First-principles study of adsorption of ethylene and ethane into doped porous carbons

Ethylene, a fundamental building block in the petrochemical industry, is mostly produced via steam cracking of hydrocarbons. However, due to similar physical properties of ethane and ethylene, the separation of these two chemicals often relies on cryogenic distillation at high pressure and low temperature, resulting in excessive consumption of energy. One of the suggested alternative solutions is using porous carbon membranes, which operate at mild pressure and room temperature conditions. In this study, we explore if turbostratic carbons synthesized via pyrolysis can serve as a promising candidate. Based on the density functional theory calculations using Quantum ESPRESSO (version 7.3), we reveal that the adsorption energy of ethylene tends to increase faster than that of ethylene along with the increase in the nitrogen composition of a modelled adsorption site. Furthermore, Bader charge analysis results imply that this phenomenon is correlated with the magnitude of positive partial charges imposed on carbon atoms adjacent to nitrogen dopants. Our findings provide theoretical insights into the selective adsorption of light hydrocarbon gas molecules into nitrogen-doped porous carbon materials.