HZSM-5中水吸附行为的实验与分子模拟(英文)

Investigation of water adsorbed on HZSM-5:experiment and molecular simulation

利用智能重量分析仪(IGA—003,HIDEN)测定了298K条件下水蒸汽在HZSM-5型分子筛中的吸附等温线。并采用巨正则系综Monte Carlo模拟方法(GCMC)研究了水在HZSM—5型分子筛中的吸附等温线,计算结果与实验结果吻合较好。分子模拟计算得到的水分子的微观吸附性质表明水分子吸附在氢离子和铝原子的周围,这是因为水分子是极性分子,分子筛上的氢在库仑力的作用下会与水分子发生强的相互作用,并导致分子筛骨架上的硅铝比与水分子的吸附量之间存在线性关系。计算结果还表明水的吸附热与H_2O/Al之间存在线性关系。

Adsorption of water vapor on HZSM-5 type zeolite is investigated experimentally and by molecular simulation. The adsorption isotherms measured by the Intelligent Gravimetric Analyzer （IGA-003, HIDEN） at 298 K compared with our simulation results by using the grand canonical ensemble Monte Carlo （GCMC） method, and good agreement are observed. Microscopic information from molecular simulation indicates that water molecules stay preferentially around H~ cations and AI atoms. Therefore, the relationship between the water and Si/AI ratio can be explained by that water molecules have strong polarity and the charge of H^＋ cation in zeolite framework influences greatly the water molecules due to the Coulomb force. In addition, there is a linear relationship between the adsorption isosteric heat of water and the H2O/Al ratios.