Polycyclic aromatic hydrocarbons in flames, in diesel fuels, and in diesel emissions
Polycyclic aromatic hydrocarbons in flames, in diesel fuels, and in diesel emissions
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DOI：
10.1016/j.combustflame.2005.09.008
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发表时间：
2006-03
影响因子：
4.4
通讯作者：
R. Dobbins;R. Fletcher;B. Benner;S. Hoeft
中科院分区：
文献类型：
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作者：
R. Dobbins;R. Fletcher;B. Benner;S. Hoeft
对实验室火焰中的气体和颗粒样品进行的大量化学分析提供了有关在燃烧由纯气态碳氢化合物组成的各种火焰类型的燃料中发现的多环芳烃 (PAH) 物质的数据库。压燃式发动机中更复杂的燃烧所使用的柴油燃料由数千种碳氢化合物组成。激光微探针质谱分析法和气相色谱法以互补的方式用于区分源自燃料的多环芳烃和发动机燃烧产生的多环芳烃。预混合和扩散火焰过程的 CxHyPAH 产物也出现在非稳态柴油燃烧中，其质量范围从 128 u（两个环，x=10，y=8）到超过 350 u（八个环，x=28，y=14）。许多实验室火焰研究人员发现的物种的氢原子数 y 与碳原子数 x 的关系图显示，这些热解多环芳烃位于描述最稳定、近缩合苯环多环芳烃的阶梯曲线上或附近。相比之下，英国和美国的柴油样品含有高氢含量的石油烷基多环芳烃。来自两个不同来源的 20 世纪 90 年代典型柴油颗粒排放样品显示了从 128 到 350 u 的全质量范围的 PAH，包括苯型 PAH 和烷基 PAH。因此，柴油排放物通常可能含有高达 206 u 的石化燃料成分，以及燃烧产生的质量范围为 228 至 302 u 的四至七环物质，这些物质具有更大的致癌效力。由于不存在大于 206 u 的成岩成分，因此有利于通过化学分析方法检测它们并将其与热成 PAH 区分开来。
Numerous chemical analyses of gaseous and particulate samples from laboratory flames provide a library of data on the polycyclic aromatic hydrocarbon (PAH) species found in diverse flame types burning fuels consisting of pure gaseous hydrocarbons. The diesel fuels utilized by the more complex combustion in compression ignition engines are composed of thousands of hydrocarbon species. Mass spectrometry by the laser microprobe and gas chromatography were used in a complementary manner to distinguish the PAHs originating in the fuel from those produced by engine combustion. The CxHyPAH products of premixed and diffusion flame processes, which also occur in the unsteady diesel combustion, range in mass from 128 u (two rings, x=10, y=8) to beyond 350 u (eight rings, x=28, y=14). Graphs of the number of hydrogen atoms y vs the number of carbon atoms x for the species found by many investigators of laboratory flames show these pyrogenic PAHs to lie on or near the staircase curve that describes the most stable, pericondensed, benzenoid PAHs. In contrast, samples of diesel fuels from the United Kingdom and the United States contain petrogenic alkyl-PAHs with high hydrogen contents. Samples of diesel particulate emissions typical of the 1990s from two different sources display the full mass range of PAHs from 128 to 350 u, including both the benzenoid PAHs and the alkyl-PAHs. Thus diesel emissions, in general, may contain petrogenic fuel components ranging up to 206 u and also the combustion-generated four- to seven-ring species in the 228 to 302 u mass range that have greater carcinogenic potency. The absence of petrogenic components larger than 206 u facilitates their detection and delineation from pyrogenic PAHs by methods of chemical analysis.