Data for: Nitration of polycyclic aromatic hydrocarbons adsorbed on silica gel and Fe2O3 particles with NO2: Effects of adsorbed water and hydrocarbons reactivity on kinetics and mechanism
Description
The nitration of polycyclic aromatic hydrocarbons (PAHs) adsorbed on silica gel and Fe2O3 particles, which are known to be abundant in PM2.5, with NO2 (9.77 ppm) was studied using a fluidized-bed column to simulate the transformation of atmospheric PAHs at night. Anthracene, phenanthrene, pyrene, chrysene, fluoranthene, and perylene were used as PAHs, and the effects of water (H2Oads) adsorbed on the substrates and PAHs reactivity on kinetics and mechanism were investigated. On hydrated silica gel (H2Oads: 4.2 wt%), the most reactive perylene was nitrated by pseudo-first-order reaction, and moderately reactive PAHs (anthracene and pyrene) and less reactive chrysene were nitrated by H+-autocatalyzed reaction, while on dry Fe2O3 (H2Oads: 0.02 wt%), the nitration of the moderately reactive PAHs proceeded by pseudo-first-order reaction and less reactive chrysene proceeded by H+-autocatalyzed reaction. On the both substrates, the nitration of PAHs changed from pseudo-first-order to H+-autocatalyzed reactions as the reactivity of PAHs decreases, showing that the nitration kinetics and mechanism are affected by the concentration of H+ formed in H2Oads by NO2 exposure. On dry Fe2O3, most reactive perylene and the moderately reactive PAHs were nitrated by NO2, while on hydrated silica gel, the moderately reactive PAHs and chrysene were nitrated by NO2+, which would be formed via a pre-equilibrium between NO2 and H+ formed by NO2 exposure and released by the nitration. The formation of NO2+ is supported by the accelerated H+-autocatalyzed nitration on the H2SO4-adsorbed hydrated silica gel and by the report of NO2+ detection on hydrated borosilicate glass.