Surface thermodynamics of hydrocarbon vapors and carbon dioxide adsorption on shales

Porous hyper-cross-linked aromatic polymers are one ofthe emergingclasses of porous organic polymers with the potential for industrialapplication. Four different porous polymeric materials have been preparedusing different precursors (indole, pyrene, carbazole, and naphthalene),and the composition and textural properties were analyzed. The materialswere characterized in detail using different physicochemical techniqueslike scanning electron microscopy, transmission electron microscopy,nitrogen adsorption at 77 K, Fourier transform infrared spectroscopy,X-ray diffraction, etc. The effect of textural properties and nitrogenspecies on carbon dioxide and nitrogen adsorption capacities and selectivitywas studied and discussed. The carbon dioxide and nitrogen adsorptioncapacities were measured using a volumetric gas adsorption system.The adsorption data were fitted into different adsorption models,and the ideal absorbed solution theory was used to calculate adsorptionselectivity. Among the studied samples, POP-4 shows the highest carbondioxide and nitrogen adsorption capacities. While POP-1 shows maximumCO2/N2 selectivity of 78.0 at 298 K and 1 barpressure. It is observed that ultra-micropores, which are presentin the prepared materials but not measured during conventional surfacearea measurement via nitrogen adsorption at 77 K, play a very importantrole in carbon dioxide adsorption capacity and determining the carbondioxide selectivity over nitrogen. Surface nitrogen also increasesthe CO2 selectivity in the dual mode by increasing carbondioxide adsorption via the acid–base interaction as well asby decreasing nitrogen adsorption due to N–N repulsion.

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

With large scale production of gas from shale resources, large volumes of pore space have been vacated. Therefore, there is a large capacity for storage of carbon dioxide in these resources. Furthermore, due to the higher affinity of the organic matter to carbon dioxide compared to methane, injection of carbon dioxide can replace the adsorbed methane and therefore, enhances the recovery of natural gas. The objective for this work is to investigate the sorption (adsorption of carbon dioxide and desorption of methane) in carbon-based organic channels using Molecular Dynamics (MD) simulations. In this study, adsorption isotherms of methane and carbon dioxide are compared by performing grand canonical Monte Carlo (GCMC) simulations in identical setups of carbon channels. Excess and absolute adsorption isotherms of these gases are plotted and compared. Furthermore, the surface selectivity of carbon dioxide over methane is computed to determine the competitive adsorption of these two gases. To simulate the displacement process, MD simulations of displacement of methane molecules with carbon dioxide molecules in presence and absence of pressure gradients are performed. The results are compared for different values of gas pressures and pressure gradients. According to the results, adsorption capability of carbon dioxide is found to be higher than that of methane under the same pressure and temperature. The selectivity values of carbon dioxide over methane is found to be higher than the ones for pressure range of 100 to 200 atm, which shows that carbon dioxide molecules have higher affinity to the surface compared with methane. It is also found that carbon dioxide molecules replace adsorbed methane molecules due to their higher affinity to the surface. Concentration of methane sharply decreases as carbon dioxide molecules are introduced in the channel. The results show that the amount of carbon dioxide storage and methane production rate increases as injection pressure increases. The results in this study can impact on the research and development of new tools for both candidate selection (selection of the sites for carbon dioxide storage) and development of predictive models for estimating of the amount of carbon dioxide intake.

Significance of extra-framework monovalent and divalent cation motion upon CO2 and N2 sorption in zeolite X

Five nitrogen sources (glycine, β‐alanine, urea, melamine and nicotinamide) and three heating methods (thermal, monomodal microwave and multimodal microwave) are used to prepare nitrogen‐doped Starbons® derived from starch. The materials are initially produced at 250–300 °C (SNx300y), then heated in vacuo to 800 °C to produce nitrogen‐doped SNx800y’s. Melamine gives the highest nitrogen incorporation without destroying the Starbon® pore structure and the microwave heating methods give higher nitrogen incorporations than thermal heating. The carbon dioxide adsorption capacities of the nitrogen‐doped Starbons® determined gravimetrically, in many cases exceed those of S300 and S800. The carbon dioxide, nitrogen and methane adsorption isotherms of the most promising materials are measured volumetrically. Most of the nitrogen‐doped materials show higher carbon dioxide adsorption capacities than S800, but lower methane and nitrogen adsorption capacities. As a result, the nitrogen‐doped Starbons® exhibit significantly enhanced carbon dioxide versus nitrogen and methane versus nitrogen selectivities compared to S800.

