Diffusivities of Ternary Mixtures of n-Alkanes with Dissolved Gases by Dynamic Light Scattering.
Theoretical approaches suggest that dynamic light scattering (DLS) signals from low-molecular-weight ternary mixtures are governed by fluctuations in temperature as well as two individual contributions from fluctuations in concentration that are related to the eigenvalues of the Fick diffusion matrix. Until now, this could not be proven experimentally in a conclusive way. In the present study, a detailed analysis of DLS signals in ternary mixtures consisting of n-dodecane (n-C12H26) and n-octacosane (n-C28H58) with dissolved hydrogen (H2), carbon monoxide (CO), or water (H2O) as well as of n-C12H26or n-C28H58with dissolved H2and CO is given for temperatures up to 523 K and pressures up to 4.1 MPa. Thermal diffusivities of pure n-C12H26and n-C28H58as well as thermal and mutual diffusivities of their binary mixtures being the basis for the ternary mixtures with dissolved gas were studied for comparison purposes. For the investigated ternary mixtures, three individual signals could be distinguished in the time-resolved analysis of scattered light intensity by using photon correlation spectroscopy (PCS). For the first time, it could be evidenced that these signals are clearly associated with hydrodynamic modes. In most cases, the fastest mode observable for ternary mixtures is associated with the thermal diffusivity. The two further modes obviously related to the molecular mass transport are observable on different time scales and comparable to the modes associated with the concentration fluctuations in the respective binary mixtures. Comparison of the experimental data with results from molecular dynamics simulations revealed very good agreement.
Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT), University of Erlangen-Nuremberg , Paul-Gordan-Straße 6, 91052 Erlangen, Germany.
Andreas
A
Heller
Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT), University of Erlangen-Nuremberg , Paul-Gordan-Straße 6, 91052 Erlangen, Germany.
Cédric
C
Giraudet
National Centre for Scientific Research "Demokritos", Institute of Nanoscience and Nanotechnology, Molecular Thermodynamics and Modelling of Materials Laboratory , GR-15310 Aghia Paraskevi Attikis, Greece.
Zoi A
ZA
Makrodimitri
Shell Global Solutions International B.V. , Grasweg 31, 1031 HW Amsterdam, The Netherlands.
Matthieu S H
MSH
Fleys
Shell Global Solutions International B.V. , Grasweg 31, 1031 HW Amsterdam, The Netherlands.
Jiaqi
J
Chen
Shell Global Solutions International B.V. , Grasweg 31, 1031 HW Amsterdam, The Netherlands.
Gerard P
GP
van der Laan
National Centre for Scientific Research "Demokritos", Institute of Nanoscience and Nanotechnology, Molecular Thermodynamics and Modelling of Materials Laboratory , GR-15310 Aghia Paraskevi Attikis, Greece.|Texas A&M University at Qatar , Chemical Engineering Program, Education City, PO Box 23874, Doha, Qatar.
Ioannis G
IG
Economou
Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT), University of Erlangen-Nuremberg , Paul-Gordan-Straße 6, 91052 Erlangen, Germany.
Michael H
MH
Rausch
Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT), University of Erlangen-Nuremberg , Paul-Gordan-Straße 6, 91052 Erlangen, Germany.
Andreas P
AP
Fröba