Salt Effect on the High-Pressure Multiphase Behavior of the Ternary System (Ethene + Water + 2-Propanol)

Abstract

At temperatures from (289 to 353) K, the ternary system (ethene + water + 2-propanol) is known to exhibit a region of liquid−liquid−vapor (L1L2V) equilibria at elevated pressures that is bordered by the lower ((L1 = L2)V) and upper (L1(L2 = V)) critical end point lines. This particular demixing effect is commonly known as “salting out by a supercritical gas”. In this work, the effect of adding different electrolytes on the pressure of both critical end points at (293 and 333) K is investigated.

Phase Equilibria and Partitioning of l-Histidine and Three Pharmaceuticals to pH-Adjusted High-Pressure Liquid Phases of the Ternary System (Ethene + Water + 2-Propanol)

“…The high-pressure apparatus operates according to a static-analytical method and can be employed between about (263 and 353) K and up to a maximum pressure of 30 MPa. The equipment was arranged in exactly the same way as described in previous papers. − Its main part is a nonmagnetic, pivot-mounted cylindrical view-cell with a volume of about 30 cm . The cell is equipped with sapphire windows at both ends and two sampling loops.…”

“…The entire equipment is placed in an air thermostat. Further details were given in previous publications − or are available in Ulanova's doctoral thesis…”

“…It is important to mention that any modification of the ternary phase-forming system requires an obligatory redetermination of the critical end points which border the three-phase L 1 L 2 V equilibrium. For a comprehensive as well as detailed description, the reader is referred to previous publications and the references cited therein. , …”

“…The experimental uncertainties of such a partitioning experiment consist of the uncertainties in temperature and pressure as well as those resulting from the analysis of the solute-free ternary phase-forming system (see again refs and for details) and the contribution of the HPLC analysis of the solute. The maximum total uncertainty of the temperature measurement is estimated to be ± 0.1 K. The uncertainty of the experimental results for the pressure is ± 0.005 MPa (± 0.01 MPa) for pressures below (above) 10 MPa.…”

“…The phase behavior of several pH-neutral ternary phase-forming systems was investigated in our laboratories in previous investigations. − In those studies, the existence and characteristics of high-pressure phase equilibria were mapped systematically, the composition data of both coexisting liquid phases were determined, and an equation-of-state model was developed to describe the phase behavior. − The effect of different electrolytes on the ternary system (ethene + water + 2-propanol) at (293 and 333) K was the subject of a continuative study, as the addition of an electrolyte was expected to amplify the (gas-induced) salting-out effect. In such experiments, a shift was observed for both the lower and the upper critical end point to lower pressures (with a stronger impact on the lower critical end point, since the electrolytes prefer the aqueous phase L 1 ).…”