Process for separation of the constituents of a mixture in the gas phase using a composite membrane

Process for separation of a mixture of at least two constituents A and B in which (a) said mixture in the gas or vapor phase is contacted with the first face of a membrane composed of (i) at least one active layer less than 100 micrometers in thickness comprising a solid adsorbent phase, selective for constituent A, dispersed in a non-porous, non-elastomeric polymer constituting a continuous phase and (ii) a porous support adhering directly to said at least one active layer, (b) the partial pressure of constituent A is kept lower at the second face of the membrane than at the first face and a mixture enriched in constituent A and impoverished in constituent B is collected on the second face of said membrane without a change in phase and (c) a mixture enriched in constituent B and impoverished in constituent A is collected on the first side of said membrane, a process wherein the thickness of the active layer is less than 100 micrometers and the ratio of the mass of the dispersed phase to the mass of the continuous phase in the active layer is greater than 1.