Graphitic Slit Pores Research Articles

Investigating the impact of pore structure and surface chemistry on CO2 adsorption in graphitic slit-pores using GCMC simulation

Carbon capture, storage, and utilization from post-combustion processes using adsorption phenomena has emerged as a promising solution to the greenhouse gas emission crisis. The capacity of solid porous adsorbents dictates the performance of such carbon capture processes. Developments of porous adsorbents with favourable structural and chemical characteristics of the pore have been a major research area. Computational tools, notably the Grand Canonical Monte Carlo (GCMC) simulation, are widely employed to characterize the adsorption process in crystalline adsorbents like metal-organic frameworks and zeolites. Activated carbons are becoming promising alternatives to conventionally-used zeolite adsorbents for CO2 adsorption, because of their abundant microporosity and cost performance. However, the amorphous nature of the activated carbon materials poses a challenge in accurately modelling their pore characteristics and their adsorption process. Therefore, this study systematically explores the effect of pore size distribution and type of functional groups on the adsorption of CO2 on activated carbons using a simplified slit-pore graphite structure representing the activated carbon adsorbent. Four different pore sizes (7 Å, 8.9 Å, 18.5 Å, and 27.9 Å) and three oxygen-containing functional groups (Carbonyl, Hydroxyl, and Carboxyl) were selected to model the graphite structures. Results from the GCMC simulation reveal a significant rise in the CO2 adsorption capacity (from 4 mmol/g to 21 mmol/g) as the pore size was increased from 7 Å to 27.9 Å. Likewise, the functional groups enhance the low-pressure adsorption process by reducing the onset pressure of the pore filling by a factor of 100, especially in ultra-micropores. Likewise, we demonstrate the increase in the isosteric heat of adsorption due to the reduction in the pore size and the presence of functional groups. Additionally, the study illustrates the adsorbed phase behaviour of CO2 concerning the pore characteristics, a facet often overlooked in the existing literature. The adsorbed phase local density and molecular orientation distribution are analysed to understand the variation in the adsorption uptake and isosteric heat of adsorption properties. The study further identifies the adsorbed phase monolayer to multilayer transition and the ‘T′-shaped orientation of the adsorbed CO2 molecules as the key contributors to the high isosteric heat of adsorption in 8.9 Å pore size. It is envisaged that this study will navigate the precision adsorbent development for an efficient carbon capture process.

Molecular simulation of the impact of surface roughness on carbon dioxide adsorption in organic-rich shales

This study investigates the adsorption behavior of carbon dioxide in organic nanopores with different surface roughness. The nanopores are constructed by sinusoidally corrugating the graphite slit pore walls. By computing the density distributions, adsorption quantities and orientation of carbon dioxide under various pressure and roughness conditions, we elucidate the impacts of surface roughness on carbon dioxide adsorption in organic nanopores. The Langmuir-Freundlich adsorption model is utilized to fit the isotherms of CO2 adsorption under three different roughness conditions. the results show that increasing surface roughness led to the increase in the adsorption of carbon dioxide, as the relative roughness increased from 0% to 12.92%, the average CO2 adsorption capacity increased by 0.003 mmol/m2. Both the adsorbed layer density and monolayer maximum adsorption capacity increased concurrently with escalating roughness. Moreover, carbon dioxide molecules preferentially aligned parallel to the rough organic surface within the adsorption layer, consistent with the smooth graphitic wall configuration. All simulations, observations, and calculations were performed through grand canonical Monte Carlo (GCMC) simulations. These findings provide insights into the influence of surface roughness on CO2 adsorption, especially in organic nanopores, which has substantial implications for carbon capture and geological sequestration applications. The results could facilitate optimization of strategies for efficient, secure geological CO2 storage.

Collisions, adsorption and self diffusion of gas in nanometric channels by molecular dynamics and stochastic simulation and the case of helium gas in graphitic slit pore

We investigate and model the collisions and the self diffusion processes of dilute Helium gas in nanometric graphite channels using molecular dynamics. At high temperature, collisions are mostly specular with short resident time. At temperature as low as 50 K-75 K, the gas atoms stay longer near the surface and the surface diffusion becomes dominant. Both ballistic and diffusive transport regimes are present before the desorption. A waiting time model based on the residence time distribution and coupled with ballistic-diffusive surface motion of atoms and with Cercignani-Lampis scattering model is proposed. The stochastic simulation of self diffusion based on the waiting time model agrees with the MD simulations and theoretical results in literature. The Arrhenius law is used to model the variation of the obtained Knudsen diffusivity as functions of temperature.

