Heterogeneous Reactions between Toluene and NO₂ on Mineral Particles under Simulated Atmospheric Conditions

Heterogeneous reactions between organic and inorganic gases with aerosols are important for the study of smog occurrence and development. In this study, heterogeneous reactions between toluene and NO₂ with three atmospheric mineral particles in the presence or absence of UV light were investigated. The three mineral particles were SiO₂, α-Fe₂O₃, and BS (butlerite and szmolnokite). In a dark environment, benzaldehyde was produced on α-Fe₂O₃. For BS, nitrotoluene and benzaldehyde were obtained. No aromatic products were produced in the absence of NO₂ in the system. In the presence of UV irradiation, benzaldehyde was detected on the SiO₂ surface. Identical products were produced in the presence and absence of UV light over α-Fe₂O₃ and BS. UV light promoted nitrite to nitrate on mineral particles surface. On the basisi of the X-ray photoelectron spectroscopy (XPS) results, a portion of BS was reduced from Fe³⁺ to Fe²⁺ with the adsorption of toluene or the reaction with toluene and NO₂. Sulfate may play a key role in the generation of nitrotoluene on BS particles. From this research, the heterogeneous reactions between organic and inorganic gases with aerosols that occur during smog events will be better understood.