water at pressuresto 6800 pounds per square inch at 77?F and at pressures to 1500 psia attemperatures to 300'F. It has been shown, that the presence of water will materially affect thephase equilibrium of hydrocarbon systems. In order to make experimental studieson the quantitative effect of the presence of water in naturally-occurringhydrocarbon systems, it is desirable to have data available on binaryhydrocarbon-water systems. T.P. 2778