Process for separating liquid mixtures

Process for separating a feed stream of a liquid mixture comprising at least a first liquid compound and a second liquid compound, comprising:

• passing a liquid stream of the liquid mixture over a permeable non-porous selective membrane, said membrane being selective for said first liquid compound by having a permeability for vapor of said first liquid compound that is higher than the permeability of the membrane for vapor of said second liquid compound, whereby at least part of the liquid stream passes through said membrane leaving the other side of said membrane as a vapor, with the remainder of the liquid stream forming a retentate stream, and
• condensing said vapor on a condenser surface having a lower temperature than the liquid stream to give a distillate stream, said condenser surface forming a non-permeable heat conducting separation wall between said distillate stream and a cooling stream;
• wherein the cooling stream is
• a) said feed stream, in case the feed stream has a sufficiently low temperature to serve as a suitable cooling medium for the condensation of the vapor, or
• b) said retentate stream, in case the feed stream has such a high temperature that would make it unsuitable as a cooling medium for the condensation of the vapor,
• so that heat can be transferred between the vapor and the cooling stream,
• wherein a distance between said membrane and said condenser surface is smaller than 10 mm,
• wherein the vapor pressure of said distillate stream is lower than the vapor pressure of the compounds in the liquid stream for which the permeable non-porous selective membrane is selective, resulting in sufficient driving force for the separation to occur,
• wherein the distillate stream has a concentration of the first compound that is higher than the concentration of the first compound in the feed stream,
• wherein at least part of the liquid stream passes said non-porous selective membrane with a flux in the range of 0.5-5 kgm−2h−1, and
• wherein a difference in vapor pressure between the distillate stream and the liquid stream is in the range of 15-200 kPa.