Separation of acetylene, ethylene and ethane over single layered graphdiyne membranes: Performance and insights from quantum mechanical views

Ethylene is nearly the most crucial basic chemicals all over the word for polymer industry. In the process of ethylene preparation by traditional steam cracking, by-products such as acetylene and ethane are released unavoidably. How to effectively separate these three hydrocarbon gases, acetylene, ethylene, and ethane, has plagued the industrial process of ethylene production for a long time. This work explores the separation performance of acetylene, ethylene and ethane over single layered graphdiyne membranes from viewpoint of quantum chemistry. The diffusion energy barrier, selectivity and permeability of the three gases separated by graphdiyne membranes are investigated in details by using the density functional theory calculations. The results show that the selectivity of acetylene/ethylene, acetylene/ethane, and ethylene/ethane can reach 2 x 10(6),5 x 10(8) and 184 respectively at 300 K. The permeability of acetylene at 300 K is about 1.9 x 10(-4) mol.m(-2).s(-1).Pa-1, which is about 5 orders of magnitude higher than the industry standard. The permeability for ethylene can reach the industry standard at about 400 K. Combined with energy decomposition analysis (EDA) and reduced density gradient (RDG) analysis, the interaction of the three gas in diffusion processes over graphdiyne membranes is explored, and the quantum mechanical explanation of the separation performance is given. According to EDA results, gas adsorption behavior is dominated by the dispersion effect. However, the repulsive effect and electrostatic effect increase in the gas diffusion approaching to the membrane, and the dispersion effect decreases. In addition, the interaction strength, area and type of gas molecules and graphdiyne membrane are visually depicted via RDG analysis.

Automated summary

This study investigates the separation performance of acetylene, ethylene, and ethane using graphdiyne membranes. The results show that the membranes have high selectivity and permeability, making them promising for ethylene production.