Molecular simulation of graphyne separation performance for ethane, ethylene and acetylene

Ethylene is an important chemical raw material. In the process of traditional steam cracking to produce ethylene, by-products such as acetylene and ethane are produced. How to effectively separate these three hydrocarbon gases is very important. Based on the density functional theory, this paper systematically explored the adsorption, selection and permeation properties of the graphyne membrane for three gases. Combining adsorption analysis and reduced density gradient analysis, the interaction type, strength and action area of the three gas molecules penetrating the graphyne membrane were explored, and a quantum mechanical explanation of the separation performance was given. The results show that the selectivity of graphyne membrane to acetylene/ethylene, acetylene/ethane, ethylene/ethane can reach 2 × 10⁵, 4 × 10⁷, 165, respectively at room temperature; the permeability of acetylene at room temperature is about 6.54 × 10⁻⁵ mol/(m²·s·Pa), which is about 5 orders of magnitude higher than the industrial standard, and the ethylene permeability reaches the industrial standard at about 400 K. Through the analysis of quantum mechanics, the interaction area between the gas molecules and the graphyne film is between the gas molecules and the center of the graphyne framework, and the type of action is mainly van der Waals interaction, as the gas molecules penetrate closer to the graphite acetylene membrane, the interaction becomes stronger and the strength of interaction is higher than that of acetylene, which is consistent with the energy barrier calculation.