Configurational-bias Monte Carlo simulations in the Gibbs ensemble (CBMC-GE) are used to investigate the adsorption of both linear and branched alkanes (ethane, propane, n-butane, and 2-methylpropane) from dilute solutions in liquid methane onto a carbon slit pore at T=160K and at either the saturation pressure or pext=100atm. Thermodynamic properties (adsorption isotherms, selectivities, and Henry's law constants) and structural properties (density and orientational distributions) are presented. Both the Henry's law constants and the separation factors depend exponentially on the number of carbon atoms for the linear alkanes, whereas chain branching and higher pressure lead to a reduction of these properties. The solute density profiles show oscillatory behavior along the surface normal, and peaks in the number density are correlated with a preference for parallel orientations. The CBMC-GE approach allows for the efficient calculation of these selective adsorption phenomena, and data for multiple solutes (in the dilute regime) can be extracted from a single simulation.
Bibliographical noteFunding Information:
We thank Jiri Kolafa for helpful discussion regarding simulation details used in Ref.  . Financial support from the National Science Foundation ( CBET-0756641 and CBET-1159837 ) and a Graduate School Fellowship (P.B.) is gratefully acknowledged. Part of the computer resources were provided by the Minnesota Supercomputing Institute.
- Carbon slit pore
- Gibbs ensemble
- Monte Carlo simulation
- Selective adsorption