Sorption of methane,ethane, propane,butane, carbon dioxide,and nitrogen on kerogen

Sorption isotherms of nitrogen, methane (in the pressure range of 0.1–40 MPa), ethane (0.1–3.7MPa), propane (0.01–1 MPa), butane (0.01–0.2 MPa), and carbon dioxide (0.1–6 MPa) are measured on two adsorbents with kerogen contents of 16 and 75% at temperatures of 303, 323, 343 K. Adsorption volumes are calculated for all adsorption systems using two independent methods. The BET technique is used to determine the surface area values of the two adsorbents on the basis of sorption data for ethane, propane, butane, and carbon dioxide. The initial and isosteric adheat of sorption values are calculated on the basis of sorption isotherms of ethane, propane, butane, carbon dioxide measured at three temperatures. It is found from comparing the dependences of isosteric heat of sorption on the two adsorbents that molecules of the above gases diffuse into its bulk (adsorbent 2) in addition to sorbing on the outside surface formed by kerogen molecules, while sorption of the same gases on the rock (adsorbent 1) is similar to sorption on a smooth hard adsorbent surface.     

The solubility of ethane, propane, and carbon dioxide in aqueous solutions of sodium cumene sulfonate

Measurements have been made to determine the solubilities of ethane, C2H6, propane, C3H8, and carbon dioxide, CO2, in aqueous solutions of sodium cumene sulfonate (NaCS) at 25 degrees C. The solubilities measured for each gas satisfy Henry's law at all concentrations of NaCS. The solubilities of C2H6 and C3H8 exhibit quite similar behavior with respect to added NaCS. The solubilities of these two gases are very low in pure water and are found to be nearly independent of NaCS concentration over a concentration range of 0-0.4 mol NaCS/kg H2O. At intermediate concentrations of NaCS, the solubilities of C2H6 and C3H8 exhibit a gradual increase with added NaCS concentrations ranging from 0.4 to 2.0 mol NaCS/kg H2O. At NaCS concentrations greater than 2.0 mol NaCS/kg H2O, the solubilities of these two gases increase with added NaCS in an approximately linear manner, with the solubility of C3H8 increasing more rapidly than that for C2H6 (by a factor of approximately 2.5). CO2 is much more soluble in pure water than the hydrocarbon gases and exhibits markedly different behavior with respect to added NaCS. The solubility of CO2 decreases with added NaCS over a concentration range of 0-0.9 mol NaCS/kg H2O, passes through a minimum at a concentration of approximately 1.0 mol NaCS/kg H2O, and then increases with added NaCS at higher NaCS concentrations in a manner similar to that observed with C2H6 and C3H8. The trends in solubility observed for these three gases dissolved in aqueous solutions of NaCS resemble those found previously with aqueous solutions of ordinary surfactants. The solubility data measured for these three gases can be interpreted surprisingly well in terms of the mass-action model for micellization, in which salting-out effects due to monomer salt ions suppress gas solubility at low NaCS concentrations and gas solubilization by small micelles of NaCS acts to enhance gas solubility at the higher NaCS concentrations.     

Sorption of methane and CO2 for enhanced coalbed methane recovery and carbon dioxide sequestration

Sequestration of CO2 in deep and unmineable coal seams is one of the attractive alternatives to reduce its atmospheric concentration. Injection of CO2 in coal seams may help in enhancing the recovery of coalbed methane. An experimental study has been carried out using coal samples from three different coal seams, to evaluate the enhanced gas recovery and sequestration potential of these coals. The coals were first saturated with methane and then by depressurization some of the adsorbed methane was desorbed. After partial desorption, CO2 was injected into the coals and subsequently they were depressurized again. Desorption of methane after the injections was studied, to investigate the ability of CO2 to displace and enhance the recovery of methane from the coals. The coals exhibited varying behavior of adsorption of CO2 and release of methane. For one coal, the release of methane was enhanced by injection of CO2, suggesting preferential adsorption of CO2 and desorption of methane. For the other two coals, CO2 injection did not produce incremental methane initially, as there was initial resistance to methane release. However with continued CO2 injection, most of the remaining methane was produced. The study suggested that preferential sorption behavior of coal and enhanced gas recovery pattern could not be generalized for all coals.     

