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

The adsorption of pure ethane and carbon dioxide, and binary mixtures of these components, in MCM-41 has been studied experimentally and by grand canonical Monte Carlo (GCMC) simulation, at temperatures between 264 and 303 K and pressures up to 3 MPa. The experimental isotherms were measured using a bench-scale, open-flow adsorption/desorption apparatus. The simulations were carried out using three different models for MCM-41 with different degrees of surface heterogeneity. Model 1 has a nearly homogeneous pore surface while model 2, which is derived from a matrix of crystalline α-quartz, has a heterogeneous but nevertheless regular surface. These two models give generally good predictions of the adsorption of ethane in MCM-41, except at low pressures where the surface heterogeneity of MCM-41 dominates the adsorption. Model 3 has an amorphous structure, generated by an energy-minimization procedure; this model gives better predictions for ethane adsorption, especially at low pressures, suggesting that it incorporates a good representation of the heterogeneity of the real MCM-41 material. Excellent predictions of the adsorption of pure carbon dioxide and binary mixtures of ethane and carbon dioxide in MCM-41 are obtained with model 3, further confirming the realism of this model. Long-ranged electrostatic interactions are included for the simulation of carbon dioxide; these interactions, which play an important role, are treated by a simple one-dimensional summation method, which gives an accurate calculation of the potential.

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.

The aim of this work is to predict the adsorption of pure-component and binary mixtures of methane and carbon dioxide in a specific activated carbon, A35/4, using grand canonical Monte Carlo (GCMC) simulation. Methane is modeled as a one-center Lennard-Jones (LJ) fluid and carbon dioxide as a two-center LJ plus point quadrupole fluid. Experimental adsorption data for the system have been obtained with a new flow desorption apparatus. The pore size distribution (PSD) for the carbon was determined from both of the experimental CH4 and CO2 isotherms at 293 K. To extract numerically the PSD, GCMC-simulated isotherms for both pure components in slit-shaped pores ranging from 5.7 to 72.2 A were used. Using only pure experimental CO2 isotherm data, it was not possible to determine a PSD that allowed a reasonable prediction of the pure methane adsorption. However, with both experimental data sets for the pure components, it was possible to derive a PSD that allowed both experimental pure-component isotherms to be...

Surface thermodynamics of hydrocarbon vapors and carbon dioxide adsorption on shales

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

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

Equilibrium data for the adsorption of hydrogen, carbon dioxide, and binary mixture of both gases on activated carbon were determined experimentally. Pure component isotherms were presented along with pressures up to 30 atm at 301 K, 323 K and 348 K. Also, the binary equilibria were obtained at various temperatures same above for pressure of 1.5, 10 and 20 atm, respectively. For the pure component system, Freundlich isotherm was shown to be fitted best to the experimental results. However, in the binary system, the ideal adsorption solution (IAS) theory gave good representation of the binary experimental data in high pressure range.

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

Knowledge of the adsorption behavior of coal‐bed gases, mainly under supercritical high‐pressure conditions, is important for optimum design of production processes to recover coal‐bed methane and to sequester CO2 in coal‐beds. Here, we compare the two most rigorous adsorption methods based on the statistical mechanics approach, which are Density Functional Theory (DFT) and Grand Canonical Monte Carlo (GCMC) simulation, for single and binary mixtures of methane and carbon dioxide in slit‐shaped pores ranging from around 0.75 to 7.5 nm in width, for pressure up to 300 bar, and temperature range of 308‐348 K, as a preliminary study for the CO2 sequestration problem. For single component adsorption, the isotherms generated by DFT, especially for CO2, do not match well with GCMC calculation, and simulation is subsequently pursued here to investigate the binary mixture adsorption. For binary adsorption, upon increase of pressure, the selectivity of carbon dioxide relative to methane in a binary mixture initially increases to a maximum value, and subsequently drops before attaining a constant value at pressures higher than 300 bar. While the selectivity increases with temperature in the initial pressure‐sensitive region, the constant high‐pressure value is also temperature independent. Optimum selectivity at any temperature is attained at a pressure of 90‐100 bar at low bulk mole fraction of CO2, decreasing to approximately 35 bar at high bulk mole fractions. © 2005 American Institute of Chemical Engineers AIChE J, 2006

In this work, the adsorptions of carbon dioxide, methane, nitrogen, and hydrogen sulfide and the separation of their binary mixtures into NUM-3a Metal-Organic Framework (MOF) were studied through Grand Canonical Monte Carlo (GCMC) simulation method. The simulated pure gas uptakes using three generic force fields (UFF, Dreiding, and OPLS) at 298K were compared with the experimental values. The accuracy of the applied force fields for each gas was compared with the experimental isotherms and discussed. Our results show that OPLS has the best accuracy in the case of methane while Dreiding was the best for CO2 and N2. Simulated gas uptakes indicated that H2S was more adsorbed by NUM-3a than CO2, CH4, and N2. The calculated adsorption selectivity of NUM-3a for the binary mixtures of CH4 with H2S is larger than that of CO2. NUM-3a possess more affinity for H2S and CO2 than for CH4, where it may be a promising adsorbent material for separating carbon dioxide and hydrogen sulfide from methane. Furthermore, the most probable sites for the adsorption of the studied gases on the NUM-3a were investigated. The heats of adsorptions, as well as Henry's law constants, were also calculated, and it was in line with the observed gas adsorptions. The most preferred sites for the adsorption of carbon dioxide and hydrogen sulfide are the carboxyl groups and inside the channels and around the metal centers. However, methane and nitrogen are mainly accumulating in the channels' s apexes of NUM-3a around the metal center.

Adsorption of carbon dioxide, methane, and their mixture by montmorillonite in the presence of water

The adsorption of carbon dioxide on the MOF-5 metal–organic framework and modifications of it obtained by replacing the hydrogen atoms in the organic ligands with electron donor (–CH3,–OCH3) or electron acceptor groups (–CN,–NO2) is investigated using the grand canonical Monte Carlo (GCMC) method and density functional theory (DFT). It is shown that the adsorption of carbon dioxide molecules on the structures of metal–organic frameworks is most likely on Zn4O clusters, and that the adsorption of carbon dioxide is of a physical nature. The presence of substituents–CH3,–OCH3,–CN in metal–organic frameworks increases their capacity to adsorb carbon dioxide, while that of nitro groups (–NO2) has the opposite effect.

A theoretical study on the selective adsorption behavior of dimethyl ether and carbon monoxide on H-FER zeolites

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

Characterization of adsorption isotherm and density profile in cylindrical nanopores: Modeling and measurement