Displacement of Methane by Coadsorbed Carbon Dioxide Is Facilitated In Narrow Carbon Nanopores

Abstract

By using simulation methods, we studied the adsorption of binary CO 2 −CH 4 mixtures on various CH 4 preadsorbed carbonaceous materials (e.g., triply periodic carbon minimal surfaces, slit-shaped carbon micropores, and Harris's virtual porous carbons) at 293 K. Regardless of the different micropore geometry, two-stage mechanism of CH 4 displacement from carbon nanospaces by coadsorbed CO 2 has been proposed. In the first stage, the coadsorbed CO 2 molecules induced the enhancement of CH 4 adsorbed amount. In the second stage, the stronger affinity of CO 2 to flat/ curved graphitic surfaces as well as CO 2 −CO 2 interactions cause the displacement of CH 4 molecules from carbonaceous materials. The operating conditions of CO 2 -induced cleaning of the adsorbed phase from CH 4 mixture component strongly depend on the size of the carbon micropores, but, in general, the enhanced adsorption field in narrow carbon ultramicropores facilitates the nonreactive displacement of CH 4 by coadsorbed CO 2 . This is because in narrow carbon ultramicropores the equilibrium CO 2 /CH 4 selectivity (i.e., preferential adsorption toward CO 2 ) increased significantly. The adsorption field in wider micropores (i.e., the overall surface energy) for both CO 2 and CH 4 is very similar, which decreases the preferential CO 2 adsorption. This suppresses the displacement of CH 4 by coadsorbed CO 2 and assists further adsorption of CH 4 from the bulk mixture (i.e., CO 2 /CH 4 mixing in adsorbed phase).

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

“…This is because of the fact that in narrow carbon ultramicropores, the equilibrium CO 2 /CH 4 selectivity (i.e. preferential adsorption towards CO 2 ) significantly increased (Kowalczyk et al 2012). The selectivities in the activated carbon is lower than that obtained on carbon nanotubes (Huang et al 2007), but close to the selectivity in C168 models (Babarao et al 2007).…”

Simulation to Enhance Shale Gas Recovery Using Carbon Dioxide in Silica Nanopores with Different Sizes

“…Simulation studies provide detailed microinformation in such complex geology conditions. For example, Kowalczyk et al . investigated the displacement of CH 4 by coadsorbed CO 2 in narrow carbon nanopores with the aim to enhance coal bed methane recovery (ECBM) by CO 2 .…”

“…Research on the displacemento fC H 4 by CO 2 in nanoporous media has been conducted both experimentally and by using computer simulations. [20,23,24] Simulation studies provide detailed microinformation in such complex geology conditions.F or example,K owalczyk et al [25] investigatedt he displacement of CH 4 by coadsorbed CO 2 in narrow carbon nanopores with the aim to enhance coal bed methaner ecovery (ECBM) by CO 2 .Y uan et al [26] examined the displacement of confined CH 4 by CO 2 in carbon nanotubes (CNTs) to imitate the CO 2 -EGR in shale nanopores with organic matter. Zhang and Cao [27] studied the variation of the CH 4 displaced by CO 2 in slit shale matrix, whichw as composed of montmorillonite sheets and methylnaphthalene molecules,a t different geological depths.P reviously,w ee xplored the microscopic mechanism of the displacement of CH 4 by CO 2 in calcite slit nanopores.…”

Which is the most efficient candidate for the recovery of confined methane: Water, carbon dioxide or nitrogen?

“…In addition, since CO 2 has a stronger affinity on the shale than CH 4 , CO 2 injection is proved to be a potential way to displace CH 4 in ESGR [19][20][21]. Moreover, CO 2 displacement is an efficient and economical way in ESGR compared with fracking [22][23][24][25]. Besides, N 2 is an inert and compressible gas with low viscosity.…”