Abstract: Fractionation by adsorption of a hydrogen-containing gas mixture can be achieved by passing the gas mixture over an adsorption bed containing an activated-carbon layer a downstream molecular sieve layer of the 5 A type, and positioned between the activated-carbon layer and the downstream molecular sieve layer, an intermediate layer containing molecular sieve of the X type. A hydrogen-rich gas mixture is then removed. The molecular sieve(s) of the X type, can be a CaX type, an NaX type, or combinations thereof.