SO2-Enhanced Nitration of Fluoranthene and Pyrene Adsorbed on Particulate Matter in the Heterogeneous Reaction in the Presence of NO2

Heterogeneous photoreaction of fluoranthene (FL) or pyrene (PY) adsorbed on solid support under 10 ppm NO₂-air in the presence or absence of SO₂ was investigated in order to clarify the effect of SO₂ on nitroarene formation. Formation yield of nitrofluoranthenes (NFs) and nitropyrenes (NPs) were increased by the addition of SO₂ to reaction atmosphere. 1-, 2-, 7-, and 8-NFs were formed in the presence of SO₂ while 1-, 2-, and 7-NF were detected in the absence of SO₂. After the reaction for 4 h, yield of 2-NF in the presence of 10 ppm of SO₂ was 1.5 times as large as that in the absence of SO₂. 1-NP and 1,3-, 1,6-, 1,8-dinitropyrenes (DNPs) were formed both in the presence and in the absence of SO₂. After the reaction for 2 h, yields of 1-NP and DNPs in the presence of 10 ppm of SO₂ were about three times and twice as large as those in the absence of SO₂, respectively. While the yield of 1-NP and degradation rate of PY were hardly affected by the concentration of SO₂, the yield of DNPs increased with the increase in SO₂ concentration. The isomer distributions of NFs and NPs indicated that NFs and NPs were formed by non-electrophilic nitration and electrophilic nitration, respectively.