PNNL

Abstract

The 19F, 1H, and 2H relaxation times of perfluorobenzene, benzene, and perdeuteriobenzene were measured in carbon dioxide using capillary high-pressure NMR spectroscopy. The pressure range for the measurement of the 19F, 1H, and 2H nuclear relaxation times was between 400 and 2300 atm over a temperature range of 298-423 K. The density regime of the solvent, carbon dioxide, over these conditions was between 0.55 and 1.27 g/cm3. Over this wide range of solvent conditions, the contributions to the molecular relaxation processes for both 1H and 19F in CO2 were determined. These conditions were chosen to address the occurrence of specific molecular interactions between CO2 and fluorine. From the comparison of the relaxation processes for 19F and 1H in CO2, especially at high densities, any interaction between fluorine and carbon dioxide should be prevalent. No specific interaction between fluorine and CO2 contributing to the molecular relaxation of these nuclei was noted over the temperature and pressure range investigated in this study.