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.