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Spectroscopic investigation into polarity and solvent strength of supercritical carbon dioxide

 
: Löbbecke, S.; Eberhardt, R.; Krause, H.

Eckl, W. ; Fraunhofer-Institut für Chemische Technologie -ICT-, Pfinztal:
Combustion and detonation
Pfinztal: ICT, 1997 (Proceedings of the International Annual Conference of ICT 28)
ISSN: 0722-4087
pp.110.1-110-12
Fraunhofer-Institut für Chemische Technologie (Internationale Jahrestagung) <28, 1997, Karlsruhe>
Fraunhofer-Institut für Chemische Technologie (International Annual Conference) <28, 1997, Karlsruhe>
English
Conference Paper
Fraunhofer ICT ()

Abstract
The variable polarity and solvent strength of supercrit. (su) CO2 was investigated by solvatochromic indicators based on empirical solvent polarity scale ET(30) of Dimroth and Reichardt to det. the optimum soly. parameters of energetic materials in su-CO2. The polarity of su-CO2 was examd. as a function of temp. and pressure, resp. d., by measuring the solvatochromism of a specific betaine dye (2,4,6-tri-(p-tert.-butyl)-1-pyridinio)-2,6-di(p-tert.-butylphenyl)- phenolate (ET'). The solvatochromic absorption band of ET' shows a hypsochromic (blue-) shift with increasing pressure and therefore an increase in s.c.-CO2 polarity. The absorption wavelength ranges from 1000-880 nm, corresponding to ET(30) values between 28.5 and 32.7 kcal/mol. Comparison of ET(30) values obtained for s.c.-CO2 and org. solvents revealed that the polarity of s.c.-CO2 at pressures .ltoreq. 300 bar is lower than the polarity of non-polar org. solvents. Comparison of ET(30) values at different temps. but same pres sures reveals that the solvation capability of s.c.-CO2 is pressure- and not d.-dependent. The solvent capability of s.c.-CO2 increases linear with pressure.

: http://publica.fraunhofer.de/documents/PX-34426.html