Separation process

Claim 1

IN A PERMEATION PROCESS FOR SEPARATING MIXTURES OF HYDROCARBONS WHEREIN A FLUID FEED MIXTURE COMPRISING AT LEAST TWO DIFFERENT HYDROCARBONS IS CONTACTED WITH ONE SIDE OF A PLASTIC PERMEATION MEMBRANE UNDER PERMEATION OPERATING CONDITIONS AND THERE IS REMOVED FROM THE OTHER SIDE OF SAID MEMBRANCE A FLUID PERMEATE FRACTION OF SAID FLUID FEED HYDROCARBONS HAVING A COMPOSITION ENRICHED WITH RESPECT TO ONE HYDROCARBON OF SAID FLUID FEED, THE IMPROVEMENT WHICH COMPRISES EMPLOYING A NON-POROUS PERMEATION MEMBRANE WHICH IS COMPRISED OF A CELLULOSE DERIVATIVE CONSISTING ESSENTIALLY OF CELLULOSE OF WHOSE THREE HYDROXYL GROUPS PER ANHYDROGLUCOSE UNITS ALL BUT 0.1 TO 2.0 ARE REPLACED BY GROUPS SELECTED FROM THE CLASS CONSISTING OF ESTER GROUPS, ETHER GROUPS, AND MIXTURES THEREOF, AND THE REMAINING 0.1 TO 2.0 HYDROXYL GROUPS ARE REPLACED WITH ORGANIC GROUPS DERIVED FROM AN ORGANIC REAGENT REACTIVE WITH THE REMAINING HYDROXYL GROUPS, WHICH REAGENT IS SELECTED FROM THE GROUP CONSISTING OF ALDEHYDES, ORGANIC DIISOCYANATE, ORGANIC MONOISOCYANATE, ORGANO-PHOSPHORUS-CHLORIDES AND ORGANO-SULFUR-CHLORIDES.