利用真空FTIR比较研究油酸薄膜和油酸包覆粉煤灰分别与臭氧的非均相化学反应动力学（英文）

发布时间：2018-08-05 14:29

【摘要】：气溶胶老化是目前大气颗粒物物理化学领域的研究热点之一。通过真空型傅里叶红外光谱仪原位观测并对比了油酸(OA)薄膜和油酸包覆粉煤灰两种样品分别与臭氧发生的化学反应动力学,并评估了其中粉煤灰在非均相化学反应中所起到的作用。除了指纹区特征峰的不同,在反应前纯油酸薄膜和纯油酸包覆粉煤灰样品的主要红外特征吸收峰是相似的。当两种样品分别处于20ppm臭氧浓度、室温和干燥的反应环境中,=CH的特征吸收峰(3 050cm-1)强度降低而—OH伸缩振动特征峰(3 430cm~(-1))强度增加。此外,随着臭氧氧化反应的进行,处于1 710cm-1的羧酸C=O伸缩振动特征峰强度下降,反之,产物酯类物质的伸缩振动特征峰在1 740cm~(-1)出现并增强。通过红外光谱的变化趋势能够得到两组样品的OA成分在反应中逐步消耗并转化为含有羟基和酯类官能团的产物。通过位于1 740cm-1处的C=O特征峰的变化能够得到准一级反应速率常数Kapp和摄取系数γ。粉煤灰样品的准一级反应速率常数大体是油酸薄膜反应体系的两倍。对于比表面积,粉煤灰样品要大于油酸薄膜,而两种反应体系的臭氧浓度一致,油酸薄膜和油酸包覆粉煤灰的γ值分别为(2.70±0.11)×10~(-4)和(3.70±0.13)×10~(-4)。较大的催化表面积和较快的催化效率是导致粉煤灰样品较油酸薄膜反应快的原因。由此证明了当粉煤灰与不饱和有机酸结合并处在臭氧氧化环境中时会常易促进二次有机气溶胶的形成。
[Abstract]:Aerosol aging is one of the research hotspots in the field of physical chemistry of atmospheric particulates. The kinetics of chemical reaction of oleic acid (OA) film and oleic acid-coated fly ash with ozone was observed and compared by vacuum Fourier transform infrared spectrometer. The role of fly ash in heterogeneous chemical reaction was evaluated. In addition to the difference of fingerprint characteristic peaks, the main infrared characteristic absorption peaks of pure oleic acid film and fly ash coated with pure oleic acid before reaction are similar. When the two samples were in 20ppm ozone concentration, the intensity of the characteristic absorption peak (3 050cm-1) of Ch decreased while the intensity of the characteristic peak of -OH stretching vibration (3 430 cm ~ (-1) increased at room temperature and in dry reaction environment. In addition, with the ozone oxidation reaction, the intensity of the extensional vibration characteristic peak of carboxylic acid Con O at 1 710cm-1 decreases, whereas the stretching vibration characteristic peak of the product esters appears and increases at 1 740 cm ~ (-1). The OA components of the two groups of samples can be gradually consumed and converted into products containing hydroxyl groups and ester functional groups through the change trend of IR spectra. The quasi-first-order reaction rate constant Kapp and uptake coefficient 纬 can be obtained by changing the characteristic peak of Con O at 1 740cm-1. The quasi first order reaction rate constant of fly ash samples is about twice as high as that of oleic acid film reaction system. For the specific surface area, the fly ash sample is larger than the oleic acid film, and the ozone concentration of the two reaction systems is the same. The 纬 values of oleic acid film and oleic acid-coated fly ash are (2.70 卤0.11) 脳 10 ~ (-4) and (3.70 卤0.13) 脳 10 ~ (-4), respectively. The larger catalytic surface area and faster catalytic efficiency are the reasons for the faster reaction of fly ash sample than oleic acid film. It is proved that the formation of secondary organic aerosol is easy to be promoted when fly ash binds to unsaturated organic acid and is in ozone oxidation environment.
【作者单位】：北京理工大学化学学院化学物理研究所;
【基金】：supported by the National Natural Science Foundational of China(41175119,21373026,21473009)
【分类号】：O657.33;O643.1

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