有机蒸气透过SiO_2陶瓷膜的分子动力学模拟

采用分子动力学模拟的方法研究有机蒸气通过二氧化硅(SiO2)陶瓷膜的渗透情况。以丙酮/氮气通过SiO2膜的渗透为模拟体系,对不同温度、不同膜孔径、不同气体浓度等情况下混合气体透过膜的渗透情况进行动力学模拟。模拟结果表明,对于孔径在纳米范围的膜,主要的分离机理为毛细管冷凝。通过对不同条件下丙酮、氮气在膜孔内和膜表面的数量及聚集状态的分析,确定温度在288K左右分离效果较好;膜孔径为1.5nm时易发生毛细管冷凝,分离效果好;有机蒸气浓度在20%左右适用烧结的SiO2膜回收。

Molecular Dynamics Calculations of Organic Vapor Through Microporous Silica Membranes

The separation of acetone from the acetone and nitrogen mixture using microporous silica membranes was calculated by molecular dynamic(MD) method.The results show that the acetone and nitrogen molecules diffuse toward the membrane surface firstly,then the nitrogen molecules can permeate through the membrane pore,but the acetone only rest on membrane surface or in membrane pore.After the membrane pore was filled with acetone,no nitrogen molecules were observed permeating through the membrane pore.This phenomenon suggests that the separation of acetone/nitrogen mixture follows the capillary condensation mechanism.The influence of process parameters,which including operating temperature,membrane pore size and the ratio of nitrogen to acetone on calculation results were also studied.The calculation results indicate that the operating temperature and the membrane pore size are important variables.The separation factor increases when the operation temperature increase from 273K to 288K,but it decreases when the operation temperature increase from 288K to 303 K,which can be explained by the temperature dependencies of the capillary condensation and solubility of nitrogen in acetone.The optimum parameters are the operation temperature of 288K and the membrane pore size of 1.5nm from MD calculation,which consisted with the experimental results.