A wide-range experimental and modeling study of oxidation and combustion of n-propylbenzene

The oxidation of n-propylbenzene (NPB) was studied in a jet-stirred reactor (JSR) equipped with online GC and GC-MS for temperatures ranging between 700 and 1100 K, at φ = 0.4-2.0. In addition, laminar flame speeds were measured at p = 1, 3 and 6 bar at a preheat temperature of T = 473 K, and ignition delay times in a shock tube device behind reflected shock waves, for stoichiometric mixtures at around p = 16 bar. Mole fraction profiles of 25 intermediates including six species, namely 1-propenylbenzene, 2-propenylbenzene, α-methylstyrene, naphthalene, indene, and benzofuran were observed additionally. With φ increasing, NPB consumption shifts to higher temperatures, and the reaction temperature zone becomes broader. Based on the experimental measurements and on new calculations of the rate constants for the H-abstractions from NPB with OH, an updated kinetic model involving 292 species and 1919 reactions was developed with a reasonable agreement with the measured species profiles, flame speed values, and ignition delay times. Rate of production analysis reveals that NPB consumption is generally governed by CH bond cleavage to form three A1C3H6 radicals, which mostly transform to styrene under rich condition and to benzaldehyde under lean condition. Compared to the aromatics formed in the oxidation of two other aromatic C9 fuels, 1,3,5-trimethylbenzene and 1,2,4-trimethylbenzene, NPB exhibits to be the most reactive fuel with the least aldehyde intermediates. Moreover, the present model gives a reasonable agreement with the literature-reported ignition delay times and JSR data. These results can improve the understanding of the oxidation and combustion of NPB as a surrogate fuel constituent for kerosene and diesel.