NOVELTY - An auto-thermal reactor (70) comprises: (1) a liquid fluid spray injector (72) for spraying liquid hydrocarbon fuel into the mixing region (80); (2) an air/steam inlet pipe (74); (3) an electrically heated catalyst (EHC) region (84) positioned adjacent to the radiant shield. The mixing region mixes the air/steam mixture into the fuel mixture. The EHC region is electrically heated at the start-up of the system to generate an exothermic reaction.    USE - In a fuel processing system (claimed) for generating hydrogen-rich gas from liquid hydrocarbon fuel e.g. gasoline.    ADVANTAGE - The reactor reduces the start-up time of the fuel processing system by quickly heating the catalysts by various configurations when the system is turned on. The EHC region can be turned off after the fuel mixture reaches a predetermined temperature so that the exothermic reaction in the light-off catalyst generates the heat necessary to sustain the catalytic reaction.    DETAILED DESCRIPTION - An auto-thermal reactor (70) comprises:    (1) a liquid fluid spray injector (72) for spraying liquid hydrocarbon fuel into the mixing region (80);    (2) an air/steam inlet pipe (74);    (3) an electrically heated catalyst (EHC) region (84) positioned adjacent to the radiant shield.    The mixing region mixes the air/steam mixture into the fuel mixture. The EHC region is electrically heated at the start-up of the system to generate an exothermic reaction.    The reactor also has a light-off catalyst region (90) to receive fuel from EHC region; a main catalyst region (92) to receive fuel from light-off catalyst region; and a thermocouple (88) to provide temperature output reading.    An INDEPENDENT CLAIM is included for a tail gas combustor in fuel processing system.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of an auto-thermal reactor.    auto-thermal reactor (70)    spray injector (72, 94)    air/steam inlet pipe (74)    mixing region (80)    electrically heated catalyst region (84)    thermocouple (88)    light-off catalyst region (90)    main catalyst region. (92)