Impact of Fe Content in Laboratory-Produced Soot Aerosol on its Composition, Structure, and Thermo-Chemical Properties
Impact of Fe Content in Laboratory-Produced Soot Aerosol on its Composition, Structure, and Thermo-Chemical Properties
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DOI：
10.1080/02786826.2012.711917
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发表时间：
2012-01-01
影响因子：
5.2
通讯作者：
Niessner, Reinhard
中科院分区：
文献类型：
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作者：
Bladt, Henrike;Schmid, Johannes;Niessner, Reinhard
煤烟气溶胶是城市大气中的主要污染物，它不仅含有碳质物质，而且还含有无机物。这些物质，例如铁化合物，来源于燃料或润滑油中的杂质、添加剂或发动机磨损，可能会改变烟灰的物理化学特性，从而改变其对环境的影响。我们研究了不同铁含量的实验室产生的烟尘气溶胶的组成，结构和氧化反应性的变化。通过调节五羰基铁Fe（CO）（5）的掺杂量，在丙烷/空气扩散火焰中生成了不同铁含量的碳烟。扫描电子显微镜（SEM）/能量色散X射线光谱（EDX）与聚类分析（CA）相结合，将单个颗粒分离成可定义的组，这些组具有相似的化学组成，代表依赖于烟灰中铁含量的颗粒类型。拉曼显微光谱（RM）和红外光谱的石墨烟灰结构，碳氢化合物和铁物种的表征。对于烟灰反应性的分析，使用程序升温氧化（TPO）。它表明，铁是最主要存在于无定形的Fe（III）氧化物的形式结晶赤铁矿α-Fe 2 O3热处理后。铁污染物并不改变烟灰的微观结构至关重要，但Fe（CO）（5）掺杂的火焰影响碳氢化合物的组成。碳烟氧化反应性强烈地依赖于铁含量，因为最大碳（二）氧化物排放的温度T-max随着碳烟中铁含量的增加而遵循指数衰减。根据实验室生产的内部混合含铁烟灰的热化学表征结果，我们可以得出结论，当前的热光学分析方案无法明确表征含铁燃烧气溶胶样品。
Soot aerosol, which is a major pollutant in the atmosphere of urban areas, often contains not only carbonaceous matter but also inorganic material. These species, for example, iron compounds, originated from impurities in fuel or lubricating oil, additives or engine wear may change the physico-chemical characteristics of soot and hence its environmental impact. We studied the change of composition, structure, and oxidation reactivity of laboratory-produced soot aerosol with varying iron content. Soot types of various iron contents were generated in a propane/air diffusion flame by adjusting the doping amount of iron pentacarbonyl Fe(CO)(5) to the flame. Scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) was combined with cluster analysis (CA) to separate individual particles into definable groups of similar chemical composition representing the particle types in dependence of the iron content in soot. Raman microspectroscopy (RM) and infrared spectroscopy were applied for the characterization of the graphitic soot structure, hydrocarbons, and iron species. For the analysis of soot reactivity, temperature-programmed oxidation (TPO) was used. It is demonstrated that iron is most dominantly present in the form of amorphous Fe (III) oxide crystallizing to hematite alpha-Fe2O3 upon thermal treatment. Iron contaminations do not change the soot microstructure crucially, but Fe(CO)(5) doping of the flame impacts hydrocarbon composition. Soot oxidation reactivity strongly depends on the iron content, as the temperature of maximum carbon (di)oxide emission T-max follows an exponential decay with increasing iron content in soot. Based on the results of the thermo-chemical characterization of laboratory-produced internally mixed iron-containing soot, we can conclude that iron-containing combustion aerosol samples cannot be characterized unambiguously by current thermo-optical analysis protocols.