Kinetic study of the reactions of NO_2 with polycyclic aromatic hydrocarbons adsorbed on silica particles

摘要

This experimental work deals with the kinetic study of the reactions of nitrogen dioxide (NO_2) radical with tri- to hexa-aromatic hydrocarbons adsorbed on silica particles. Measurements were performed using a flow-tube, at 295 K, in the absence of light. Polycyclic aromatic hydrocarbons (PAHs) were extracted from particles by focused microwave extraction and analyses were performed using gas chromatography coupled to mass spectrometry (GC/MS). Rate constants varied from 1.4 x 10~(-3) to 4 x 10~(-8)s~(-1), depending on the structure of the PAH, for NO_2 concentration of 1.5 x 10~(12) molecules cm~(-3). Benzo[a]pyrene was the most reactive, with a lifetime regarding NO_2 of a few minutes in polluted air conditions. The comparison of these results with those previously reported for carbonaceous particles leads to the conclusion that gas/solid interface reactivity of PAHs depends on the nature of the particle.