Formation of 2-nitrofluoranthene in gas-solid heterogeneous photoreaction of fluoranthene supported on oxide particles in the presence of nitrogen dioxide

Heterogeneous reaction of fluoranthene (FL) supported on eight kinds of inorganic particles has been investigated in the presence of NO2 both under photoirradiation and in the dark to simulate atmospheric transformations of FL. In the air containing 10 ppm NO2, 2-nitrofluoranthene (2-NF), the most abundant nitroarene found on airborne particles, was produced under photoirradiation for the first time in a laboratory heterogeneous system while the reaction did not proceed in the dark in 24 h. The maximum yield of 2-NF ranged from 7.9% for FL supported on CaO to 1.2% on Fe2O3. The other NFs identified in the photoirradiated sustem were 1- and 7-NFs with maximum yields varying with the kind of support material. This isomer distribution was quite different from that reported for electrophilic substitution and similar to that for radical reaction. Also the degraded percentage of FL in the reaction for 4 h was dependent on the support material in the range from 20.9% on graphite to 79.5% on TiO2, respectively. The presence of O2 in the reaction atmosphere caused promotion of 2-NF formation and suppression of 7-NF formation. Both 3- and 8-NFs, reported to exist in vehicle exhaust particles, were formed only in trace amounts for all the photoirradiated systems.