Sun Zhenyu, Kong Lingdong, Ding Xiaoxiao, Du Chengtian, Zhao Xi, Chen Jianmin, Fu Hongbo, Yang Xin, Cheng Tiantao
Shanghai Key Laboratory of Atmospheric Particle Pollution, Prevention, Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, China.
Phys Chem Chem Phys. 2016 Apr 14;18(14):9367-76. doi: 10.1039/c5cp05632b. Epub 2016 Jan 8.
Heterogeneous reactions of nitrogen oxides on the surface of aluminium oxide result in the formation of adsorbed nitrite and nitrate. However, little is known about the effects of other species on these heterogeneous reactions and their products. In this study, diffuse reflectance infrared spectroscopy (DRIFTS) was used to analyze the process of the heterogeneous reaction of NO2 on the surface of aluminium oxide particles in the presence of pre-adsorbed organic species (acetaldehyde, glyoxal and acetic acid) at 298 K and reveal the influence of these organic species on the formation of adsorbed nitrite and nitrate. It was found that the pre-adsorption of organic species (acetaldehyde, glyoxal and acetic acid) on γ-Al2O3 could suppress the formation of nitrate to different extents. Under the same experimental conditions, the suppression of the formation of nitrate by the pre-adsorption of acetic acid is much stronger than that by pre-adsorption of acetaldehyde and glyoxal, indicating that the influence of acetic acid on the heterogeneous reaction of NO2 is different from that of acetaldehyde and glyoxal. Surface nitrite is formed and identified to be an intermediate product. For the heterogeneous reaction of NO2 on the surface of γ-Al2O3 with and without the pre-adsorption of acetaldehyde and glyoxal, it is firstly formed and then gradually disappears as the reaction proceeds, but for the reaction with the pre-adsorption of acetic acid, it is the final main product besides nitrate. This indicates that the pre-adsorption of acetic acid would promote the formation of nitrite, while the others would not change the trend of the formation of nitrite. The possible influence mechanisms of the pre-adsorption of acetaldehyde, glyoxal and acetic acid on the heterogeneous conversion of NO2 on γ-Al2O3 are proposed and atmospheric implications based on these results are discussed.
氮氧化物在氧化铝表面的非均相反应会导致吸附的亚硝酸盐和硝酸盐的形成。然而，对于其他物种对这些非均相反应及其产物的影响知之甚少。在本研究中，采用漫反射红外光谱（DRIFTS）分析了在298 K下预吸附有机物种（乙醛、乙二醛和乙酸）存在时，二氧化氮在氧化铝颗粒表面的非均相反应过程，并揭示了这些有机物种对吸附的亚硝酸盐和硝酸盐形成的影响。研究发现，有机物种（乙醛、乙二醛和乙酸）在γ -氧化铝上的预吸附能够不同程度地抑制硝酸盐的形成。在相同实验条件下，乙酸预吸附对硝酸盐形成的抑制作用远强于乙醛和乙二醛的预吸附，这表明乙酸对二氧化氮非均相反应的影响与乙醛和乙二醛不同。表面亚硝酸盐被形成并确定为中间产物。对于二氧化氮在γ -氧化铝表面有无乙醛和乙二醛预吸附的非均相反应，它首先形成，然后随着反应进行逐渐消失，但对于有乙酸预吸附的反应，它是除硝酸盐外的最终主要产物。这表明乙酸的预吸附会促进亚硝酸盐的形成，而其他物质不会改变亚硝酸盐的形成趋势。提出了乙醛、乙二醛和乙酸预吸附对γ -氧化铝上二氧化氮非均相转化的可能影响机制，并基于这些结果讨论了其对大气的影响。