Molecular simulation of confined ethaline‐based deep eutectic solvents for separations of carbon dioxide from methane

AbstractClassical molecular dynamics (MD) simulations were used to study the separation of carbon dioxide from methane by three formulations of the deep eutectic solvent (DES) ethaline (choline chloride: ethylene glycol at 1:2, 1:4, and 1:8 molar ratios), confined inside graphite and titania (rutile) slit pores of two different pore widths, 2 and 5 nm. In addition, equivalent DES systems in the bulk were studied, which can also be viewed as a model supported DES membrane with μm‐sized pores. Our results indicate that variations in the ratio of ethylene glycol, which in turn affect the interactions of all DES species with the gas molecules and the different pore walls, plus confinement effects resulting from varying the pore sizes, can affect the gas separation performance of these systems in complex ways. The highest permselectivities (~20), computed as the product of the diffusivity and solubility selectivities, are observed for 1:2 ethaline in a 5 nm graphite pore, followed by the 1:4 DES in a 5 nm graphite pore, 1:2 ethaline in a 2 nm graphite pore, and the 1:8 bulk DES. In bulk systems, all three selectivities reach their highest values for 1:8 ethaline. When the DESs are confined in the nanopores, the solubility selectivity for most systems improves compared to the equivalent bulk systems, with the graphite pores having the largest solubility selectivities for any given ethylene glycol ratio. In contrast, the diffusivity selectivities in confined systems tend to be similar to the values observed in the bulk DESs. Interaction energies and local density profiles were used to rationalize absorption and diffusivity of gases in our systems. Confining ethaline in graphite and rutile nanopores tends to weaken the CO2‐ethylene glycol and CO2‐cation interactions compared to the values observed in equivalent bulk ethaline systems, which also affect the local density profiles. Our results confirm that variations in ethylene glycol ratio, pore size, and pore wall material can lead to significant changes in gas separation performance. Other porous matrices, for example, nanoporous polymer formulations and graphene oxides, should be considered in follow‐up studies as they may lead to significant improvements in gas separation performance as compared to the bulk DES.

Elastic Properties of Confined Fluids in Nanopores: An Acoustic-Propagation Model.

Following the compressibility route in statistical mechanics, the local isothermal modulus is derived for nanoconfined fluids. Based on this inhomogeneous modulus, an acoustic-propagation model (APM) is first proposed for averaged isothermal modulus in the pore. By utilizing the density profiles obtained from classical density functional theory, the inhomogeneous modulus of supercritical methane in the graphite slit pore is calculated. It is found that the profile of the modulus in the pore is out of phase with that of density. Further, employing the proposed APM method, the averaged isothermal modulus is calculated, and the effects of pressure, pore size, and temperature on the averaged modulus are investigated. It is found that (i) averaged modulus obtained from APM method still satisfies the Tait-Murnaghan (TM) equation, (ii) the averaged modulus is proportional to the reciprocal pore width for wider pores, while it oscillates with the reciprocal pore width for narrower pores, and (iii) the reciprocal modulus is proportional to temperature, while the linearization coefficient is insensitive to the pore size. These findings bear important implications for understanding the elasticity in fluid-saturated nanoporous media and may shed light on the capture or storage of special gases in the fields of geochemistry and geophysics.

Molecular Simulation of Benzene Adsorption in Graphitic and Amorphous Carbon Slit Pores

Molecular Simulation of Benzene Adsorption in Graphitic and Amorphous Carbon Slit Pores

Impact of confinement and polarizability on dynamics of ionic liquids.

Polarizability is a key factor when it comes to an accurate description of different ionic systems. The general importance of including polarizability into molecular dynamics simulations was shown in various recent studies for a wide range of materials, ranging from proteins to water to complex ionic liquids and for solid-liquid interfaces. While most previous studies focused on bulk properties or static structure factors, this study investigates in more detail the importance of polarizable surfaces on the dynamics of a confined ionic liquid in graphitic slit pores, as evident in modern electrochemical capacitors or in catalytic processes. A recently developed polarizable force field using Drude oscillators is modified in order to describe a particular room temperature ionic liquid accurately and in agreement with recently published experimental results. Using the modified parameters, various confinements are investigated and differences between non-polarizable and polarizable surfaces are discussed. Upon introduction of surface polarizability, changes in the dipole orientation and in the density distribution of the anions and cations at the interface are observed and are also accompanied with a dramatic increase in the molecular diffusivity in the contact layer. Our results thus clearly underline the importance of considering not only the polarizability of the ionic liquid but also that of the surface.