Sorption of methane and CO2 for enhanced coalbed methane recovery and carbon dioxide seauestration

Sequestration of CO2 in deep and unmineable coal seams is one of the attractive alternatives to reduce its atmospheric concentration. Injection of CO2 in coal seams may help in enhancing the recovery of coalbed methane. An experimental study has been carried out using coal samples from three different coal seams, to evaluate the enhanced gas recovery and sequestration potential of these coals. The coals were first saturated with methane and then by depressurization some of the adsorbed methane was desorbed. After partial desorption, CO2 was injected into the coals and subsequently they were depressurized again. Desorption of methane after the injections was studied, to investigate the ability of CO2 to displace and enhance the recovery of methane from the coals. The coals exhibited varying behavior of adsorption of CO2 and release of methane. For one coal, the release of methane was enhanced by injection of CO2, suggesting preferential adsorption of CO2 and desorption of methane. For the other two coals, CO2 injection did not produce incremental methane initially, as there was initial resistance to methane release. However with continued CO2 injection, most of the remaining methane was produced. The study suggested that preferential sorption behavior of coal and enhanced gas recovery pattern could not be generalized for all coals.     

Heats of adsorption and adsorption heterogeneity for methane, ethane, and carbon dioxide in MCM-41

We report the adsorption isotherms and the isosteric heats of adsorption of pure methane, ethane, and CO2 and a mixture of methane and CO2 in the periodic mesoporous silica MCM-41 using a multicomponent adsorption calorimeter of the Tian-Calvet type, looking in particular at the degree of heterogeneity in the adsorption of these species. The adsorption of methane and ethane in MCM-41 was found to be essentially homogeneous, while the adsorption of pure CO2 and of CO2 from a CO2/methane mixture was found to be significantly heterogeneous, reflecting the electrostatic interactions between CO2 and the adsorbent.     

Formation and decomposition of ethane, propane, and carbon dioxide hydrates in silica gel mesopores under high pressure

The experimental data on decomposition temperatures for the gas hydrates of ethane, propane, and carbon dioxide dispersed in silica gel mesopores are reported. The studies were performed at pressures up to 1 GPa. It is shown that the experimental dependence of hydrate decomposition temperature on the size of pores that limit the size of hydrate particles can be described on the basis of the Gibbs-Thomson equation only if one takes into account changes in the shape coefficient that is present in the equation; in turn, the value of this coefficient depends on a method of mesopore size determination. A mechanism of hydrate formation in mesoporous medium is proposed. Experimental data providing evidence of the possibility of the formation of hydrate compounds in hydrophobic matrixes under high pressure are reported. Decomposition temperature of those hydrate compounds is higher than that for the bulk hydrates of the corresponding gases.     

Solubility of carbon dioxide,methane, and ethane in 1-butanol and saturated liquid densities and viscosities

A designed pressure–volume–temperature (PVT) apparatus has been used to measure the (vapor + liquid) equilibrium properties of three binary mixtures (methane +, ethane +, and carbon dioxide + 1-butanol) at two temperatures (303 and 323) K and at the pressures up to 6 MPa. The solubility of the compressed gases in 1-butanol and the saturated liquid densities and viscosities were measured. In addition, the density and viscosity of pure 1-butanol were measured at two temperatures (303 and 323) K and at the pressures up to 10 MPa. The experimental results show that the solubility of the gases in 1-butanol increases with pressure and decreases with temperature. The dissolution of gases in 1-butanol causes a decline in the viscosity of liquid phase. The saturated liquid density follows a decreasing trend with the solubility of methane and ethane. However, the dissolution of carbon dioxide in 1-butanol leads to an increase in the density of liquid phase. The experimental data are well correlated with Soave–Redlich–Kwong (SRK) and Peng–Robinson (PR) equations of state (EOSs). SRK EOS was slightly superior for correlating the saturated liquid densities.     

Solubility of carbon dioxide,methane, and propane in silicone polymers. Effect of polymer backbone chains

The solubility of carbon dioxide, methane, and propane in poly(dimethyl silmethylene) [(CH₃)₂SiCH₂]_x and poly(tetramethyl silhexylene siloxane) [(CH₃)₂Si (CH₂)₆Si (CH₃)₂O]_x was measured in the temperature range from 10.0 to 55.0°C and at elevated pressures. The present results are compared with similar measurements made with other silicone polymers. At a given temperature and pressure, the solubility of the above three gases is highest in poly(dimethyl siloxane) (Me₂SiO)_x. The gas solubility is decreased by either backbone-chain or side-chain substitutions of functional groups in (Me₂SiO)_x which increase the stiffness of the polymer chains and decrease the specific or fractional free volume of the polymers. It is conjectured that a decrease in the free volume of silicone polymers has a greater effect in decreasing the gas solubility than differences in gas/polymer interactions [with the exception of specific interactions (e.g., between CO₂ and polar groups in the polymer)]. © 1993 John Wiley & Sons, Inc.     

