NOVELTY - The reformer comprises a catalytic reactor assembly (22) including parallel reactor tubes (46) and catalyst assemblies disposed in the reactor tubes, an inlet manifold assembly (20) including an inlet plenum and parallel inlet tubes, an outlet manifold (24) including an outlet plenum, and an exhaust duct (12) defining an exhaust plenum (13) for receiving exhaust gas from an engine. The parallel reactor tubes have open first longitudinal ends and closed second longitudinal ends. Each catalyst assembly includes two thermally-conductive, porous catalyst substrates, and a powder catalyst.    USE - The reformer is useful for reforming an alcohol such as ethanol to a gaseous reformate mixture comprising hydrogen, which is useful as a fuel for an internal combustion engine.    ADVANTAGE - The lightweight reformer has excellent heat transfer efficiency, and is capable of efficiently reforming the alcohol to the gaseous reformate mixture while maintaining its high catalytic activity.    DETAILED DESCRIPTION - The reformer comprises a catalytic reactor assembly (22) including parallel reactor tubes (46) and catalyst assemblies disposed in the reactor tubes, an inlet manifold assembly (20) including an inlet plenum and parallel inlet tubes, an outlet manifold (24) including an outlet plenum, and an exhaust duct (12) defining an exhaust plenum (13) for receiving exhaust gas from an engine. The parallel reactor tubes have open first longitudinal ends and closed second longitudinal ends. Each catalyst assembly includes two thermally-conductive, porous catalyst substrates, and a powder catalyst loaded on the catalyst substrate for reforming alcohol to the gaseous reformate mixture comprising hydrogen, surrounds a corresponding one of the inlet tubes in the corresponding reactor tube, and is present in thermal contact with an interior wall of the corresponding reactor tube. The inlet plenum of the inlet manifold assembly is adapted for receiving alcohol from an alcohol source. The parallel inlet tubes of the inlet manifold assembly extend axially through the open first longitudinal ends of the parallel reactor tubes for delivering alcohol to the catalyst assemblies, and have inlets disposed in the inlet plenum and outlets adjacent to the closed second longitudinal ends of the reactor tubes. The outlet plenum of the outlet manifold is present in fluid communication with the open first longitudinal ends of the reactor tubes for receiving the reformate mixture from the reactor tubes. The powder catalyst includes a copper-nickel catalyst configured to reform alcohol at a temperature of below 400 degrees C. The catalyst assembly further includes a thermally-conductive, porous filter that is free from an alcohol-reforming catalyst. The catalyst substrates of the catalyst assembly are loaded with the powder catalyst. The porous filter is disposed axially between the two catalyst substrates and separates the two catalyst substrates loaded with the powder catalyst. Each reactor tube includes thermally-conductive fins extending laterally outward from an exterior surface of the reactor tube. The catalytic reactor assembly is mounted on the exhaust duct such that the parallel reactor tubes extend into the exhaust plenum. The reformer is combined with an alcohol reformate power system. The alcohol reformate power system includes an internal combustion engine, an alcohol reformate line for delivering alcohol reformate from the reformer to the engine, and an exhaust line for receiving combusted alcohol reformate from the engine. The exhaust duct is present in fluid communication with the exhaust line. The reformer further comprises: a cylindrical, rolled reformer housing including opposing sheets of thermally conductive material defining a catalyst chamber; an inlet header for delivering alcohol into the catalyst chamber; an outlet header for removing the reformate mixture from the catalyst chamber; a spacer disposed between adjacent turns of the rolled reformer housing to define exhaust plenums that are placed between the adjacent turns of the rolled reformer housing and extend longitudinally with respect to the reformer housing; a shell defining a catalyst plenum having opposite first and second longitudinal ends; and baffles placed in the catalyst plenum. The exhaust plenums define a flow path for exhaust gas from an engine to flow longitudinally through the rolled reformer in thermal contact with the opposing sheets of the rolled reformer housing. The opposing sheets of the reformer housing include material having a thermal conductivity constant of 10 W/(m.K). The shell has an inlet port adjacent to the first longitudinal end of the catalyst plenum for receiving alcohol from an alcohol source, and an outlet port adjacent to the second longitudinal end of the catalyst plenum for receiving the reformate mixture from the catalyst plenum. The catalyst substrate includes openings through which the exhaust tubes extend in thermal contact with the catalyst substrate. The baffles are disposed between the inlet port and the outlet port for directing the flow of alcohol through the catalyst plenum. An INDEPENDENT CLAIM is included for a catalyst assembly for reforming an alcohol to a gaseous reformate mixture comprising hydrogen for combustion in an engine.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic longitudinal sectional view of a reformer.    Exhaust duct (12)    Exhaust plenum (13)    Inlet manifold assembly (20)    Catalytic reactor assembly (22)    Outlet manifold (24)    Parallel reactor tubes. (46)