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arXiv 0904.4436physics.chem-phphysics.comp-ph
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不同于Lennard-Jones参数的汽液平衡

Unlike Lennard-Jones Parameters for Vapor-Liquid Equilibria

T. Schnabel, J. Vrabec, H. Hasse

摘要:

考察了Lennard-Jones(LJ)参数对混合物汽液平衡的影响,并对11种组合规则的性能进行了评价。在第一部分的工作中,系统地研究了CO+ $\rm C_2H_6$和$\rm N_2$ + $\rm C_3H_6$两种混合物的不同LJ尺寸和能量参数对蒸汽压、气泡密度和露点组成的影响。结果发现,混合物的蒸汽压强烈地依赖于尺寸和能量参数,而气泡密度主要取决于尺寸参数和露点组成是相当不敏感的两个参数。在前面的工作中,不同的LJ参数调整到实验的二元汽液平衡44真实的混合物。在这些结果的基础上,在工作的第二部分,11个组合规则进行评估,其预测能力。与调整后的不同LJ参数确定的拟合的比较表明,没有11个组合规则产生适当的参数一般。为了获得准确的混合物模型,异色散相互作用,因此,应调整到实验的二进制数据。结果表明,对于异LJ尺寸参数,采用Lorenz规则,并将异LJ能量参数与蒸汽压拟合,就足够了。

英文摘要:

The influence of the unlike Lennard-Jones (LJ) parameters on vapor-liquid equilibria of mixtures is investigated and the performance of eleven combining rules is assessed. In the first part of the work, the influence of the unlike LJ size and energy parameter on vapor pressure, bubble density and dew point composition is systematically studied for the mixtures CO+$\rm C_2H_6$ and $\rm N_2$ + $\rm C_3H_6$, respectively. It is found that mixture vapor pressure depends strongly both on the size and the energy parameter whereas the bubble density depends mostly on the size parameter and the dew point composition is rather insensitive to both parameters. In preceding work, unlike LJ parameters were adjusted to experimental binary vapor-liquid equilibria for 44 real mixtures. On the basis of these results, in the second part of the work eleven combining rules are assessed regarding their predictive power. A comparison with the adjusted unlike LJ parameters determined from the fit shows that none of the eleven combining rules yields appropriate parameters in general. To obtain an accurate mixture model, the unlike dispersive interaction should therefore be adjusted to experimental binary data. The results from the present work indicate that it is sufficient to use the Lorenz rule for the unlike LJ size parameter and to fit the unlike LJ energy parameter to the vapor pressure.

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