常用夹带剂在超临界CO_2中无限稀释扩散系数的MD计算

Molecular Dynamics Simulation for Calculating the Diffusion Coefficients of Acetone, Ethyl Acetate and Cyclohexane at Infinite Dilution Solution of Supercritical CO_2

缺乏物性数据是制约超临界流体(SCF)技术在化工领域广泛应用的瓶颈问题之一。基于Einstein理论,使用分子动力学(MD)技术计算了三种常用夹带剂丙酮、乙酸乙酯和环己烷在超临界CO2中的无限稀释扩散系数,并针对Einstein法测定扩散系数的误差因素提出了一种数据处理的新方法。最后采用Taylor分散法和超临界色谱技术对夹带剂丙酮和乙酸乙酯在超临界CO2中的扩散系数进行了实验验证,结果表明使用新的数据处理法方法得到的扩散系数和实验测定结果吻合良好。

Acetone, ethyl acetate and cyclohexane are three commonly used entrainers in supercritical CO2 extraction process. Molecular dynamics simulations of infinite dilute solution of these three widely used entrainers in supercritical COEwere conducted based on COMPASS force field. The NVT ensemble was applied to calculate their diffusion coefficients in supercritical CO2 extraction in the pressure range from 8 to 35 MPa and the temperature range from 290 to 340 K. In order to obtain more accurate value of diffusion coefficients, a new method dealing with the simulated data processing was proposed. Moreover, supercritical fluid chromatography was used to determine experimentally the diffusion coefficients of acetone and ethyl acetate by the Taylor dispersion technique. The simulated diffusion coefficients obtained from the new method proposed agree well with the experimental results, thus confirming the validity of the new method proposed in this paper.