Characterization of Water Solubility in n-Octacosane Using Raman Spectroscopy

Journal article
(Original article)


Publication Details

Author(s): Giraudet C, Papavasileiou KD, Rausch MH, Chen J, Kalantar A, van der Laan GP, Economou IG, Fröba AP
Journal: Journal of Physical Chemistry B
Publisher: AMER CHEMICAL SOC
Publication year: 2017
Volume: 121
Journal issue: 47
Pages range: 10665-10673
ISSN: 1520-6106
eISSN: 1520-5207
Language: English


Abstract

In this study, we demonstrate the ability of polarization-difference Raman spectroscopy (PDRS) to detect dissolved free water molecules in a n-octacosane (n-C28H58) 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.


FAU Authors / FAU Editors

Fröba, Andreas Paul Prof. Dr.-Ing.
Lehrstuhl für Advanced Optical Technologies - Thermophysical Properties
Giraudet, Cédric Dr.
Erlangen Graduate School in Advanced Optical Technologies
Rausch, Michael Heinrich Dr.-Ing.
Lehrstuhl für Advanced Optical Technologies - Thermophysical Properties


Additional Organisation
Erlangen Graduate School in Advanced Optical Technologies


External institutions with authors

National Centre for Scientific Research (NCSR) "Demokritos"
Shell Global Solutions International B.V.


How to cite

APA:
Giraudet, C., Papavasileiou, K.D., Rausch, M.H., Chen, J., Kalantar, A., van der Laan, G.P.,... Fröba, A.P. (2017). Characterization of Water Solubility in n-Octacosane Using Raman Spectroscopy. Journal of Physical Chemistry B, 121(47), 10665-10673. https://dx.doi.org/10.1021/acs.jpcb.7b07580

MLA:
Giraudet, Cédric, et al. "Characterization of Water Solubility in n-Octacosane Using Raman Spectroscopy." Journal of Physical Chemistry B 121.47 (2017): 10665-10673.

BibTeX: 

Last updated on 2018-23-07 at 03:10