水、乙醇、丁醇、丙酮在PDMS中扩散行为的研究

Study on diffusivities of water,ethanol,butanol and acetone through polydimethylsiloxane

为了研究生物质发酵主要产物水、乙醇、丁醇、丙酮的扩散行为,从理论角度指导实践,提高产物分离效率.本实验通过制备聚二甲基硅氧烷(polydimethylsiloxane,PDMS)均质膜,用实验方法测定扩散系数,利用Accelrys公司的Material Studio软件对4种分子进行了分子动力学模拟并得出其扩散系数.最终得到4种分子的扩散系数实验测定值分别为1.120×10^(-5),2.405×10^(-6),3.607×10^(-6),5.77×10^(-7),计算值分别为2.257×10^(-5),2.562×10^(-6),3.672×10^(-6),1.238×10^(-6).其中乙醇和丙酮的实验值和计算值最为接近.针对水和丁醇计算值与实验值的差异,从样条在液体中形变方面进行解释;对乙醇、丁醇、丙酮分子的溶解选择性、扩散选择性以及理想选择性进行分析评价,获得阻碍3种分子分离的主要因素.针对阻碍3种分子分离的主要因素,给出相应的理论解决方法.

In this paper, the diffusion coefficients of water, ethanol, butanol and acetonet in a self-made polydimethylsiloxane （PDMS）film were measured. In addition, the diffusion coefficients of the four molecules were also calculated by the molecular dynamics （MD） simulations by using the software of Material Studio of Accelrys. The diffusion coefficients of butanol and acetone in PDMS film were first reported in this work. The experimental values of the four kinds of molecules were 1.120×10-5,2.405×10-6,3.607×10-6,5.77×10-7, and the calculated values were 2.257×10-5,2.562×10-6,3.672×10-6,1.238×10-6, respectively. The experimental and calculated values were fitted very well especially for ethanol and acetone. In this experiment, the difference between the calculated value and the experimental value of water and butanol was explained from the aspect of the deformation of the sample in liquid. The separation properties of ethanol, butanol and acetone were evaluated in the aspact of adsorption selectivity, diffusion selectivity and ideal selectivity. The main factors that hinder the separation of the three molecules were analysed and the theoretical solutions were given.