The effects of nitrogen functional groups and narrow micropore sizes on CO2 adsorption onto N-doped biomass-based porous carbon under different pressure

The biomass-derived N-doped porous carbons have been proved promising adsorbent material, due to their good CO 2 /N 2 selectivity and excellent CO 2 adsorption performance. However, many researchers simply studied the effect of nitrogen groups or narrow micropores (less than 0.7 nm) on CO 2 uptake at 1 bar and ignored the role of different pressures. In this study, a promising porous carbon derived from eucalyptus bark with high CO 2 adsorption capacity was prepared by urea-assisted hydrothermal and KOH activation. The obtained porous carbons were found to be mainly microporous and showed rich nitrogen content. Among the materials, at 1 bar, NPC700 exhibits high CO 2 adsorption of 4.20 mmol/g and 6.98 mmol/g at 25 °C and 0 °C, respectively. Based on Grand canonical Monte Carlo (GCMC) simulation, the adsorption density and adsorption energy on graphite slit pore with different pore sizes (0.6–2.0 nm) and N-doped functional groups (pyridinic-N, pyrrole-N and graphitic-N) were calculated. And the results showed that the nitrogen functional groups played a crucial contribution on CO 2 adsorption capacity at relative low pressure (0–0.16 bar). In the case of relative high pressure (0.16–1 bar), the narrow micropores volume determined the CO 2 uptake capacity. • N-doped porous carbons derived from eucalyptus bark were synthesized. • Porous carbon possessed rich nitrogen content up to 3.80 wt%. • The prepared NPC700 showed the highest CO 2 uptake to 4.20 mmol/g at 25 °C. • The nitrogen functional groups determined CO 2 uptake at low pressure (0–0.16 bar). • The narrow micropore volume decided CO 2 uptake at high pressure (0.16–1 bar).

A preliminary study on assessing the Brunauer-Emmett-Teller analysis for disordered carbonaceous materials

The surface area is an important property of porous materials, commonly evaluated through the Brunauer-Emmett-Teller (BET) analysis applied to nitrogen adsorption isotherms at 77 K. However, the applicability of the BET analysis for disordered carbonaceous materials remains under debate. In this work, the disordered carbonaceous materials (coal, kerogen of shale and artificial samples), were chosen as the objective for their BET evaluation. These samples were considered as collections of independent graphite slit pores; the isotherms of these uniform slit pores (kernels) were calculated with Grand Canonical Monte Carlo (GCMC) simulation. Then, the kernels were integrated by following the pore size distribution (PSD) of these real samples to simulate nitrogen adsorption isotherms at 77 K. The BET analysis was conducted for both these simulated isotherms and the uniform slit pores. The results show that the performance of the BET analysis for the carbon slit pores varies with the pore size. As for the mesoporous materials, we found that the BET area derived from the two consistency criteria is reliable, with a maximum overestimation of 18%. For micropores-containing materials, the two consistency criteria shows no obvious advantage over the standard method when the micropore is smaller than 1.8 nm and the micropore volume is non-negligible; the prediction of the BET area (consistency criteria) can be justified by considering the micropore size and percentage of micropore volume. These findings improve the understanding of the BET area and verify the BET analysis on some relevant disordered carbonaceous materials.

Monte Carlo Simulation and Experimental Studies of CO2, CH4 and Their Mixture Capture in Porous Carbons.

Adsorption of carbon dioxide and methane in porous activated carbon and carbon nanotube was studied experimentally and by Grand Canonical Monte Carlo (GCMC) simulation. A gravimetric analyzer was used to obtain the experimental data, while in the simulation we used graphitic slit pores of various pore size to model activated carbon and a bundle of graphitic cylinders arranged hexagonally to model carbon nanotube. Carbon dioxide was modeled as a 3-center-Lennard-Jones (LJ) molecule with three fixed partial charges, while methane was modeled as a single LJ molecule. We have shown that the behavior of adsorption for both activated carbon and carbon nanotube is sensitive to pore width and the crossing of isotherms is observed because of the molecular packing, which favors commensurate packing for some pore sizes. Using the adsorption data of pure methane or carbon dioxide on activated carbon, we derived its pore size distribution (PSD), which was found to be in good agreement with the PSD obtained from the analysis of nitrogen adsorption data at 77 K. This derived PSD was used to describe isotherms at other temperatures as well as isotherms of mixture of carbon dioxide and methane in activated carbon and carbon nanotube at 273 and 300 K. Good agreement between the computed and experimental isotherm data was observed, thus justifying the use of a simple adsorption model.

