Adsorption microcalorimetry of methane and carbon dioxide on various zeolites

Early studies that compared the adsorption of both carbon dioxide and methane in coals were done, principally, on bituminous coal samples from the United States and Canada. At normal reservoir temperatures, these coals were found to adsorb approximately twice the volume of carbon dioxide as methane. This two-to-one ratio has been widely reported in the literature, and has approached the status of conventional wisdom. In contrast, new adsorption isotherms determined on 13 samples of low-rank coals (lignite and subbituminous) from the Northern Great Plains and Texas demonstrate that these coals can adsorb from 6 to 18 times more carbon dioxide than methane.

The adsorption of carbon dioxide, methane, and their mixtures in nanoporous carbons in the presence of water is studied using experiments and molecular simulations. Both the experimental and numerical samples contain polar groups that account for their partially hydrophilicity. For small amounts of adsorbed water, although the shape of the adsorption isotherms remain similar, both the molecular simulations and experiments show a slight decrease in the CO2 and CH4 adsorption amounts. For large amounts of adsorbed water, the experimental data suggest the formation of methane or carbon dioxide clathrates in agreement with previous work. In contrast, the molecular simulations do not account for the formation of such clathrates. Another important difference between the simulated and experimental data concerns the number of water molecules that desorb upon increasing the pressure of carbon dioxide and methane. Although the experimental data indicate that water remains adsorbed upon carbon dioxide and methane adsorption, the molecular simulations suggest that 40 to 75% of the initial amount of adsorbed water desorbs with carbon dioxide or methane pressure. Such discrepancies show that differences between the simulated and experimental samples are crucial to account for the rich phase behavior of confined water-gas systems. Our simulations for carbon dioxide-methane coadsorption in the presence of water suggest that the pore filling is not affected by the presence of water and that adsorbed solution theory can be applied for pressures as high as 15 MPa.

Adsorption of methane, ethane, ethylene, and carbon dioxide in H-ZSM-5, Na-ZSM-5, H-ZSM-8, Na-ZSM-8, Silicalite, and ALPO-5 at 303–473 K has been investigated using a gas chromatography pulse technique. The zeolites have been compared for the heat of adsorption of the adsorbates at near zero adsorbate loading and also for the specific retention volume (or thermodynamic adsorption equilibrium constant) of ethane, ethylene, and carbon dioxide relative to that of methane. Among the zeolites, ALPO-5 has a high potential for the separation of methane, ethane, ethylene, and carbon dioxide from their mixture.

Surface thermodynamics of hydrocarbon vapors and carbon dioxide adsorption on shales

Selectivity of new siliceous zeolites for separation of methane and carbon dioxide by Monte Carlo simulation

Adsorption of methane, ethane, ethylene, and carbon dioxide on silicalite-l

The adsorption of carbon dioxide and methane in nanoporous carbons in the presence of water is studied using experiments and molecular simulations. For all amounts of adsorbed water molecules, the adsorption isotherms for carbon dioxide and methane resemble those obtained for pure fluids. The pore filling mechanism does not seem to be affected by the presence of the water molecules. Moreover, the pressure at which the maximum adsorbed amount of methane or carbon dioxide is reached is nearly insensitive to the loading of preadsorbed water molecules. In contrast, the adsorbed amount of methane or carbon dioxide decreases linearly with the number of guest water molecules. Typical molecular configurations obtained using molecular simulation indicate that the water molecules form isolated clusters within the host porous carbon due to the nonfavorable interaction between carbon dioxide or methane and water.

Experimental and theoretical studies have been carried out to study the adsorption of methane and carbon dioxide on 5A molecular sieve. Adsorption equilibrium isotherms of methane and carbon dioxide are reported for the temperature range 303– 333 K and pressure up to 2.5MPa. Experimental data were obtained using a static system for gas–solid adsorption. The Langmuir adsorption equilibrium equation gavegood predictions. Adsorption of methane and carbon dioxide on 5A molecular sieve is purely physical since the isosteric heat of adsorption was found to be equal to 14.804 and 37.218 kJ mole-1 for methane and carbon dioxide, respectively.

Porous Metal-Organic Frameworks: Promising Materials for Methane Storage

Selective adsorption of supercritical carbon dioxide and methane binary mixture in shale kerogen nanopores

Methane is the main component in biogas and natural gas along with contaminants such as water and carbon dioxide. Separation of methane from these contaminants is therefore an important step in the upgrading process. Zeolite adsorbents and zeolite membranes have great potential to be cost-efficient candidates for upgrading biogas and natural gas, and in both of these applications, knowing the nature of the competitive adsorption is of great importance to further develop the properties of the zeolite materials. The binary adsorption of methane and carbon dioxide in zeolites has been studied to some extent, but the influence of water has been much less studied. In the present work, in situ ATR (attenuated total reflection)–FTIR (Fourier transform infrared) spectroscopy was used to study the adsorption of water/methane and water/carbon dioxide from binary mixtures in a high-silica Na-ZSM-5 zeolite film at various gas compositions and temperatures. Adsorbed concentrations for all species were determined from ...

