학술논문
多环芳烃在超临界环己烷中的溶解:分子动力学模拟研究 / Dissolution of polycyclic aromatic hydrocarbons in super critical cyclohexane:A molecular dynamics simulation study
Document Type
Academic Journal
Author
Source
原子与分子物理学报 / Journal of Atomic and Molecular Physics. 41(2):15-23
Subject
Language
Chinese
ISSN
1000-0364
Abstract
重油中大量存在的多环芳烃会经过缩合反应会形成稠环芳烃,而溶解扩散的限制会导致稠环芳烃之间的聚合从形成残焦,使得对重油的利用率大大降低,所以多环芳烃热解过程的溶解扩散是重油改质的关键因素之一.因此,基于环己烷对烃类良好的溶解性,本文采用分子动力学模拟的方法研究了多环芳烃及其混合物在超临界环己烷中的溶解行为,结果表明在不同温度与密度下超临界环己烷对于具有NAP均具有良好的溶解性,而温度对于Bghip溶解的影响较小.在多环芳烃混合物的油滴溶解过程中,NAP优先溶解到环己烷相中,而Bghip则集中在粒径减小的油滴中.通过计算体系中多环芳烃的径向分配函数与溶剂化自由能发现环己烷与多环芳烃间之间能相互吸引,环己烷在多环芳烃分子周围形成的溶剂壳能抑制多环芳烃分子间的聚合.温度升高以及密度的将降低会导致多环芳烃的内聚能密度降低,增加了多环芳烃与超临界环己烷之间的相互作用.环己烷密度越小以及温度的升高可以促进多环芳烃或多环芳烃混合物在超临界环己烷中的溶解.
A large number of polycyclic aromatic hydrocarbons in heavy oil will undergo a condensation reaction to form polycyclic aromatic hydrocarbons(PAHs),and the limitation of dissolution and diffusion will cause the polymerization between polycyclic aromatic hydrocarbons to form residual coke,which greatly reduces the utiliza-tion rate of heavy oil.Therefore,dissolution and diffusion in the pyrolysis process of PAHS is one of the key fac-tors for the improvement of heavy oil.Based on the good solubility of cyclohexane to hydrocarbons,the molecular dynamics simulation method was used to study the dissolution behavior of polycyclic aromatic hydrocarbons and their mixtures in supercritical cyclohexane.Critical cyclohexane has good solubility for NAP,while temperature has little effect on the dissolution of Bghip.During the dissolution of oil droplets in the PAH mixture,NAP was preferentially dissolved into the cyclohexane phase,while Bghip was concentrated in the oil droplets with reduced particle size.By calculating the radial distribution function and solvation free energy of PAHs in the system,it is found that cyclohexane and PAHs can attract each other,and the solvent shell formed by cyclohexane around PAH molecules can inhibit of intermolecular polymerization PAHs.The increase in temperature and the decrease in density will lead to a decrease in the cohesive energy density of PAHs,increasing the interaction between PAHs and supercritical cyclohexane.The lower density of cyclohexane and the increase in temperature can pro-mote the dissolution of polycyclic aromatic hydrocarbons or mixtures of polycyclic aromatic hydrocarbons in super-critical cyclohexane.
A large number of polycyclic aromatic hydrocarbons in heavy oil will undergo a condensation reaction to form polycyclic aromatic hydrocarbons(PAHs),and the limitation of dissolution and diffusion will cause the polymerization between polycyclic aromatic hydrocarbons to form residual coke,which greatly reduces the utiliza-tion rate of heavy oil.Therefore,dissolution and diffusion in the pyrolysis process of PAHS is one of the key fac-tors for the improvement of heavy oil.Based on the good solubility of cyclohexane to hydrocarbons,the molecular dynamics simulation method was used to study the dissolution behavior of polycyclic aromatic hydrocarbons and their mixtures in supercritical cyclohexane.Critical cyclohexane has good solubility for NAP,while temperature has little effect on the dissolution of Bghip.During the dissolution of oil droplets in the PAH mixture,NAP was preferentially dissolved into the cyclohexane phase,while Bghip was concentrated in the oil droplets with reduced particle size.By calculating the radial distribution function and solvation free energy of PAHs in the system,it is found that cyclohexane and PAHs can attract each other,and the solvent shell formed by cyclohexane around PAH molecules can inhibit of intermolecular polymerization PAHs.The increase in temperature and the decrease in density will lead to a decrease in the cohesive energy density of PAHs,increasing the interaction between PAHs and supercritical cyclohexane.The lower density of cyclohexane and the increase in temperature can pro-mote the dissolution of polycyclic aromatic hydrocarbons or mixtures of polycyclic aromatic hydrocarbons in super-critical cyclohexane.