Mutual and Thermal Diffusivities in Mixtures of Cyclohexane, n-Hexadecane, n-Octacosane, or n-Hexanoic Acid with Carbon Dioxide Obtained by Dynamic Light Scattering and Molecular Dynamics Simulations,Journal of Chemical & Engineering Data

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Mutual and Thermal Diffusivities in Mixtures of Cyclohexane, n-Hexadecane, n-Octacosane, or n-Hexanoic Acid with Carbon Dioxide Obtained by Dynamic Light Scattering and Molecular Dynamics Simulations
Journal of Chemical & Engineering Data ( IF 2.0 ) Pub Date : 2022-09-26 , DOI: 10.1021/acs.jced.2c00487
Maximilian Piszko ₁ , Frances D. Lenahan ₁ , Lukas Friedl ₁ , Tobias Klein ₁ , Andreas P. Fröba ₁

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The present work reports Fick diffusion coefficients D₁₁ in the saturated liquid phases of binary mixtures of cyclohexane, n-hexadecane, n-octacosane, or n-hexanoic acid and dissolved carbon dioxide (CO₂) as a function of composition. D₁₁ is experimentally determined by dynamic light scattering (DLS) and predicted by equilibrium molecular dynamics (EMD) simulations within or close to saturation conditions at temperatures between 303 and 423 K and CO₂ mole fractions x_CO2 up to 0.99. Thermal diffusivity data obtained simultaneously by DLS are reported as well. The mixture composition of the liquid phases is experimentally determined by polarization-difference Raman spectroscopy (PDRS). The combination of PDRS experiments and EMD simulations, where the latter allows a direct insight into or the detection of changes of the fluid structure, is used to investigate the influence of the phase behavior and the resulting fluid structure on D₁₁. The behavior of the experimentally determined D₁₁ and that obtained from EMD simulations by the independent calculation of the Maxwell–Stefan diffusivity and the thermodynamic factor show generally good agreement. Distinct structural changes are reflected by the thermodynamic factors, which are between about 0.35 and 1.4. D₁₁ as a function of x_CO2 at a given temperature is nearly constant in mixtures of n-hexanoic acid and CO₂ due to the opposing kinetic and thermodynamic contributions to D₁₁. Pronounced composition-dependent behaviors are observed in the other mixtures due to the proximity to a liquid–liquid miscibility gap or the mixtures’ critical line.

中文翻译：

通过动态光散射和分子动力学模拟获得的环己烷、正十六烷、正二十八烷或正己酸与二氧化碳的混合物中的相互扩散和热扩散

目前的工作报告了环己烷、正十六烷、正二十八烷或正己酸和溶解的二氧化碳 (CO ₂ )的二元混合物的饱和液相中的Fick 扩散系数D ₁₁作为组成的函数。D _{11通过动态光散射 (DLS) 实验确定，并通过平衡分子动力学 (EMD) 模拟在 303 和 423 K 之间的温度和 CO}₂摩尔分数x _CO2内或接近饱和条件下进行预测高达 0.99。还报告了通过 DLS 同时获得的热扩散率数据。液相的混合物组成通过偏振差拉曼光谱 (PDRS) 实验确定。PDRS 实验和 EMD 模拟相结合，后者允许直接洞察或检测流体结构的变化，用于研究相行为和由此产生的流体结构对D ₁₁的影响。实验确定的D _11的行为并且通过独立计算 Maxwell-Stefan 扩散率和热力学因子从 EMD 模拟中获得的结果总体上表现出良好的一致性。热力学因素反映了明显的结构变化，热力学因素在 0.35 和 1.4 之间。由于对D ₁₁的相反的动力学和热力学贡献，在给定温度下作为x _CO2函数的D _11在正己酸和 CO ₂的混合物中几乎是恒定的。由于接近液-液混溶性间隙或混合物的临界线，在其他混合物中观察到明显的成分依赖性行为。

更新日期：2022-09-26

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