The main component in biogas and natural gas is methane, but these gases also contain water and carbon dioxide that often have to be removed in order to increase the calorific value of the gas. Membrane and adsorbent-based technologies using zeolites are interesting alternatives for efficient separation of these components. To develop efficient processes, it is essential to know the adsorption properties of the zeolite. In the present work, adsorption of methane, carbon dioxide, and water from ternary mixtures in high silica zeolite Na-ZSM-5 was studied using in situ ATR (attenuated total reflection)–FTIR (Fourier transform infrared) spectroscopy. Adsorbed concentrations were extracted from the infrared spectra, and the obtained loadings were compared to values predicted by the ideal adsorbed solution theory (IAST). The IAST could not fully capture the adsorption behavior of this ternary mixture, indicating that the adsorbed phase is not behaving as an ideal mixture. The CO2/CH4 adsorption selectivities d...

The majority of research reported on methane adsorption characteristics of coal seams has focused on vitrinite-rich coals. However, western Canadian coals are more inertinite-rich than those of the western United States and are shown to differ in gas adsorption characteristics. The influence of maceral composition upon gas adsorption characteristics of medium-volatile coal samples from the middle Cretaceous Gates Formation of northeastern British Columbia was investigated. Lithotype (coal facies) samples were analyzed for surface area, maceral and mineral composition, and methane adsorption; standard coal analyses were also performed (proximate, low-temperature ash, and equilibrium moisture). The vitrinite content of the samples analyzed ranges from 18 to 95% (vol. %, min ral matter free); the ash yield varies from 4.4 to 33.7% (wt. %). Both maceral composition and mineral matter content have an important influence on adsorption characteristics as indicated by carbon dioxide surface areas and methane adsorption isotherms. On a mineral matter-free basis, the amount of methane adsorbed generally increases with vitrinite enrichment. The lowest methane adsorption occurs in the sample with the highest inertinite content. Carbon dioxide surface areas of the lithotypes range from 87 to 176 m2/g on a raw-coal basis, and from 99 to 184 m2/g on a mineral matter-free basis. Surface area generally decreases with increased mineral matter content and increases with increased vitrinite content. The increase in adsorption of both methane and carbon dioxide with increased vitrinite concentration is interpreted a resulting from differences in the pore size distribution of vitrinite and inertinite: vitrinite is predominantly microporous whereas inertinite is meso- to macroporous. The monolayer volumes of carbon dioxide (as calculated from the DubininRadushkevich equation) are higher than those of methane (as determined from the Langmuir equation), but are correlated. The methane adsorption isotherms and surface area data indicate that the maceral compositional variations in coal are at least as significant as coal rank in determining the potential volume of adsorbed methane and thus the coalbed methane potential of a deposit.

Nitrogen adsorption at 77 K is the current standard means for pore size determination of adsorbent materials. However, nitrogen adsorption reaches limitations when dealing with materials such as molecular sieving carbon with a high degree of ultramicroporosity. In this investigation, methane and carbon dioxide adsorption is explored as a possible alternative to the standard nitrogen probe. Methane and carbon dioxide adsorption equilibria and kinetics are measured in a commercially derived carbon molecular sieve over a range of temperatures. The pore size distribution is determined from the adsorption equilibrium, and the kinetics of adsorption is shown to be Fickian for carbon dioxide and non-Fickian for methane. The non-Fickian response is attributed to transport resistance at the pore mouth experienced by the methane molecules but not by the carbon dioxide molecules. Additionally, the change in the rate of adsorption with loading is characterized by the Darken relation in the case of carbon dioxide diffusion but is greater than that predicted by the Darken relation for methane transport. Furthermore, the proposition of inkbottle-shaped micropores in molecular sieving carbon is supported by the determination of the activation energy for the transport of methane and subsequent sizing of the pore-mouth barrier by molecular potential calculations.

To produce natural gas (methane) and simultaneously sequester CO2 in unconventional geologic reservoirs such as gas shale, coalbeds and so on, it is necessary to understand the adsorption behavior of methane and CO2 in these reservoir formations. In this article, adsorption behavior of methane and CO2 on shale samples from Gondwana Basin and KG Basin of India are studied. Adsorption experiments are conducted on as‐received shale samples from these basins at a temperature of 313 K to a maximum equilibrium pressure of approximately 9 MPa for methane and 6 MPa for CO2. The methane and CO2 adsorption data are applied to test the applicability of Langmuir, Dubinin‐Polanyi, BET, and Ono‐Kondo models. A comparison of these models is performed using linear and nonlinear Chi‐squared methods. It was observed that Dubinin‐Astakhov equation was the most accurate adsorption isotherm model for adsorption of methane and CO2 on tested shales. Further, the better fitting by Dubinin‐Polanyi equation over BET, Langmuir, and Ono‐Kondo models suggest that the mechanism of volume filling may be applicable during the adsorption of methane and CO2 on shales. The preferential adsorption of methane and carbon dioxide on Pakur, KG, and Salanpur shales were investigated. The Pakur shale had CO2:CH4 adsorption ratio ~1. © 2019 American Institute of Chemical Engineers Environ Prog, 38: 13222, 2019