Effects of nitrogen and oxygen functional groups and pore width of activated carbon on carbon dioxide capture: Temperature dependence

In this work, activated carbon (AC) was prepared from bamboo waste using heat treatment. The AC was then modified to be nitrogen- and oxygen-enriched ACs by integration with urea, air oxidation, and KOH activation. At 25 °C, the nitrogen-enriched sample showed the highest CO2 adsorption affinity (uptake in pore at low pressures) and capacity (uptake in pore at moderate pressures, i.e., 1 bar). Whereas even at 0 °C, it still gave the highest affinity, but its capacity was reduced to be slightly lower than other samples. Consequently, a Grand Canonical Monte Carlo simulation was performed to macroscopically and microscopically investigate the CO2 adsorption behavior occurring in the experiments. The graphitic slit pore, in the pore width range of 0.7–1.5 nm, without a surface functional group (SFG), with pyridine (N-6), and with hydroxyl (OH) functional groups were modeled. (1) Adsorption affinity: the active site of SFG is dominant where CO2 molecules have the strongest interaction with N-functional group for all studied temperatures. The simulated results are consistent with the experimental data. (2) Adsorption capacity: the effect of pore width is more relevant. A sample with a more effective pore size gives higher capacity. However, the effective pore widths oscillated with temperature. High capacity at a suitable pore width resulted from the balance between the energy of motion and the packing of adsorbed molecules in order to optimize the energy. The energy of motion is more distinctive at high temperature; whereas, the commensurate packing is essential at low temperature.

A temperature-dependent potential model for mercury in the description of vapour-liquid equilibrium & adsorption in activated carbon

A practical potential equation for mercury was developed, by incorporating the long-ranged interaction and multi-body effects into the temperature-dependent dispersion parameters, to describe the thermodynamic properties of the liquid-vapour equilibrium and adsorption in carbonaceous materials. The collision diameter (σ) decreases and the well depth of interaction energy (ε) increases with temperature, with the product σ6ε (a measure of attraction) decreasing with temperature. The critical temperature derived from this model, 1745 K, agrees well with the experimental value of 1751 K, and the wetting temperature of mercury on graphite was found to be 1600 K, supporting the fact that mercury does not wet carbon under ambient conditions. Furthermore, it was illustrated with mercury can fill ultrafine graphitic slit pores, whose widths less than 0.7 nm, under ambient temperatures, because of the enhancement of the solid-fluid potential and the strong intermolecular interactions, and the simulation results qualitatively agree well with experimental data.

Corresponding state behaviour of capillary condensation of confined alkanes

ABSTRACTThe corresponding state behaviour of capillary condensation of confined alkanes is studied by means of GC-TMMC simulations. In this study, alkane is considered under graphite and mica slit pore confinements of various slit widths. Corresponding state phase coexistence envelopes of capillary condensation display insignificant effect of surface chemistry for slit pore confinements of 6 Å for methane and 15 Å for n-butane and n-octane. On the other hand, the significant effect of surface chemistry on the corresponding state coexistence envelope is observed for larger slit pore width. Moreover, at a given slit width, more shrinking in the corresponding state coexistence envelope of alkane is observed with the mica slit pore as compared to graphite slit pore. The local behaviour of capillary condensation of corresponding state is also investigated in some typical cases using local density profiles, to understand the overall behaviour of corresponding state capillary condensation. Moreover, for a given slit pore width smaller size alkane has shown more shrinking of the corresponding state coexistence envelope, irrespective of surface chemistry. However, the effect of surface chemistry on the corresponding state coexistence envelope of different alkanes becomes insignificant in smaller slit pore width. Fluctuating positive and negative deviations in the corresponding state vapour–liquid equilibrium pressure with respect to corresponding bulk values are observed in studied slit pore confinements. The corresponding state vapour−liquid interfacial tension of alkanes is less in mica slit pore as compared to graphite slit pore for the studied range of reduced temperatures.

