The Photochemical Reaction Of Gasous NO₂ With Benzene And Chlorobenzene On Mineral Particle Surfaces

The photochemical reaction of NO2 with benzene and chlorobenzene in the gas phase and on typical mineral particle surfaces (α-Fe2O3,α-Al2O3 and SiO2) at 308 nm UV light and in the dark was investigated using Fourier transform infrared spectroscopy (HPLC) and high performance liquid chromatography (HPLC). In addition, the effect of different factors (time, initial concentration, temperature, relative humidity, ultraviolet light wavelength, particle size) on the reactions was systematically studied. And furthermore, the reaction mechanism of photochemical reactions was also inferred. Based on the experimental results and practical atmospheric environmental condition, In-cloud oxidation model in atmospheric environment were applied to calculate the generation rate of p-chlorophenol (p-NP). Increased of liquid water concentrations in practical atmosphere environment, the production rate of p-NP from photochemical reaction of NO2 with benzene and chlorobenzene on particle surfaces were higher than those in the gas phase apparently, and the results consistent with experiment results. The main conclusions are as follows:The photolysis reaction of benzene and chlorobenzene in the gas phase would occur neither in the dark nor at 308 nm UV light. When temperature was 25℃, RH=0%, NO2 was 300 Pa, benzene or chlorobenzene was 400 Pa, the product formed from photochemical reaction of NO2 with benzene or chlorobenzene in the gas phase and on α-Fe2O3,α-Al2O3 and SiO2 surfaces were NO. And the concentration of NO increased with the increase of illumination time. At illumination time of 100 min, the concentration of NO formed from photochemical reaction of NO2 with benzene in the gas phase and on α-Fe2O3, α-Al2O3 and SiO2 surfaces were 1.47×1015 molecule/cm3, 2.19×1015 molecule/cm3,2.14×1015 molecule/cm3 and 1.80×1015 molecule/cm3, respectively. The concentration of NO formed from photochemical reaction of NO2 with chlorobenzene in the gas phase and on α-Fe2O3, α-Al2O3 and SiO2 surfaces were 1.35×1015 molecule/cm3,2.16×1015 molecule/cm3,2.09×1015 molecule/cm3 and 1.76×105 molecule/cm, respectively. Under the same experimental conditions, the concentration of NO:α-Fe2O3>α-Al2O3>SiO2>gas phase.When temperature was 25℃, NO2 was 300 Pa, benzene or chlorobenzene was 400 Pa, NO, HONO and p-NP formed from photochemical reaction at 308 nm illumination for 40 min, the concentration of NO, HONO and p-NP increased as relative humidity increased,α-Fe2O3>α-Al2O3>SiO2>gas phase. When RH=70%, the concentration of HONO formed from photochemical reaction of NO2 with benzene on α-Fe2O3,α-Al2O3 and SiO2 surfaces were about 2.99,2.28 and 2.01 times higher than those in the gas phase, respectively. The concentration of p-NP formed from NO2 with benzene on particle surfaces were about 3.59,3.02 and 1.92 times higher than those in the gas phase, respectively. The concentration of HONO formed from photochemical reaction of NO2 with chlorobenzene on α-Fe2O3, α-Al2O3 and SiO2 surfaces were about 3.00,2.23 and 2.01 times higher than those in the gas phase, respectively. The concentration of p-NP formed from NO2 with chlorobenzene on particle surfaces were about 3.00×1013 molecule/cm3,2.41×1013 molecule/cm3 and 1.57×1013 molecule/cm3, and they were about 3.51,2.82 and 1.84 times higher than those in the gas phase, respectively.The simulation results by using In-cloud oxidation model in atmospheric environment showed that as the increasing of liquid water concentrations in practical atmosphere environment, the production rate of p-NP from photochemical reaction of NO2 with benzene and chlorobenzene on particle surfaces were higher than those in the gas phase apparently. When water concentration of water was 1.0 g/m3, the production rate of p-NP formed from photochemical reaction of NO2 with benzene on α-Fe2O3, α-Al2O3 and SiO2 surfaces were about 5.02,2.93 and 1.49 times higher than those in the gas phase, respectively. The production rate of p-NP formed from photochemical reaction of NO2 with chlorobenzene on α-Fe2O3, α-Al2O3 and SiO2 surfaces were about 3.98,3.08 and 1.21 times higher than those in the gas phase, respectively.