Adsorption of CH₄−CF₄ Mixtures in Silicalite:  Simulation, Experiment, and Theory

Abstract

Grand canonical Monte Carlo (GCMC) simulations of binary Lennard-Jones mixtures in the zeolite silicalite have been used to predict the adsorption of CH4 and CF4 mixtures as a function of gas phase composition, total pressure, and temperature. For single components and mixtures, predictions of adsorption isotherms and isosteric heats are in good agreement with experiment at room temperature. Within the experimental pressure range of 0 to 17 bar, the mixtures are well described by the ideal adsorbed solution (IAS) theory. For very high loading, deviations from IAS theory appear. The configurations generated in the simulation were used to calculate sorbate−zeolite interaction energy distributions for different types of siting locations within the zeolite pores. These distributions display a pore shape related energetic heterogeneity in different regions of silicalite. Near saturation at a total loading of 12 molecules per unit cell, the shape of the observed energy distribution is relatively independent of the composition in the pore. Nevertheless, the energetic heterogeneity is responsible for a mild segregation in the adsorbed mixtures, with methane adsorbed preferentially in the silicalite zigzag channels and CF4 preferentially in the straight channels.

Local Ordered Structure of Propylene Carbonate in Slit-Shaped Carbon Nanopores by GCMC Simulation

“…Grand canonical Monte Carlo (GCMC) simulation is a powerful tool to understand molecular behavior and structure in nanopores. It has been used to evaluate and estimate the unique behaviors of simple molecules such as N 2 , Ar, and 2 ISRN Nanotechnology CH 4 adsorbed in nanopores [16][17][18][19][20][21][22][23][24]. However, molecular simulation of a cyclic hydrocarbon is much more difficult because of its complexity.…”

Modeling of Transport and Accessibility in Zeolites

“…They have investigated the idea of analyzing the influence of several factors such as temperature, pressure, chemical composition, zeolite topology, and pore size on the adsorption [204,[208][209][210][211][212][213][214] and transport [124,203,205,[215][216][217][218] of these mixtures. For example, Krishna et al reported molecular simulations for the self-diffusion of pure and equimolar mixture of carbon dioxide and methane in DDR, CHA, and MFI structures [205], and in a follow-up study, by using MC and MD simulations, screened 12 zeolite topologies looking for the optimal structure to separate the mixture, thereby finding the highest permeation selectivities for DDR and CHA zeolites [214].…”

Liquid-liquid phase separation of binary Lennard-Jones fluid in slit nanopores

“…Binary truncated and shifted LJ fluids in a slit-shaped pore made of LJ silica were employed as a model sys- Interactions with silicon atoms were neglected and only the bound oxygen atoms were considered as the interaction sites, as assumed in many of the previous related studies (Heuchel et al 1997). For oxygen, the parameters ε/k and σ were determined as 230.0 K and 0.27 nm, respectively (Brodka and Zerda 1996).…”