Adsorption of carbon dioxide on hydrotalcite-like compounds of different compositions

Thermodynamic effects of cycling carbon dioxide injectivity in shale reservoirs

Influence of nickel oxide on carbon dioxide adsorption behaviors of activated carbons

Molecular level investigation of methane and carbon dioxide adsorption on SiO2 surface

Adsorption isotherms of methane and carbon dioxide adsorption isotherms on shale samples are measured and the simplified local density (SLD) model is used to match the experimental data. The SLD equation also has the generic modeling capabilities to draw the deviation from bulk properties as a function of fluid-solid interaction energies. Still, compared to other available techniques such as molecular simulation, SLD has an advantage of mathematical simplicity and being run at shorter time interval. The model also has satisfactory potential to paint the underlying mechanisms for adsorption preference of one fluid component over the other. The higher adsorption preference of carbon dioxide is reflected in the measurement data and the adsorption model is successfully used to fit the data. In addition to different critical properties of carbon dioxide compared to methane, the main important factor that may describe the high adsorption affinity of carbon dioxide is the fluid-solid potential energy. As shown in this work, the potential energy function shows deeper well depth, the deeper the well depth, the stronger the interaction between the fluid particles and solid surface. By storing gas in high density, liquid like adsorbed phase, the adsorption mechanism can enhance the overall storage capacity of CO2 in deep reservoir rock relative to if there were a free phase alone.

The development of new methods for obtaining nitrogen-containing sorbents to bind carbon dioxide is an important task to combat climate change, minimize a carbon trace and obtain industrially valuable products in heterogeneous catalytic processes. In this regard, the effect of the temperature of pyrolysis of polyphenylenepyridines on the chemical composition and sorption. The X-ray photoelectron spectroscopy (XPS) method was used to demonstrate the formation of nitrogen-containing products of high-temperature (800 − 1000 °C) carbonization of polyphenylenepyridines and polybiphenylenepyridines containing surface hydroxyl, ether, and carboxyl functional groups. According to the study of carbon dioxide adsorption-desorption isotherms, the new materials have a specific surface area of about 1000 m2g−1 and a micropore diameter of up to 0.48 nm (Non-Local Density Functional Theory (NLDFT)). The resulting carbon materials had a high adsorption capacity for carbon dioxide, as well as the ability to cooperatively desorb it in accordance with the second-order kinetic equation. It was shown that the rate of carbon dioxide desorption decreased with increasing pyrolysis temperature used to form nitrogen-containing carbon material. Simultaneously with increasing pyrolysis temperature, a decrease in the mass fraction of nitrogen in the samples was observed with an increase in the adsorption capacity of the formed adsorbents with respect to carbon dioxide. Thus, the increase in the specific surface had a greater effect on the amount of carbon dioxide adsorption than the N/C value ratio did.

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

Adsorption isotherms of carbon dioxide were measured on six high-silica zeolites TNU-9, IM-5, SSZ-74, ferrierite, ZSM-5 and ZSM-11 comprising three-dimensional 10-ring (8-ring for ferrierite) at 273, 293, 313 and 333 K. Based on the known temperature dependence of CO2 adsorption, isosteric heats of adsorption were calculated. The obtained adsorption capacities and isosteric adsorption heats related to the amount of CO2 adsorbed have provided detailed insight into the carbon dioxide interaction with zeolites of different framework topology. The zeolites TNU-9 and ferrierite are characterized by pronounced energetic heterogeneity whereas due to the location of Na+ cations in the same positions the isosteric adsorption heats of CO2 adsorption on IM-5, ZSM-5 and ZSM-11 zeolites are rather constant for molecular ratio CO2/Na+ < 1. As IM-5 zeolite has a maximum adsorption capacity, it appears to have optimum properties for carbon dioxide separation.

According to the present data, KA zeolite, which can adsorb only water vapor, helium, and hydrogen, has the greatest selectivity in drying. The feasibility of using this zeolite in devices for selective drying of gases used in gas-analysis systems was studied. The results of the experiments were approximated by the thermal equation of the theory of bulk filling of micropores. The limiting value of the adsorption depends on the temperature, and it can be calculated according to the density of the adsorbed phase and the adsorption volume. The critical diameters of the water and carbon dioxide molecules are close to the dimensions of the KA-zeolite pores, something that determines the activated nature of the adsorption of these substances. Experiments on coadsorption of water vapor and carbon dioxide by a fixed bed of KA-zeolite under dynamic conditions showed that the adsorption of these substances has a frontal nature. The time of the protective action of the layer of zeolite during adsorption af water vapor exceeded by more than an order the time of the protective action during adsorption of carbon dioxide. The results showed that this adsorbent can be used for selective drying of gas mixtures containing carbon dioxide in batch-operationmore » devices. Beforehand, the adsorbent should be regenerated with respect to moisture, and then it should be saturated with carbon dioxide by blowing the adsorbent with a gas mixture of the working composition until the equilibrium state is reached.« less

Effects of potential models on the adsorption of carbon dioxide on graphitized thermal carbon black: GCMC computer simulations