Investigating the impact of two-dimensional BC membrane geometry on ethane/ethylene separation using molecular dynamics

To address the need for efficient separation of ethylene and ethane in the industry, this research employed molecular dynamics simulations using the LAMMPS Software. To explore the effect of pore size on separation, circular holes of varying diameters were created in the BC membrane (graphene modified with boron) by removing specific numbers of atoms. Triangular arrangements of atoms were also removed, distinct from the circular ones, to further delve into the separation mechanisms mediated by different pore shapes. Among the studied pores, the circular hole P2 with a diameter of 4.23 Å and area of 14 Å emerged as the most effective pore for separation. P2 boasts an infinite selectivity coefficient for ethylene over ethane, meaning it allows only ethylene to pass through, and an impressive ethylene flow rate of 463 mol/ms. Trailing P2 in performance, the triangular P9 (13.36 Å) exhibits notable separation efficiency. It allows ethylene to pass through four times easier than ethane (selectivity coefficient 4), impressing with an ethylene flow rate of 195 mol/ms while strictly limiting ethane to 48.7 mol/ms. This superior performance can be attributed to the shape and size of the sheet and the specific arrangement of boron and carbon atoms at its edges. These factors influence the electron charge density around the cavity, ultimately affecting the overlap with gas molecules. The optimized cavity diameter effectively restricts the passage of larger ethane molecules while allowing ethylene to permeate freely, achieving complete separation.