NOVELTY - Hydrogen and carbon dioxide are produced from hydrocarbonaceous feedstock by supplying gaseous hydrocarbonaceous feedstock and steam to reaction zone comprising steam reforming catalyst (5), and catalytically reforming the feedstock; supplying molecular oxygen-comprising gas to permeate side of first hydrogen separation membrane (6); and contacting remainder of hydrogen with second hydrogen separation membrane (9), and allowing hydrogen to permeate through the second membrane to obtain first effluent comprising pure stream of hydrogen.    USE - For production of hydrogen and carbon dioxide for fuel cell used in fuel cell system.    ADVANTAGE - The process is capable of producing pure hydrogen and concentrated carbon dioxide without the need for additional separate burners or pure or concentrated oxygen.    DETAILED DESCRIPTION - The production of hydrogen and carbon dioxide from hydrocarbonaceous feedstock comprises:    (A) supplying gaseous hydrocarbonaceous feedstock and steam to reaction zone comprising steam reforming catalyst, and catalytically reforming the feedstock to produce reformed gas comprising hydrogen and carbon dioxide;    (B) supplying molecular oxygen-comprising gas to permeate side of first hydrogen separation membrane;    (C) contacting a part of hydrogen with the first membrane, allowing the hydrogen to permeate through the first membrane, and combusting the hydrogen with the molecular oxygen at the permeate side of the first membrane to produce heat for catalytic reforming the feedstock;    (D) contacting the remainder of hydrogen with a second hydrogen separation membrane, which is separate from the first membrane, and allowing the hydrogen to permeate through the second membrane to obtain first effluent comprising pure stream of hydrogen; and    (E) removing a stream rich in carbon dioxide from the reaction zone as a second effluent.    INDEPENDENT CLAIMS are included for:    (1) a reactor (1) for the production of hydrogen and carbon dioxide from hydrocarbonaceous feedstock; and    (2) a fuel cell system comprising in series the reactor and a fuel cell having an inlet for hydrogen.    The hydrogen separation membrane comprises palladium, platinum, or their alloy.    DESCRIPTION OF DRAWING(S) - The figure is a longitudinal section of the reactor.    Reactor (1)    Reaction zone (2)    Inlet for feedstock (3)    Inlet for steam (4)    Steam reforming catalyst (5)    Hydrogen separation membranes (6, 9)