Eckelt, J., Wolf, B.A.

"Thermodynamic interaction parameters for the system water/NMMO hydrate"

Journal of Physical Chemistry B 2008, 112, 3397-3401.

Abstract: Vapor pressures of water were measured for aqueous solutions of N-methyl morpholin N-oxide (NMMO) at 80, 90 and 100 °C. The Flory-Huggins interaction parameters, chi, calculated from these data as a function of phi , the volume fraction of NMMO, are negative at all concentrations; at low phi they decrease by more than a factor of two as T is raised, whereas they remain almost unchanged as phi approaches unity. Accordingly the heat of mixing is pronouncedly endothermal at low NMMO concentrations but close to athermal at low water content. The composition dependence of chi can be equally well described by the Redlich-Kister equation and by an approach subdividing the mixing process into two separate steps. The opportunities of the latter modeling for a better molecular understanding of the mixing processes are discussed.

preprint number: 288