Cobalt and Iron Nanocrystals as Combustion Catalyst for Propulsion Applications.
- Dispersed nanocyrstal catalysts in jet fuels could aid in regeneratively-cooled engines, especial for ramjet application at low Mach speeds. Catalysts could allow combustion at lower temperatures than catalyst-free fuels and can assist in both the oxidation and dehydrogenation steps. N-hexane oxidation was used as a surrogate for jet fuel combustion. The catalyst was also studied in the solid phase, ... read morerather than dispersed in the fuel. Co3O4, Fe2O3, and Fe2O3 doped with Co3O4 nanocrystals were prepared hydrothermally in an oleic acid/ethanol/oleylamine system. The resulting particle size was 3-20 nm in solution depending on the preparation method. The nanocrystals were used as oxidation catalysts for n-hexane. Real-time NDIR analysis monitored the CO2 evolution and reaction progress. Pure Co3O4 nanocrystals showed the highest activity of all of the samples tested. Activity began at 250° C and was reached complete combustion by 300° C. Activity at multiple temperatures with low conversion was measured to determine the apparent activation energy (k=A*e-Ea/(RT)), 114 kJ/mol. The solubility of Co3O4 nanocrystals in liquid hexane was found to be 2 mg/mL by gravimetric analysis. The Co3O4 nanocrystals have sufficient solubility to be dispersed in hexane at catalytic concentrations.read less