NOVELTY - The process for transitioning gaseous fuel reformation to liquid fuel reformation in a reactor, comprises steadily reforming gaseous fuel by inputting the gaseous fuel into an autothermal reforming reactor, reducing the gaseous fuel input into the autothermal reforming reactor while increasing the input of a vaporized, superheated liquid fuel/water mixture until a substantial amount of the autothermal reforming reactor input comprises liquid fuel, and reforming the liquid fuel in the autothermal reforming reactor.    USE - The process is useful for transitioning gaseous fuel reformation to liquid fuel reformation in a reactor.    ADVANTAGE - The process is capable of simply and rapidly transitioning gaseous fuel reformation to liquid fuel reformation thus obtaining good hydrogen selectivity while offering high thermal efficiency.    DETAILED DESCRIPTION - The process for transitioning gaseous fuel reformation to liquid fuel reformation in a reactor, comprises steadily reforming gaseous fuel by inputting the gaseous fuel into an autothermal reforming reactor, reducing the gaseous fuel input into the autothermal reforming reactor while increasing the input of a vaporized, superheated liquid fuel/water mixture until a substantial amount of the autothermal reforming reactor input comprises liquid fuel, reforming the liquid fuel in the autothermal reforming reactor, maintaining a ratio of sulfur/carbon (S/C) of 2.5-3.5, a ratio of oxygen/carbon (O2/C) of 0.2-0.3 and a gas hourly space velocity (GHSV) of 3750-4250 hr-1 when a substantial amount of the autothermal reforming reactor input comprises liquid fuel, and maintaining an autothermal reforming reactor temperature of 600-700 degrees C. The autothermal reforming reactor temperature is stable during the transition process by controlling the amount of air and water flow. The ethanol conversion is greater than 99%. The water mixed with the liquid fuel is deionized water. The liquid fuel/water mixture is superheated to 375 degrees C, where the superheating comprises mixing the liquid fuel/water mixture with pre-heated air. The fuel reformation comprises biofuel reformation, and the gaseous fuel comprises natural gas. An INDEPENDENT CLAIM is included for an apparatus for transitioning gaseous fuel reformation to liquid fuel reformation.    DESCRIPTION OF DRAWING(S) - The diagram shows a process and an apparatus for gaseous fuel (e.g. natural gas) and liquid fuel (e.g. ethanol) reformation.    Pumps (P1, P2)    Valves. (V1, V2, V3, V4, V5, V6)