纳米多孔石墨烯膜分离N_2/CH_4的密度泛函计算与分子动力学模拟  

Density Functional Theory and Molecular Dynamic Simulation of N_2/CH_4 Separation Over Nanoporous Graphene Membranes

作　　者：贾晓霞[1,2] 杨江峰 王勇[1,2] 李晋平 JIA Xiaoxia;YANG Jiangfeng;WANG Yong;LI Jinping(Research Institute of Special Chemicals,Taiyuan University of Technology,Taiyuan 030024,China;Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization,Taiyuan 030024,China)

机构地区：[1]太原理工大学精细化工研究所,山西太原030024 [2]气体能源高效清洁利用山西省重点实验室,山西太原030024

出　　处：《石油学报（石油加工）》2018年第6期1247-1254,共8页Acta Petrolei Sinica(Petroleum Processing Section)

基　　金：国家自然科学基金项目(21706180)资助

摘　　要：天然气是最重要的能源之一,具有高热值、高效和低污染等优点,但N_2杂质的存在降低了天然气的燃烧热值。为利用低质量天然气(例如低浓度煤层气),需要从天然气(CH_4)中分离N_2。通过密度泛函计算(DFT)和分子动力学模拟(MD)相结合的方式,系统研究了H饱和的多孔石墨烯对N_2/CH_4气体混合物的分离性能。发现孔径约为0.406nm的H-pore-13多孔石墨烯膜能够高效地从CH_4中分离N_2。H-pore-13具有较高的N_2/CH_4选择性,N_2的气体渗透率达到105 GPU (1GPU=3.35×10^(-10) mol/(s·m^2·Pa)),远远高于传统的聚合物分离膜。因此,多孔石墨烯分离膜在天然气纯化方面具有广阔的应用前景。此外,通过理论计算,对多孔石墨烯膜的气体分离机制进行了探讨,结果表明,石墨烯膜与气体分子的电子密度等势面交叠程度对石墨烯膜的气体分离性能具有很大影响。Natural gas is one of the most important energy sources,which is of high calorific value,high efficiency,and low pollution.However,N 2 impurity reduces the heating value of natural gas.Thus,to utilize low-quality natural gas,such as low concentrations of coal bed methane,separation of N 2 from natural gas(CH 4)is required.A systematic study through the combination of density functional theory calculation(DFT)and molecular dynamics simulation(MD)was performed to investigate the capability of graphene membranes with H-passivated nanopores for the separation of N 2/CH 4 gas mixtures.It is found that the graphene membrane H-pore-13,with pore size of 0.406 nm,efficiently separates N 2 from CH 4.H-pore-13 exhibits much higher N 2 selectivity over CH 4 with a N 2 permeance of 10 5 GPU(gas permeation unit,(1 GPU=3.35×10-10 mol/(s·m 2·Pa))than those of conventional membranes.Thus,the nanoporous graphene membrane presents great potential applications in the upgrading of natural gas.In addition,according to the theory calculations,the gas separation mechanism in graphene membranes was investigated.Results indicate that the gas separation performance of graphene membranes is dependent on the extent of electron density overlap among graphene membranes and gases.

关 键 词：纳米多孔石墨烯 密度泛函理论 分子动力学 气体分离 扩散能垒 

分 类 号：TQ028.1[化学工程]