Simultaneous Determination of Thermal and Mutual Diffusivity of Binary Mixtures of <i>n</i>-Octacosane with Carbon Monoxide, Hydrogen, and Water by Dynamic Light Scattering

Heller, Andreas; Koller, Thomas M.; Rausch, Michael H.; Fleys, Matthieu; Bos, A.N.R.; Laan, Gerard P. van der; Μakrodimitri, Zoi Α.; Economou, Ioannis G.; Fröba, Andreas P.

doi:10.1021/jp500300y

Cited by 44 publications

(121 citation statements)

References 27 publications

Supporting

Mentioning

110

Contrasting

Order By: Relevance

“…It explains the increase in solubility resulting from an increase in temperature at saturation. Moreover, the presence of only free water molecules dissolved in the bulk confirms that results from DLS under similar conditions 54 are associated with pure molecular diffusion and not with that of clathrate-like structures.…”

Section: ■ Introductionsupporting

confidence: 76%

See 1 more Smart Citation

Characterization of Water Solubility in n-Octacosane Using Raman Spectroscopy

et al. 2017

Self Cite

View full text Add to dashboard Cite

In this study, we demonstrate the ability of polarization-difference Raman spectroscopy (PDRS) to detect dissolved free water molecules in a n-octacosane (n-CH) liquid-rich phase, and thus to determine its solubility, at temperatures and pressures relevant to the Fischer-Tropsch synthesis. Our results for the pure alkane reveal thermal decomposition above a temperature of 500 K as well as an increase of gauche conformers of the alkane chains with an increase in temperature. For binary homogeneous mixtures, raw spectra obtained from two different polarization scattering geometries did not show a relevant signal in the OH stretching frequency range. In contrast, isotropic spectra obtained from the PDRS technique reveal a narrow and tiny peak associated with the dangling OH bonds. Over the complete range of temperatures and pressures, no signature of hydrogen-bonded water molecules was observed in the isotropic Raman scattering intensities. A thorough investigation covering a large range of temperatures and pressures using PDRS signals showed that the higher the fraction of gauche conformers of hydrocarbon, the higher the solubility of water. The proportion of gauche and trans conformers was found to be water-concentration-independent, and the intensity of the OH-dangling peak increased linearly with increasing the vapor partial pressure of water. Therefore, we established a relation between a relevant intensity ratio and the concentration of water obtained from SAFT calculations. Contrary to the results from relevant literature, the calibration factor was found to be temperature-independent between 424 and 572 K. The isotropic Raman scattering intensities are corrected in order to provide a better representation of the vibrational density of states. The influence of correction of the isotropic scattering intensities on the solubility measurements as well as on the analysis of the molecular arrangement is discussed.

show abstract

Section: ■ Introductionsupporting

confidence: 76%

“…On average, the temperature stability was of 0.6 mK per hour and the pressure stability was of 0.004 MPa per hour. More details about the temperature control, the sample cell, and the manifold system can be found in ref 54.…”

Section: ■ Introductionmentioning

confidence: 99%

Characterization of Water Solubility in n-Octacosane Using Raman Spectroscopy

et al. 2017

Self Cite

View full text Add to dashboard Cite

show abstract

“…The limitation regarding the resolution of multiple hydrodynamic modes accessible by DLS is not only restricted to the supercritical state close to the vicinity of the plait critical point. It was also observed close to the consolute critical point of a ternary mixture [8,9], in the saturated liquid phase of a binary mixture at vapor-liquid equilibrium [10][11][12], and in the liquid state for binary mixtures near their plait critical point [13]. For the last two cases, this limitation was observed close to the region where thermal and Fick diffusivities match.…”

Section: Introductionmentioning

confidence: 71%

“…This is, however, restricted to the case where Le ≫ 1. When Le and ℜ are close to unity, the single hydrodynamic mode reflects within combined uncertainty the dynamics of both temperature and concentration fluctuations [10,12].…”

Section: Rayleigh Scattering From the Bulk Of A Binary Mixturementioning

confidence: 99%

Diffusivities of an Equimolar Methane–Propane Mixture Across the Two-Phase Region by Dynamic Light Scattering

2020

Self Cite

View full text Add to dashboard Cite

The present contribution examines the accessibility of diffusivities across the twophase region of an equimolar methane-propane mixture for dynamic light scattering (DLS) experiments. Heterodyne DLS experiments and theoretical calculations of the Rayleigh ratio were performed at 125 different thermodynamic states including the gas, liquid, supercritical, and the two-phase region. The present measurements document that two diffusivities can be determined simultaneously in the liquid state and saturated liquid phase for temperatures and pressures which correspond to densities larger than 1.15 times the critical density. Based on a rigorous assignment of the signals detected in this work, the slow and fast diffusivities could be associated with the Fick and thermal diffusivities. For all other thermodynamic states, a single hydrodynamic mode or signal was obtained experimentally. With the help of theoretical Rayleigh ratios as well as from the general behavior of the diffusivities as a function of temperature and pressure, the signals were identified to be related to the Fick diffusivity in the supercritical state and to a mixed diffusivity in the gas state and the saturated vapor phase. The results are discussed in connection with the behavior of the diffusivities along certain paths in the pressure-temperature projection of the phase diagram of the mixture.

show abstract

“…Although there is a large amount of experimental data available for the viscosity of n-alkanes and the self-diffusivity of solutes in n-alkanes [1][2][3][4][5], not all information relevant for processes design can be gathered by experiments. Consequently, suitable theoretical models or accurate computational approaches provide an appealing alternative with respect to time and cost.…”

Section: Introductionmentioning

confidence: 99%