Low-Temperature Oxidation of n‑Propylbenzene in Blend with n‑Heptane

C₇-C₁₀ aromatics are indispensable components of aviation fuels to meet the swelling need for sealing rings in aero engines. Aromatics with a short and single substituent have weak low-temperature reactivity, yet this may be enhanced under a fuel blend environment. In this work, we investigated low-temperature oxidation chemistry of n-propylbenzene, a representative C₉ aromatic in a blend with n-heptane, in a jet-stirred reactor. Time-of-flight molecular beam mass spectrometry using synchrotron vacuum ultraviolet radiation as a photon ionization source was used for product analysis and species identification. Thirty-six species were identified by comparison of measured photoionization efficiency curves and calculated species ionization energies, and six of them are key reaction intermediates of n-propylbenzene oxidation. Kinetic model simulations captured the measured mole fractions of reactants, main products, and intermediates with some discrepancies. Furthermore, many oxygenated aromatics are missing in the model, reflecting insufficient understanding of n-propylbenzene low-temperature chemistry. Low-temperature oxidation pathways were proposed based on molecular structures of reaction intermediates. This work explored low-temperature oxidation of n-propylbenzene under a fuel blend environment, which might be useful to unravel the low-temperature chemistry of C₇-C₁₀ aromatics in practical jet fuels.