Aromatic solvent upgrading using membranes

摘要

The present invention is directed to a process for producing high quality aromatic solvents in the middle distillate range containing 95+% aromatics by contacting the liquid feed with a perm selective membrane under pressure thereby selectively permeating the aromatic components as the high quality solvents. This separation can be performed by contacting the feed stream in combination with a low boiling light polar aromatics extraction solvent (such as acetonitrile) with the membrane. The middle distillate feed has a molecular weight range of about 120 to 250 g/mole and an aromatic content of 75 to 90 volume percent aromatics and preferably 80 to 90 volume percent aromatics. The membranes which can be employed to effect this separation are selected from the group of regenerated cellulose, cellulose acetate and polyimide membranes, preferably the polyimide membranes.