NOVELTY - Separation of stream comprising hydrogen, methane, ethane and at least 3C hydrocarbon into at least three streams of different composition, comprises passing stream through pressure swing adsorption unit, thus producing hydrogen-enriched product stream and tail gas stream; compressing and cooling the tail gas stream; and passing portion of tail gas stream to membrane separation unit containing rubbery polymeric membrane.    USE - For separating a stream comprising hydrogen, methane, ethane and 34C hydrocarbon into at least three streams of different composition: a hydrogen-enriched stream for use as source of hydrogen, an ethane-enriched stream for use as fuel gas, and optionally, a liquid at least 3C hydrocarbon stream for use as source of liquefied petroleum gas (LPG).    ADVANTAGE - The invention increases hydrogen production compared with prior art techniques, and production of a discrete LPG stream. It has the ability to debottleneck plants where fuel gas production is at maximum.    DETAILED DESCRIPTION - Separation of stream comprising hydrogen, methane, ethane and at least 3C hydrocarbon into at least three streams of different composition, comprises:    (a) passing the stream (101) through a pressure swing adsorption unit (102), thus producing a hydrogen-enriched product stream (103) and a tail gas stream (104);    (b) compressing and cooling (105) the tail gas stream;    (c) passing a portion of the compressed, cooled tail gas stream across the feed side of a membrane separation unit (108) containing a rubbery polymeric membrane, having a feed side and a permeate side and being selectively permeable to 1-6C hydrocarbons over hydrogen, under conditions that the membrane exhibits an ethane/hydrogen selectivity of at least 3.5;    (d) withdrawing from the permeate side a permeate stream enriched in ethane and the at least 3C hydrocarbon compared with the tail gas stream; and    (e) withdrawing from the feed side a residue stream enriched in hydrogen compared with the tail gas stream.    An INDEPENDENT CLAIM is also included for a hydrocarbon conversion process comprising reacting a hydrocarbon feedstock in a hydrocarbon conversion reactor; withdrawing an effluent stream comprising hydrogen and hydrocarbon from the reactor; and separating from the effluent stream a liquid phase and a vapor phase comprising hydrogen, methane, ethane and at least 3C hydrocarbon.    DESCRIPTION OF DRAWING(S) - The figure is a schematic view of a process for separating hydrogen from hydrocarbons.    Feed stream (101)    Pressure swing adsorption unit (102)    Hydrogen-enriched product stream (103)    Tail gas stream (104)    Compressing and cooling (105)    Membrane separation unit (108)    Portion (109)