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- GERG-2008 equation of state (2)
- Volumetric data (2)
- Copper hydroxide (1)
- Gas solubility (1)
- Gravimetric preparation (1)
- Henry's law constant (1)
- Hydrogen-containing mixture (1)
- Hydrogen-enriched natural gas (1)
- Ionic liquid (1)
- Nickel foam (1)
Organisationseinheit der BAM
Most of the experimental density data of the methane−hydrogen binary system available at the time of the development of the equation of state for natural gases and related mixtures, GERG-2008, at temperatures above 270 K were limited to hydrogen contents higher than 0.20 (amount-of-substance fraction). On the contrary, for mixtures with hydrogen contents lower than 0.20, experimental data were limited to temperatures below 270 K. This work intends to close the gap and provides accurate experimental (p, ρ, and T) data for three binary mixtures of methane and hydrogen, (0.95 CH4 + 0.05 H2), (0.90 CH4 + 0.10 H2), and (0.50 CH4 + 0.50 H2), at temperatures of 240, 250, 260, 275, 300, 325, and 350 K, thus extending the range of available experimental data to higher temperatures for mixtures with hydrogen contents lower than 0.20 and, accordingly, to lower temperatures for mixtures with hydrogen contents higher than 0.20. The density measurements were performed by using a single-sinker densimeter with magnetic suspension coupling at pressures up to 20 MPa. Experimental data were compared to the corresponding densities calculated from the GERG-2008 and the AGA8-DC92 equations of state, respectively. The experimental data are within the uncertainty of both equations of state, except at the lower temperatures of 240 and 250 K and pressures over 14 MPa for the mixtures with a hydrogen content of 0.05 and 0.10, respectively. The virial coefficients B(T, x) and C(T, x), as well as the second interaction virial coefficient B12(T) for the methane−hydrogen binary system, were also calculated from the experimental data set at temperatures from 240 to 350 K using the virial equation of state.
Solubility data of carbon dioxide (CO2) in the two ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] and 1-butyl-3-methylimidazolium tetrachloroferrate [BMIM][FeCl4] at T = (273.15-413.15) K and pressures up to p = 4.5 MPa are presented. In Addition to the experiments, a literature review was done to compare the new results with published solubility data. The measurements were carried out using an isochoric method which operates in decrements of deltaT = 20 K within the investigated temperature range and at selected four different pressure steps ranging from a pressure p of around 4.5 MPa to around 0.5 MPa. The solubility of CO2 decreases in both ionic liquids with increasing temperatures. Within the p,T-range investigated, CO2 displayed a solubility in [BMIM][BF4] from a mole fraction x = 0.0117 and a corresponding molality m = 0.0526 mol/kg at T = 413.15 K and p = 0.417 MPa up to x = 0.4876 and m = 4.2094 mol/kg at T = 293.15 K and p = 4.349 MPa. The corresponding values for the solubility in [BMIM][FeCl4] start at a mole fraction x = 0.0268 and a corresponding molality m = 0.0818 mol/kg at T = 413.15 K and p = 0.443 MPa and end at x = 0.5126 and m = 3.1216 mol/kg at T = 293.15 K and p = 4.478 MPa. At a constant temperature, CO2 is better soluble in [BMIM][FeCl4] than in [BMIM][BF4] and the mean value of the solubility difference related to mole fraction x over the pressure range investigated amounts to about 4 % at T = 273.15 K and monotonously increases to about 92 % at T = 413.15 K. Henry's law constant as well as derived thermodynamic properties, such as the Gibbs energy of solvation, the enthalpy of solvation, the entropy of solvation, and the heat capacity of solvation, were calculated and discussed regarding the solute-solvent molecular interactions.
The present study investigated decoration of Cu(OH)₂ with different morphologies by copper precursors on 3D nickel foam. The Cu(OH)₂-A (nano flower)electrode showed an excellent capacitance of 1332 Fg⁻¹ at current density of 2 Ag⁻¹ compared to the Cu(OH)₂-C (nano ribbon, 1100 Fg⁻¹) and Cu(OH)₂-S (nano Long leaf, 1013 Fg⁻¹) electrodes. An asymmetric supercapacitor (ASC) was fabricated and showed a Maximum capacitance of 165 Fg⁻¹ at current density of 2 Ag⁻¹ with high energy density of 66.7 Wh kg⁻¹ and power density of 5698 W kg⁻¹ with excellent stability of 80 % after 10,000 cycles.
The GERG-2008 equation of state is the approved ISO standard (ISO 20765-2) for the calculation of thermophysical properties of natural gas mixtures. The composition of natural gas can vary considerably due to the diversity of origin. Further diversification was generated by adding hydrogen, biogas, or other non-conventional energy gases. In this work, high-precision experimental (p, rho, T) data for two gravimetrically prepared synthetic natural gas mixtures are reported. One mixture resembled a conventional natural gas of 11 components (11 M) with a nominal mixture composition (amount-of-substance fraction) of 0.8845 for methane as the matrix compound with the other compounds being 0.005 for oxygen, 0.04 for nitrogen, 0.015 for carbon dioxide, 0.04 for ethane, 0.01 for propane, 0.002 each for n- and isobutane, and ultimately 0.0005 each for isopentane, n-pentane, and nhexane. The other mixture was a 13-component hydrogen-enriched natural gas with a low calorific value featuring a nominal composition of 0.7885 for methane, 0.03 for hydrogen, 0.005 for helium, 0.12 for nitrogen, 0.04 for carbon dioxide, 0.0075 for ethane, 0.003 for propane, 0.002 each for n- and isobutane, and 0.0005 each for neopentane, isopentane, npentane, and n-hexane. Density measurements were performed in an isothermal operational mode at temperatures between 260 and 350 K and at pressures up to 20 MPa by using a single-sinker densimeter with magnetic suspension coupling. The data were compared with the corresponding densities calculated from both GERG-2008 and AGA8-DC92 equations of state to test their performance on real mixtures. The average absolute Deviation from GERG-2008 (AGA8-DC92) is 0.027% (0.078%) for 11 M and 0.095% (0.062%) for the 13-component H2-enriched mixture, respectively. The corresponding maximum relative Deviation from GERG-2008 (AGA8-DC92) amounts to 0.095% (0.127%) for 11 M and 0.291% (0.193%) for the H2-enriched mixture.