The influence of pressure and temperature on the phase behaviour of the system H2O + C12+ C7E5 and relevant binary subsystems

Abstract

Abstract Sassen, C.L., Gonzalez Casielles, A., de Loos, Th.W. and de Swaan Arons, J., 1992. The influence of pressure and temperature on the phase behaviour of the system H 2 O + C 12 + C 7 E 5 and relevant binary subsystems. Fluid Phase Equilibria, 72: 173-187. The influence of pressure on the phase behaviour of the systems H 2 O + C 7 E 5 and C 12 + C 7 E 5 (C 7 E 5 , n -heptylpentaoxyethylene) was studied over a temperature range of 271–358 K and a pressure range of 0.1–100 MPa. It appeared that the system H 2 O + C 7 E 5 shows a miscibility gap with an upper critical solution pressure ( p β ) which rises with increasing temperature. The system C 12 + C 7 E 5 shows a miscibility gap with a lower critical solution pressure ( p α ) which also rises with increasing temperature. It was found that d p β /d T is larger than d p α /d T which supports the experimental observation that in ternary water + oil + non-ionic surfactant systems the region in which three liquid phases are in equilibrium, widens and shifts to higher pressures with increasing temperature. The UNIQUAC equation was used to correlate the measurements at atmospheric pressure and to predict the phase behaviour in the ternary system H 2 O + C 12 + C 7 E 5 . Finally, a three-phase region was measured and compared with the predicted phase behaviour in the ternary system.