Grand Canonical Monte Carlo Simulation Experiences of Methane and Ethane Adsorption Behaviors on Simplified Organic Shale Formed by Graphene Layering

Abstract

Methane and ethane gases are two major components in shale gas, and the adsorption isotherms are first measured to assess the relative adsorption capacity of organic and inorganic shale structures. In this comparative study, essentially using Monte Carlo and Grand Canonical Monte Carlo (MD+GCMC) simulations with the LAMMPS package, the adsorption behavior of pure methane and ethane in one-, two-, three-, and fourlayer graphene slit-shaped with apertures ranging from 1.0 to 4.0 nm, for pressures up to 1 MPa (1,10,20 and 30 MPa) and temperatures of 320 K, were examined. Consequently, the adsorption capacity in apertures less than 2 nm was found to be sensitive to the number of graphene layers in the wall of nanopores, and the probability of methane and ethane adsorption through graphene nanopores was related to the thickness of the graphene nanopores. The results of MD+GCMC simulations showed that methane and ethane adsorption in multilayer graphenes was most sensitive to the thickness of the graphene layer that constructs the walls of nanopores with various apertures (10, 20, 30, and 40 Å). The observed interaction potential energy and the density profile changes in the gas distributions revealed an increased adsorption of methane and ethane through monolayer graphene nanopores (Type-1) compared with that through two-layer (Type-2), three-layer (Type-3), and four-layer (Type-4) graphene nanopores. The research on the wall thickness of nanopores could help us to improve our understanding of the factors that affect the adsorption of gases in nanopores. This could lead to the development of new and improved methods for gas separation and membrane design. The investigation is a promising area of research with the potential to lead to a variety of new applications. Furthermore, this study will reveal the uncertainties of the provided results of molecular simulations, which can be useful in applications of molecular models in molecular simulations.