Co₃O₄ Nanosheet Wrapped Commercial HZSM-5 for Promoting Catalytic Cracking of n-Decane and Anticoking Activities

Endothermic hydrocarbon fuel has many advantages as a cooling medium in hypersonic aircraft; however substantial application has been greatly hindered due to easy coking, uncontrollable gas products, and low heat sink issues. Catalytic cracking of hydrocarbon fuel has been regarded as one of the most effective ways to improve the heat sink via modulating the cracking pathway. The incipient-wetness impregnation method was selected to load Co salts in commercial ZSM-5 in a large-scale manner; subsequent calcination in Ar gas resulted in Co3O4 nanosheet wrapped HZSM-5 composites. Salinization treatment was adopted to facilitate the dispersion of catalyst in a nonpolar solvent. The ratio of Brönsted/Lewis acidity decreased from 8.00 to 2.79 after modification by Co3O4 nanosheets. The synergistically catalytic effect between Co3O4 nanosheets and ZSM-5 was beneficial to the generation of a larger gas production rate with higher content of alkene, and thus resulting in a higher heat sink than benchmarked fuels. Catalytic cracking of n-decane (C10) in the presence of 0.1 wt % Co3O4 nanosheets@ZSM-5 could yield a heat sink as high as 4.64 MJ/kg at 758 °C, much higher than those of bare ZSM-5 (2.99 MJ/kg at 687 °C) and thermal cracking of C10 (3.77 MJ/kg at 728 °C). Meanwhile, the smart combination of Co3O4 nanosheets and commercial ZSM-5 could effectively suppress the coke deposition on the external surface of composites, thus resulting in efficient catalytic cracking at elevated temperatures for obtaining a higher heat sink.