Theoretical Calculations of CO2/CH4 Separation through Windowed Carbon Nanotube Membranes

Abstract Distinct topological features endow windowed carbon nanotube (CNT) membranes with great potential as molecular sieves for efficient gas separation and purification. In this work, molecular dynamics (MD) simulations were adopted to systematically investigate the CO2/CH4 selective separation performance of such membranes. Key structural and operational parameters, including CNT diameter, pressure, initial feed gas molar ratio, and nanowindow density, were modulated to comprehensively evaluate the molecular sieving capacity toward CO2 and CH4. Simulation results reveal that heteroatom-functionalized windowed CNT membranes exhibit outstanding CO2 permselectivity and superior CH4 purification capacity, with a maximum CO2/CH4 separation selectivity of 41. Among all simulated configurations, the 4N5F-modified nanowindow CNT membrane exhibits the optimal separation performance, yielding a CO2 capture fraction of 0.77 and recovered CH4 purity of 97.6%. Such excellent molecular sieving performance confirms that windowed CNT membranes hold promising prospects for direct CO2 capture and raw shale gas purification.