Phases of ethane adsorbed on purified HiPco single-walled carbon nanotubes

Abstract

have measured adsorption isotherms of ethane on purified HiPco SWNTs for coverages in the first layer. We wanted to investigate the existence of different phases for ethane as a function of coverage on this substrate, and to compare the results to those on planar graphite. We measured isotherms at 103, 110,150, 160, and 165K. We used the low-coverage isotherm data to obtain an estimate for the binding energy of ethane on the SWNTs; we found a value of 363 meV for this quantity. This binding energy value is 1.81 times greater than the corresponding one for this quantity on planar graphite. We have also determined the coverage dependence of isosteric heat of adsorption for ethane using the results for isotherms obtained at above-mentioned temperatures.

Thermodynamics of adsorption of light alkanes and alkenes in single-walled carbon nanotube bundles

“…The general decreasing behavior of q st with monolayer coverage is according to what has been observed before, in experimental adsorption measurements of ethane onto bundles of closedended SWCNTs. 60 Tubes with small diameters do not exhibit interstitial adsorption, so they essentially possess external surface and groove sites available to physisorb molecules. Our curves seems to highlight the fact that there exists two different kinds of adsorptive sites available for fluid molecules, as evidenced by the two different plateaus mentioned before.…”

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

“…In the case of carbon nanotube substrates, few experimental reports are available even for single-component gas adsorption of ethane or ethylene . The reports that are available describe measurements performed at cryogenic temperatures , (which do not provide the information needed for room temperature applications).…”

Adsorption kinetics of diatomic molecules

“…During the last decade, the adsorption behavior of linear hydrocarbons on nanotube bundles has been investigated via experiments and simulations. [9][10][11][12][13][14][15][16][17][18] Most of these studies are focused on equilibrium properties; only very recently has the kinetics of adsorption of linear alkanes been explored experimentally. 18 In that study, the equilibration time of a series of alkane molecules of increasing length (from ethane to pentane), adsorbing on the exterior of a nanotube bundle, was measured.…”

“…This allows us to directly compare with the experimental results mentioned above for ethane adsorption on closed-end nanotube bundles. 15,18 Although we will be somewhat focusing on this system as a particular example (due to the availability of experimental results for the whole alkane series), the model and results presented here are in fact relevant for the kinetic behavior of other homo-nuclear diatomic adsorbates such as H 2 , N 2 , and O 2 . Diatomic molecules are the shortest non-spherical adsorbates possible, and this work is a sensible first step to later analyze the increasingly larger effects of the non-spherical nature of longer molecules.…”