Phase behavior of hydrocarbons in nano-pores

Inside nanopores, solid-fluid interactions are of the same order of magnitude as intermolecular interactions of fluid molecules. This fact strongly modifies the thermodynamic properties of confined fluids with respect to bulk phases. Tight oil and shale gas reservoirs, where the proportion of micro (below 2 nm) and mesopores (between 2 and 50 nm) can reach more than 20% of the volume distribution, represent an environment with such problems and industrial challenges to hydrocarbon fluid pressure/volume/temperature (PVT) modeling. This study provides a detailed understanding of the thermodynamic behavior of confined fluid and reference data of the thermodynamic properties of pure components (methane, ethane, n-pentane, n-decane) and mixtures (methane/ethane, ethane/n-pentane) confined in graphite slit pores. Furthermore, a detailed explanation of the different pressures considered in a porous medium with nano-pores is given. The Gibbs Ensemble Monte Carlo (GEMC) NVT simulation is used for pure components instead of the more traditional Grand Canonical Monte Carlo ensemble (GCMC) simulation to get more precise results of liquid and vapor confined pressure avoiding the phase change location determination problem. The evolution of critical temperature and pressure versus pore radius is compared to literature correlations and confined vapor and liquid densities are calculated. A new and robust method in the GEMC ensemble called GEMC NPT Bubble point Monte Carlo (BPMC) completed with GEMC NVT simulations has been developed to get thermodynamic properties including pressures at equilibrium of confined mixtures. Pressure versus density diagrams, pressure versus molar fraction isotherms and examples of pressure versus temperature diagram for a specific composition are built. The phase envelope of the confined fluid is shifted and closes with respect to phase envelope of bulk fluid. The critical temperature and pressure are shifted from the bulk value to a lower value and the bubble point pressure is decreased as the dew point pressure is increased. With regards to the selectivity of the confined system compared to the bulk fluid, for the methane/ethane and ethane/n-pentane mixtures, the heavier component is preferentially adsorbed in the vapor phase and the lighter component is preferentially adsorbed in the liquid phase. All these results for pure components and mixtures provide relevant information concerning the understanding of the phase behavior in confined systems such as shale gas and tight oil reservoirs, emphasizing the difference from the bulk fluid. Furthermore all these data may be used as references for pore radius dependent equation of state (EOS) calibration.

Competitive Sorption of CO2 with Gas Mixtures in Nanoporous Shale for Enhanced Gas Recovery from Density Functional Theory.

CO2 competitive sorption with shale gas under various conditions from simple to complex pore characteristics is studied using a molecular density functional theory (DFT) that reduces to perturbed chain-statistical associating fluid theory in the bulk fluid region. The DFT model is first verified by grand canonical Monte Carlo simulation in graphite slit pores for pure and binary component systems at different temperatures, pressures, pore sizes, and bulk gas compositions for methane/ethane with CO2. Then, the model is utilized in multicomponent systems that include CH4, C2H6, and C3+ components of different compositions. It is shown that the selectivity of CO2 decreases with increases in temperature, pressure, nanopore size, and average molecular weight of shale gas. Extending the model to more realistic situations, we consider the impact of water present in the pore and consider the effect of permeation of fluid molecules into the kerogen that forms the pore walls. The water-graphite interaction is calibrated with contact angle from molecular simulation data from the literature. The kerogen pore model prediction of gas absolute sorption is compared with experimental and molecular simulation values in the literature. It is shown that the presence of water reduces the CO2 adsorption but improves the CO2 selectivity. The dissolution of gases into the kerogen matrix also leads to the increase in CO2 selectivity. The effect of kerogen type and maturity on the gas sorption amount and CO2 selectivity is also studied. The associated mechanisms are discussed to provide fundamental understanding for gas recovery by CO2.

CHF3–CHClF2 Binary Competitive Adsorption Equilibria in Graphitic Slit Pores: Monte Carlo Simulations and Breakthrough Curve Experiments

The separation and recovery of the greenhouse gases CHF3 and CHClF2 from emissions is essential to avoid adverse environmental effects. Nanoporous carbons are excellent candidates for the capture of CHF3. However, little research has been done on the effect of pore size on the adsorption capacity and selectivity of CHClF2 over CHF3 in nanoporous carbon materials. The effect of the pore size on the competitive adsorption of a binary CHF3–CHClF2 mixture in graphitic slit pores has been investigated using a combination of Monte Carlo simulations and breakthrough curve experiments over a wide range of pressures and temperatures. The entropy changes have a considerable effect on selectivity of CHClF2 over CHF3 because the size of the adsorbate molecule is close to the effective height of the pores; conversely, adsorption energy has a significant impact. The selectivity of CHClF2 over CHF3 at 0.05–1.0 MPa increases in the order 19.47 < 16.62 < 13.20 < 11.77 < 8.30 < 5.17 < 5.67 A. The mechanisms for adsorption ...

