超临界氮气在单壁碳纳米管内吸附行为的GCMC模拟研究  

GCMC simulation of supercritical N_(2) adsorption in single-walled carbon nanotubes

作　　者：赵明慧 刘忠军 姬帅[1] 刘晨 敖庆波[2] Zhao Ming-Hui;Liu Zhong-Jun;Ji Shuai;Liu Chen;Ao Qing-Bo(School of Materials science and Engineering,Xi’an Shiyou University,Xi’an 710065,China;State Key Laboratory of Porous Metal Materials,Northwest Institute for Nonferrous Metal Research,Xi’an 710016,China)

机构地区：[1]西安石油大学材料科学与工程学院,西安710065 [2]西北有色金属研究院,金属多孔材料国家重点实验室,西安710016

出　　处：《物理学报》2022年第22期6-15,共10页Acta Physica Sinica

基　　金：西安石油大学校青年创新团队项目(批准号:2019QNKYCXTD12);陕西省教育厅科学研究计划服务地方专项(批准号:20JC028);陕西省自然科学基金(批准号:2021JM-410)。

摘　　要：超临界流体技术发展日益成熟,开展超临界流体在纳米多孔材料内的吸附行为研究,对超临界流体技术的开发与应用推广具有理论意义和使用价值.本文利用巨正则蒙特卡罗法,主要模拟了超临界状态下氮气在单壁碳纳米管内的吸附行为.结果表明超临界条件下,氮气在单壁碳纳米管内的吸附等温线不严格遵循层状吸附机制;氮气吸附等温线出现峰值,且峰值随温度的升高而逐渐减小.与亚临界条件不同,超临界条件下流体局部密度分布曲线的吸附峰并不能代表过剩吸附量的增加,且本体气相密度对吸附过程产生的影响不可忽略.通过对超临界条件下的吸附积分摩尔焓进行研究,发现过剩积分摩尔焓随孔径增大而减小;吸附积分摩尔焓在较低压力下随孔径增大而减小,但在较高压力下随孔径的增大而增加.The development of supercritical fluid technology is becoming more and more mature. The research on the adsorption behaviors of supercritical fluid in nanoporous materials has theoretical significance and application value for the development and application of supercritical fluid technology. In this paper, the grand canonical Monte Carlo(GCMC) method is used to simulate the adsorption behaviors of N_(2) in single-walled carbon nanotubes under supercritical condition and subcritical condition, and the isosteric heat of adsorption and integral molar enthalpy change in different adsorption systems are discussed. The results show that the adsorption isotherms of N_(2) in SWCNT do not strictly follow the layered adsorption mechanism under supercritical condition, as a result of the increase of molecular thermal motion, the degree of free mobility becomes higher, and it is easier for nitrogen molecule to intersperse and jump between different molecular layers. The nitrogen adsorption isotherm has a peak, which decreases gradually with the increase of temperature, while the critical pressure at peak increases with the temperature increasing. Around the critical point temperature(126 K), a small change in pressure can cause large fluctuations in the bulk gas phase density, resulting in a sharp drop in the adsorption isotherm after peaking. What is different from the subcritical condition is that the adsorption peak of local density distribution curve of the fluid under supercritical condition cannot represent the increase of excess adsorption capacity, and the influence of gas phase density on the adsorption process cannot be ignored. By studying the adsorption integral molar enthalpy under the supercritical condition, it is found that the excess integral molar enthalpy decreases with the pore size increasing;the adsorption integral molar enthalpy decreases with the augment of pore size at lower pressure,but due to a fact that the proportion of gas phase fluid in large-pore SWCNTs increases at higher pressure, on the co

关 键 词：超临界 吸附 蒙特卡罗 积分摩尔焓 

分 类 号：O647.3[理学—物理化学]