石墨炔对乙烷、乙烯和乙炔分离性能的分子模拟

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

乙烯作为重要的化工原料,在传统蒸汽裂解生产乙烯的过程中,会产生乙炔、乙烷等副产物,如何有效地将这三种烃类气体分离至关重要。本文基于密度泛函理论系统探究了石墨炔膜对三种气体的吸附、选择和渗透性能,并结合吸附作用分析和约化密度梯度分析,探索了三种气体分子穿透过石墨炔膜的相互作用类型、强度以及作用区域,并给出了分离性能的量子力学解释。结果表明,石墨炔膜常温下对乙炔/乙烯、乙炔/乙烷、乙烯/乙烷的选择性分别可以达到2×10^(5)、4×10^(7)、165;乙炔在常温下的渗透率约为6.54×10^(−5) mol/(m^(2)·s·Pa),高出工业标准约五个数量级,乙烯渗透率在400 K左右时达到工业标准。通过量子力学角度分析,气体分子与石墨炔膜相互作用区域在气体分子与石墨炔骨架上的中心位置之间,作用类型主要表现为范德华作用,随着气体分子逐渐穿透靠近石墨炔膜的过程中,相互作用逐渐增强,作用强度乙炔<乙烯<乙烷,与能垒计算结果保持一致。

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 2×10^(5),4×10^(7),165,respectively at room temperature;the permeability of acetylene at room temperature is about 6.54×10^(−5) mol/(m^(2)·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.