Ethane/Ethylene Adsorption on Carbon Nanotubes: Temperature and Size Effects on Separation Capacity

Abstract

We present the results of Monte Carlo simulations of the adsorption of single-component ethane and ethylene and of equimolar mixtures of these two gases on bundles of closed, single-walled carbon nanotubes. Two types of nanotube bundles were used in the simulations: homogeneous (i.e., those in which all the nanotubes have identical diameters) and heterogeneous (those in which nanotubes of different diameters are allowed). We found that at the same pressure and temperature more ethane than ethylene adsorbs on the bundles over the entire range of pressures and temperatures explored. The simulation results for the equimolar mixtures show that the pressure at which maximum separation is attained is a very sensitive function of the diameter of the nanotubes present in the bundles. Simulations using heterogeneous bundles yield better agreement with single-component experimental data for isotherms and isosteric heats than those obtained from simulations using homogeneous bundles. Possible applications of nanotubes in gas separation are discussed. We explored the effect of the diameter of the nanotubes on the separation ability of these sorbents, both for the internal and for the external sites. We found that substrate selectivity is a decreasing function of temperature.

Review on carbon nanotubes and carbon nanotube bundles for gas/ion separation and water purification studied by molecular dynamics simulation

“…Besides this, the grooves of the bundle play a (2011) significant role in the enhancement of selectivity at lower pressures although at higher pressures those are less important since confinement is practiced at all sites. Albesa and team accomplished Monte Carlo simulations to study the adsorption of single component of pure ethane and ethylene and also equimolar mixtures of them on the bundles of closed single-walled CNTs (Albesa et al 2012). Two types of nanotube bundles were applied in their simulations, including homogeneous (CNTs with the same diameters) and heterogeneous (CNTs with different diameters).…”

Adsorption of CO2/CH4 Mixtures in a Molecular Model of Activated Carbon through Monte Carlo Simulations

“…The isosteric heat of adsorption for the ith component of an ideal gas mixture (q st,i ) can be calculated using the following expression (Albesa et al 2012): (4) where p i = Py i represents the partial pressure of the ith component (P and y i are total gas pressure and molar fraction in gas phase) in equilibrium with n i moles in the adsorbed phase, T is the temperature and R is the gas constant. However, as previously noted, equation (4) is not a practical method for calculating the isosteric heat because the data required for using equation (4) are rarely found in the literature.…”

Ordered phases of ethylene adsorbed on charged fullerenes and their aggregates

“…Several later experimental and theoretical studies have been published which were devoted to ethylene adsorbed on graphite [14,18] , bundles of nanotubes [19–23] , or crystals of C 60 [24] . Surprisingly, none addressed the possible existence of commensurate phases nor the orientation of the adsorbed molecules.…”