NOVELTY - A hydrogen purification device comprises hydrogen-sensitive membrane(s) supported within a compartment and including a first adapted to be contacted by a mixed gas stream and a permeate surface opposed to the first surface. An enclosure defining the compartment includes an alloy comprising nickel and copper and has a coefficient of thermal expansion that is within 10% of that of the hydrogen-selective membrane(s).    USE - For fuel processing and other industries in which hydrogen gas is produced and/or utilized.    ADVANTAGE - The assembly includes a separation assembly adapted to receive the mixed gas stream and to produce a permeate or hydrogen-rich stream and that is also adapted to trap or otherwise retain at least a substantial portion of the other gases, which will be removed as a byproduct stream as the assembly is replaced, regenerated or otherwise recharged.    DETAILED DESCRIPTION - A hydrogen purification device comprises an enclosure (12) defining an internal compartment (18) and comprising pair(s) of end plates. The enclosure is adapted to receive under pressure a mixed gas stream (24) comprising hydrogen gas (26) and other gases (28) through input port(s) and to separate the mixed gas stream, via a pressure-driven separation process, into product stream(s) and byproduct stream(s) (36). The enclosure further includes product port(s) adapted to permit removal from the compartment of product stream(s) and byproduct port(s) adapted to permit removal from the internal compartment of byproduct stream(s). At least one hydrogen-sensitive membrane is supported within the compartment. It includes a first surface adapted to be contacted by the mixed gas stream and a permeate surface opposed to the first surface. The product stream is formed from a portion of the mixed gas stream that passes through the hydrogen-selective membrane(s) to the permeate surface. The byproduct stream is formed from a portion of the mixed gas stream that does not pass through the hydrogen-selective membrane(s). The enclosure has a different composition than the hydrogen-selective membrane. It is formed from a composition that includes an alloy comprising nickel and copper. It has a coefficient of thermal expansion that is within 10% of the coefficient of thermal expansion of the hydrogen-selective membrane. A support for the hydrogen-selective membrane permits the product stream to flow to the product port(s).    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a hydrogen purification device.    Enclosure (12)    Internal compartment (18)    Separation assembly (20)    Mixed gas stream (24)    Hydrogen gas (26)    Other gases (28)    Mixed gas region (30)    Permeate region (32)    Pure hydrogen gas stream (34)    Byproduct stream (36)    Heating assembly (42)