Chatwell René Spencer, Guevara-Carrion Gabriela, Gaponenko Yuri, Shevtsova Valentina, Vrabec Jadran
Thermodynamics and Process Engineering, Technische Universität Berlin, 10587 Berlin, Germany.
Microgravity Research Center, Université Libre de Bruxelles, 1050 Bruxelles, Belgium.
Phys Chem Chem Phys. 2021 Feb 4;23(4):3106-3115. doi: 10.1039/d0cp04985a.
The effect of traces of ethanol in supercritical carbon dioxide on the mixture's thermodynamic properties is studied by molecular simulations and Taylor dispersion measurements. This mixture is investigated along the isobar p = 10 MPa in the temperature range between T = 304 and 343 K. Along this path, the mixture undergoes two transitions: First, the Widom line is crossed, marking the transition from liquid-like to gas-like conditions. A second transition occurs from the supercritical gas-like domain to a subcritical gas. The Widom line crossover entails inflection points for most of the studied properties, i.e. density, enthalpy, shear viscosity, Maxwell-Stefan and intradiffusion coefficients. On the other hand, the transition between the super- and subcritical regions is found to be generally smooth, an observation that is qualitatively confirmed by experimental Taylor dispersion measurements. Dedicated atomistic simulations show the presence of microheterogeneities due to ethanol self-association along the investigated path, which lead to the mixture's anomalous behavior in its extended critical region.
通过分子模拟和泰勒色散测量研究了超临界二氧化碳中痕量乙醇对混合物热力学性质的影响。在10 MPa等压条件下，对该混合物在304至343 K的温度范围内进行了研究。沿此路径，混合物经历了两个转变：首先，穿过维德曼线，标志着从类液态到类气态条件的转变。第二个转变是从超临界类气态区域到亚临界气体。维德曼线交叉导致大多数研究性质出现拐点，即密度、焓、剪切粘度、麦克斯韦-斯蒂芬扩散系数和内扩散系数。另一方面，超临界和亚临界区域之间的转变通常是平滑的，这一观察结果在实验泰勒色散测量中得到了定性证实。专门的原子模拟表明，在所研究的路径上，由于乙醇自缔合存在微观不均匀性，这导致混合物在其扩展临界区域出现异常行为。