Solubility of carbon dioxide,methane, and propane in silicone polymers: Effect of polymer side chains

The solubility of methane, carbon dioxide, and propane in five silicone polymers was measured at 10.0, 35.0 and 55.0°C and at pressures up to 26 atm. The polymers were poly(dimethyl siloxane), poly(methyl propyl siloxane), poly(methyl octyl siloxane), poly(trifluoropropyl methyl siloxane), and poly(phenyl methyl siloxane). At a given temperature and pressure, the solubility of the penetrant gases decreases with increasing bulkiness of the polymer side chains, and with decreasing critical temperature of the penetrant. The solubility of carbon dioxide in poly(trifluoropropyl methyl siloxane) appears to be anomalously high, possibly because of specific penetrant/polymer interactions. The temperature and pressure dependence of the solubility coefficients for the penetrant/polymer systems studied are described, and different methods of correlating these coefficients are compared.     

Solubilization of methane,ethane, propane andn-butane in aqueous solutions of sodium dodecylsulfate

The solubilities of methane, ethane, propane, and n-butane were measured in aqueous solutions of sodium dodecylsulfate (NaDS) (0–0.1M) from 15 to 27°C. From these measurements the standard Gibbs energies, entropies, and enthalpies for the process of transferring the solute molecules from the gaseous phase into the solutions were calculated. An approximate relationship was found relating the volume fraction of the micelles to NaDS concentration.     

Homogeneous nucleation in supersaturated vapors of methane, ethane, and carbon dioxide predicted by brute force molecular dynamics

Molecular dynamics (MD) simulation is applied to the condensation process of supersaturated vapors of methane, ethane, and carbon dioxide. Simulations of systems with up to a 10(6) particles were conducted with a massively parallel MD program. This leads to reliable statistics and makes nucleation rates down to the order of 10(30) m(-3) s(-1) accessible to the direct simulation approach. Simulation results are compared to the classical nucleation theory (CNT) as well as the modification of Laaksonen, Ford, and Kulmala (LFK) which introduces a size dependence of the specific surface energy. CNT describes the nucleation of ethane and carbon dioxide excellently over the entire studied temperature range, whereas LFK provides a better approach to methane at low temperatures.     

Reactions of phenylium ions with gaseous hydrocarbons. 1. methane,ethane, and propane

The reaction of free tritiated phenylium ion, generated from nuclear decay of [l,4-T₂]-benzene in the presence of simple gaseous hydrocarbons RH (R = CH₃, C₂H₅, C₃H₇; partial pressure: 10-100 torr), yields predominantly the corresponding tritiated C₆H₅R products. The effects of gaseous nucleophilic acceptors (NuH = NH₃, CH₃OH) on the reaction with CH₄, were also investigated. Phenylium ion confirms its exceedingly high reactivity even toward pure σ- -type substrates, as well as its considerable site selectivity, demonstrated by the distinct preference for the C-H bonds of the substrate. The stability features of the ionic intermediates from addition of phenylium ion with RH have been evaluated, as well as their fragmentation and isomerization mechanisms. The behaviour of phenylium ion toward simple aliphatic hydrocarbons in the gas phase (10-100 torr) is discussed and compared with previous mechanistic hypotheses from ICR mass spectrometric studies, carried out at much lower pressures (10^-5 torr).     

Adsorption isotherms and Sips models of nitrogen,methane, ethane,and propane on commercial activated carbons and polyvinylidene chloride

In this paper we present the measured isotherms of nitrogen, methane, ethane, and propane on three carbons: Norit RB2, Chemviron AP 4-60, and highly activated Saran. The measurements are taken at temperatures between 300 and 400 K, in 20 K steps. The measured data is fitted to the Sips adsorption model, where the Sips parameters are determined by a linearization method. The Sips parameters are further adjusted to realize a logic dependence on temperature and the parameter characteristics are discussed. Subsequently, the Sips model is modified to incorporate the temperature dependence. Including the temperature dependence results in a slightly higher error relative to the experimental results (typically 10 % as compared to 6 %). The immediate research product is a convenient expression for every adsorbate-adsorbent system which is discussed in this paper, for calculating the adsorption concentration as a function of temperature and pressure. A more general research product is a better understanding of the Sips parameter characteristics that should help in developing future adsorbents on demand.     

