NOVELTY - The membrane reactor generates a desired gas, e.g. hydrogen produced by steam reforming liquid fuels, and provides thermal integration between the heating source and the reaction catalyst by heat conduction through a solid medium. A gas purification system extracts energy from the waste gases to heat the membrane reactor.    USE - The apparatus is for the generation of a gas and the separation and purification of the generated gas from a mixed gas flow, more particularly, the generation of hydrogen by steam reforming liquid fuel and the purification of hydrogen from a mixture of gases using a hydrogen selective membrane. The apparatus may be combined with a hydrogen consuming fuel cell.    ADVANTAGE - A more efficient gas purification process.    DETAILED DESCRIPTION - A gas purification system comprises:    (a) a reactor (10) having a reactor volume and a reactor wall having an interior side (18) and an exterior side (16), and defining a communicating portal therebetween for a mixed gas flow;    (b) a heat conduit within the reactor volume having a conduit wall having an interior side and an exterior side, and defining a channel therethrough for passing a heated material through the reactor volume;    (c) a reaction catalyst coating (28) in contact with the exterior side of the conduit wall;    (d) a gas selective membrane within the reactor volume disposed between the reactor wall and the conduit wall, so that the gas membrane is in contact with the mixed gas flow and selectively passes a constituent gas of the mixed gas flow therethrough, such that a raffinate of the mixed gas flow is retained in contact with the membrane;    (e) an outlet channel (24) for removing the raffinate from contact with the selective membrane; and    (f) a passageway (26) for the removal of the constituent gas from the interior of the reactor.    INDEPENDENT CLAIMS are also included for 3 other similar gas purification systems.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a membrane reactor apparatus including a reaction catalyst coated on the external wall of the reactor.    Reactor (10)    Reactor wall exterior side (16)    Reactor wall interior side (18)    Tube having selective membrane (20)    Raffinate outlet (24)    Purified gas outlet (26)    Reaction catalyst coating (28)