Experimental and reactive molecular dynamic study on the oil-dispersible Pd nanoparticles for cracking aviation kerosene RP-3

Fully utilizing the chemical heat sink generated by hydrocarbon fuel cracking is critical for enhancing the endothermic cooling capacity of the fuel. In this study, a catalytic strategy based on oil-dispersible palladium nanoparticles (Pd NPs) is proposed for the supercritical cracking of RP-3. Pd NPs with an average size of 2.85 nm are synthesized and uniformly dispersed in RP-3, exhibiting long-term stability with a sedimentation rate below 7 % after 60 days. To evaluate the catalytic performance and reveal the complex catalytic cracking mechanism of hydrocarbon fuels under supercritical conditions, a combined approach of tubular reactor experiments and reactive force field molecular dynamics (ReaxFF MD) simulations is employed. Both experimental and simulation results demonstrate that, compared to thermal cracking, Pd/RP-3 catalytic cracking exhibits significant improvements in conversion, gas yield, olefin selectivity, and heat sink. At 700 °C, 200 ppm Pd NPs increase the heat sink of RP-3 from 2.52 MJ/kg to 2.77 MJ/kg. Kinetic analysis reveals that the enhancement is ascribed to the remarkable catalytic abilities of Pd NPs to reduce the activation energies for RP-3 cracking, C-C and C-H bond cleavage by approximately 66.7 %, 80.7 %, and 78.7 %, respectively. Pd also enhances dehydrogenation reactions, leading to higher yields of hydrogen and olefins, while effectively facilitating benzene rings decomposition within the aromatic components of RP-3. The synthesized oil-dispersible Pd NPs present great potential for enhancing the cooling capacity and the catalytic cracking mechanism proposed here may provide a theoretical foundation for designing efficient future catalysts.