Miniature NH₃ cracker based on microfibrous entrapped Ni-CeO₂/Al₂O₃ catalyst monolith for portable fuel cell power supplies

A miniature ammonia cracker, with an overall weight of ≈195 g and volume of ≈50 cm³, has been developed for portable fuel cell power supply. The cracker is composed of a SS-316L tube body, a heating rod and monolithic microfibrous CeO₂-promoted Ni/Al₂O₃ catalysts incorporated within the annular housings between the heating rod and the inner wall of the tubular body. The catalyst monolith is obtained by placing CeO₂ and Ni onto the microfibrous carrier consisting of 3.5 vol% 8 μm diameter nickel fibers and 38 vol% 100-200 μm Al₂O₃ particulates through stepwise incipient wetness impregnation method using cerium and nickel nitrate precursors. This cracker shows pleasing operability for high efficiency H₂ production via ammonia cracking with low pressure drop. Roughly 158 W equivalents of H₂ can be produced with ammonia conversion of >99.9% at 600 °C and 1100 standard cubic centimeter per minute (sccm) ammonia feed gas rate within this cracker through the entire 300 h test. Power density and energy density are estimated to be ≈3160 W/L and ≈2150 Wh/kg, respectively.