Liquid Ammonia as a Potential High Heat Sink Fuel via Catalytic Decomposition over Ru/CeO₂–Al₂O₃ Coatings

Abstract

Endothermic hydrocarbon fuel is the most utilized coolant in regenerative cooling technology for the high-speed aircraft, but it is challenged by the limited heat sink and severe coke deposition. In this study, we propose liquid ammonia as a promising carbon-free fuel with high heat sink for advanced vehicles or aircrafts. The chemical heat sink originates from the endothermic decomposition reaction of ammonia. A series of Ru/ CeO 2 −Al 2 O 3 catalytic coatings were fabricated on stainless-steel tubes using the washcoating method to catalyze the ammonia decomposition reaction and enhance chemical heat sink. The catalytic performance of these Ru/CeO 2 −Al 2 O 3 coatings for ammonia decomposition was evaluated using an electrically heated tubular reactor. With the Ru/CeO 2 −Al 2 O 3 coatings of 19 μm, ammonia conversion reaches up to 65%, and a remarkable high heat sink of 5.9 MJ/kg was achieved at 800 °C and 5 MPa. This value is ca. 68% higher than that of the typical hydrocarbon fuel JP-7. This work shows that liquid ammonia can serve as a novel generation high heat sink fuel for advanced engines and aircrafts.