Modeling Adsorption Properties on the Basis of Microscopic, Molecular, and Structural Descriptors for Nonpolar Adsorbents

Abstract

We propose a method for analytically predicting single-component adsorption isotherms from molecular, microscopic and structural descriptors of the adsorbate-adsorbent system and concepts of statistical thermodynamics. Expressions for Henry's constant and the heat of adsorption at zero coverage are derived. These functions depend on the pore size, pore shape, chemical composition, and density of the adsorbent material. They quantify the strength of the solid-fluid interaction, which governs the low-pressure part of the adsorption isotherm. For intermediate and high pressures, the fluid-fluid interactions must also be taken into account. Both solid-fluid and fluid-fluid interactions are combined within the framework of the Ruthven statistical model (RSM). The RSM thus constructs theoretical adsorption isotherms that are entirely based on microscopic molecular and structural descriptors. The theoretical results that we obtained are compared with experimental data for the adsorption of pure CO2 and CH4 on all-silica zeolites. The developed methodology allows for the estimation of the optimum properties of a nonpolar adsorbent for the adsorption of CO2 in cyclic adsorption processes.

Diffusion of interacting particles in discrete geometries: Equilibrium and dynamical properties

“…One of the first such analyses was performed by Ruthven [31]. Similar studies have been performed both analytically [32][33][34][35][36][37] and numerically [29,38,39]. We refer to Ref.…”

Methane storage in nanoporous material at supercritical temperature over a wide range of pressures

“…To depict exactly the gas storage behavior in nanoporous materials, the macroscopic properties of gas storage must be linked to the microscopic properties of a gas molecules-wall system 61 . The key descriptors of gas storage in nanoporous materials include the strength of the gas intermolecular interaction and the strength of the gas molecule-wall interaction.…”

“…For gas storage in nanopores with walls having homogeneous chemical and physical properties, while the interaction between gas molecules and nanopores walls dominates ( F S-F / F F-F > 1, where F S-F is the interaction force between gas molecules and nanopores walls and F F-F is the gas intermolecular interaction force. ), gas storage amount first increases sharply with pressure in the low pressure region, then increases slowly in the relatively high pressure region 11 60 , and finally becomes constant due to the storage saturation limited by the space available for gas molecules 61 (see Fig. 1a ).…”

Equation of state for methane in nanoporous material at supercritical temperature over a wide range of pressure

“…1d and e), the gas intermolecular interaction gradually becomes strong, non-negligible in contribution of gas storage behavior, and is determined by the intrinsic microscopic properties of the gas molecule, such as its shape, polarizability, and permanent electric moments 61 . The interaction strength can be characterized by the equilibrium constant for gas, (4) where, ff is the potential of gas molecules-molecules, and expressed as 61 ,…”

“…1d and e), the gas intermolecular interaction dominates the gas storage behavior, and this process can be quantitatively depicted by an appropriate EOS 61 . For methane at supercritical temperature, Redlich-Kwong (RK) EOS 92 is chosen as the basic equation for developing our EOS, due to its excellent prediction for light hydrocarbons in the supercritical region 93 .…”