Gas hydrates of methane, ethane, propane, and carbon dioxide in the presence of single NaCl, KCl, and CaCl2 aqueous solutions: Experimental measurements and predictions of dissociation conditions

Experimental dissociation data for methane, ethane, propane, and carbon dioxide simple hydrates in the presence of NaCl, KCl, and CaCl₂ aqueous solutions with different concentrations of single salt are reported in this communication. The experimental data were generated using a reliable isochoric technique. Some of the experimental hydrate dissociation data measured in this study are compared with some selected experimental data from the literature and the agreements are generally found acceptable, which is a guarantee for the reliability of our experimental technique and the data generated here. All the experimental data are finally compared with the predictions of a general correlation and a thermodynamic model and good agreements between the experimental and predicted data are generally observed.     

Preparation of highly dispersed RhPt alloy catalysts in mesoporous silica using supercritical carbon dioxide and selective synthesis of ethane in butane hydrogenolysis

RhPt alloy catalysts were prepared in mesoporous silica using supercritical carbon dioxide in impregnation to achieve high dispersion with controlled morphology; catalytic activity and ethane selectivity are enhanced in butane hydrogenolysis.     

Sorption of carbon dioxide in fluorinated poyimides

Sorption isotherms of CO₂ for ten fluorinated polyimides measured at 35°C and up to about 25 atm are analyzed according to the dual-mode sorption model. Sorption properties for these polyimides are compared with those for other glassy Polymers including unfluorinated polyimides. The glassy polymers with higher glass transition temperatures T_g tend to show greater CO₂ sorption. Introduction of a ? C (CF₃)₂? linkage into the repeat unit of the main chain increases the sorption by 20–80%. For glassy polymers, including the fluorinated and unfluorinated polyimides, the Langmuir affinity constant b and Henry's law solubility constant k_D are correlated with the content of functional (carbonyl or sulfonyl) groups [FG], and composite parameter reflecting the magnitude of both [FG] and free-space fraction V_F, respectively, with some exceptions. The Langmuir capacity constant C′_H is correlated with T_g, but there are two correlation lines; one for unfluorinated polyimides and a different one for other glassy polymers including fluorinated polyimides. The slope of the former group is smaller probably because of smaller differences in thermal probably because of smaller differences in thermal expansion coefficients in rubbery and glassy states. Most fluorinated polyimides show greater solubility of CO₂ than unfluorinated polyimides and other glassy polymers, because of their larger C′_H and k_D. © 1993 John Wiley & Sons, Inc.     

Sorption of methane and ethane high-molecular tars at supercritical temperatures in the Henry region

A theoretical and experimental study of the absorption of methane and ethane by high-molecular tars occurring in oil-gas-condensate deposits is carried out. An original approach to determining the physicochemical parameters of high-molecular tars and to constructing isotherms of absorption of the main components of natural gas by such tars was proposed. The model of the process was developed by analogy with the theory of dissolution of gases in liquids. The sorption of gases by the tar at supercritical temperatures was described within the framework of the van’t Hoff theory of dilute solutions. The proposed approach made it possible to develop a new effective thermodynamic method for calculating the solubility of the component of natural gas in tar at supercritical temperatures and pressure typical of the conditions of natural gas recovery.     

Spectroscopic calculation of CH bond dissociation energy in the series of chloro derivatives of methane, ethane, and propane

The bond-dissociation energy of CH bonds in chloro derivatives of methane, ethane, and propane has been determined by spectroscopic and quantum chemical methods. Spectroscopic values for CH bond dissociation energy were computed, basing on fundamental absorption bands in the anharmonic approximation, by the variational method with the use of the Morse anharmonic basis. Quantum chemical computations were performed using the basis 6-311G(3df, 3pd)/B3LYP. There are discussed the obtained regularities of changes in the bond dissociation energy when the structure of a molecule is changed.