苯分子在Y沸石中跳跃扩散机制的动力学Monte Carlo模拟  

Self-diffusivity of benzene in zeolite Y:different jump diffusion mechanisms investigated by KMC simulations

作　　者：张舟[1] 刘辉[1] 陈标华[1] 

机构地区：[1]北京化工大学可控化学反应科学与技术基础教育部重点实验室,北京100029

出　　处：《化工学报》2006年第5期1147-1152,共6页CIESC Journal

基　　金：教育部科学技术研究重点项目(02017);国家重点基础研究发展规划项目(2004CB217804).~~

摘　　要：利用动力学MonteCarlo(KMC)模拟方法计算了苯在Y沸石中扩散的自扩散系数,并考察了3种不同W W位间跳跃扩散机制下的自扩散系数及其对温度和浓度的依赖关系.实验测量结果表明,苯在Y沸石中的长程运动主要是经SⅡW SⅡ笼间的跳跃,基本不发生W W之间的跳跃.相应得到的自扩散系数对温度的依赖关系较接近实验值;自扩散系数浓度依赖变化趋势为:先随覆盖量的增加而减小,到覆盖量大于S位的饱和覆盖量(每个超笼中4个分子)后,则随覆盖量增加先增后减,但也不会大于零覆盖量时扩散系数值,该情形与考虑W W之间跳跃时完全不同.此外,模拟结果表明,使用正确的跳跃机制是KMC方法能正确模拟客体分子在沸石内扩散行为的关键.Kinetic Monte Carlo （KMC） simulations of self-diffusivities of benzene in zeolite Y were performed for three possible jump diffusion mechanisms of the diffusant, and the corresponding dependence of self-diffusivity on loadings and temperature was investigated. It was demonstrated that different jump mechanisms resulted in significantly different temperature and concentration dependence relationships of self-diffusivity in zeolite Y. It was found and verified by comparison with literature data that SⅡ-W -SⅡ cage to cage jump was the dominant mechanism for diffusion of benzene in zeolite Y, while W-W jump played no role in the process. In this case, simulated temperature and concentration dependence relationships were closer to the experimental results than that predicted by the other two mechanisms.

关 键 词：苯 Y沸石 KMC模拟 跳跃频率 

分 类 号：O414.2[理学—理论物理]