Characterization of Water Solubility in n-Octacosane Using Raman Spectroscopy

Giraudet C, Papavasileiou KD, Rausch MH, Chen J, Kalantar A, van der Laan GP, Economou IG, Fröba AP (2017)

Publication Language: English

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2017

Journal

Journal of Physical Chemistry B American Chemical Society

Publisher: AMER CHEMICAL SOC

Book Volume: 121

Pages Range: 10665-10673

Journal Issue: 47

DOI: 10.1021/acs.jpcb.7b07580

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.

Authors with CRIS profile

Cédric Giraudet Erlangen Graduate School in Advanced Optical Technologies Michael Rausch Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP) Andreas Paul Fröba Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP)

Additional Organisation(s)

Erlangen Graduate School in Advanced Optical Technologies

Related research project(s)

Study of diffusion as well as viscosity and surface tension for mixtures related to Fischer-Tropsch synthesis Aug. 1, 2011 - Dec. 31, 2017

Involved external institutions

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

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.

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