Fully atomistic molecular dynamics simulations of the behavior of a simple model of crude oil confined between graphene planes.

We present and discuss the results of molecular dynamics computer simulations of crude oil confined between graphene planes. The crude oil is represented as a mixture of alkanes having 6 </= n </= 30 carbons that contain explicit hydrogen atoms; the confining structure is a floor and ceiling, each comprised of graphene sheets. At low temperature, the system adsorbs completely onto the confining layers, showing an interesting domain structure in its own right. As the temperature increases, various species desorb in order of increasing molecular mass and enter the vapor phase between the confining sheets. Desorption proceeds through a roughening of the adsorbed layers but does not appear to couple to any inter- or intramolecular phase transition on the surfaces for any given species. Allowing the graphene sheets to be flexible affects the rate of adsorption as well as the in-plane order and molecular confirmations of the adsorbate. Cursory simulations with more than one layer show droplet-like adsorption at low temperatures and complicated dynamics, which shift the initial desorption temperatures to lower values than those for the monolayer and cause the desorption temperature and process to be much less defined. The results presented here are suggestive of a method of separating alkane mixtures at temperatures significantly different from those of conventional refining processes.