NOVELTY - A catalytic hydrocarbon reformer has a catalytic element (12) disposed within reformer tube wall (26) and spaced by material pad (128) formed of primary material, an incoming air flow space outside the reformer tube wall for entry of air to reformer, and a mixing zone (22) adjacent to the catalytic element. The reformer comprises the material pad extending over a portion (A) of the side of catalytic element adjacent to reformer tube wall, and an air gap (140) and/or a thermally-conductive secondary material (142) disposed between the catalytic element and reformer tube wall.    USE - Catalytic hydrocarbon reformer is used for fuel cell system (claimed) e.g. solid oxide fuel cell.    ADVANTAGE - The catalytic hydrocarbon reformer exhibits rapid transient response and convective cooling effect, and provides molecular hydrogen and carbon monooxide as gaseous fuel to the fuel cell system. The catalyst has improved durability even at rapid start-up of reformer and fuel vaporization.    DETAILED DESCRIPTION - A catalytic hydrocarbon reformer has a catalytic element disposed within a reformer tube wall and spaced by a material pad formed of a primary material, an incoming air flow space outside the reformer tube wall for entry of air to the reformer, and a mixing zone adjacent to the catalytic element for receiving and mixing injected fuel (20) with the incoming air before entry of the fuel-air mixture into the catalytic element for generating reformate. The reformer comprises the material pad extending over only a portion (A) of the side of catalytic element adjacent to reformer tube wall, and an air gap extending over portion (B) of the side of catalytic element adjacent to the reformer tube wall and/or a thermally-conductive secondary material disposed between the catalytic element and reformer tube wall over portion (B) of the side of catalytic element. An INDEPENDENT CLAIM is included for fuel cells system.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic longitudinal cross-sectional view of catalytic hydrocarbon reformer.    Catalytic element (12)    Injected fuel (20)    Mixing zone (22)    Reformer tube wall (26)    Material pad (128)    Air gap (140)    Thermally-conductive secondary material (142)