Temperature dependence of dielectric spectra of carbon dioxide and methanol mixtures at high-pressures

Dielectric spectra can quantify how the solution structure of hydrogen-bonding solutions changes with composition and thermodynamic state. In our research, [Rev. Sci. Instrum. 71 (2000) 4226-4230], we developed a new dielectric probe and apparatus that can be applied to high-pressure liquids and gases. In this work, we study carbon dioxide and methanol mixtures over the temperature range of 313-333K and at pressures up to 15MPa. The characteristic relaxation times of methanol were found to exhibit a maximum in composition that persisted with increasing temperature. The increase in the relaxation time of carbon dioxide and methanol mixtures over that of pure methanol indicates that attraction occurs between the methanol dipole and the carbon dioxide quadrupole. Data are analyzed using experimental volumetric behavior of the system and according to the theory of Eyring. Regions of composition where carbon dioxide is incorporated into the methanol hydrogen-bonding structure are identified and an estimation is made on the region where the methanol associated structures probably dissociate.