SEPARATION OF DEWAXING SOLVENT FROM DEWAXED OIL IN A LUBE OIL DEWAXING PROCESS USING ASYMMETRIC POLYIMIDE MEMBRANES

摘要

Dewaxing solvents, particularly ketone solvents and ketone/toluene solvents, are separated from a mixture of dewaxing solvents and dewaxed oil in a lube oil dewaxing process by use of an asymmetric permselective polyimide membrane. Said asymmetric polyimide membrane permits the selective permeation of the ketone or ketone/toluene dewaxing solvents while being less permeable to oil. Said separation is conducted by contacting the ketone or ketone/toluene solvent/oil mixture with the dense side [(1),] of the asymmetric polyimide membrane [(4),] under pressure. The recovered ketone or ketone/toluene solvent is of high enough purity to be returned to the dewaxing process without further treatment. The recovered oil is passed to subsequent conventional treatment means (e.g., distillation) for removal of any ketone or ketone/toluene solvent remaining therein.