Molecular simulation of shale gas adsorption in organic-matter nanopore

Shale gas is a kind of unconventional oil-gas resource with tremendous potential. For thorough understanding of the methane adsorption and micromechanism in organic-matter nanopores of the shale and better acquaintances of the occurrence form, graphite slit-pores were set up as a representation of organic-matter nanopores by using Material Studio, and the grand canonical Monte Carlo method, molecular mechanics and molecular dynamics were used for the simulation of adsorption and diffusion behaviors in organic-matter pores on CH4 and CO2 at the shale gas common burial depth of 2–4 km in the Upper Yangtze Plate. The results indicated that the adsorptions of CH4 and CO2 were physical and the optimal storage depth was 2 km; The mixed adsorption data showed the rationality of exploit shale gas by injecting CO2 to exchange CH4, and the optimal burial depth was 4 km; The relative density of CH4 and CO2 along the normal direction of the pore inwall showed a trend of symmetric distribution and apparent adsorption stratifications appeared. As a whole, the self-diffusion coefficient of CH4 and CO2 increased with the increase of burial depth, and it's consistent with the reasons for such changes of adsorption amount and adsorption heat.

An efficient kinetic Monte Carlo scheme for computing Helmholtz free energy and entropy in bulk fluids and adsorption systems

We present an efficient kinetic Monte Carlo scheme to determine the Helmholtz free energy and entropy of bulk fluids and adsorption systems. The method is made possible because this technique enables the accurate determination of the chemical potential. The Helmholtz free energy, A, is obtained by integrating the chemical potential with respect to the number of molecules, at constant volume and temperature, and the entropy is then determined from the fundamental thermodynamic equation A = E − TS. The entropy of bulk argon is found to be in excellent agreement with values calculated from the established equation of state (EOS). In a system with two co-existing phases we show that our method can determine the surface tension at the Gibbs dividing surface, without recourse to the mechanical route of Irving, Kirkwood and Buff.We show that the intrinsic integral molecular Helmholtz free energy and entropy of the adsorbed phase, corrected for the surface excess, are independent of the size of the simulation box for all chemical potentials tested.The new procedure is illustrated for a range of gases commonly used in the characterization of porous solids (argon, nitrogen, carbon dioxide and ammonia) as adsorbates and a graphitic slit pore as the model adsorbent.

Estimation of adsorption-induced pore pressure and confinement in a nanoscopic slit pore by a density functional theory

This study aims at characterising the adsorption-induced pore pressure and confinement in nanoscopic pores by molecular non-local density functional theory (DFT). Considering its important potential industrial applications, the adsorption of methane in graphitic slit pores has been selected as the test case. While retaining the accuracy of molecular simulations at pore scale, DFT has a very low computational cost that allows obtaining highly resolved pore pressure maps as a function of both pore width and thermodynamic conditions. The dependency of pore pressure on these parameters (pore width, pressure and temperature) is carefully analysed in order to highlight the effect of each parameter on the confined fluid properties that impact the solid matrix.

Adsorption and Phase Behavior of Pure/Mixed Alkanes in Nanoslit Graphite Pores: An iSAFT Application.

The prediction of fluid phase behavior in nanoscale pores is critical for shale gas/oil development. In this work, we use a molecular density functional theory (DFT) to study the effect of molecular size and shape on partitioning to graphite nanopores as a model of shale. Here, interfacial statistical associating fluid theory (iSAFT) is applied to model alkane (C1 - C8) adsorption/desorption/phase behavior in graphite slit pores for both pure fluids and mixtures. The pure component parameters were fit to the bulk saturated liquid density and vapor pressure data in selected temperature ranges. The potential of interaction between the fluid and graphite is modeled with a Steele 10-4-3 potential that is fit to the potential of mean force from single-molecule simulations. Good agreement is found between theory and molecular simulation for the density distributions of pure components in slit pores. The critical properties of methane, ethane, and their mixtures as well as the shift in bubble point and dew point densities were studied, showing good agreement with simulation. The competitive adsorption of mixtures of normal and branched alkanes in graphite pores was also studied. Heavier components more strongly adsorb up to the point that the entropic penalty due to confinement reduces adsorption.