NOVELTY - A fuel processor comprises: (i) a primary reactor for converting a hydrocarbon-based fuel to hydrogen, carbon dioxide, carbon monoxide and water; (ii) water-gas-shift reactor having an inlet in fluid communication with an outlet of the primary reactor; and (iii) a water adsorbent within a flow path between the outlet of the primary reactor and an outlet of the water-gas-shift reactor.    USE - For generating hydrogen gas.    ADVANTAGE - The water adsorbent having a high heat of adsorption produces heat as it adsorbs water in the reformate. Heat generated by water adsorption enhances the rate at which the fuel processor components, e.g. the water-gas-shift reactor, reach their operating temperatures. In addition water adsorption reduces water condensation on the water-gas-shift reactor catalyst. Once the fuel processor components attain their operating temperatures, water desorbs from the adsorbent and is available for converting carbon monoxide to carbon dioxide and hydrogen in the water-gas-shift reactor.    DETAILED DESCRIPTION - A fuel processor comprises:    (a) a primary reactor (102) for converting a hydrocarbon-based fuel to hydrogen, carbon dioxide, carbon monoxide and water;    (b) water-gas-shift reactor (104) having an inlet in fluid communication with an outlet (108) of the primary reactor; and    (c) a water adsorbent (124) located within a flow path between the outlet of the primary reactor and an outlet (120) of the water-gas-shift reactor.    The water-gas-shift reactor contains a catalyst (118) adapted to convert a portion of carbon monoxide from the primary reactor to carbon dioxide and hydrogen. The water adsorbent generates heat during startup of the fuel processor by adsorbing a portion of the water from the primary reactor.    An INDEPENDENT CLAIM is included for a method of heating the fuel processor during startup, comprising providing the water adsorbent within the flow path between the outlet of the primary reactor and the outlet of the water-gas-shift reactor.    DESCRIPTION OF DRAWING(S) - The figure is a schematic drawing of a portion of a fuel processor.    Primary reactor (102)    Water-gas-shift reactor (104)    Preferential oxidation reactor (106)    Outlet of the primary reactor (108)    Catalyst (118)    Outlet of the water-gas-shift reactor (120)    Water adsorbent (124)    Second water adsorbent (130)